- 26 Oct, 2020 7 commits
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Josef Bacik authored
I got the following lockdep splat with tree locks converted to rwsem patches on btrfs/104: ====================================================== WARNING: possible circular locking dependency detected 5.9.0+ #102 Not tainted ------------------------------------------------------ btrfs-cleaner/903 is trying to acquire lock: ffff8e7fab6ffe30 (btrfs-root-00){++++}-{3:3}, at: __btrfs_tree_read_lock+0x32/0x170 but task is already holding lock: ffff8e7fab628a88 (&fs_info->commit_root_sem){++++}-{3:3}, at: btrfs_find_all_roots+0x41/0x80 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&fs_info->commit_root_sem){++++}-{3:3}: down_read+0x40/0x130 caching_thread+0x53/0x5a0 btrfs_work_helper+0xfa/0x520 process_one_work+0x238/0x540 worker_thread+0x55/0x3c0 kthread+0x13a/0x150 ret_from_fork+0x1f/0x30 -> #2 (&caching_ctl->mutex){+.+.}-{3:3}: __mutex_lock+0x7e/0x7b0 btrfs_cache_block_group+0x1e0/0x510 find_free_extent+0xb6e/0x12f0 btrfs_reserve_extent+0xb3/0x1b0 btrfs_alloc_tree_block+0xb1/0x330 alloc_tree_block_no_bg_flush+0x4f/0x60 __btrfs_cow_block+0x11d/0x580 btrfs_cow_block+0x10c/0x220 commit_cowonly_roots+0x47/0x2e0 btrfs_commit_transaction+0x595/0xbd0 sync_filesystem+0x74/0x90 generic_shutdown_super+0x22/0x100 kill_anon_super+0x14/0x30 btrfs_kill_super+0x12/0x20 deactivate_locked_super+0x36/0xa0 cleanup_mnt+0x12d/0x190 task_work_run+0x5c/0xa0 exit_to_user_mode_prepare+0x1df/0x200 syscall_exit_to_user_mode+0x54/0x280 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #1 (&space_info->groups_sem){++++}-{3:3}: down_read+0x40/0x130 find_free_extent+0x2ed/0x12f0 btrfs_reserve_extent+0xb3/0x1b0 btrfs_alloc_tree_block+0xb1/0x330 alloc_tree_block_no_bg_flush+0x4f/0x60 __btrfs_cow_block+0x11d/0x580 btrfs_cow_block+0x10c/0x220 commit_cowonly_roots+0x47/0x2e0 btrfs_commit_transaction+0x595/0xbd0 sync_filesystem+0x74/0x90 generic_shutdown_super+0x22/0x100 kill_anon_super+0x14/0x30 btrfs_kill_super+0x12/0x20 deactivate_locked_super+0x36/0xa0 cleanup_mnt+0x12d/0x190 task_work_run+0x5c/0xa0 exit_to_user_mode_prepare+0x1df/0x200 syscall_exit_to_user_mode+0x54/0x280 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #0 (btrfs-root-00){++++}-{3:3}: __lock_acquire+0x1167/0x2150 lock_acquire+0xb9/0x3d0 down_read_nested+0x43/0x130 __btrfs_tree_read_lock+0x32/0x170 __btrfs_read_lock_root_node+0x3a/0x50 btrfs_search_slot+0x614/0x9d0 btrfs_find_root+0x35/0x1b0 btrfs_read_tree_root+0x61/0x120 btrfs_get_root_ref+0x14b/0x600 find_parent_nodes+0x3e6/0x1b30 btrfs_find_all_roots_safe+0xb4/0x130 btrfs_find_all_roots+0x60/0x80 btrfs_qgroup_trace_extent_post+0x27/0x40 btrfs_add_delayed_data_ref+0x3fd/0x460 btrfs_free_extent+0x42/0x100 __btrfs_mod_ref+0x1d7/0x2f0 walk_up_proc+0x11c/0x400 walk_up_tree+0xf0/0x180 btrfs_drop_snapshot+0x1c7/0x780 btrfs_clean_one_deleted_snapshot+0xfb/0x110 cleaner_kthread+0xd4/0x140 kthread+0x13a/0x150 ret_from_fork+0x1f/0x30 other info that might help us debug this: Chain exists of: btrfs-root-00 --> &caching_ctl->mutex --> &fs_info->commit_root_sem Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&fs_info->commit_root_sem); lock(&caching_ctl->mutex); lock(&fs_info->commit_root_sem); lock(btrfs-root-00); *** DEADLOCK *** 3 locks held by btrfs-cleaner/903: #0: ffff8e7fab628838 (&fs_info->cleaner_mutex){+.+.}-{3:3}, at: cleaner_kthread+0x6e/0x140 #1: ffff8e7faadac640 (sb_internal){.+.+}-{0:0}, at: start_transaction+0x40b/0x5c0 #2: ffff8e7fab628a88 (&fs_info->commit_root_sem){++++}-{3:3}, at: btrfs_find_all_roots+0x41/0x80 stack backtrace: CPU: 0 PID: 903 Comm: btrfs-cleaner Not tainted 5.9.0+ #102 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-2.fc32 04/01/2014 Call Trace: dump_stack+0x8b/0xb0 check_noncircular+0xcf/0xf0 __lock_acquire+0x1167/0x2150 ? __bfs+0x42/0x210 lock_acquire+0xb9/0x3d0 ? __btrfs_tree_read_lock+0x32/0x170 down_read_nested+0x43/0x130 ? __btrfs_tree_read_lock+0x32/0x170 __btrfs_tree_read_lock+0x32/0x170 __btrfs_read_lock_root_node+0x3a/0x50 btrfs_search_slot+0x614/0x9d0 ? find_held_lock+0x2b/0x80 btrfs_find_root+0x35/0x1b0 ? do_raw_spin_unlock+0x4b/0xa0 btrfs_read_tree_root+0x61/0x120 btrfs_get_root_ref+0x14b/0x600 find_parent_nodes+0x3e6/0x1b30 btrfs_find_all_roots_safe+0xb4/0x130 btrfs_find_all_roots+0x60/0x80 btrfs_qgroup_trace_extent_post+0x27/0x40 btrfs_add_delayed_data_ref+0x3fd/0x460 btrfs_free_extent+0x42/0x100 __btrfs_mod_ref+0x1d7/0x2f0 walk_up_proc+0x11c/0x400 walk_up_tree+0xf0/0x180 btrfs_drop_snapshot+0x1c7/0x780 ? btrfs_clean_one_deleted_snapshot+0x73/0x110 btrfs_clean_one_deleted_snapshot+0xfb/0x110 cleaner_kthread+0xd4/0x140 ? btrfs_alloc_root+0x50/0x50 kthread+0x13a/0x150 ? kthread_create_worker_on_cpu+0x40/0x40 ret_from_fork+0x1f/0x30 BTRFS info (device sdb): disk space caching is enabled BTRFS info (device sdb): has skinny extents This happens because qgroups does a backref lookup when we create a delayed ref. From here it may have to look up a root from an indirect ref, which does a normal lookup on the tree_root, which takes the read lock on the tree_root nodes. To fix this we need to add a variant for looking up roots that searches the commit root of the tree_root. Then when we do the backref search using the commit root we are sure to not take any locks on the tree_root nodes. This gets rid of the lockdep splat when running btrfs/104. Reviewed-by:Filipe Manana <fdmanana@suse.com> Signed-off-by:
Josef Bacik <josef@toxicpanda.com> Signed-off-by:
David Sterba <dsterba@suse.com>
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Josef Bacik authored
When enabling qgroups we walk the tree_root and then add a qgroup item for every root that we have. This creates a lock dependency on the tree_root and qgroup_root, which results in the following lockdep splat (with tree locks using rwsem), eg. in tests btrfs/017 or btrfs/022: ====================================================== WARNING: possible circular locking dependency detected 5.9.0-default+ #1299 Not tainted ------------------------------------------------------ btrfs/24552 is trying to acquire lock: ffff9142dfc5f630 (btrfs-quota-00){++++}-{3:3}, at: __btrfs_tree_read_lock+0x35/0x1c0 [btrfs] but task is already holding lock: ffff9142dfc5d0b0 (btrfs-root-00){++++}-{3:3}, at: __btrfs_tree_read_lock+0x35/0x1c0 [btrfs] which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (btrfs-root-00){++++}-{3:3}: __lock_acquire+0x3fb/0x730 lock_acquire.part.0+0x6a/0x130 down_read_nested+0x46/0x130 __btrfs_tree_read_lock+0x35/0x1c0 [btrfs] __btrfs_read_lock_root_node+0x3a/0x50 [btrfs] btrfs_search_slot_get_root+0x11d/0x290 [btrfs] btrfs_search_slot+0xc3/0x9f0 [btrfs] btrfs_insert_item+0x6e/0x140 [btrfs] btrfs_create_tree+0x1cb/0x240 [btrfs] btrfs_quota_enable+0xcd/0x790 [btrfs] btrfs_ioctl_quota_ctl+0xc9/0xe0 [btrfs] __x64_sys_ioctl+0x83/0xa0 do_syscall_64+0x2d/0x70 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #0 (btrfs-quota-00){++++}-{3:3}: check_prev_add+0x91/0xc30 validate_chain+0x491/0x750 __lock_acquire+0x3fb/0x730 lock_acquire.part.0+0x6a/0x130 down_read_nested+0x46/0x130 __btrfs_tree_read_lock+0x35/0x1c0 [btrfs] __btrfs_read_lock_root_node+0x3a/0x50 [btrfs] btrfs_search_slot_get_root+0x11d/0x290 [btrfs] btrfs_search_slot+0xc3/0x9f0 [btrfs] btrfs_insert_empty_items+0x58/0xa0 [btrfs] add_qgroup_item.part.0+0x72/0x210 [btrfs] btrfs_quota_enable+0x3bb/0x790 [btrfs] btrfs_ioctl_quota_ctl+0xc9/0xe0 [btrfs] __x64_sys_ioctl+0x83/0xa0 do_syscall_64+0x2d/0x70 entry_SYSCALL_64_after_hwframe+0x44/0xa9 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(btrfs-root-00); lock(btrfs-quota-00); lock(btrfs-root-00); lock(btrfs-quota-00); *** DEADLOCK *** 5 locks held by btrfs/24552: #0: ffff9142df431478 (sb_writers#10){.+.+}-{0:0}, at: mnt_want_write_file+0x22/0xa0 #1: ffff9142f9b10cc0 (&fs_info->subvol_sem){++++}-{3:3}, at: btrfs_ioctl_quota_ctl+0x7b/0xe0 [btrfs] #2: ffff9142f9b11a08 (&fs_info->qgroup_ioctl_lock){+.+.}-{3:3}, at: btrfs_quota_enable+0x3b/0x790 [btrfs] #3: ffff9142df431698 (sb_internal#2){.+.+}-{0:0}, at: start_transaction+0x406/0x510 [btrfs] #4: ffff9142dfc5d0b0 (btrfs-root-00){++++}-{3:3}, at: __btrfs_tree_read_lock+0x35/0x1c0 [btrfs] stack backtrace: CPU: 1 PID: 24552 Comm: btrfs Not tainted 5.9.0-default+ #1299 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba527-rebuilt.opensuse.org 04/01/2014 Call Trace: dump_stack+0x77/0x97 check_noncircular+0xf3/0x110 check_prev_add+0x91/0xc30 validate_chain+0x491/0x750 __lock_acquire+0x3fb/0x730 lock_acquire.part.0+0x6a/0x130 ? __btrfs_tree_read_lock+0x35/0x1c0 [btrfs] ? lock_acquire+0xc4/0x140 ? __btrfs_tree_read_lock+0x35/0x1c0 [btrfs] down_read_nested+0x46/0x130 ? __btrfs_tree_read_lock+0x35/0x1c0 [btrfs] __btrfs_tree_read_lock+0x35/0x1c0 [btrfs] ? btrfs_root_node+0xd9/0x200 [btrfs] __btrfs_read_lock_root_node+0x3a/0x50 [btrfs] btrfs_search_slot_get_root+0x11d/0x290 [btrfs] btrfs_search_slot+0xc3/0x9f0 [btrfs] btrfs_insert_empty_items+0x58/0xa0 [btrfs] add_qgroup_item.part.0+0x72/0x210 [btrfs] btrfs_quota_enable+0x3bb/0x790 [btrfs] btrfs_ioctl_quota_ctl+0xc9/0xe0 [btrfs] __x64_sys_ioctl+0x83/0xa0 do_syscall_64+0x2d/0x70 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Fix this by dropping the path whenever we find a root item, add the qgroup item, and then re-lookup the root item we found and continue processing roots. Reported-by: -
Filipe Manana authored
Very sporadically I had test case btrfs/069 from fstests hanging (for years, it is not a recent regression), with the following traces in dmesg/syslog: [162301.160628] BTRFS info (device sdc): dev_replace from /dev/sdd (devid 2) to /dev/sdg started [162301.181196] BTRFS info (device sdc): scrub: finished on devid 4 with status: 0 [162301.287162] BTRFS info (device sdc): dev_replace from /dev/sdd (devid 2) to /dev/sdg finished [162513.513792] INFO: task btrfs-transacti:1356167 blocked for more than 120 seconds. [162513.514318] Not tainted 5.9.0-rc6-btrfs-next-69 #1 [162513.514522] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [162513.514747] task:btrfs-transacti state:D stack: 0 pid:1356167 ppid: 2 flags:0x00004000 [162513.514751] Call Trace: [162513.514761] __schedule+0x5ce/0xd00 [162513.514765] ? _raw_spin_unlock_irqrestore+0x3c/0x60 [162513.514771] schedule+0x46/0xf0 [162513.514844] wait_current_trans+0xde/0x140 [btrfs] [162513.514850] ? finish_wait+0x90/0x90 [162513.514864] start_transaction+0x37c/0x5f0 [btrfs] [162513.514879] transaction_kthread+0xa4/0x170 [btrfs] [162513.514891] ? btrfs_cleanup_transaction+0x660/0x660 [btrfs] [162513.514894] kthread+0x153/0x170 [162513.514897] ? kthread_stop+0x2c0/0x2c0 [162513.514902] ret_from_fork+0x22/0x30 [162513.514916] INFO: task fsstress:1356184 blocked for more than 120 seconds. [162513.515192] Not tainted 5.9.0-rc6-btrfs-next-69 #1 [162513.515431] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [162513.515680] task:fsstress state:D stack: 0 pid:1356184 ppid:1356177 flags:0x00004000 [162513.515682] Call Trace: [162513.515688] __schedule+0x5ce/0xd00 [162513.515691] ? _raw_spin_unlock_irqrestore+0x3c/0x60 [162513.515697] schedule+0x46/0xf0 [162513.515712] wait_current_trans+0xde/0x140 [btrfs] [162513.515716] ? finish_wait+0x90/0x90 [162513.515729] start_transaction+0x37c/0x5f0 [btrfs] [162513.515743] btrfs_attach_transaction_barrier+0x1f/0x50 [btrfs] [162513.515753] btrfs_sync_fs+0x61/0x1c0 [btrfs] [162513.515758] ? __ia32_sys_fdatasync+0x20/0x20 [162513.515761] iterate_supers+0x87/0xf0 [162513.515765] ksys_sync+0x60/0xb0 [162513.515768] __do_sys_sync+0xa/0x10 [162513.515771] do_syscall_64+0x33/0x80 [162513.515774] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [162513.515781] RIP: 0033:0x7f5238f50bd7 [162513.515782] Code: Bad RIP value. [162513.515784] RSP: 002b:00007fff67b978e8 EFLAGS: 00000206 ORIG_RAX: 00000000000000a2 [162513.515786] RAX: ffffffffffffffda RBX: 000055b1fad2c560 RCX: 00007f5238f50bd7 [162513.515788] RDX: 00000000ffffffff RSI: 000000000daf0e74 RDI: 000000000000003a [162513.515789] RBP: 0000000000000032 R08: 000000000000000a R09: 00007f5239019be0 [162513.515791] R10: fffffffffffff24f R11: 0000000000000206 R12: 000000000000003a [162513.515792] R13: 00007fff67b97950 R14: 00007fff67b97906 R15: 000055b1fad1a340 [162513.515804] INFO: task fsstress:1356185 blocked for more than 120 seconds. [162513.516064] Not tainted 5.9.0-rc6-btrfs-next-69 #1 [162513.516329] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [162513.516617] task:fsstress state:D stack: 0 pid:1356185 ppid:1356177 flags:0x00000000 [162513.516620] Call Trace: [162513.516625] __schedule+0x5ce/0xd00 [162513.516628] ? _raw_spin_unlock_irqrestore+0x3c/0x60 [162513.516634] schedule+0x46/0xf0 [162513.516647] wait_current_trans+0xde/0x140 [btrfs] [162513.516650] ? finish_wait+0x90/0x90 [162513.516662] start_transaction+0x4d7/0x5f0 [btrfs] [162513.516679] btrfs_setxattr_trans+0x3c/0x100 [btrfs] [162513.516686] __vfs_setxattr+0x66/0x80 [162513.516691] __vfs_setxattr_noperm+0x70/0x200 [162513.516697] vfs_setxattr+0x6b/0x120 [162513.516703] setxattr+0x125/0x240 [162513.516709] ? lock_acquire+0xb1/0x480 [162513.516712] ? mnt_want_write+0x20/0x50 [162513.516721] ? rcu_read_lock_any_held+0x8e/0xb0 [162513.516723] ? preempt_count_add+0x49/0xa0 [162513.516725] ? __sb_start_write+0x19b/0x290 [162513.516727] ? preempt_count_add+0x49/0xa0 [162513.516732] path_setxattr+0xba/0xd0 [162513.516739] __x64_sys_setxattr+0x27/0x30 [162513.516741] do_syscall_64+0x33/0x80 [162513.516743] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [162513.516745] RIP: 0033:0x7f5238f56d5a [162513.516746] Code: Bad RIP value. [162513.516748] RSP: 002b:00007fff67b97868 EFLAGS: 00000202 ORIG_RAX: 00000000000000bc [162513.516750] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007f5238f56d5a [162513.516751] RDX: 000055b1fbb0d5a0 RSI: 00007fff67b978a0 RDI: 000055b1fbb0d470 [162513.516753] RBP: 000055b1fbb0d5a0 R08: 0000000000000001 R09: 00007fff67b97700 [162513.516754] R10: 0000000000000004 R11: 0000000000000202 R12: 0000000000000004 [162513.516756] R13: 0000000000000024 R14: 0000000000000001 R15: 00007fff67b978a0 [162513.516767] INFO: task fsstress:1356196 blocked for more than 120 seconds. [162513.517064] Not tainted 5.9.0-rc6-btrfs-next-69 #1 [162513.517365] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [162513.517763] task:fsstress state:D stack: 0 pid:1356196 ppid:1356177 flags:0x00004000 [162513.517780] Call Trace: [162513.517786] __schedule+0x5ce/0xd00 [162513.517789] ? _raw_spin_unlock_irqrestore+0x3c/0x60 [162513.517796] schedule+0x46/0xf0 [162513.517810] wait_current_trans+0xde/0x140 [btrfs] [162513.517814] ? finish_wait+0x90/0x90 [162513.517829] start_transaction+0x37c/0x5f0 [btrfs] [162513.517845] btrfs_attach_transaction_barrier+0x1f/0x50 [btrfs] [162513.517857] btrfs_sync_fs+0x61/0x1c0 [btrfs] [162513.517862] ? __ia32_sys_fdatasync+0x20/0x20 [162513.517865] iterate_supers+0x87/0xf0 [162513.517869] ksys_sync+0x60/0xb0 [162513.517872] __do_sys_sync+0xa/0x10 [162513.517875] do_syscall_64+0x33/0x80 [162513.517878] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [162513.517881] RIP: 0033:0x7f5238f50bd7 [162513.517883] Code: Bad RIP value. [162513.517885] RSP: 002b:00007fff67b978e8 EFLAGS: 00000206 ORIG_RAX: 00000000000000a2 [162513.517887] RAX: ffffffffffffffda RBX: 000055b1fad2c560 RCX: 00007f5238f50bd7 [162513.517889] RDX: 0000000000000000 RSI: 000000007660add2 RDI: 0000000000000053 [162513.517891] RBP: 0000000000000032 R08: 0000000000000067 R09: 00007f5239019be0 [162513.517893] R10: fffffffffffff24f R11: 0000000000000206 R12: 0000000000000053 [162513.517895] R13: 00007fff67b97950 R14: 00007fff67b97906 R15: 000055b1fad1a340 [162513.517908] INFO: task fsstress:1356197 blocked for more than 120 seconds. [162513.518298] Not tainted 5.9.0-rc6-btrfs-next-69 #1 [162513.518672] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [162513.519157] task:fsstress state:D stack: 0 pid:1356197 ppid:1356177 flags:0x00000000 [162513.519160] Call Trace: [162513.519165] __schedule+0x5ce/0xd00 [162513.519168] ? _raw_spin_unlock_irqrestore+0x3c/0x60 [162513.519174] schedule+0x46/0xf0 [162513.519190] wait_current_trans+0xde/0x140 [btrfs] [162513.519193] ? finish_wait+0x90/0x90 [162513.519206] start_transaction+0x4d7/0x5f0 [btrfs] [162513.519222] btrfs_create+0x57/0x200 [btrfs] [162513.519230] lookup_open+0x522/0x650 [162513.519246] path_openat+0x2b8/0xa50 [162513.519270] do_filp_open+0x91/0x100 [162513.519275] ? find_held_lock+0x32/0x90 [162513.519280] ? lock_acquired+0x33b/0x470 [162513.519285] ? do_raw_spin_unlock+0x4b/0xc0 [162513.519287] ? _raw_spin_unlock+0x29/0x40 [162513.519295] do_sys_openat2+0x20d/0x2d0 [162513.519300] do_sys_open+0x44/0x80 [162513.519304] do_syscall_64+0x33/0x80 [162513.519307] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [162513.519309] RIP: 0033:0x7f5238f4a903 [162513.519310] Code: Bad RIP value. [162513.519312] RSP: 002b:00007fff67b97758 EFLAGS: 00000246 ORIG_RAX: 0000000000000055 [162513.519314] RAX: ffffffffffffffda RBX: 00000000ffffffff RCX: 00007f5238f4a903 [162513.519316] RDX: 0000000000000000 RSI: 00000000000001b6 RDI: 000055b1fbb0d470 [162513.519317] RBP: 00007fff67b978c0 R08: 0000000000000001 R09: 0000000000000002 [162513.519319] R10: 00007fff67b974f7 R11: 0000000000000246 R12: 0000000000000013 [162513.519320] R13: 00000000000001b6 R14: 00007fff67b97906 R15: 000055b1fad1c620 [162513.519332] INFO: task btrfs:1356211 blocked for more than 120 seconds. [162513.519727] Not tainted 5.9.0-rc6-btrfs-next-69 #1 [162513.520115] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [162513.520508] task:btrfs state:D stack: 0 pid:1356211 ppid:1356178 flags:0x00004002 [162513.520511] Call Trace: [162513.520516] __schedule+0x5ce/0xd00 [162513.520519] ? _raw_spin_unlock_irqrestore+0x3c/0x60 [162513.520525] schedule+0x46/0xf0 [162513.520544] btrfs_scrub_pause+0x11f/0x180 [btrfs] [162513.520548] ? finish_wait+0x90/0x90 [162513.520562] btrfs_commit_transaction+0x45a/0xc30 [btrfs] [162513.520574] ? start_transaction+0xe0/0x5f0 [btrfs] [162513.520596] btrfs_dev_replace_finishing+0x6d8/0x711 [btrfs] [162513.520619] btrfs_dev_replace_by_ioctl.cold+0x1cc/0x1fd [btrfs] [162513.520639] btrfs_ioctl+0x2a25/0x36f0 [btrfs] [162513.520643] ? do_sigaction+0xf3/0x240 [162513.520645] ? find_held_lock+0x32/0x90 [162513.520648] ? do_sigaction+0xf3/0x240 [162513.520651] ? lock_acquired+0x33b/0x470 [162513.520655] ? _raw_spin_unlock_irq+0x24/0x50 [162513.520657] ? lockdep_hardirqs_on+0x7d/0x100 [162513.520660] ? _raw_spin_unlock_irq+0x35/0x50 [162513.520662] ? do_sigaction+0xf3/0x240 [162513.520671] ? __x64_sys_ioctl+0x83/0xb0 [162513.520672] __x64_sys_ioctl+0x83/0xb0 [162513.520677] do_syscall_64+0x33/0x80 [162513.520679] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [162513.520681] RIP: 0033:0x7fc3cd307d87 [162513.520682] Code: Bad RIP value. [162513.520684] RSP: 002b:00007ffe30a56bb8 EFLAGS: 00000202 ORIG_RAX: 0000000000000010 [162513.520686] RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007fc3cd307d87 [162513.520687] RDX: 00007ffe30a57a30 RSI: 00000000ca289435 RDI: 0000000000000003 [162513.520689] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 [162513.520690] R10: 0000000000000008 R11: 0000000000000202 R12: 0000000000000003 [162513.520692] R13: 0000557323a212e0 R14: 00007ffe30a5a520 R15: 0000000000000001 [162513.520703] Showing all locks held in the system: [162513.520712] 1 lock held by khungtaskd/54: [162513.520713] #0: ffffffffb40a91a0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x15/0x197 [162513.520728] 1 lock held by in:imklog/596: [162513.520729] #0: ffff8f3f0d781400 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x4d/0x60 [162513.520782] 1 lock held by btrfs-transacti/1356167: [162513.520784] #0: ffff8f3d810cc848 (&fs_info->transaction_kthread_mutex){+.+.}-{3:3}, at: transaction_kthread+0x4a/0x170 [btrfs] [162513.520798] 1 lock held by btrfs/1356190: [162513.520800] #0: ffff8f3d57644470 (sb_writers#15){.+.+}-{0:0}, at: mnt_want_write_file+0x22/0x60 [162513.520805] 1 lock held by fsstress/1356184: [162513.520806] #0: ffff8f3d576440e8 (&type->s_umount_key#62){++++}-{3:3}, at: iterate_supers+0x6f/0xf0 [162513.520811] 3 locks held by fsstress/1356185: [162513.520812] #0: ffff8f3d57644470 (sb_writers#15){.+.+}-{0:0}, at: mnt_want_write+0x20/0x50 [162513.520815] #1: ffff8f3d80a650b8 (&type->i_mutex_dir_key#10){++++}-{3:3}, at: vfs_setxattr+0x50/0x120 [162513.520820] #2: ffff8f3d57644690 (sb_internal#2){.+.+}-{0:0}, at: start_transaction+0x40e/0x5f0 [btrfs] [162513.520833] 1 lock held by fsstress/1356196: [162513.520834] #0: ffff8f3d576440e8 (&type->s_umount_key#62){++++}-{3:3}, at: iterate_supers+0x6f/0xf0 [162513.520838] 3 locks held by fsstress/1356197: [162513.520839] #0: ffff8f3d57644470 (sb_writers#15){.+.+}-{0:0}, at: mnt_want_write+0x20/0x50 [162513.520843] #1: ffff8f3d506465e8 (&type->i_mutex_dir_key#10){++++}-{3:3}, at: path_openat+0x2a7/0xa50 [162513.520846] #2: ffff8f3d57644690 (sb_internal#2){.+.+}-{0:0}, at: start_transaction+0x40e/0x5f0 [btrfs] [162513.520858] 2 locks held by btrfs/1356211: [162513.520859] #0: ffff8f3d810cde30 (&fs_info->dev_replace.lock_finishing_cancel_unmount){+.+.}-{3:3}, at: btrfs_dev_replace_finishing+0x52/0x711 [btrfs] [162513.520877] #1: ffff8f3d57644690 (sb_internal#2){.+.+}-{0:0}, at: start_transaction+0x40e/0x5f0 [btrfs] This was weird because the stack traces show that a transaction commit, triggered by a device replace operation, is blocking trying to pause any running scrubs but there are no stack traces of blocked tasks doing a scrub. After poking around with drgn, I noticed there was a scrub task that was constantly running and blocking for shorts periods of time: >>> t = find_task(prog, 1356190) >>> prog.stack_trace(t) #0 __schedule+0x5ce/0xcfc #1 schedule+0x46/0xe4 #2 schedule_timeout+0x1df/0x475 #3 btrfs_reada_wait+0xda/0x132 #4 scrub_stripe+0x2a8/0x112f #5 scrub_chunk+0xcd/0x134 #6 scrub_enumerate_chunks+0x29e/0x5ee #7 btrfs_scrub_dev+0x2d5/0x91b #8 btrfs_ioctl+0x7f5/0x36e7 #9 __x64_sys_ioctl+0x83/0xb0 #10 do_syscall_64+0x33/0x77 #11 entry_SYSCALL_64+0x7c/0x156 Which corresponds to: int btrfs_reada_wait(void *handle) { struct reada_control *rc = handle; struct btrfs_fs_info *fs_info = rc->fs_info; while (atomic_read(&rc->elems)) { if (!atomic_read(&fs_info->reada_works_cnt)) reada_start_machine(fs_info); wait_event_timeout(rc->wait, atomic_read(&rc->elems) == 0, (HZ + 9) / 10); } (...) So the counter "rc->elems" was set to 1 and never decreased to 0, causing the scrub task to loop forever in that function. Then I used the following script for drgn to check the readahead requests: $ cat dump_reada.py import sys import drgn from drgn import NULL, Object, cast, container_of, execscript, \ reinterpret, sizeof from drgn.helpers.linux import * mnt_path = b"/home/fdmanana/btrfs-tests/scratch_1" mnt = None for mnt in for_each_mount(prog, dst = mnt_path): pass if mnt is None: sys.stderr.write(f'Error: mount point {mnt_path} not found\n') sys.exit(1) fs_info = cast('struct btrfs_fs_info *', mnt.mnt.mnt_sb.s_fs_info) def dump_re(re): nzones = re.nzones.value_() print(f're at {hex(re.value_())}') print(f'\t logical {re.logical.value_()}') print(f'\t refcnt {re.refcnt.value_()}') print(f'\t nzones {nzones}') for i in range(nzones): dev = re.zones[i].device name = dev.name.str.string_() print(f'\t\t dev id {dev.devid.value_()} name {name}') print() for _, e in radix_tree_for_each(fs_info.reada_tree): re = cast('struct reada_extent *', e) dump_re(re) $ drgn dump_reada.py re at 0xffff8f3da9d25ad8 logical 38928384 refcnt 1 nzones 1 dev id 0 name b'/dev/sdd' $ So there was one readahead extent with a single zone corresponding to the source device of that last device replace operation logged in dmesg/syslog. Also the ID of that zone's device was 0 which is a special value set in the source device of a device replace operation when the operation finishes (constant BTRFS_DEV_REPLACE_DEVID set at btrfs_dev_replace_finishing()), confirming again that device /dev/sdd was the source of a device replace operation. Normally there should be as many zones in the readahead extent as there are devices, and I wasn't expecting the extent to be in a block group with a 'single' profile, so I went and confirmed with the following drgn script that there weren't any single profile block groups: $ cat dump_block_groups.py import sys import drgn from drgn import NULL, Object, cast, container_of, execscript, \ reinterpret, sizeof from drgn.helpers.linux import * mnt_path = b"/home/fdmanana/btrfs-tests/scratch_1" mnt = None for mnt in for_each_mount(prog, dst = mnt_path): pass if mnt is None: sys.stderr.write(f'Error: mount point {mnt_path} not found\n') sys.exit(1) fs_info = cast('struct btrfs_fs_info *', mnt.mnt.mnt_sb.s_fs_info) BTRFS_BLOCK_GROUP_DATA = (1 << 0) BTRFS_BLOCK_GROUP_SYSTEM = (1 << 1) BTRFS_BLOCK_GROUP_METADATA = (1 << 2) BTRFS_BLOCK_GROUP_RAID0 = (1 << 3) BTRFS_BLOCK_GROUP_RAID1 = (1 << 4) BTRFS_BLOCK_GROUP_DUP = (1 << 5) BTRFS_BLOCK_GROUP_RAID10 = (1 << 6) BTRFS_BLOCK_GROUP_RAID5 = (1 << 7) BTRFS_BLOCK_GROUP_RAID6 = (1 << 8) BTRFS_BLOCK_GROUP_RAID1C3 = (1 << 9) BTRFS_BLOCK_GROUP_RAID1C4 = (1 << 10) def bg_flags_string(bg): flags = bg.flags.value_() ret = '' if flags & BTRFS_BLOCK_GROUP_DATA: ret = 'data' if flags & BTRFS_BLOCK_GROUP_METADATA: if len(ret) > 0: ret += '|' ret += 'meta' if flags & BTRFS_BLOCK_GROUP_SYSTEM: if len(ret) > 0: ret += '|' ret += 'system' if flags & BTRFS_BLOCK_GROUP_RAID0: ret += ' raid0' elif flags & BTRFS_BLOCK_GROUP_RAID1: ret += ' raid1' elif flags & BTRFS_BLOCK_GROUP_DUP: ret += ' dup' elif flags & BTRFS_BLOCK_GROUP_RAID10: ret += ' raid10' elif flags & BTRFS_BLOCK_GROUP_RAID5: ret += ' raid5' elif flags & BTRFS_BLOCK_GROUP_RAID6: ret += ' raid6' elif flags & BTRFS_BLOCK_GROUP_RAID1C3: ret += ' raid1c3' elif flags & BTRFS_BLOCK_GROUP_RAID1C4: ret += ' raid1c4' else: ret += ' single' return ret def dump_bg(bg): print() print(f'block group at {hex(bg.value_())}') print(f'\t start {bg.start.value_()} length {bg.length.value_()}') print(f'\t flags {bg.flags.value_()} - {bg_flags_string(bg)}') bg_root = fs_info.block_group_cache_tree.address_of_() for bg in rbtree_inorder_for_each_entry('struct btrfs_block_group', bg_root, 'cache_node'): dump_bg(bg) $ drgn dump_block_groups.py block group at 0xffff8f3d673b0400 start 22020096 length 16777216 flags 258 - system raid6 block group at 0xffff8f3d53ddb400 start 38797312 length 536870912 flags 260 - meta raid6 block group at 0xffff8f3d5f4d9c00 start 575668224 length 2147483648 flags 257 - data raid6 block group at 0xffff8f3d08189000 start 2723151872 length 67108864 flags 258 - system raid6 block group at 0xffff8f3db70ff000 start 2790260736 length 1073741824 flags 260 - meta raid6 block group at 0xffff8f3d5f4dd800 start 3864002560 length 67108864 flags 258 - system raid6 block group at 0xffff8f3d67037000 start 3931111424 length 2147483648 flags 257 - data raid6 $ So there were only 2 reasons left for having a readahead extent with a single zone: reada_find_zone(), called when creating a readahead extent, returned NULL either because we failed to find the corresponding block group or because a memory allocation failed. With some additional and custom tracing I figured out that on every further ocurrence of the problem the block group had just been deleted when we were looping to create the zones for the readahead extent (at reada_find_extent()), so we ended up with only one zone in the readahead extent, corresponding to a device that ends up getting replaced. So after figuring that out it became obvious why the hang happens: 1) Task A starts a scrub on any device of the filesystem, except for device /dev/sdd; 2) Task B starts a device replace with /dev/sdd as the source device; 3) Task A calls btrfs_reada_add() from scrub_stripe() and it is currently starting to scrub a stripe from block group X. This call to btrfs_reada_add() is the one for the extent tree. When btrfs_reada_add() calls reada_add_block(), it passes the logical address of the extent tree's root node as its 'logical' argument - a value of 38928384; 4) Task A then enters reada_find_extent(), called from reada_add_block(). It finds there isn't any existing readahead extent for the logical address 38928384, so it proceeds to the path of creating a new one. It calls btrfs_map_block() to find out which stripes exist for the block group X. On the first iteration of the for loop that iterates over the stripes, it finds the stripe for device /dev/sdd, so it creates one zone for that device and adds it to the readahead extent. Before getting into the second iteration of the loop, the cleanup kthread deletes block group X because it was empty. So in the iterations for the remaining stripes it does not add more zones to the readahead extent, because the calls to reada_find_zone() returned NULL because they couldn't find block group X anymore. As a result the new readahead extent has a single zone, corresponding to the device /dev/sdd; 4) Before task A returns to btrfs_reada_add() and queues the readahead job for the readahead work queue, task B finishes the device replace and at btrfs_dev_replace_finishing() swaps the device /dev/sdd with the new device /dev/sdg; 5) Task A returns to reada_add_block(), which increments the counter "->elems" of the reada_control structure allocated at btrfs_reada_add(). Then it returns back to btrfs_reada_add() and calls reada_start_machine(). This queues a job in the readahead work queue to run the function reada_start_machine_worker(), which calls __reada_start_machine(). At __reada_start_machine() we take the device list mutex and for each device found in the current device list, we call reada_start_machine_dev() to start the readahead work. However at this point the device /dev/sdd was already freed and is not in the device list anymore. This means the corresponding readahead for the extent at 38928384 is never started, and therefore the "->elems" counter of the reada_control structure allocated at btrfs_reada_add() never goes down to 0, causing the call to btrfs_reada_wait(), done by the scrub task, to wait forever. Note that the readahead request can be made either after the device replace started or before it started, however in pratice it is very unlikely that a device replace is able to start after a readahead request is made and is able to complete before the readahead request completes - maybe only on a very small and nearly empty filesystem. This hang however is not the only problem we can have with readahead and device removals. When the readahead extent has other zones other than the one corresponding to the device that is being removed (either by a device replace or a device remove operation), we risk having a use-after-free on the device when dropping the last reference of the readahead extent. For example if we create a readahead extent with two zones, one for the device /dev/sdd and one for the device /dev/sde: 1) Before the readahead worker starts, the device /dev/sdd is removed, and the corresponding btrfs_device structure is freed. However the readahead extent still has the zone pointing to the device structure; 2) When the readahead worker starts, it only finds device /dev/sde in the current device list of the filesystem; 3) It starts the readahead work, at reada_start_machine_dev(), using the device /dev/sde; 4) Then when it finishes reading the extent from device /dev/sde, it calls __readahead_hook() which ends up dropping the last reference on the readahead extent through the last call to reada_extent_put(); 5) At reada_extent_put() it iterates over each zone of the readahead extent and attempts to delete an element from the device's 'reada_extents' radix tree, resulting in a use-after-free, as the device pointer of the zone for /dev/sdd is now stale. We can also access the device after dropping the last reference of a zone, through reada_zone_release(), also called by reada_extent_put(). And a device remove suffers the same problem, however since it shrinks the device size down to zero before removing the device, it is very unlikely to still have readahead requests not completed by the time we free the device, the only possibility is if the device has a very little space allocated. While the hang problem is exclusive to scrub, since it is currently the only user of btrfs_reada_add() and btrfs_reada_wait(), the use-after-free problem affects any path that triggers readhead, which includes btree_readahead_hook() and __readahead_hook() (a readahead worker can trigger readahed for the children of a node) for example - any path that ends up calling reada_add_block() can trigger the use-after-free after a device is removed. So fix this by waiting for any readahead requests for a device to complete before removing a device, ensuring that while waiting for existing ones no new ones can be made. This problem has been around for a very long time - the readahead code was added in 2011, device remove exists since 2008 and device replace was introduced in 2013, hard to pick a specific commit for a git Fixes tag. CC: stable@vger.kernel.org # 4.4+ Reviewed-by: -
Filipe Manana authored
If we fail to find suitable zones for a new readahead extent, we end up leaving a stale pointer in the global readahead extents radix tree (fs_info->reada_tree), which can trigger the following trace later on: [13367.696354] BUG: kernel NULL pointer dereference, address: 00000000000000b0 [13367.696802] #PF: supervisor read access in kernel mode [13367.697249] #PF: error_code(0x0000) - not-present page [13367.697721] PGD 0 P4D 0 [13367.698171] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI [13367.698632] CPU: 6 PID: 851214 Comm: btrfs Tainted: G W 5.9.0-rc6-btrfs-next-69 #1 [13367.699100] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 [13367.700069] RIP: 0010:__lock_acquire+0x20a/0x3970 [13367.700562] Code: ff 1f 0f b7 c0 48 0f (...) [13367.701609] RSP: 0018:ffffb14448f57790 EFLAGS: 00010046 [13367.702140] RAX: 0000000000000000 RBX: 29b935140c15e8cf RCX: 0000000000000000 [13367.702698] RDX: 0000000000000002 RSI: ffffffffb3d66bd0 RDI: 0000000000000046 [13367.703240] RBP: ffff8a52ba8ac040 R08: 00000c2866ad9288 R09: 0000000000000001 [13367.703783] R10: 0000000000000001 R11: 00000000b66d9b53 R12: ffff8a52ba8ac9b0 [13367.704330] R13: 0000000000000000 R14: ffff8a532b6333e8 R15: 0000000000000000 [13367.704880] FS: 00007fe1df6b5700(0000) GS:ffff8a5376600000(0000) knlGS:0000000000000000 [13367.705438] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [13367.705995] CR2: 00000000000000b0 CR3: 000000022cca8004 CR4: 00000000003706e0 [13367.706565] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [13367.707127] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [13367.707686] Call Trace: [13367.708246] ? ___slab_alloc+0x395/0x740 [13367.708820] ? reada_add_block+0xae/0xee0 [btrfs] [13367.709383] lock_acquire+0xb1/0x480 [13367.709955] ? reada_add_block+0xe0/0xee0 [btrfs] [13367.710537] ? reada_add_block+0xae/0xee0 [btrfs] [13367.711097] ? rcu_read_lock_sched_held+0x5d/0x90 [13367.711659] ? kmem_cache_alloc_trace+0x8d2/0x990 [13367.712221] ? lock_acquired+0x33b/0x470 [13367.712784] _raw_spin_lock+0x34/0x80 [13367.713356] ? reada_add_block+0xe0/0xee0 [btrfs] [13367.713966] reada_add_block+0xe0/0xee0 [btrfs] [13367.714529] ? btrfs_root_node+0x15/0x1f0 [btrfs] [13367.715077] btrfs_reada_add+0x117/0x170 [btrfs] [13367.715620] scrub_stripe+0x21e/0x10d0 [btrfs] [13367.716141] ? kvm_sched_clock_read+0x5/0x10 [13367.716657] ? __lock_acquire+0x41e/0x3970 [13367.717184] ? scrub_chunk+0x60/0x140 [btrfs] [13367.717697] ? find_held_lock+0x32/0x90 [13367.718254] ? scrub_chunk+0x60/0x140 [btrfs] [13367.718773] ? lock_acquired+0x33b/0x470 [13367.719278] ? scrub_chunk+0xcd/0x140 [btrfs] [13367.719786] scrub_chunk+0xcd/0x140 [btrfs] [13367.720291] scrub_enumerate_chunks+0x270/0x5c0 [btrfs] [13367.720787] ? finish_wait+0x90/0x90 [13367.721281] btrfs_scrub_dev+0x1ee/0x620 [btrfs] [13367.721762] ? rcu_read_lock_any_held+0x8e/0xb0 [13367.722235] ? preempt_count_add+0x49/0xa0 [13367.722710] ? __sb_start_write+0x19b/0x290 [13367.723192] btrfs_ioctl+0x7f5/0x36f0 [btrfs] [13367.723660] ? __fget_files+0x101/0x1d0 [13367.724118] ? find_held_lock+0x32/0x90 [13367.724559] ? __fget_files+0x101/0x1d0 [13367.724982] ? __x64_sys_ioctl+0x83/0xb0 [13367.725399] __x64_sys_ioctl+0x83/0xb0 [13367.725802] do_syscall_64+0x33/0x80 [13367.726188] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [13367.726574] RIP: 0033:0x7fe1df7add87 [13367.726948] Code: 00 00 00 48 8b 05 09 91 (...) [13367.727763] RSP: 002b:00007fe1df6b4d48 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 [13367.728179] RAX: ffffffffffffffda RBX: 000055ce1fb596a0 RCX: 00007fe1df7add87 [13367.728604] RDX: 000055ce1fb596a0 RSI: 00000000c400941b RDI: 0000000000000003 [13367.729021] RBP: 0000000000000000 R08: 00007fe1df6b5700 R09: 0000000000000000 [13367.729431] R10: 00007fe1df6b5700 R11: 0000000000000246 R12: 00007ffd922b07de [13367.729842] R13: 00007ffd922b07df R14: 00007fe1df6b4e40 R15: 0000000000802000 [13367.730275] Modules linked in: btrfs blake2b_generic xor (...) [13367.732638] CR2: 00000000000000b0 [13367.733166] ---[ end trace d298b6805556acd9 ]--- What happens is the following: 1) At reada_find_extent() we don't find any existing readahead extent for the metadata extent starting at logical address X; 2) So we proceed to create a new one. We then call btrfs_map_block() to get information about which stripes contain extent X; 3) After that we iterate over the stripes and create only one zone for the readahead extent - only one because reada_find_zone() returned NULL for all iterations except for one, either because a memory allocation failed or it couldn't find the block group of the extent (it may have just been deleted); 4) We then add the new readahead extent to the readahead extents radix tree at fs_info->reada_tree; 5) Then we iterate over each zone of the new readahead extent, and find that the device used for that zone no longer exists, because it was removed or it was the source device of a device replace operation. Since this left 'have_zone' set to 0, after finishing the loop we jump to the 'error' label, call kfree() on the new readahead extent and return without removing it from the radix tree at fs_info->reada_tree; 6) Any future call to reada_find_extent() for the logical address X will find the stale pointer in the readahead extents radix tree, increment its reference counter, which can trigger the use-after-free right away or return it to the caller reada_add_block() that results in the use-after-free of the example trace above. So fix this by making sure we delete the readahead extent from the radix tree if we fail to setup zones for it (when 'have_zone = 0'). Fixes: 31945021 ("btrfs: reada: bypass adding extent when all zone failed") CC: stable@vger.kernel.org # 4.9+ Reviewed-by:
Johannes Thumshirn <johannes.thumshirn@wdc.com> Reviewed-by:
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Daniel Xu authored
If there's no parity and num_stripes < ncopies, a crafted image can trigger a division by zero in calc_stripe_length(). The image was generated through fuzzing. CC: stable@vger.kernel.org # 5.4+ Reviewed-by:
Qu Wenruo <wqu@suse.com> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=209587Signed-off-by:
Daniel Xu <dxu@dxuuu.xyz> Signed-off-by:
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Pujin Shi authored
This patch addresses a compile warning: fs/btrfs/extent-tree.c: In function '__btrfs_free_extent': fs/btrfs/extent-tree.c:3187:4: warning: format '%lu' expects argument of type 'long unsigned int', but argument 8 has type 'unsigned int' [-Wformat=] Fixes: 1c2a07f5 ("btrfs: extent-tree: kill BUG_ON() in __btrfs_free_extent()") Reviewed-by:
Pujin Shi <shipujin.t@gmail.com> Reviewed-by:
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Josef Bacik authored
Dave reported a problem with my rwsem conversion patch where we got the following lockdep splat: ====================================================== WARNING: possible circular locking dependency detected 5.9.0-default+ #1297 Not tainted ------------------------------------------------------ kswapd0/76 is trying to acquire lock: ffff9d5d25df2530 (&delayed_node->mutex){+.+.}-{3:3}, at: __btrfs_release_delayed_node.part.0+0x3f/0x320 [btrfs] but task is already holding lock: ffffffffa40cbba0 (fs_reclaim){+.+.}-{0:0}, at: __fs_reclaim_acquire+0x5/0x30 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (fs_reclaim){+.+.}-{0:0}: __lock_acquire+0x582/0xac0 lock_acquire+0xca/0x430 fs_reclaim_acquire.part.0+0x25/0x30 kmem_cache_alloc+0x30/0x9c0 alloc_inode+0x81/0x90 iget_locked+0xcd/0x1a0 kernfs_get_inode+0x1b/0x130 kernfs_get_tree+0x136/0x210 sysfs_get_tree+0x1a/0x50 vfs_get_tree+0x1d/0xb0 path_mount+0x70f/0xa80 do_mount+0x75/0x90 __x64_sys_mount+0x8e/0xd0 do_syscall_64+0x2d/0x70 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #3 (kernfs_mutex){+.+.}-{3:3}: __lock_acquire+0x582/0xac0 lock_acquire+0xca/0x430 __mutex_lock+0xa0/0xaf0 kernfs_add_one+0x23/0x150 kernfs_create_dir_ns+0x58/0x80 sysfs_create_dir_ns+0x70/0xd0 kobject_add_internal+0xbb/0x2d0 kobject_add+0x7a/0xd0 btrfs_sysfs_add_block_group_type+0x141/0x1d0 [btrfs] btrfs_read_block_groups+0x1f1/0x8c0 [btrfs] open_ctree+0x981/0x1108 [btrfs] btrfs_mount_root.cold+0xe/0xb0 [btrfs] legacy_get_tree+0x2d/0x60 vfs_get_tree+0x1d/0xb0 fc_mount+0xe/0x40 vfs_kern_mount.part.0+0x71/0x90 btrfs_mount+0x13b/0x3e0 [btrfs] legacy_get_tree+0x2d/0x60 vfs_get_tree+0x1d/0xb0 path_mount+0x70f/0xa80 do_mount+0x75/0x90 __x64_sys_mount+0x8e/0xd0 do_syscall_64+0x2d/0x70 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #2 (btrfs-extent-00){++++}-{3:3}: __lock_acquire+0x582/0xac0 lock_acquire+0xca/0x430 down_read_nested+0x45/0x220 __btrfs_tree_read_lock+0x35/0x1c0 [btrfs] __btrfs_read_lock_root_node+0x3a/0x50 [btrfs] btrfs_search_slot+0x6d4/0xfd0 [btrfs] check_committed_ref+0x69/0x200 [btrfs] btrfs_cross_ref_exist+0x65/0xb0 [btrfs] run_delalloc_nocow+0x446/0x9b0 [btrfs] btrfs_run_delalloc_range+0x61/0x6a0 [btrfs] writepage_delalloc+0xae/0x160 [btrfs] __extent_writepage+0x262/0x420 [btrfs] extent_write_cache_pages+0x2b6/0x510 [btrfs] extent_writepages+0x43/0x90 [btrfs] do_writepages+0x40/0xe0 __writeback_single_inode+0x62/0x610 writeback_sb_inodes+0x20f/0x500 wb_writeback+0xef/0x4a0 wb_do_writeback+0x49/0x2e0 wb_workfn+0x81/0x340 process_one_work+0x233/0x5d0 worker_thread+0x50/0x3b0 kthread+0x137/0x150 ret_from_fork+0x1f/0x30 -> #1 (btrfs-fs-00){++++}-{3:3}: __lock_acquire+0x582/0xac0 lock_acquire+0xca/0x430 down_read_nested+0x45/0x220 __btrfs_tree_read_lock+0x35/0x1c0 [btrfs] __btrfs_read_lock_root_node+0x3a/0x50 [btrfs] btrfs_search_slot+0x6d4/0xfd0 [btrfs] btrfs_lookup_inode+0x3a/0xc0 [btrfs] __btrfs_update_delayed_inode+0x93/0x2c0 [btrfs] __btrfs_commit_inode_delayed_items+0x7de/0x850 [btrfs] __btrfs_run_delayed_items+0x8e/0x140 [btrfs] btrfs_commit_transaction+0x367/0xbc0 [btrfs] btrfs_mksubvol+0x2db/0x470 [btrfs] btrfs_mksnapshot+0x7b/0xb0 [btrfs] __btrfs_ioctl_snap_create+0x16f/0x1a0 [btrfs] btrfs_ioctl_snap_create_v2+0xb0/0xf0 [btrfs] btrfs_ioctl+0xd0b/0x2690 [btrfs] __x64_sys_ioctl+0x6f/0xa0 do_syscall_64+0x2d/0x70 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #0 (&delayed_node->mutex){+.+.}-{3:3}: check_prev_add+0x91/0xc60 validate_chain+0xa6e/0x2a20 __lock_acquire+0x582/0xac0 lock_acquire+0xca/0x430 __mutex_lock+0xa0/0xaf0 __btrfs_release_delayed_node.part.0+0x3f/0x320 [btrfs] btrfs_evict_inode+0x3cc/0x560 [btrfs] evict+0xd6/0x1c0 dispose_list+0x48/0x70 prune_icache_sb+0x54/0x80 super_cache_scan+0x121/0x1a0 do_shrink_slab+0x16d/0x3b0 shrink_slab+0xb1/0x2e0 shrink_node+0x230/0x6a0 balance_pgdat+0x325/0x750 kswapd+0x206/0x4d0 kthread+0x137/0x150 ret_from_fork+0x1f/0x30 other info that might help us debug this: Chain exists of: &delayed_node->mutex --> kernfs_mutex --> fs_reclaim Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(fs_reclaim); lock(kernfs_mutex); lock(fs_reclaim); lock(&delayed_node->mutex); *** DEADLOCK *** 3 locks held by kswapd0/76: #0: ffffffffa40cbba0 (fs_reclaim){+.+.}-{0:0}, at: __fs_reclaim_acquire+0x5/0x30 #1: ffffffffa40b8b58 (shrinker_rwsem){++++}-{3:3}, at: shrink_slab+0x54/0x2e0 #2: ffff9d5d322390e8 (&type->s_umount_key#26){++++}-{3:3}, at: trylock_super+0x16/0x50 stack backtrace: CPU: 2 PID: 76 Comm: kswapd0 Not tainted 5.9.0-default+ #1297 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba527-rebuilt.opensuse.org 04/01/2014 Call Trace: dump_stack+0x77/0x97 check_noncircular+0xff/0x110 ? save_trace+0x50/0x470 check_prev_add+0x91/0xc60 validate_chain+0xa6e/0x2a20 ? save_trace+0x50/0x470 __lock_acquire+0x582/0xac0 lock_acquire+0xca/0x430 ? __btrfs_release_delayed_node.part.0+0x3f/0x320 [btrfs] __mutex_lock+0xa0/0xaf0 ? __btrfs_release_delayed_node.part.0+0x3f/0x320 [btrfs] ? __lock_acquire+0x582/0xac0 ? __btrfs_release_delayed_node.part.0+0x3f/0x320 [btrfs] ? btrfs_evict_inode+0x30b/0x560 [btrfs] ? __btrfs_release_delayed_node.part.0+0x3f/0x320 [btrfs] __btrfs_release_delayed_node.part.0+0x3f/0x320 [btrfs] btrfs_evict_inode+0x3cc/0x560 [btrfs] evict+0xd6/0x1c0 dispose_list+0x48/0x70 prune_icache_sb+0x54/0x80 super_cache_scan+0x121/0x1a0 do_shrink_slab+0x16d/0x3b0 shrink_slab+0xb1/0x2e0 shrink_node+0x230/0x6a0 balance_pgdat+0x325/0x750 kswapd+0x206/0x4d0 ? finish_wait+0x90/0x90 ? balance_pgdat+0x750/0x750 kthread+0x137/0x150 ? kthread_mod_delayed_work+0xc0/0xc0 ret_from_fork+0x1f/0x30 This happens because we are still holding the path open when we start adding the sysfs files for the block groups, which creates a dependency on fs_reclaim via the tree lock. Fix this by dropping the path before we start doing anything with sysfs. Reported-by:Anand Jain <anand.jain@oracle.com> Reviewed-by:
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- 16 Oct, 2020 1 commit
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Filipe Manana authored
When doing a fallocate() we have a short time window, after reserving an extent and before starting a transaction, where if relocation for the block group containing the reserved extent happens, we can end up missing the extent in the data relocation inode causing relocation to fail later. This only happens when we don't pass a transaction to the internal fallocate function __btrfs_prealloc_file_range(), which is for all the cases where fallocate() is called from user space (the internal use cases include space cache extent allocation and relocation). When the race triggers the relocation failure, it produces a trace like the following: [200611.995995] ------------[ cut here ]------------ [200611.997084] BTRFS: Transaction aborted (error -2) [200611.998208] WARNING: CPU: 3 PID: 235845 at fs/btrfs/ctree.c:1074 __btrfs_cow_block+0x3a0/0x5b0 [btrfs] [200611.999042] Modules linked in: dm_thin_pool dm_persistent_data (...) [200612.003287] CPU: 3 PID: 235845 Comm: btrfs Not tainted 5.9.0-rc6-btrfs-next-69 #1 [200612.004442] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 [200612.006186] RIP: 0010:__btrfs_cow_block+0x3a0/0x5b0 [btrfs] [200612.007110] Code: 1b 00 00 02 72 2a 83 f8 fb 0f 84 b8 01 (...) [200612.007341] BTRFS warning (device sdb): Skipping commit of aborted transaction. [200612.008959] RSP: 0018:ffffaee38550f918 EFLAGS: 00010286 [200612.009672] BTRFS: error (device sdb) in cleanup_transaction:1901: errno=-30 Readonly filesystem [200612.010428] RAX: 0000000000000000 RBX: ffff9174d96f4000 RCX: 0000000000000000 [200612.011078] BTRFS info (device sdb): forced readonly [200612.011862] RDX: 0000000000000001 RSI: ffffffffa8161978 RDI: 00000000ffffffff [200612.013215] RBP: ffff9172569a0f80 R08: 0000000000000000 R09: 0000000000000000 [200612.014263] R10: 0000000000000000 R11: 0000000000000000 R12: ffff9174b8403b88 [200612.015203] R13: ffff9174b8400a88 R14: ffff9174c90f1000 R15: ffff9174a5a60e08 [200612.016182] FS: 00007fa55cf878c0(0000) GS:ffff9174ece00000(0000) knlGS:0000000000000000 [200612.017174] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [200612.018418] CR2: 00007f8fb8048148 CR3: 0000000428a46003 CR4: 00000000003706e0 [200612.019510] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [200612.020648] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [200612.021520] Call Trace: [200612.022434] btrfs_cow_block+0x10b/0x250 [btrfs] [200612.023407] do_relocation+0x54e/0x7b0 [btrfs] [200612.024343] ? do_raw_spin_unlock+0x4b/0xc0 [200612.025280] ? _raw_spin_unlock+0x29/0x40 [200612.026200] relocate_tree_blocks+0x3bc/0x6d0 [btrfs] [200612.027088] relocate_block_group+0x2f3/0x600 [btrfs] [200612.027961] btrfs_relocate_block_group+0x15e/0x340 [btrfs] [200612.028896] btrfs_relocate_chunk+0x38/0x110 [btrfs] [200612.029772] btrfs_balance+0xb22/0x1790 [btrfs] [200612.030601] ? btrfs_ioctl_balance+0x253/0x380 [btrfs] [200612.031414] btrfs_ioctl_balance+0x2cf/0x380 [btrfs] [200612.032279] btrfs_ioctl+0x620/0x36f0 [btrfs] [200612.033077] ? _raw_spin_unlock+0x29/0x40 [200612.033948] ? handle_mm_fault+0x116d/0x1ca0 [200612.034749] ? up_read+0x18/0x240 [200612.035542] ? __x64_sys_ioctl+0x83/0xb0 [200612.036244] __x64_sys_ioctl+0x83/0xb0 [200612.037269] do_syscall_64+0x33/0x80 [200612.038190] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [200612.038976] RIP: 0033:0x7fa55d07ed87 [200612.040127] Code: 00 00 00 48 8b 05 09 91 0c 00 64 c7 00 26 (...) [200612.041669] RSP: 002b:00007ffd5ebf03e8 EFLAGS: 00000206 ORIG_RAX: 0000000000000010 [200612.042437] RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007fa55d07ed87 [200612.043511] RDX: 00007ffd5ebf0470 RSI: 00000000c4009420 RDI: 0000000000000003 [200612.044250] RBP: 0000000000000003 R08: 000055d8362642a0 R09: 00007fa55d148be0 [200612.044963] R10: fffffffffffff52e R11: 0000000000000206 R12: 00007ffd5ebf1614 [200612.045683] R13: 00007ffd5ebf0470 R14: 0000000000000002 R15: 00007ffd5ebf0470 [200612.046361] irq event stamp: 0 [200612.047040] hardirqs last enabled at (0): [<0000000000000000>] 0x0 [200612.047725] hardirqs last disabled at (0): [<ffffffffa6eb5ab3>] copy_process+0x823/0x1bc0 [200612.048387] softirqs last enabled at (0): [<ffffffffa6eb5ab3>] copy_process+0x823/0x1bc0 [200612.049024] softirqs last disabled at (0): [<0000000000000000>] 0x0 [200612.049722] ---[ end trace 49006c6876e65227 ]--- The race happens like this: 1) Task A starts an fallocate() (plain or zero range) and it calls __btrfs_prealloc_file_range() with the 'trans' parameter set to NULL; 2) Task A calls btrfs_reserve_extent() and gets an extent that belongs to block group X; 3) Before task A gets into btrfs_replace_file_extents(), through the call to insert_prealloc_file_extent(), task B starts relocation of block group X; 4) Task B enters btrfs_relocate_block_group() and it sets block group X to RO mode; 5) Task B enters relocate_block_group(), it calls prepare_to_relocate() whichs joins/starts a transaction and then commits the transaction; 6) Task B then starts scanning the extent tree looking for extents that belong to block group X - it does not find yet the extent reserved by task A, since that extent was not yet added to the extent tree, as its delayed reference was not even yet created at this point; 7) The data relocation inode ends up not having the extent reserved by task A associated to it; 8) Task A then starts a transaction through btrfs_replace_file_extents(), inserts a file extent item in the subvolume tree pointing to the reserved extent and creates a delayed reference for it; 9) Task A finishes and returns success to user space; 10) Later on, while relocation is still in progress, the leaf where task A inserted the new file extent item is COWed, so we end up at __btrfs_cow_block(), which calls btrfs_reloc_cow_block(), and that in turn calls relocation.c:replace_file_extents(); 11) At relocation.c:replace_file_extents() we iterate over all the items in the leaf and find the file extent item pointing to the extent that was allocated by task A, and then call relocation.c:get_new_location(), to find the new location for the extent; 12) However relocation.c:get_new_location() fails, returning -ENOENT, because it couldn't find a corresponding file extent item associated with the data relocation inode. This is because the extent was not seen in the extent tree at step 6). The -ENOENT error is propagated to __btrfs_cow_block(), which aborts the transaction. So fix this simply by decrementing the block group's number of reservations after calling insert_prealloc_file_extent(), as relocation waits for that counter to go down to zero before calling prepare_to_relocate() and start looking for extents in the extent tree. This issue only started to happen recently as of commit 8fccebfa ("btrfs: fix metadata reservation for fallocate that leads to transaction aborts"), because now we can reserve an extent before starting/joining a transaction, and previously we always did it after that, so relocation ended up waiting for a concurrent fallocate() to finish because before searching for the extents of the block group, it starts/joins a transaction and then commits it (at prepare_to_relocate()), which made it wait for the fallocate task to complete first. Fixes: 8fccebfa ("btrfs: fix metadata reservation for fallocate that leads to transaction aborts") Reviewed-by:
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- 07 Oct, 2020 32 commits
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Nikolay Borisov authored
Commit 8d875f95 ("btrfs: disable strict file flushes for renames and truncates") eliminated the notion of ordered operations and instead BTRFS_INODE_ORDERED_DATA_CLOSE only remained as a flag indicating that a file's content should be synced to disk in case a file is truncated and any writes happen to it concurrently. In fact this intendend behavior was broken until it was fixed in f6dc45c7 ("Btrfs: fix filemap_flush call in btrfs_file_release"). All things considered let's give the flag a more descriptive name. Also slightly reword comments. Signed-off-by:
Nikolay Borisov <nborisov@suse.com> Reviewed-by:
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Madhuparna Bhowmik authored
This patch fixes the following sparse errors in fs/btrfs/super.c in function btrfs_show_devname() fs/btrfs/super.c: error: incompatible types in comparison expression (different address spaces): fs/btrfs/super.c: struct rcu_string [noderef] <asn:4> * fs/btrfs/super.c: struct rcu_string * The error was because of the following line in function btrfs_show_devname(): if (first_dev) seq_escape(m, rcu_str_deref(first_dev->name), " \t\n\\"); Annotating the btrfs_device::name member with __rcu fixes the sparse error. Acked-by:
Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by:
Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com> Signed-off-by:
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Anand Jain authored
Many things can happen after the device is scanned and before the device is mounted. One such thing is losing the BTRFS_MAGIC on the device. If it happens we still won't free that device from the memory and cause the userland confusion. For example: As the BTRFS_IOC_DEV_INFO still carries the device path which does not have the BTRFS_MAGIC, 'btrfs fi show' still lists device which does not belong to the filesystem anymore: $ mkfs.btrfs -fq -draid1 -mraid1 /dev/sda /dev/sdb $ wipefs -a /dev/sdb # /dev/sdb does not contain magic signature $ mount -o degraded /dev/sda /btrfs $ btrfs fi show -m Label: none uuid: 470ec6fb-646b-4464-b3cb-df1b26c527bd Total devices 2 FS bytes used 128.00KiB devid 1 size 3.00GiB used 571.19MiB path /dev/sda devid 2 size 3.00GiB used 571.19MiB path /dev/sdb We need to distinguish the missing signature and invalid superblock, so add a specific error code ENODATA for that. This also fixes failure of fstest btrfs/198. CC: stable@vger.kernel.org # 4.19+ Reviewed-by:
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Josef Bacik authored
In fstest btrfs/064 a transaction abort in __btrfs_cow_block could lead to a system lockup. It gets stuck trying to write back inodes, and the write back thread was trying to lock an extent buffer: $ cat /proc/2143497/stack [<0>] __btrfs_tree_lock+0x108/0x250 [<0>] lock_extent_buffer_for_io+0x35e/0x3a0 [<0>] btree_write_cache_pages+0x15a/0x3b0 [<0>] do_writepages+0x28/0xb0 [<0>] __writeback_single_inode+0x54/0x5c0 [<0>] writeback_sb_inodes+0x1e8/0x510 [<0>] wb_writeback+0xcc/0x440 [<0>] wb_workfn+0xd7/0x650 [<0>] process_one_work+0x236/0x560 [<0>] worker_thread+0x55/0x3c0 [<0>] kthread+0x13a/0x150 [<0>] ret_from_fork+0x1f/0x30 This is because we got an error while COWing a block, specifically here if (test_bit(BTRFS_ROOT_SHAREABLE, &root->state)) { ret = btrfs_reloc_cow_block(trans, root, buf, cow); if (ret) { btrfs_abort_transaction(trans, ret); return ret; } } [16402.241552] BTRFS: Transaction aborted (error -2) [16402.242362] WARNING: CPU: 1 PID: 2563188 at fs/btrfs/ctree.c:1074 __btrfs_cow_block+0x376/0x540 [16402.249469] CPU: 1 PID: 2563188 Comm: fsstress Not tainted 5.9.0-rc6+ #8 [16402.249936] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014 [16402.250525] RIP: 0010:__btrfs_cow_block+0x376/0x540 [16402.252417] RSP: 0018:ffff9cca40e578b0 EFLAGS: 00010282 [16402.252787] RAX: 0000000000000025 RBX: 0000000000000002 RCX: ffff9132bbd19388 [16402.253278] RDX: 00000000ffffffd8 RSI: 0000000000000027 RDI: ffff9132bbd19380 [16402.254063] RBP: ffff9132b41a49c0 R08: 0000000000000000 R09: 0000000000000000 [16402.254887] R10: 0000000000000000 R11: ffff91324758b080 R12: ffff91326ef17ce0 [16402.255694] R13: ffff91325fc0f000 R14: ffff91326ef176b0 R15: ffff9132815e2000 [16402.256321] FS: 00007f542c6d7b80(0000) GS:ffff9132bbd00000(0000) knlGS:0000000000000000 [16402.256973] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [16402.257374] CR2: 00007f127b83f250 CR3: 0000000133480002 CR4: 0000000000370ee0 [16402.257867] Call Trace: [16402.258072] btrfs_cow_block+0x109/0x230 [16402.258356] btrfs_search_slot+0x530/0x9d0 [16402.258655] btrfs_lookup_file_extent+0x37/0x40 [16402.259155] __btrfs_drop_extents+0x13c/0xd60 [16402.259628] ? btrfs_block_rsv_migrate+0x4f/0xb0 [16402.259949] btrfs_replace_file_extents+0x190/0x820 [16402.260873] btrfs_clone+0x9ae/0xc00 [16402.261139] btrfs_extent_same_range+0x66/0x90 [16402.261771] btrfs_remap_file_range+0x353/0x3b1 [16402.262333] vfs_dedupe_file_range_one.part.0+0xd5/0x140 [16402.262821] vfs_dedupe_file_range+0x189/0x220 [16402.263150] do_vfs_ioctl+0x552/0x700 [16402.263662] __x64_sys_ioctl+0x62/0xb0 [16402.264023] do_syscall_64+0x33/0x40 [16402.264364] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [16402.264862] RIP: 0033:0x7f542c7d15cb [16402.266901] RSP: 002b:00007ffd35944ea8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 [16402.267627] RAX: ffffffffffffffda RBX: 00000000009d1968 RCX: 00007f542c7d15cb [16402.268298] RDX: 00000000009d2490 RSI: 00000000c0189436 RDI: 0000000000000003 [16402.268958] RBP: 00000000009d2520 R08: 0000000000000036 R09: 00000000009d2e64 [16402.269726] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002 [16402.270659] R13: 000000000001f000 R14: 00000000009d1970 R15: 00000000009d2e80 [16402.271498] irq event stamp: 0 [16402.271846] hardirqs last enabled at (0): [<0000000000000000>] 0x0 [16402.272497] hardirqs last disabled at (0): [<ffffffff910dbf59>] copy_process+0x6b9/0x1ba0 [16402.273343] softirqs last enabled at (0): [<ffffffff910dbf59>] copy_process+0x6b9/0x1ba0 [16402.273905] softirqs last disabled at (0): [<0000000000000000>] 0x0 [16402.274338] ---[ end trace 737874a5a41a8236 ]--- [16402.274669] BTRFS: error (device dm-9) in __btrfs_cow_block:1074: errno=-2 No such entry [16402.276179] BTRFS info (device dm-9): forced readonly [16402.277046] BTRFS: error (device dm-9) in btrfs_replace_file_extents:2723: errno=-2 No such entry [16402.278744] BTRFS: error (device dm-9) in __btrfs_cow_block:1074: errno=-2 No such entry [16402.279968] BTRFS: error (device dm-9) in __btrfs_cow_block:1074: errno=-2 No such entry [16402.280582] BTRFS info (device dm-9): balance: ended with status: -30 The problem here is that as soon as we allocate the new block it is locked and marked dirty in the btree inode. This means that we could attempt to writeback this block and need to lock the extent buffer. However we're not unlocking it here and thus we deadlock. Fix this by unlocking the cow block if we have any errors inside of __btrfs_cow_block, and also free it so we do not leak it. CC: stable@vger.kernel.org # 4.4+ Reviewed-by: -
Goldwyn Rodrigues authored
Since we now perform direct reads using i_rwsem, we can remove this inode flag used to co-ordinate unlocked reads. The truncate call takes i_rwsem. This means it is correctly synchronized with concurrent direct reads. Reviewed-by:
Johannes Thumshirn <jth@kernel.org> Reviewed-by:
Christoph Hellwig <hch@lst.de> Signed-off-by:
Goldwyn Rodrigues <rgoldwyn@suse.com> Reviewed-by:
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Goldwyn Rodrigues authored
Since we removed the last user of dio_end_io() when btrfs got converted to iomap infrastructure ("btrfs: switch to iomap for direct IO"), remove the helper function dio_end_io(). Reviewed-by:Johannes Thumshirn <jthumshirn@suse.de> Reviewed-by:
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Josef Bacik authored
I noticed when fixing device stats for seed devices that we simply threw away the return value from btrfs_search_slot(). This is because we may not have stat items, but we could very well get an error, and thus miss reporting the error up the chain. Fix this by returning ret if it's an actual error, and then stop trying to init the rest of the devices stats and return the error up the chain. Reviewed-by:
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Josef Bacik authored
We recently started recording device stats across the fleet, and noticed a large increase in messages such as this BTRFS warning (device dm-0): get dev_stats failed, not yet valid on our tiers that use seed devices for their root devices. This is because we do not initialize the device stats for any seed devices if we have a sprout device and mount using that sprout device. The basic steps for reproducing are: $ mkfs seed device $ mount seed device # fill seed device $ umount seed device $ btrfstune -S 1 seed device $ mount seed device $ btrfs device add -f sprout device /mnt/wherever $ umount /mnt/wherever $ mount sprout device /mnt/wherever $ btrfs device stats /mnt/wherever This will fail with the above message in dmesg. Fix this by iterating over the fs_devices->seed if they exist in btrfs_init_dev_stats. This fixed the problem and properly reports the stats for both devices. Reviewed-by:
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Nikolay Borisov authored
It's no longer used just remove the function and any related code which was initialising it for inodes. No functional changes. Removing 8 bytes from extent_io_tree in turn reduces size of other structures where it is embedded, notably btrfs_inode where it reduces size by 24 bytes. Signed-off-by:
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Nikolay Borisov authored
No need to go through a function pointer indirection simply call submit_bio_hook directly by exporting and renaming the helper to btrfs_submit_metadata_bio. This makes the code more readable and should result in somewhat faster code due to no longer paying the price for specualtive attack mitigations that come with indirect function calls. Signed-off-by:
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Nikolay Borisov authored
Instead export and rename the function to btrfs_submit_data_bio and call it directly in submit_one_bio. This avoids paying the cost for speculative attacks mitigations and improves code readability. Signed-off-by:
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Nikolay Borisov authored
Use the is_data_inode helper. Signed-off-by:
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Nikolay Borisov authored
BTRFS has 2 inode types (for the purposes of the code in submit_one_bio) - ordinary data inodes (including the freespace inode) and the btree inode. Both of these implement submit_bio_hook so btrfsic_submit_bio can never be called from submit_one_bio so just remove it. Signed-off-by:
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Nikolay Borisov authored
It's no longer used so let's remove it. Signed-off-by:
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Nikolay Borisov authored
Don't call readpage_end_io_hook for the btree inode. Instead of relying on indirect calls to implement metadata buffer validation simply check if the inode whose page we are processing equals the btree inode. If it does call the necessary function. This is an improvement in 2 directions: 1. We aren't paying the penalty of indirect calls in a post-speculation attacks world. 2. The function is now named more explicitly so it's obvious what's going on This is in preparation to removing struct extent_io_ops altogether. Signed-off-by:
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Filipe Manana authored
During an incremental send, when an inode has multiple new references we might end up emitting rename operations for orphanizations that have a source path that is no longer valid due to a previous orphanization of some directory inode. This causes the receiver to fail since it tries to rename a path that does not exists. Example reproducer: $ cat reproducer.sh #!/bin/bash mkfs.btrfs -f /dev/sdi >/dev/null mount /dev/sdi /mnt/sdi touch /mnt/sdi/f1 touch /mnt/sdi/f2 mkdir /mnt/sdi/d1 mkdir /mnt/sdi/d1/d2 # Filesystem looks like: # # . (ino 256) # |----- f1 (ino 257) # |----- f2 (ino 258) # |----- d1/ (ino 259) # |----- d2/ (ino 260) btrfs subvolume snapshot -r /mnt/sdi /mnt/sdi/snap1 btrfs send -f /tmp/snap1.send /mnt/sdi/snap1 # Now do a series of changes such that: # # *) inode 258 has one new hardlink and the previous name changed # # *) both names conflict with the old names of two other inodes: # # 1) the new name "d1" conflicts with the old name of inode 259, # under directory inode 256 (root) # # 2) the new name "d2" conflicts with the old name of inode 260 # under directory inode 259 # # *) inodes 259 and 260 now have the old names of inode 258 # # *) inode 257 is now located under inode 260 - an inode with a number # smaller than the inode (258) for which we created a second hard # link and swapped its names with inodes 259 and 260 # ln /mnt/sdi/f2 /mnt/sdi/d1/f2_link mv /mnt/sdi/f1 /mnt/sdi/d1/d2/f1 # Swap d1 and f2. mv /mnt/sdi/d1 /mnt/sdi/tmp mv /mnt/sdi/f2 /mnt/sdi/d1 mv /mnt/sdi/tmp /mnt/sdi/f2 # Swap d2 and f2_link mv /mnt/sdi/f2/d2 /mnt/sdi/tmp mv /mnt/sdi/f2/f2_link /mnt/sdi/f2/d2 mv /mnt/sdi/tmp /mnt/sdi/f2/f2_link # Filesystem now looks like: # # . (ino 256) # |----- d1 (ino 258) # |----- f2/ (ino 259) # |----- f2_link/ (ino 260) # | |----- f1 (ino 257) # | # |----- d2 (ino 258) btrfs subvolume snapshot -r /mnt/sdi /mnt/sdi/snap2 btrfs send -f /tmp/snap2.send -p /mnt/sdi/snap1 /mnt/sdi/snap2 mkfs.btrfs -f /dev/sdj >/dev/null mount /dev/sdj /mnt/sdj btrfs receive -f /tmp/snap1.send /mnt/sdj btrfs receive -f /tmp/snap2.send /mnt/sdj umount /mnt/sdi umount /mnt/sdj When executed the receive of the incremental stream fails: $ ./reproducer.sh Create a readonly snapshot of '/mnt/sdi' in '/mnt/sdi/snap1' At subvol /mnt/sdi/snap1 Create a readonly snapshot of '/mnt/sdi' in '/mnt/sdi/snap2' At subvol /mnt/sdi/snap2 At subvol snap1 At snapshot snap2 ERROR: rename d1/d2 -> o260-6-0 failed: No such file or directory This happens because: 1) When processing inode 257 we end up computing the name for inode 259 because it is an ancestor in the send snapshot, and at that point it still has its old name, "d1", from the parent snapshot because inode 259 was not yet processed. We then cache that name, which is valid until we start processing inode 259 (or set the progress to 260 after processing its references); 2) Later we start processing inode 258 and collecting all its new references into the list sctx->new_refs. The first reference in the list happens to be the reference for name "d1" while the reference for name "d2" is next (the last element of the list). We compute the full path "d1/d2" for this second reference and store it in the reference (its ->full_path member). The path used for the new parent directory was "d1" and not "f2" because inode 259, the new parent, was not yet processed; 3) When we start processing the new references at process_recorded_refs() we start with the first reference in the list, for the new name "d1". Because there is a conflicting inode that was not yet processed, which is directory inode 259, we orphanize it, renaming it from "d1" to "o259-6-0"; 4) Then we start processing the new reference for name "d2", and we realize it conflicts with the reference of inode 260 in the parent snapshot. So we issue an orphanization operation for inode 260 by emitting a rename operation with a destination path of "o260-6-0" and a source path of "d1/d2" - this source path is the value we stored in the reference earlier at step 2), corresponding to the ->full_path member of the reference, however that path is no longer valid due to the orphanization of the directory inode 259 in step 3). This makes the receiver fail since the path does not exists, it should have been "o259-6-0/d2". Fix this by recomputing the full path of a reference before emitting an orphanization if we previously orphanized any directory, since that directory could be a parent in the new path. This is a rare scenario so keeping it simple and not checking if that previously orphanized directory is in fact an ancestor of the inode we are trying to orphanize. A test case for fstests follows soon. CC: stable@vger.kernel.org # 4.4+ Reviewed-by:
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Filipe Manana authored
When doing an incremental send it is possible that when processing the new references for an inode we end up issuing rename or link operations that have an invalid path, which contains the orphanized name of a directory before we actually orphanized it, causing the receiver to fail. The following reproducer triggers such scenario: $ cat reproducer.sh #!/bin/bash mkfs.btrfs -f /dev/sdi >/dev/null mount /dev/sdi /mnt/sdi touch /mnt/sdi/a touch /mnt/sdi/b mkdir /mnt/sdi/testdir # We want "a" to have a lower inode number then "testdir" (257 vs 259). mv /mnt/sdi/a /mnt/sdi/testdir/a # Filesystem looks like: # # . (ino 256) # |----- testdir/ (ino 259) # | |----- a (ino 257) # | # |----- b (ino 258) btrfs subvolume snapshot -r /mnt/sdi /mnt/sdi/snap1 btrfs send -f /tmp/snap1.send /mnt/sdi/snap1 # Now rename 259 to "testdir_2", then change the name of 257 to # "testdir" and make it a direct descendant of the root inode (256). # Also create a new link for inode 257 with the old name of inode 258. # By swapping the names and location of several inodes and create a # nasty dependency chain of rename and link operations. mv /mnt/sdi/testdir/a /mnt/sdi/a2 touch /mnt/sdi/testdir/a mv /mnt/sdi/b /mnt/sdi/b2 ln /mnt/sdi/a2 /mnt/sdi/b mv /mnt/sdi/testdir /mnt/sdi/testdir_2 mv /mnt/sdi/a2 /mnt/sdi/testdir # Filesystem now looks like: # # . (ino 256) # |----- testdir_2/ (ino 259) # | |----- a (ino 260) # | # |----- testdir (ino 257) # |----- b (ino 257) # |----- b2 (ino 258) btrfs subvolume snapshot -r /mnt/sdi /mnt/sdi/snap2 btrfs send -f /tmp/snap2.send -p /mnt/sdi/snap1 /mnt/sdi/snap2 mkfs.btrfs -f /dev/sdj >/dev/null mount /dev/sdj /mnt/sdj btrfs receive -f /tmp/snap1.send /mnt/sdj btrfs receive -f /tmp/snap2.send /mnt/sdj umount /mnt/sdi umount /mnt/sdj When running the reproducer, the receive of the incremental send stream fails: $ ./reproducer.sh Create a readonly snapshot of '/mnt/sdi' in '/mnt/sdi/snap1' At subvol /mnt/sdi/snap1 Create a readonly snapshot of '/mnt/sdi' in '/mnt/sdi/snap2' At subvol /mnt/sdi/snap2 At subvol snap1 At snapshot snap2 ERROR: link b -> o259-6-0/a failed: No such file or directory The problem happens because of the following: 1) Before we start iterating the list of new references for inode 257, we generate its current path and store it at @valid_path, done at the very beginning of process_recorded_refs(). The generated path is "o259-6-0/a", containing the orphanized name for inode 259; 2) Then we iterate over the list of new references, which has the references "b" and "testdir" in that specific order; 3) We process reference "b" first, because it is in the list before reference "testdir". We then issue a link operation to create the new reference "b" using a target path corresponding to the content at @valid_path, which corresponds to "o259-6-0/a". However we haven't yet orphanized inode 259, its name is still "testdir", and not "o259-6-0". The orphanization of 259 did not happen yet because we will process the reference named "testdir" for inode 257 only in the next iteration of the loop that goes over the list of new references. Fix the issue by having a preliminar iteration over all the new references at process_recorded_refs(). This iteration is responsible only for doing the orphanization of other inodes that have and old reference that conflicts with one of the new references of the inode we are currently processing. The emission of rename and link operations happen now in the next iteration of the new references. A test case for fstests will follow soon. CC: stable@vger.kernel.org # 4.4+ Reviewed-by:
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Qu Wenruo authored
Commit 259ee775 ("btrfs: tree-checker: Add ROOT_ITEM check") introduced btrfs root item size check, however btrfs root item has two versions, the legacy one which just ends before generation_v2 member, is smaller than current btrfs root item size. This caused btrfs kernel to reject valid but old tree root leaves. Fix this problem by also allowing legacy root item, since kernel can already handle them pretty well and upgrade to newer root item format when needed. Reported-by:
Martin Steigerwald <martin@lichtvoll.de> Fixes: 259ee775 ("btrfs: tree-checker: Add ROOT_ITEM check") CC: stable@vger.kernel.org # 5.4+ Tested-By:
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David Sterba authored
In the definitions generated by BTRFS_SETGET_HEADER_FUNCS there's direct pointer assignment but we should use the helpers for unaligned access for clarity. It hasn't been a problem so far because of the natural alignment. Similarly for BTRFS_SETGET_STACK_FUNCS, that usually get a structure from stack that has an aligned start but some members may not be aligned due to packing. This as well hasn't caused problems so far. Move the put/get_unaligned_le8 stubs to ctree.h so we can use them. Signed-off-by: -
David Sterba authored
The free space inode stores the tracking data, checksums etc, using the io_ctl structure and moving the pointers. The data are generally aligned to at least 4 bytes (u32 for CRC) so it's not completely unaligned but for clarity we should use the proper helpers whenever a struct is initialized from io_ctl->cur pointer. Signed-off-by: -
David Sterba authored
The header is mapped onto the send buffer and thus its members may be potentially unaligned so use the helpers instead of directly assigning the pointers. This has worked so far but let's use the helpers to make that clear. Signed-off-by: -
Qu Wenruo authored
Btree inode is special compared to all other inode extent io_trees, although it has a btrfs inode, it doesn't have the track_uptodate bit at all. This means a lot of things like extent locking doesn't even need to be applied to btree io tree. Since it's so special, adds a new owner value for it to make debuging a little easier. Signed-off-by:
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Johannes Thumshirn authored
We have several occurrences of a soft lockup from fstest's generic/175 testcase, which look more or less like this one: watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [xfs_io:10030] Kernel panic - not syncing: softlockup: hung tasks CPU: 0 PID: 10030 Comm: xfs_io Tainted: G L 5.9.0-rc5+ #768 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4-rebuilt.opensuse.org 04/01/2014 Call Trace: <IRQ> dump_stack+0x77/0xa0 panic+0xfa/0x2cb watchdog_timer_fn.cold+0x85/0xa5 ? lockup_detector_update_enable+0x50/0x50 __hrtimer_run_queues+0x99/0x4c0 ? recalibrate_cpu_khz+0x10/0x10 hrtimer_run_queues+0x9f/0xb0 update_process_times+0x28/0x80 tick_handle_periodic+0x1b/0x60 __sysvec_apic_timer_interrupt+0x76/0x210 asm_call_on_stack+0x12/0x20 </IRQ> sysvec_apic_timer_interrupt+0x7f/0x90 asm_sysvec_apic_timer_interrupt+0x12/0x20 RIP: 0010:btrfs_tree_unlock+0x91/0x1a0 [btrfs] RSP: 0018:ffffc90007123a58 EFLAGS: 00000282 RAX: ffff8881cea2fbe0 RBX: ffff8881cea2fbe0 RCX: 0000000000000000 RDX: ffff8881d23fd200 RSI: ffffffff82045220 RDI: ffff8881cea2fba0 RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000032 R10: 0000160000000000 R11: 0000000000001000 R12: 0000000000001000 R13: ffff8882357fd5b0 R14: ffff88816fa76e70 R15: ffff8881cea2fad0 ? btrfs_tree_unlock+0x15b/0x1a0 [btrfs] btrfs_release_path+0x67/0x80 [btrfs] btrfs_insert_replace_extent+0x177/0x2c0 [btrfs] btrfs_replace_file_extents+0x472/0x7c0 [btrfs] btrfs_clone+0x9ba/0xbd0 [btrfs] btrfs_clone_files.isra.0+0xeb/0x140 [btrfs] ? file_update_time+0xcd/0x120 btrfs_remap_file_range+0x322/0x3b0 [btrfs] do_clone_file_range+0xb7/0x1e0 vfs_clone_file_range+0x30/0xa0 ioctl_file_clone+0x8a/0xc0 do_vfs_ioctl+0x5b2/0x6f0 __x64_sys_ioctl+0x37/0xa0 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7f87977fc247 RSP: 002b:00007ffd51a2f6d8 EFLAGS: 00000206 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f87977fc247 RDX: 00007ffd51a2f710 RSI: 000000004020940d RDI: 0000000000000003 RBP: 0000000000000004 R08: 00007ffd51a79080 R09: 0000000000000000 R10: 00005621f11352f2 R11: 0000000000000206 R12: 0000000000000000 R13: 0000000000000000 R14: 00005621f128b958 R15: 0000000080000000 Kernel Offset: disabled ---[ end Kernel panic - not syncing: softlockup: hung tasks ]--- All of these lockup reports have the call chain btrfs_clone_files() -> btrfs_clone() in common. btrfs_clone_files() calls btrfs_clone() with both source and destination extents locked and loops over the source extent to create the clones. Conditionally reschedule in the btrfs_clone() loop, to give some time back to other processes. CC: stable@vger.kernel.org # 4.4+ Reviewed-by:
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Denis Efremov authored
Replace kvzalloc() call with kvcalloc() that also checks the size internally. There's a standalone overflow check in the function so we can return invalid parameter combination. Use array_size() helper to compute the memory size for clone_sources_tmp. Cc: Kees Cook <keescook@chromium.org> Signed-off-by:
Denis Efremov <efremov@linux.com> Reviewed-by:
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Denis Efremov authored
btrfs_ioctl_send() used open-coded kvzalloc implementation earlier. The code was accidentally replaced with kzalloc() call [1]. Restore the original code by using kvzalloc() to allocate sctx->clone_roots. [1] https://patchwork.kernel.org/patch/9757891/#20529627 Fixes: 818e010b ("btrfs: replace opencoded kvzalloc with the helper") CC: stable@vger.kernel.org # 4.14+ Signed-off-by:
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Nikolay Borisov authored
The passed in ordered_extent struct is always well-formed and contains the inode making the explicit argument redundant. Signed-off-by:
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Nikolay Borisov authored
It's used to reference the csum root which can be done from the trans handle as well. Simplify the signature and while at it also remove the noinline attribute as the function uses only at most 16 bytes of stack space. Signed-off-by:
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Nikolay Borisov authored
Signed-off-by:
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Nikolay Borisov authored
Signed-off-by:
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Nikolay Borisov authored
Signed-off-by:
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Nikolay Borisov authored
This makes reading the code a tad easier by decreasing the level of indirection by one. Reviewed-by:
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Nikolay Borisov authored
It's always set to 0 by the 2 callers so move it inside __do_readpage. Reviewed-by:
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