- 10 Mar, 2014 37 commits
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Miao Xie authored
If the log sync fails, there is something wrong in the log tree, we should not continue to join the log transaction and log the metadata. What we should do is to do a full commit. This patch fixes this problem by setting ->last_trans_log_full_commit to the current transaction id, it will tell the tasks not to join the log transaction, and do a full commit. Signed-off-by:
Miao Xie <miaox@cn.fujitsu.com> Signed-off-by:
Josef Bacik <jbacik@fb.com>
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Miao Xie authored
We might commit the log sub-transaction which didn't contain the metadata we logged. It was because we didn't record the log transid and just select the current log sub-transaction to commit, but the right one might be committed by the other task already. Actually, we needn't do anything and it is safe that we go back directly in this case. This patch improves the log sync by the above idea. We record the transid of the log sub-transaction in which we log the metadata, and the transid of the log sub-transaction we have committed. If the committed transid is >= the transid we record when logging the metadata, we just go back. Signed-off-by:
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Miao Xie authored
It is possible that many tasks sync the log tree at the same time, but only one task can do the sync work, the others will wait for it. But those wait tasks didn't get the result of the log sync, and returned 0 when they ended the wait. It caused those tasks skipped the error handle, and the serious problem was they told the users the file sync succeeded but in fact they failed. This patch fixes this problem by introducing a log context structure, we insert it into the a global list. When the sync fails, we will set the error number of every log context in the list, then the waiting tasks get the error number of the log context and handle the error if need. Signed-off-by:
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Miao Xie authored
The log trans id is initialized to be 0 every time we create a log tree, and the log tree need be re-created after a new transaction is started, it means the log trans id is unlikely to be a huge number, so we can use signed integer instead of unsigned long integer to save a bit space. Signed-off-by:
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Miao Xie authored
Mutex unlock implies certain memory barriers to make sure all the memory operation completes before the unlock, and the next mutex lock implies memory barriers to make sure the all the memory happens after the lock. So it is a full memory barrier(smp_mb), we needn't add memory barriers. Remove them. Signed-off-by:
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Miao Xie authored
The old code would start the log transaction even the log tree init failed, it was unnecessary. Fix it. Signed-off-by:
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Miao Xie authored
We may abort the wait earlier if ->last_trans_log_full_commit was set to the current transaction id, at this case, we need commit the current transaction instead of the log sub-transaction. But the current code didn't tell the caller to do it (return 0, not -EAGAIN). Fix it. Signed-off-by:
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Miao Xie authored
->last_trans_log_full_commit may be changed by the other tasks without lock, so we need prevent the compiler from the optimize access just like tmp = fs_info->last_trans_log_full_commit if (tmp == ...) ... <do something> if (tmp == ...) ... In fact, we need get the new value of ->last_trans_log_full_commit during the second access. Fix it by ACCESS_ONCE(). Signed-off-by:
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Liu Bo authored
So after transaction is aborted, we need to cleanup inode resources by calling btrfs_invalidate_inodes(), and btrfs_invalidate_inodes() hopes roots' refs to be zero in old times and sets a WARN_ON(), however, this is not always true within cleaning up transaction, so we get to detect transaction abortion and not warn at all. Signed-off-by:
Liu Bo <bo.li.liu@oracle.com> Signed-off-by:
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Liu Bo authored
[13654.480669] ====================================================== [13654.480905] [ INFO: possible circular locking dependency detected ] [13654.481003] 3.12.0+ #4 Tainted: G W O [13654.481060] ------------------------------------------------------- [13654.481060] btrfs-transacti/9347 is trying to acquire lock: [13654.481060] (&(&root->ordered_extent_lock)->rlock){+.+...}, at: [<ffffffffa02d30a1>] btrfs_cleanup_transaction+0x271/0x570 [btrfs] [13654.481060] but task is already holding lock: [13654.481060] (&(&fs_info->ordered_root_lock)->rlock){+.+...}, at: [<ffffffffa02d3015>] btrfs_cleanup_transaction+0x1e5/0x570 [btrfs] [13654.481060] which lock already depends on the new lock. [13654.481060] the existing dependency chain (in reverse order) is: [13654.481060] -> #1 (&(&fs_info->ordered_root_lock)->rlock){+.+...}: [13654.481060] [<ffffffff810c4103>] lock_acquire+0x93/0x130 [13654.481060] [<ffffffff81689991>] _raw_spin_lock+0x41/0x50 [13654.481060] [<ffffffffa02f011b>] __btrfs_add_ordered_extent+0x39b/0x450 [btrfs] [13654.481060] [<ffffffffa02f0202>] btrfs_add_ordered_extent+0x32/0x40 [btrfs] [13654.481060] [<ffffffffa02df6aa>] run_delalloc_nocow+0x78a/0x9d0 [btrfs] [13654.481060] [<ffffffffa02dfc0d>] run_delalloc_range+0x31d/0x390 [btrfs] [13654.481060] [<ffffffffa02f7c00>] __extent_writepage+0x310/0x780 [btrfs] [13654.481060] [<ffffffffa02f830a>] extent_write_cache_pages.isra.29.constprop.48+0x29a/0x410 [btrfs] [13654.481060] [<ffffffffa02f879d>] extent_writepages+0x4d/0x70 [btrfs] [13654.481060] [<ffffffffa02d9f68>] btrfs_writepages+0x28/0x30 [btrfs] [13654.481060] [<ffffffff8114be91>] do_writepages+0x21/0x50 [13654.481060] [<ffffffff81140d49>] __filemap_fdatawrite_range+0x59/0x60 [13654.481060] [<ffffffff81140e13>] filemap_fdatawrite_range+0x13/0x20 [13654.481060] [<ffffffffa02f1db9>] btrfs_wait_ordered_range+0x49/0x140 [btrfs] [13654.481060] [<ffffffffa0318fe2>] __btrfs_write_out_cache+0x682/0x8b0 [btrfs] [13654.481060] [<ffffffffa031952d>] btrfs_write_out_cache+0x8d/0xe0 [btrfs] [13654.481060] [<ffffffffa02c7083>] btrfs_write_dirty_block_groups+0x593/0x680 [btrfs] [13654.481060] [<ffffffffa0345307>] commit_cowonly_roots+0x14b/0x20d [btrfs] [13654.481060] [<ffffffffa02d7c1a>] btrfs_commit_transaction+0x43a/0x9d0 [btrfs] [13654.481060] [<ffffffffa030061a>] btrfs_create_uuid_tree+0x5a/0x100 [btrfs] [13654.481060] [<ffffffffa02d5a8a>] open_ctree+0x21da/0x2210 [btrfs] [13654.481060] [<ffffffffa02ab6fe>] btrfs_mount+0x68e/0x870 [btrfs] [13654.481060] [<ffffffff811b2409>] mount_fs+0x39/0x1b0 [13654.481060] [<ffffffff811cd653>] vfs_kern_mount+0x63/0xf0 [13654.481060] [<ffffffff811cfcce>] do_mount+0x23e/0xa90 [13654.481060] [<ffffffff811d05a3>] SyS_mount+0x83/0xc0 [13654.481060] [<ffffffff81692b52>] system_call_fastpath+0x16/0x1b [13654.481060] -> #0 (&(&root->ordered_extent_lock)->rlock){+.+...}: [13654.481060] [<ffffffff810c340a>] __lock_acquire+0x150a/0x1a70 [13654.481060] [<ffffffff810c4103>] lock_acquire+0x93/0x130 [13654.481060] [<ffffffff81689991>] _raw_spin_lock+0x41/0x50 [13654.481060] [<ffffffffa02d30a1>] btrfs_cleanup_transaction+0x271/0x570 [btrfs] [13654.481060] [<ffffffffa02d35ce>] transaction_kthread+0x22e/0x270 [btrfs] [13654.481060] [<ffffffff81079efa>] kthread+0xea/0xf0 [13654.481060] [<ffffffff81692aac>] ret_from_fork+0x7c/0xb0 [13654.481060] other info that might help us debug this: [13654.481060] Possible unsafe locking scenario: [13654.481060] CPU0 CPU1 [13654.481060] ---- ---- [13654.481060] lock(&(&fs_info->ordered_root_lock)->rlock); [13654.481060] lock(&(&root->ordered_extent_lock)->rlock); [13654.481060] lock(&(&fs_info->ordered_root_lock)->rlock); [13654.481060] lock(&(&root->ordered_extent_lock)->rlock); [13654.481060] *** DEADLOCK *** [...] ====================================================== btrfs_destroy_all_ordered_extents() gets &fs_info->ordered_root_lock __BEFORE__ acquiring &root->ordered_extent_lock, while btrfs_[add,remove]_ordered_extent() acquires &fs_info->ordered_root_lock __AFTER__ getting &root->ordered_extent_lock. This patch fixes the above problem. Signed-off-by: -
Filipe David Borba Manana authored
This is an extension to my previous commit titled: "Btrfs: faster file extent item replace operations" (hash 1acae57b) Instead of inserting the new file extent item if we deleted existing file extent items covering our target file range, also allow to insert the new file extent item if we didn't find any existing items to delete and replace_extent != 0, since in this case our caller would do another tree search to insert the new file extent item anyway, therefore just combine the two tree searches into a single one, saving cpu time, reducing lock contention and reducing btree node/leaf COW operations. This covers the case where applications keep doing tail append writes to files, which for example is the case of Apache CouchDB (its database and view index files are always open with O_APPEND). Signed-off-by:
Filipe David Borba Manana <fdmanana@gmail.com> Signed-off-by:
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Stanislaw Gruszka authored
In case we do not refill, we can overwrite cur pointer from prio_head by one from not prioritized head, what looks as something that was not intended. This change make we always take works from prio_head first until it's not empty. Signed-off-by:
Stanislaw Gruszka <stf_xl@wp.pl> Signed-off-by:
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Wang Shilong authored
This reverts commit 41ce9970. Previously i was thinking we can use readonly root's commit root safely while it is not true, readonly root may be cowed with the following cases. 1.snapshot send root will cow source root. 2.balance,device operations will also cow readonly send root to relocate. So i have two ideas to make us safe to use commit root. -->approach 1: make it protected by transaction and end transaction properly and we research next item from root node(see btrfs_search_slot_for_read()). -->approach 2: add another counter to local root structure to sync snapshot with send. and add a global counter to sync send with exclusive device operations. So with approach 2, send can use commit root safely, because we make sure send root can not be cowed during send. Unfortunately, it make codes *ugly* and more complex to maintain. To make snapshot and send exclusively, device operations and send operation exclusively with each other is a little confusing for common users. So why not drop into previous way. Cc: Josef Bacik <jbacik@fb.com> Signed-off-by:
Wang Shilong <wangsl.fnst@cn.fujitsu.com> Signed-off-by:
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Wang Shilong authored
Btrfs send is assuming readonly root won't change, let's skip readonly root. Signed-off-by:
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Wang Shilong authored
Since we have introduced btrfs_previous_extent_item() to search previous extent item, just switch into it. Signed-off-by:
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Hidetoshi Seto authored
I got an error on v3.13: BTRFS error (device sdf1) in write_all_supers:3378: errno=-5 IO failure (errors while submitting device barriers.) how to reproduce: > mkfs.btrfs -f -d raid1 /dev/sdf1 /dev/sdf2 > wipefs -a /dev/sdf2 > mount -o degraded /dev/sdf1 /mnt > btrfs balance start -f -sconvert=single -mconvert=single -dconvert=single /mnt The reason of the error is that barrier_all_devices() failed to submit barrier to the missing device. However it is clear that we cannot do anything on missing device, and also it is not necessary to care chunks on the missing device. This patch stops sending/waiting barrier if device is missing. Signed-off-by:
Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com> Cc: <stable@vger.kernel.org> Signed-off-by:
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Josef Bacik authored
When I converted the BUG_ON() for the free_space_cache_inode in cow_file_range I made it so we just return an error instead of unlocking all of our various stuff. This is a mistake and causes us to hang when we run into this. This patch fixes this problem. Thanks, Signed-off-by: -
Josef Bacik authored
While trying to reproduce a delayed ref problem I noticed the box kept falling over using all 80gb of my ram with btrfs_inode's and btrfs_delayed_node's. Turns out this is because we only throttle delayed inode updates in btrfs_dirty_inode, which doesn't actually get called that often, especially when all you are doing is creating a bunch of files. So balance delayed inode updates everytime we create a new inode. With this patch we no longer use up all of our ram with delayed inode updates. Thanks, Signed-off-by: -
David Sterba authored
Help during debugging to export various interesting infromation and tunables without the need of extra mount options or ioctls. Usage: * declare your variable in sysfs.h, and include where you need it * define the variable in sysfs.c and make it visible via debugfs_create_TYPE Depends on CONFIG_DEBUG_FS. Signed-off-by:
David Sterba <dsterba@suse.cz> Signed-off-by:
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David Sterba authored
The fs_path structure uses an inline buffer and falls back to a chain of allocations, but vmalloc is not necessary because PATH_MAX fits into PAGE_SIZE. The size of fs_path has been reduced to 256 bytes from PAGE_SIZE, usually 4k. Experimental measurements show that most paths on a single filesystem do not exceed 200 bytes, and these get stored into the inline buffer directly, which is now 230 bytes. Longer paths are kmalloced when needed. Signed-off-by:
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Filipe David Borba Manana authored
We have this pattern where we do search for a contiguous group of items in a tree and everytime we find an item, we process it, then we release our path, increment the offset of the search key, do another full tree search and repeat these steps until a tree search can't find more items we're interested in. Instead of doing these full tree searches after processing each item, just process the next item/slot in our leaf and don't release the path. Since all these trees are read only and we always use the commit root for a search and skip node/leaf locks, we're not affecting concurrency on the trees. Signed-off-by:
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Filipe David Borba Manana authored
This was a leftover from the commit: 74dd17fb (Btrfs: fix btrfs send for inline items and compression) Signed-off-by:
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David Sterba authored
If cleaning the name cache fails, we could try to proceed at the cost of some memory leak. This is not expected to happen often. Signed-off-by:
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David Sterba authored
There are only 2 static callers, the BUG would normally be never reached, but let's be nice. Signed-off-by:
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David Sterba authored
We know that buf_len is at most PATH_MAX, 4k, and can merge it with the reversed member. This saves 3 bytes in favor of inline_buf. Signed-off-by:
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David Sterba authored
We don't need to keep track of that, it's available via is_vmalloc_addr. Signed-off-by:
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David Sterba authored
The member is used only to return value back from fs_path_prepare_for_add, we can do it locally and save 8 bytes for the inline_buf path. Signed-off-by:
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David Sterba authored
The buffer passed to snprintf can hold the fully expanded format string, 64 = 3x largest ULL + 3x char + trailing null. I don't think that removing the check entirely is a good idea, hence the ASSERT. Signed-off-by:
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Filipe David Borba Manana authored
The commit titled "Btrfs: fix infinite path build loops in incremental send" didn't cover a particular case where the parent-child relationship inversion of directories doesn't imply a rename of the new parent directory. This was due to a simple logic mistake, a logical and instead of a logical or. Steps to reproduce: $ mkfs.btrfs -f /dev/sdb3 $ mount /dev/sdb3 /mnt/btrfs $ mkdir -p /mnt/btrfs/a/b/bar1/bar2/bar3/bar4 $ btrfs subvol snapshot -r /mnt/btrfs /mnt/btrfs/snap1 $ mv /mnt/btrfs/a/b/bar1/bar2/bar3/bar4 /mnt/btrfs/a/b/k44 $ mv /mnt/btrfs/a/b/bar1/bar2/bar3 /mnt/btrfs/a/b/k44 $ mv /mnt/btrfs/a/b/bar1/bar2 /mnt/btrfs/a/b/k44/bar3 $ mv /mnt/btrfs/a/b/bar1 /mnt/btrfs/a/b/k44/bar3/bar2/k11 $ btrfs subvol snapshot -r /mnt/btrfs /mnt/btrfs/snap2 $ btrfs send -p /mnt/btrfs/snap1 /mnt/btrfs/snap2 > /tmp/incremental.send A patch to update the test btrfs/030 from xfstests, so that it covers this case, will be submitted soon. Signed-off-by:
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Filipe David Borba Manana authored
This fixes a case that the commit titled: Btrfs: fix infinite path build loops in incremental send didn't cover. If the parent-child relationship between 2 directories is inverted, both get renamed, and the former parent has a file that got renamed too (but remains a child of that directory), the incremental send operation would use the file's old path after sending an unlink operation for that old path, causing receive to fail on future operations like changing owner, permissions or utimes of the corresponding inode. This is not a regression from the commit mentioned before, as without that commit we would fall into the issues that commit fixed, so it's just one case that wasn't covered before. Simple steps to reproduce this issue are: $ mkfs.btrfs -f /dev/sdb3 $ mount /dev/sdb3 /mnt/btrfs $ mkdir -p /mnt/btrfs/a/b/c/d $ touch /mnt/btrfs/a/b/c/d/file $ mkdir -p /mnt/btrfs/a/b/x $ btrfs subvol snapshot -r /mnt/btrfs /mnt/btrfs/snap1 $ mv /mnt/btrfs/a/b/x /mnt/btrfs/a/b/c/x2 $ mv /mnt/btrfs/a/b/c/d /mnt/btrfs/a/b/c/x2/d2 $ mv /mnt/btrfs/a/b/c/x2/d2/file /mnt/btrfs/a/b/c/x2/d2/file2 $ btrfs subvol snapshot -r /mnt/btrfs /mnt/btrfs/snap2 $ btrfs send -p /mnt/btrfs/snap1 /mnt/btrfs/snap2 > /tmp/incremental.send A patch to update the test btrfs/030 from xfstests, so that it covers this case, will be submitted soon. Signed-off-by: -
Wang Shilong authored
find_all_leafs() dosen't need add all roots actually, add roots only if we need, this can avoid unnecessary ulist dance. Signed-off-by:
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Hugo Mills authored
The structure for BTRFS_SET_RECEIVED_IOCTL packs differently on 32-bit and 64-bit systems. This means that it is impossible to use btrfs receive on a system with a 64-bit kernel and 32-bit userspace, because the structure size (and hence the ioctl number) is different. This patch adds a compatibility structure and ioctl to deal with the above case. Signed-off-by:
Hugo Mills <hugo@carfax.org.uk> Signed-off-by:
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Filipe David Borba Manana authored
Function wait_for_parent_move() returns negative value if an error happened, 0 if we don't need to wait for the parent's move, and 1 if the wait is needed. Before this change an error return value was being treated like the return value 1, which was not correct. Signed-off-by:
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Miao Xie authored
During device replace test, we hit a null pointer deference (It was very easy to reproduce it by running xfstests' btrfs/011 on the devices with the virtio scsi driver). There were two bugs that caused this problem: - We might allocate new chunks on the replaced device after we updated the mapping tree. And we forgot to replace the source device in those mapping of the new chunks. - We might get the mapping information which including the source device before the mapping information update. And then submit the bio which was based on that mapping information after we freed the source device. For the first bug, we can fix it by doing mapping tree update and source device remove in the same context of the chunk mutex. The chunk mutex is used to protect the allocable device list, the above method can avoid the new chunk allocation, and after we remove the source device, all the new chunks will be allocated on the new device. So it can fix the first bug. For the second bug, we need make sure all flighting bios are finished and no new bios are produced during we are removing the source device. To fix this problem, we introduced a global @bio_counter, we not only inc/dec @bio_counter outsize of map_blocks, but also inc it before submitting bio and dec @bio_counter when ending bios. Since Raid56 is a little different and device replace dosen't support raid56 yet, it is not addressed in the patch and I add comments to make sure we will fix it in the future. Reported-by:
Qu Wenruo <quwenruo@cn.fujitsu.com> Signed-off-by:
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Miao Xie authored
the alloc list of the filesystem is protected by ->chunk_mutex, we need get that mutex when we insert the new device into the list. Signed-off-by:
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Kusanagi Kouichi authored
EXDEV seems an appropriate error if an operation fails bacause it crosses file system boundaries. Reviewed-by:
Kusanagi Kouichi <slash@ac.auone-net.jp> Signed-off-by:
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Miao Xie authored
There was a problem in the old code: If we failed to log the csum, we would free all the ordered extents in the log list including those ordered extents that were logged successfully, it would make the log committer not to wait for the completion of the ordered extents. This patch doesn't insert the ordered extents that is about to be logged into a global list, instead, we insert them into a local list. If we log the ordered extents successfully, we splice them with the global list, or we will throw them away, then do full sync. It can also reduce the lock contention and the traverse time of list. Signed-off-by:
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- 15 Feb, 2014 2 commits
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Filipe David Borba Manana authored
For non compressed extents, iterate_extent_inodes() gives us offsets that take into account the data offset from the file extent items, while for compressed extents it doesn't. Therefore we have to adjust them before placing them in a send clone instruction. Not doing this adjustment leads to the receiving end requesting for a wrong a file range to the clone ioctl, which results in different file content from the one in the original send root. Issue reproducible with the following excerpt from the test I made for xfstests: _scratch_mkfs _scratch_mount "-o compress-force=lzo" $XFS_IO_PROG -f -c "truncate 118811" $SCRATCH_MNT/foo $XFS_IO_PROG -c "pwrite -S 0x0d -b 39987 92267 39987" $SCRATCH_MNT/foo $BTRFS_UTIL_PROG subvolume snapshot -r $SCRATCH_MNT $SCRATCH_MNT/mysnap1 $XFS_IO_PROG -c "pwrite -S 0x3e -b 80000 200000 80000" $SCRATCH_MNT/foo $BTRFS_UTIL_PROG filesystem sync $SCRATCH_MNT $XFS_IO_PROG -c "pwrite -S 0xdc -b 10000 250000 10000" $SCRATCH_MNT/foo $XFS_IO_PROG -c "pwrite -S 0xff -b 10000 300000 10000" $SCRATCH_MNT/foo # will be used for incremental send to be able to issue clone operations $BTRFS_UTIL_PROG subvolume snapshot -r $SCRATCH_MNT $SCRATCH_MNT/clones_snap $BTRFS_UTIL_PROG subvolume snapshot -r $SCRATCH_MNT $SCRATCH_MNT/mysnap2 $FSSUM_PROG -A -f -w $tmp/1.fssum $SCRATCH_MNT/mysnap1 $FSSUM_PROG -A -f -w $tmp/2.fssum -x $SCRATCH_MNT/mysnap2/mysnap1 \ -x $SCRATCH_MNT/mysnap2/clones_snap $SCRATCH_MNT/mysnap2 $FSSUM_PROG -A -f -w $tmp/clones.fssum $SCRATCH_MNT/clones_snap \ -x $SCRATCH_MNT/clones_snap/mysnap1 -x $SCRATCH_MNT/clones_snap/mysnap2 $BTRFS_UTIL_PROG send $SCRATCH_MNT/mysnap1 -f $tmp/1.snap $BTRFS_UTIL_PROG send $SCRATCH_MNT/clones_snap -f $tmp/clones.snap $BTRFS_UTIL_PROG send -p $SCRATCH_MNT/mysnap1 \ -c $SCRATCH_MNT/clones_snap $SCRATCH_MNT/mysnap2 -f $tmp/2.snap _scratch_unmount _scratch_mkfs _scratch_mount $BTRFS_UTIL_PROG receive $SCRATCH_MNT -f $tmp/1.snap $FSSUM_PROG -r $tmp/1.fssum $SCRATCH_MNT/mysnap1 2>> $seqres.full $BTRFS_UTIL_PROG receive $SCRATCH_MNT -f $tmp/clones.snap $FSSUM_PROG -r $tmp/clones.fssum $SCRATCH_MNT/clones_snap 2>> $seqres.full $BTRFS_UTIL_PROG receive $SCRATCH_MNT -f $tmp/2.snap $FSSUM_PROG -r $tmp/2.fssum $SCRATCH_MNT/mysnap2 2>> $seqres.full Signed-off-by:Chris Mason <clm@fb.com>
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Anand Jain authored
bdev is null when disk has disappeared and mounted with the degrade option stack trace --------- btrfs_sysfs_add_one+0x105/0x1c0 [btrfs] open_ctree+0x15f3/0x1fe0 [btrfs] btrfs_mount+0x5db/0x790 [btrfs] ? alloc_pages_current+0xa4/0x160 mount_fs+0x34/0x1b0 vfs_kern_mount+0x62/0xf0 do_mount+0x22e/0xa80 ? __get_free_pages+0x9/0x40 ? copy_mount_options+0x31/0x170 SyS_mount+0x7e/0xc0 system_call_fastpath+0x16/0x1b --------- reproducer: ------- mkfs.btrfs -draid1 -mraid1 /dev/sdc /dev/sdd (detach a disk) devmgt detach /dev/sdc [1] mount -o degrade /dev/sdd /btrfs ------- [1] github.com/anajain/devmgt.git Signed-off-by:
Anand Jain <Anand.Jain@oracle.com> Tested-by:
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- 14 Feb, 2014 1 commit
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Josef Bacik authored
A user was running into errors from an NFS export of a subvolume that had a default subvol set. When we mount a default subvol we will use d_obtain_alias() to find an existing dentry for the subvolume in the case that the root subvol has already been mounted, or a dummy one is allocated in the case that the root subvol has not already been mounted. This allows us to connect the dentry later on if we wander into the path. However if we don't ever wander into the path we will keep DCACHE_DISCONNECTED set for a long time, which angers NFS. It doesn't appear to cause any problems but it is annoying nonetheless, so simply unset DCACHE_DISCONNECTED in the get_default_root case and switch btrfs_lookup() to use d_materialise_unique() instead which will make everything play nicely together and reconnect stuff if we wander into the defaul subvol path from a different way. With this patch I'm no longer getting the NFS errors when exporting a volume that has been mounted with a default subvol set. Thanks, cc: bfields@fieldses.org cc: ebiederm@xmission.com Signed-off-by:
"Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by:
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