- 18 Nov, 2019 40 commits
-
-
Nikolay Borisov authored
This function is used only during the final phase of freespace cache writeout. This is necessary since using the plain btrfs_join_transaction api is deadlock prone. The deadlock looks like: T1: btrfs_commit_transaction commit_cowonly_roots btrfs_write_dirty_block_groups btrfs_wait_cache_io __btrfs_wait_cache_io btrfs_wait_ordered_range <-- Triggers ordered IO for freespace inode and blocks transaction commit until freespace cache writeout T2: <-- after T1 has triggered the writeout finish_ordered_fn btrfs_finish_ordered_io btrfs_join_transaction <--- this would block waiting for current transaction to commit, but since trans commit is waiting for this writeout to finish The special purpose functions prevents it by simply skipping the "wait for writeout" since it's guaranteed the transaction won't proceed until we are done. Reviewed-by:Qu Wenruo <wqu@suse.com> Signed-off-by:
Nikolay Borisov <nborisov@suse.com> Reviewed-by:
David Sterba <dsterba@suse.com> Signed-off-by:
-
Nikolay Borisov authored
Using an ASSERT in btrfs_pin_extent allows to more stringently observe whether the function is called under a transaction or not. Reviewed-by:
Johannes Thumshirn <jthumshirn@suse.de> Signed-off-by:
-
David Sterba authored
The helper is trivial and we can understand what the atomic_inc on something named refs does. Reviewed-by:
Anand Jain <anand.jain@oracle.com> Signed-off-by:
-
Tejun Heo authored
During a cyclic writeback, extent_write_cache_pages() uses done_index to update the writeback_index after the current run is over. However, instead of current index + 1, it gets to to the current index itself. Unfortunately, this, combined with returning on EOF instead of looping back, can lead to the following pathlogical behavior. 1. There is a single file which has accumulated enough dirty pages to trigger balance_dirty_pages() and the writer appending to the file with a series of short writes. 2. balance_dirty_pages kicks in, wakes up background writeback and sleeps. 3. Writeback kicks in and the cursor is on the last page of the dirty file. Writeback is started or skipped if already in progress. As it's EOF, extent_write_cache_pages() returns and the cursor is set to done_index which is pointing to the last page. 4. Writeback is done. Nothing happens till balance_dirty_pages finishes, at which point we go back to #1. This can almost completely stall out writing back of the file and keep the system over dirty threshold for a long time which can mess up the whole system. We encountered this issue in production with a package handling application which can reliably reproduce the issue when running under tight memory limits. Reading the comment in the error handling section, this seems to be to avoid accidentally skipping a page in case the write attempt on the page doesn't succeed. However, this concern seems bogus. On each page, the code either: * Skips and moves onto the next page. * Fails issue and sets done_index to index + 1. * Successfully issues and continue to the next page if budget allows and not EOF. IOW, as long as it's not EOF and there's budget, the code never retries writing back the same page. Only when a page happens to be the last page of a particular run, we end up retrying the page, which can't possibly guarantee anything data integrity related. Besides, cyclic writes are only used for non-syncing writebacks meaning that there's no data integrity implication to begin with. Fix it by always setting done_index past the current page being processed. Note that this problem exists in other writepages too. CC: stable@vger.kernel.org # 4.19+ Signed-off-by:
Tejun Heo <tj@kernel.org> Reviewed-by:
-
Marcos Paulo de Souza authored
Commit 4617ea3a (" Btrfs: fix necessary chunk tree space calculation when allocating a chunk") removed the is_allocation argument from check_system_chunk, since the formula for reserving the necessary space for allocation or removing a chunk would be the same. So, rework the comment by removing the mention of is_allocation argument. Signed-off-by:
Marcos Paulo de Souza <marcos.souza.org@gmail.com> Reviewed-by:
-
Qu Wenruo authored
Unlike read time tree checker errors, write time error can't be inspected by "btrfs inspect dump-tree", so we need extra information to determine what's going wrong. The patch will add the following output for write time tree checker error: - The content of the offending tree block To help determining if it's a false alert. - Kernel WARN_ON() for debug build This is helpful for us to detect unexpected write time tree checker error, especially fstests could catch the dmesg. Since the WARN_ON() is only triggered for write time tree checker, test cases utilizing dm-error won't trigger this WARN_ON(), thus no extra noise. Signed-off-by:
-
Qu Wenruo authored
Refactor the check for prev_key->objectid of the following key types into one function, check_prev_ino(): - EXTENT_DATA - INODE_REF - DIR_INDEX - DIR_ITEM - XATTR_ITEM Also add the check of prev_key for INODE_REF. Signed-off-by:
-
Chris Mason authored
extent_write_locked_range() is used when we're falling back to buffered IO from inside of compression. It allocates its own wbc and should associate it with the inode's i_wb to make sure the IO goes down from the correct cgroup. Reviewed-by:
Josef Bacik <josef@toxicpanda.com> Signed-off-by:
Chris Mason <clm@fb.com> Signed-off-by:
-
Chris Mason authored
Async CRCs and compression submit IO through helper threads, which means they have IO priority inversions when cgroup IO controllers are in use. This flags all of the writes submitted by btrfs helper threads as REQ_CGROUP_PUNT. submit_bio() will punt these to dedicated per-blkcg work items to avoid the priority inversion. For the compression code, we take a reference on the wbc's blkg css and pass it down to the async workers. For the async CRCs, the bio already has the correct css, we just need to tell the block layer to use REQ_CGROUP_PUNT. Reviewed-by:
-
Chris Mason authored
The btrfs writepages function collects a large range of pages flagged for delayed allocation, and then sends them down through the COW code for processing. When compression is on, we allocate one async_chunk structure for every 512K, and then run those pages through the compression code for IO submission. writepages starts all of this off with a single page, locked by the original call to extent_write_cache_pages(), and it's important to keep track of this page because it has already been through clear_page_dirty_for_io(). The btrfs async_chunk struct has a pointer to the locked_page, and when we're redirtying the page because compression had to fallback to uncompressed IO, we use page->index to decide if a given async_chunk struct really owns that page. But, this is racey. If a given delalloc range is broken up into two async_chunks (chunkA and chunkB), we can end up with something like this: compress_file_range(chunkA) submit_compress_extents(chunkA) submit compressed bios(chunkA) put_page(locked_page) compress_file_range(chunkB) ... Or: async_cow_submit submit_compressed_extents <--- falls back to buffered writeout cow_file_range extent_clear_unlock_delalloc __process_pages_contig put_page(locked_pages) async_cow_submit The end result is that chunkA is completed and cleaned up before chunkB even starts processing. This means we can free locked_page() and reuse it elsewhere. If we get really lucky, it'll have the same page->index in its new home as it did before. While we're processing chunkB, we might decide we need to fall back to uncompressed IO, and so compress_file_range() will call __set_page_dirty_nobufers() on chunkB->locked_page. Without cgroups in use, this creates as a phantom dirty page, which isn't great but isn't the end of the world. What can happen, it can go through the fixup worker and the whole COW machinery again: in submit_compressed_extents(): while (async extents) { ... cow_file_range if (!page_started ...) extent_write_locked_range else if (...) unlock_page continue; This hasn't been observed in practice but is still possible. With cgroups in use, we might crash in the accounting code because page->mapping->i_wb isn't set. BUG: unable to handle kernel NULL pointer dereference at 00000000000000d0 IP: percpu_counter_add_batch+0x11/0x70 PGD 66534e067 P4D 66534e067 PUD 66534f067 PMD 0 Oops: 0000 [#1] SMP DEBUG_PAGEALLOC CPU: 16 PID: 2172 Comm: rm Not tainted RIP: 0010:percpu_counter_add_batch+0x11/0x70 RSP: 0018:ffffc9000a97bbe0 EFLAGS: 00010286 RAX: 0000000000000005 RBX: 0000000000000090 RCX: 0000000000026115 RDX: 0000000000000030 RSI: ffffffffffffffff RDI: 0000000000000090 RBP: 0000000000000000 R08: fffffffffffffff5 R09: 0000000000000000 R10: 00000000000260c0 R11: ffff881037fc26c0 R12: ffffffffffffffff R13: ffff880fe4111548 R14: ffffc9000a97bc90 R15: 0000000000000001 FS: 00007f5503ced480(0000) GS:ffff880ff7200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000000000d0 CR3: 00000001e0459005 CR4: 0000000000360ee0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: account_page_cleaned+0x15b/0x1f0 __cancel_dirty_page+0x146/0x200 truncate_cleanup_page+0x92/0xb0 truncate_inode_pages_range+0x202/0x7d0 btrfs_evict_inode+0x92/0x5a0 evict+0xc1/0x190 do_unlinkat+0x176/0x280 do_syscall_64+0x63/0x1a0 entry_SYSCALL_64_after_hwframe+0x42/0xb7 The fix here is to make asyc_chunk->locked_page NULL everywhere but the one async_chunk struct that's allowed to do things to the locked page. Link: https://lore.kernel.org/linux-btrfs/c2419d01-5c84-3fb4-189e-4db519d08796@suse.com/ Fixes: 771ed689 ("Btrfs: Optimize compressed writeback and reads") Reviewed-by: -
Chris Mason authored
Now that we're not using btrfs_schedule_bio() anymore, delete all the code that supported it. Reviewed-by:
-
Chris Mason authored
btrfs_schedule_bio() hands IO off to a helper thread to do the actual submit_bio() call. This has been used to make sure async crc and compression helpers don't get stuck on IO submission. To maintain good performance, over time the IO submission threads duplicated some IO scheduler characteristics such as high and low priority IOs and they also made some ugly assumptions about request allocation batch sizes. All of this cost at least one extra context switch during IO submission, and doesn't fit well with the modern blkmq IO stack. So, this commit stops using btrfs_schedule_bio(). We may need to adjust the number of async helper threads for crcs and compression, but long term it's a better path. Reviewed-by:
-
David Sterba authored
The attribute is more relaxed than const and the functions could dereference pointers, as long as the observable state is not changed. We do have such functions, based on -Wsuggest-attribute=pure . The visible effects of this patch are negligible, there are differences in the assembly but hard to summarize. Reviewed-by:
-
David Sterba authored
For some reason the attribute is called __attribute_const__ and not __const, marks functions that have no observable effects on program state, IOW not reading pointers, just the arguments and calculating a value. Allows the compiler to do some optimizations, based on -Wsuggest-attribute=const . The effects are rather small, though, about 60 bytes decrese of btrfs.ko. Reviewed-by:
-
David Sterba authored
The attribute can mark functions supposed to be called rarely if at all and the text can be moved to sections far from the other code. The attribute has been added to several functions already, this patch is based on hints given by gcc -Wsuggest-attribute=cold. The net effect of this patch is decrease of btrfs.ko by 1000-1300, depending on the config options. Reviewed-by:
-
David Sterba authored
The parameter is now always set to NULL and could be dropped. The last user was get_default_root but that got reworked in 05dbe683 ("Btrfs: unify subvol= and subvolid= mounting") and the parameter became unused. Reviewed-by:
-
Josef Bacik authored
We hit the following warning while running down a different problem [ 6197.175850] ------------[ cut here ]------------ [ 6197.185082] refcount_t: underflow; use-after-free. [ 6197.194704] WARNING: CPU: 47 PID: 966 at lib/refcount.c:190 refcount_sub_and_test_checked+0x53/0x60 [ 6197.521792] Call Trace: [ 6197.526687] __btrfs_release_delayed_node+0x76/0x1c0 [ 6197.536615] btrfs_kill_all_delayed_nodes+0xec/0x130 [ 6197.546532] ? __btrfs_btree_balance_dirty+0x60/0x60 [ 6197.556482] btrfs_clean_one_deleted_snapshot+0x71/0xd0 [ 6197.566910] cleaner_kthread+0xfa/0x120 [ 6197.574573] kthread+0x111/0x130 [ 6197.581022] ? kthread_create_on_node+0x60/0x60 [ 6197.590086] ret_from_fork+0x1f/0x30 [ 6197.597228] ---[ end trace 424bb7ae00509f56 ]--- This is because the free side drops the ref without the lock, and then takes the lock if our refcount is 0. So you can have nodes on the tree that have a refcount of 0. Fix this by zero'ing out that element in our temporary array so we don't try to kill it again. CC: stable@vger.kernel.org # 4.14+ Reviewed-by:
-
Anand Jain authored
Its very helpful if we had logged the device scanner process name to debug the race condition between the systemd-udevd scan and the user initiated device forget command. This patch adds process name and pid to the scan message. Signed-off-by:
-
Nikolay Borisov authored
That function adds unnecessary indirection between backref_in_log and the caller. Furthermore it also "downgrades" backref_in_log's return value to a boolean, when in fact it could very well be an error. Rectify the situation by simply opencoding name_in_log_ref in replay_one_name and properly handling possible return codes from backref_in_log. Signed-off-by:
-
Nikolay Borisov authored
This function can return a negative error value if btrfs_search_slot errors for whatever reason or if btrfs_alloc_path runs out of memory. This is currently problemattic because backref_in_log is treated by its callers as if it returns boolean. Fix this by adding proper error handling in callers. That also enables the function to return the direct error code from btrfs_search_slot. Signed-off-by:
-
Nikolay Borisov authored
Direct replacement, though note that the inside of the loop in btrfs_find_name_in_backref is organized in a slightly different way but is equvalent. Signed-off-by:
-
Qu Wenruo authored
The state was introduced in commit 4a9d8bde ("Btrfs: make the state of the transaction more readable"), then in commit 302167c5 ("btrfs: don't end the transaction for delayed refs in throttle") the state is completely removed. So we can just clean up the state since it's only compared but never set. Signed-off-by:
-
Qu Wenruo authored
Add an overview of the basic btrfs transaction transitions, including the following states: - No transaction states - Transaction N [[TRANS_STATE_RUNNING]] - Transaction N [[TRANS_STATE_COMMIT_START]] - Transaction N [[TRANS_STATE_COMMIT_DOING]] - Transaction N [[TRANS_STATE_UNBLOCKED]] - Transaction N [[TRANS_STATE_COMPLETED]] For each state, the comment will include: - Basic explaination about current state - How to go next stage - What will happen if we call various start_transaction() functions - Relationship to transaction N+1 This doesn't provide tech details, but serves as a cheat sheet for reader to get into the code a little easier. Signed-off-by:
-
David Sterba authored
Replace is_power_of_2 with the helper that is self-documenting and remove the open coded call in alloc_profile_is_valid. Signed-off-by: -
David Sterba authored
As is_power_of_two takes unsigned long, it's not safe on 32bit architectures, but we could pass any u64 value in seveal places. Add a separate helper and also an alias that better expresses the purpose for which the helper is used. Signed-off-by: -
Anand Jain authored
When balance reduces the number of copies of metadata, it reduces the redundancy, use the term redundancy instead of integrity. Signed-off-by:
-
David Sterba authored
The function belongs to the family of locking functions, so move it there. The 'noinline' keyword is dropped as it's now an exported function that does not need it. Reviewed-by:
-
David Sterba authored
The function belongs to the family of locking functions, so move it there. The 'noinline' keyword is dropped as it's now an exported function that does not need it. Reviewed-by:
-
David Sterba authored
The function btrfs_assert_tree_locked is used outside of the locking code so it is exported, however we can make it static inine as it's fairly trivial. This is the only locking assertion used in release builds, inlining improves the text size by 174 bytes and reduces stack consumption in the callers. Reviewed-by:
-
David Sterba authored
I've noticed that none of the btrfs_assert_*lock* debugging helpers is inlined, despite they're short and mostly a value update. Making them inline shaves 67 from the text size, reduces stack consumption and perhaps also slightly improves the performance due to avoiding unnecessary calls. Reviewed-by:
-
Omar Sandoval authored
Commit ac0c7cf8 ("btrfs: fix crash when tracepoint arguments are freed by wq callbacks") added a void pointer, wtag, which is passed into trace_btrfs_all_work_done() instead of the freed work item. This is silly for a few reasons: 1. The freed work item still has the same address. 2. work is still in scope after it's freed, so assigning wtag doesn't stop anyone from using it. 3. The tracepoint has always taken a void * argument, so assigning wtag doesn't actually make things any more type-safe. (Note that the original bug in commit bc074524 ("btrfs: prefix fsid to all trace events") was that the void * was implicitly casted when it was passed to btrfs_work_owner() in the trace point itself). Instead, let's add some clearer warnings as comments. Reviewed-by:
Filipe Manana <fdmanana@suse.com> Signed-off-by:
Omar Sandoval <osandov@fb.com> Reviewed-by:
-
Omar Sandoval authored
Commit 9e0af237 ("Btrfs: fix task hang under heavy compressed write") worked around the issue that a recycled work item could get a false dependency on the original work item due to how the workqueue code guarantees non-reentrancy. It did so by giving different work functions to different types of work. However, the fixes in the previous few patches are more complete, as they prevent a work item from being recycled at all (except for a tiny window that the kernel workqueue code handles for us). This obsoletes the previous fix, so we don't need the unique helpers for correctness. The only other reason to keep them would be so they show up in stack traces, but they always seem to be optimized to a tail call, so they don't show up anyways. So, let's just get rid of the extra indirection. While we're here, rename normal_work_helper() to the more informative btrfs_work_helper(). Reviewed-by:
-
Omar Sandoval authored
Currently, scrub_missing_raid56_worker() puts and potentially frees sblock (which embeds the work item) and then submits a bio through scrub_wr_submit(). This is another potential instance of the bug in "btrfs: don't prematurely free work in run_ordered_work()". Fix it by dropping the reference after we submit the bio. Reviewed-by:
-
Omar Sandoval authored
Currently, reada_start_machine_worker() frees the reada_machine_work and then calls __reada_start_machine() to do readahead. This is another potential instance of the bug in "btrfs: don't prematurely free work in run_ordered_work()". There _might_ already be a deadlock here: reada_start_machine_worker() can depend on itself through stacked filesystems (__read_start_machine() -> reada_start_machine_dev() -> reada_tree_block_flagged() -> read_extent_buffer_pages() -> submit_one_bio() -> btree_submit_bio_hook() -> btrfs_map_bio() -> submit_stripe_bio() -> submit_bio() onto a loop device can trigger readahead on the lower filesystem). Either way, let's fix it by freeing the work at the end. Reviewed-by:
-
Omar Sandoval authored
Currently, end_workqueue_fn() frees the end_io_wq entry (which embeds the work item) and then calls bio_endio(). This is another potential instance of the bug in "btrfs: don't prematurely free work in run_ordered_work()". In particular, the endio call may depend on other work items. For example, btrfs_end_dio_bio() can call btrfs_subio_endio_read() -> __btrfs_correct_data_nocsum() -> dio_read_error() -> submit_dio_repair_bio(), which submits a bio that is also completed through a end_workqueue_fn() work item. However, __btrfs_correct_data_nocsum() waits for the newly submitted bio to complete, thus it depends on another work item. This example currently usually works because we use different workqueue helper functions for BTRFS_WQ_ENDIO_DATA and BTRFS_WQ_ENDIO_DIO_REPAIR. However, it may deadlock with stacked filesystems and is fragile overall. The proper fix is to free the work item at the very end of the work function, so let's do that. Reviewed-by:
-
Omar Sandoval authored
We hit the following very strange deadlock on a system with Btrfs on a loop device backed by another Btrfs filesystem: 1. The top (loop device) filesystem queues an async_cow work item from cow_file_range_async(). We'll call this work X. 2. Worker thread A starts work X (normal_work_helper()). 3. Worker thread A executes the ordered work for the top filesystem (run_ordered_work()). 4. Worker thread A finishes the ordered work for work X and frees X (work->ordered_free()). 5. Worker thread A executes another ordered work and gets blocked on I/O to the bottom filesystem (still in run_ordered_work()). 6. Meanwhile, the bottom filesystem allocates and queues an async_cow work item which happens to be the recently-freed X. 7. The workqueue code sees that X is already being executed by worker thread A, so it schedules X to be executed _after_ worker thread A finishes (see the find_worker_executing_work() call in process_one_work()). Now, the top filesystem is waiting for I/O on the bottom filesystem, but the bottom filesystem is waiting for the top filesystem to finish, so we deadlock. This happens because we are breaking the workqueue assumption that a work item cannot be recycled while it still depends on other work. Fix it by waiting to free the work item until we are done with all of the related ordered work. P.S.: One might ask why the workqueue code doesn't try to detect a recycled work item. It actually does try by checking whether the work item has the same work function (find_worker_executing_work()), but in our case the function is the same. This is the only key that the workqueue code has available to compare, short of adding an additional, layer-violating "custom key". Considering that we're the only ones that have ever hit this, we should just play by the rules. Unfortunately, we haven't been able to create a minimal reproducer other than our full container setup using a compress-force=zstd filesystem on top of another compress-force=zstd filesystem. Suggested-by:
-
Omar Sandoval authored
Commit fc97fab0 ("btrfs: Replace fs_info->qgroup_rescan_worker workqueue with btrfs_workqueue.") converted qgroup_rescan_work to be initialized with btrfs_init_work(), but it left behind an unnecessary memset(). Get rid of the memset(). Reviewed-by:
-
Josef Bacik authored
This needs to be cleaned up in the future, but for now it belongs to the extent-io-tree stuff since it uses the internal tree search code. Needed to export get_state_failrec and set_state_failrec as well since we're not going to move the actual IO part of the failrec stuff out at this point. Signed-off-by:
-
Josef Bacik authored
This utilizes internal stuff to the extent_io_tree, so we need to export it before we move it. Signed-off-by:
-
Josef Bacik authored
extent_io.c/h are huge, encompassing a bunch of different things. The extent_io_tree code can live on its own, so separate this out. Signed-off-by:
-
