We call btrfs_write_dirty_block_groups() in the critical section of a
transaction's commit, when no other tasks can join the transaction and
add more block groups to the transaction's list of dirty block groups,
so we not taking the dirty block groups spinlock when checking for the
list's emptyness, grabbing its first element or deleting elements from
it.
However there's a special and rare case where we can have a concurrent
task adding elements to this list. We trigger writeback for space
caches before at btrfs_start_dirty_block_groups() and in past iterations
of the loop at btrfs_write_dirty_block_groups(), this means that when
the writeback finishes (which happens asynchronously) it creates a
task for the endio free space work queue that executes
btrfs_finish_ordered_io() - this function is able to join the transaction,
through btrfs_join_transaction_nolock(), and update the free space cache's
inode item in the root tree, which can result in COWing nodes of this tree
and therefore allocation of a new block group can happen, which gets added
to the transaction's list of dirty block groups while the transaction
commit task is operating on it concurrently.
So fix this by taking the dirty block groups spinlock before doing
operations on the dirty block groups list at
btrfs_write_dirty_block_groups().
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Pull btrfs fixes from Chris Mason:
"A couple of small fixes"
* 'for-linus-4.4' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs:
Btrfs: check prepare_uptodate_page() error code earlier
Btrfs: check for empty bitmap list in setup_cluster_bitmaps
btrfs: fix misleading warning when space cache failed to load
Btrfs: fix transaction handle leak in balance
Btrfs: fix unprotected list move from unused_bgs to deleted_bgs list
Writing to /proc/$pid/coredump_filter always returns -ESRCH because commit
774636e19e ("proc: convert to kstrto*()/kstrto*_from_user()") removed
the setting of ret after the get_proc_task call and incorrectly left it as
-ESRCH. Instead, return 0 when successful.
Example breakage:
echo 0 > /proc/self/coredump_filter
bash: echo: write error: No such process
Fixes: 774636e19e ("proc: convert to kstrto*()/kstrto*_from_user()")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: <stable@vger.kernel.org> [4.3+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When running fstests btrfs/070, with a higher number of fsstress
operations, I ran frequently into two different locking bugs when
defragging directories.
The first bug produced the following traces:
[133860.229792] ------------[ cut here ]------------
[133860.251062] WARNING: CPU: 2 PID: 26057 at fs/btrfs/locking.c:46 btrfs_set_lock_blocking_rw+0x57/0xbd [btrfs]()
[133860.253576] Modules linked in: btrfs crc32c_generic xor raid6_pq nfsd auth_rpcgss oid_registry nfs_acl nfs lockd grace fscache sunrpc loop fuse parport_pc i2c_piix4 psmouse parport
[133860.282566] CPU: 2 PID: 26057 Comm: btrfs Tainted: G W 4.3.0-rc5-btrfs-next-17+ #1
[133860.284393] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.8.1-0-g4adadbd-20150316_085822-nilsson.home.kraxel.org 04/01/2014
[133860.286827] 0000000000000000 ffff880207697b78 ffffffff812566f4 0000000000000000
[133860.288341] ffff880207697bb0 ffffffff8104d0a6 ffffffffa052d4c1 ffff880178f60e00
[133860.294219] ffff880178f60e00 0000000000000000 00000000000000f6 ffff880207697bc0
[133860.295831] Call Trace:
[133860.306518] [<ffffffff812566f4>] dump_stack+0x4e/0x79
[133860.307473] [<ffffffff8104d0a6>] warn_slowpath_common+0x9f/0xb8
[133860.308619] [<ffffffffa052d4c1>] ? btrfs_set_lock_blocking_rw+0x57/0xbd [btrfs]
[133860.310068] [<ffffffff8104d172>] warn_slowpath_null+0x1a/0x1c
[133860.312552] [<ffffffffa052d4c1>] btrfs_set_lock_blocking_rw+0x57/0xbd [btrfs]
[133860.314630] [<ffffffffa04d5787>] btrfs_set_lock_blocking+0xe/0x10 [btrfs]
[133860.323596] [<ffffffffa04d99cb>] btrfs_realloc_node+0xb3/0x341 [btrfs]
[133860.325233] [<ffffffffa050e396>] btrfs_defrag_leaves+0x239/0x2fa [btrfs]
[133860.332427] [<ffffffffa04fc2ce>] btrfs_defrag_root+0x63/0xca [btrfs]
[133860.337259] [<ffffffffa052a34e>] btrfs_ioctl_defrag+0x78/0x14e [btrfs]
[133860.340147] [<ffffffffa052b00b>] btrfs_ioctl+0x746/0x24c6 [btrfs]
[133860.344833] [<ffffffff81087481>] ? arch_local_irq_save+0x9/0xc
[133860.346343] [<ffffffff8113ad61>] ? __might_fault+0x4c/0xa7
[133860.353248] [<ffffffff8113ad61>] ? __might_fault+0x4c/0xa7
[133860.354242] [<ffffffff8113adba>] ? __might_fault+0xa5/0xa7
[133860.355232] [<ffffffff81171139>] ? cp_new_stat+0x15d/0x174
[133860.356237] [<ffffffff8117c610>] do_vfs_ioctl+0x427/0x4e6
[133860.358587] [<ffffffff81171175>] ? SYSC_newfstat+0x25/0x2e
[133860.360195] [<ffffffff8118574d>] ? __fget_light+0x4d/0x71
[133860.361380] [<ffffffff8117c726>] SyS_ioctl+0x57/0x79
[133860.363578] [<ffffffff8147cd97>] entry_SYSCALL_64_fastpath+0x12/0x6f
[133860.366217] ---[ end trace 2cadb2f653437e49 ]---
[133860.367399] ------------[ cut here ]------------
[133860.368162] kernel BUG at fs/btrfs/locking.c:307!
[133860.369430] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
[133860.370205] Modules linked in: btrfs crc32c_generic xor raid6_pq nfsd auth_rpcgss oid_registry nfs_acl nfs lockd grace fscache sunrpc loop fuse parport_pc i2c_piix4 psmouse parport
[133860.370205] CPU: 2 PID: 26057 Comm: btrfs Tainted: G W 4.3.0-rc5-btrfs-next-17+ #1
[133860.370205] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.8.1-0-g4adadbd-20150316_085822-nilsson.home.kraxel.org 04/01/2014
[133860.370205] task: ffff8800aec6db40 ti: ffff880207694000 task.ti: ffff880207694000
[133860.370205] RIP: 0010:[<ffffffffa052d466>] [<ffffffffa052d466>] btrfs_assert_tree_locked+0x10/0x14 [btrfs]
[133860.370205] RSP: 0018:ffff880207697bc0 EFLAGS: 00010246
[133860.370205] RAX: 0000000000000000 RBX: ffff880178f60e00 RCX: 0000000000000000
[133860.370205] RDX: ffff88023ec4fb50 RSI: 00000000ffffffff RDI: ffff880178f60e00
[133860.370205] RBP: ffff880207697bc0 R08: 0000000000000001 R09: 0000000000000000
[133860.370205] R10: 0000160000000000 R11: ffffffff81651000 R12: ffff880178f60e00
[133860.370205] R13: 0000000000000000 R14: 00000000000000f6 R15: ffff8801ff409000
[133860.370205] FS: 00007f763efd48c0(0000) GS:ffff88023ec40000(0000) knlGS:0000000000000000
[133860.370205] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[133860.370205] CR2: 0000000002158048 CR3: 000000003fd6c000 CR4: 00000000000006e0
[133860.370205] Stack:
[133860.370205] ffff880207697bd8 ffffffffa052d4d0 0000000000000000 ffff880207697be8
[133860.370205] ffffffffa04d5787 ffff880207697c80 ffffffffa04d99cb ffff8801ff409590
[133860.370205] ffff880207697ca8 000000f507697c80 ffff880183c11bb8 0000000000000000
[133860.370205] Call Trace:
[133860.370205] [<ffffffffa052d4d0>] btrfs_set_lock_blocking_rw+0x66/0xbd [btrfs]
[133860.370205] [<ffffffffa04d5787>] btrfs_set_lock_blocking+0xe/0x10 [btrfs]
[133860.370205] [<ffffffffa04d99cb>] btrfs_realloc_node+0xb3/0x341 [btrfs]
[133860.370205] [<ffffffffa050e396>] btrfs_defrag_leaves+0x239/0x2fa [btrfs]
[133860.370205] [<ffffffffa04fc2ce>] btrfs_defrag_root+0x63/0xca [btrfs]
[133860.370205] [<ffffffffa052a34e>] btrfs_ioctl_defrag+0x78/0x14e [btrfs]
[133860.370205] [<ffffffffa052b00b>] btrfs_ioctl+0x746/0x24c6 [btrfs]
[133860.370205] [<ffffffff81087481>] ? arch_local_irq_save+0x9/0xc
[133860.370205] [<ffffffff8113ad61>] ? __might_fault+0x4c/0xa7
[133860.370205] [<ffffffff8113ad61>] ? __might_fault+0x4c/0xa7
[133860.370205] [<ffffffff8113adba>] ? __might_fault+0xa5/0xa7
[133860.370205] [<ffffffff81171139>] ? cp_new_stat+0x15d/0x174
[133860.370205] [<ffffffff8117c610>] do_vfs_ioctl+0x427/0x4e6
[133860.370205] [<ffffffff81171175>] ? SYSC_newfstat+0x25/0x2e
[133860.370205] [<ffffffff8118574d>] ? __fget_light+0x4d/0x71
[133860.370205] [<ffffffff8117c726>] SyS_ioctl+0x57/0x79
[133860.370205] [<ffffffff8147cd97>] entry_SYSCALL_64_fastpath+0x12/0x6f
This bug happened because we assumed that by setting keep_locks to 1 in
our search path, our path after a call to btrfs_search_slot() would have
all nodes locked, which is not always true because unlock_up() (called by
btrfs_search_slot()) will unlock a node in a path if the slot of the node
below it doesn't point to the last item or beyond the last item. For
example, when the tree has a heigth of 2 and path->slots[0] has a value
smaller than btrfs_header_nritems(path->nodes[0]) - 1, the node at level 2
will be unlocked (also because lowest_unlock is set to 1 due to the fact
that the value passed as ins_len to btrfs_search_slot is 0).
This resulted in btrfs_find_next_key(), called before btrfs_realloc_node(),
to release out path and call again btrfs_search_slot(), but this time with
the cow parameter set to 0, meaning the resulting path got only read locks.
Therefore when we called btrfs_realloc_node(), with path->nodes[1] having
a read lock, it resulted in the warning and BUG_ON when calling
btrfs_set_lock_blocking() against the node, as that function expects the
node to have a write lock.
The second bug happened often when the first bug didn't happen, and made
us hang and hitting the following warning at fs/btrfs/locking.c:
251 void btrfs_tree_lock(struct extent_buffer *eb)
252 {
253 WARN_ON(eb->lock_owner == current->pid);
This happened because the tree search we made at btrfs_defrag_leaves()
before calling btrfs_find_next_key() locked a leaf and all the other
nodes in the path, so btrfs_find_next_key() had no need to release the
path and make a new search (with path->lowest_level set to 1). This
made btrfs_realloc_node() attempt to write lock the same leaf again,
resulting in a hang/deadlock.
So fix these issues by calling btrfs_find_next_key() after calling
btrfs_realloc_node() and setting the search path's lowest_level to 1
to avoid the hang/deadlock when attempting to write lock the leaves
at btrfs_realloc_node().
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Now we can finally hook up everything so we can actually use free space
tree. The free space tree is enabled by passing the space_cache=v2 mount
option. On the first mount with the this option set, the free space tree
will be created and the FREE_SPACE_TREE read-only compat bit will be
set. Any time the filesystem is mounted from then on, we must use the
free space tree. The clear_cache option will also clear the free space
tree.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
The free space tree is updated in tandem with the extent tree. There are
only a handful of places where we need to hook in:
1. Block group creation
2. Block group deletion
3. Delayed refs (extent creation and deletion)
4. Block group caching
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
This tests the operations on the free space tree trying to excercise all
of the main cases for both formats. Between this and xfstests, the free
space tree should have pretty good coverage.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
The free space cache has turned out to be a scalability bottleneck on
large, busy filesystems. When the cache for a lot of block groups needs
to be written out, we can get extremely long commit times; if this
happens in the critical section, things are especially bad because we
block new transactions from happening.
The main problem with the free space cache is that it has to be written
out in its entirety and is managed in an ad hoc fashion. Using a B-tree
to store free space fixes this: updates can be done as needed and we get
all of the benefits of using a B-tree: checksumming, RAID handling,
well-understood behavior.
With the free space tree, we get commit times that are about the same as
the no cache case with load times slower than the free space cache case
but still much faster than the no cache case. Free space is represented
with extents until it becomes more space-efficient to use bitmaps,
giving us similar space overhead to the free space cache.
The operations on the free space tree are: adding and removing free
space, handling the creation and deletion of block groups, and loading
the free space for a block group. We can also create the free space tree
by walking the extent tree and clear the free space tree.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
The on-disk format for the free space tree is straightforward. Each
block group is represented in the free space tree by a free space info
item that stores accounting information: whether the free space for this
block group is stored as bitmaps or extents and how many extents of free
space exist for this block group (regardless of which format is being
used in the tree). Extents are (start, FREE_SPACE_EXTENT, length) keys
with no corresponding item, and bitmaps instead have the
FREE_SPACE_BITMAP type and have a bitmap item attached, which is just an
array of bytes.
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
We're also going to load the free space tree from caching_thread(), so
we should refactor some of the common code.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
We're finally going to add one of these for the free space tree, so
let's add the same nice helpers that we have for the incompat bits.
While we're add it, also add helpers to clear the bits.
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
Sanity test the extent buffer bitmap operations (test, set, and clear)
against the equivalent standard kernel operations.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
When doing a direct IO write, __blockdev_direct_IO() can call the
btrfs_get_blocks_direct() callback one or more times before it calls the
btrfs_submit_direct() callback. However it can fail after calling the
first callback and before calling the second callback, which is a problem
because the first one creates ordered extents and the second one is the
one that submits bios that cover the ordered extents created by the first
one. That means the ordered extents will never complete nor have any of
the flags BTRFS_ORDERED_IO_DONE / BTRFS_ORDERED_IOERR set, resulting in
subsequent operations (such as other direct IO writes, buffered writes or
hole punching) that lock the same IO range and lookup for ordered extents
in the range to hang forever waiting for those ordered extents because
they can not complete ever, since no bio was submitted.
Fix this by tracking a range of created ordered extents that don't have
yet corresponding bios submitted and completing the ordered extents in
the range if __blockdev_direct_IO() fails with an error.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
If readpages() (triggered by defrag or buffered reads) is called while a
direct IO write is in progress, we have a small time window where we can
deadlock, resulting in traces like the following being generated:
[84723.212993] INFO: task fio:2849 blocked for more than 120 seconds.
[84723.214310] Tainted: G W 4.3.0-rc5-btrfs-next-17+ #1
[84723.215640] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[84723.217313] fio D ffff88023ec75218 0 2849 2835 0x00000000
[84723.218778] ffff880122dfb6e8 0000000000000092 0000000000000000 ffff88023ec75200
[84723.220458] ffff88000e05d2c0 ffff880122dfc000 ffff88023ec75200 7fffffffffffffff
[84723.230597] 0000000000000002 ffffffff8147891a ffff880122dfb700 ffffffff8147856a
[84723.232085] Call Trace:
[84723.232625] [<ffffffff8147891a>] ? bit_wait+0x3c/0x3c
[84723.233529] [<ffffffff8147856a>] schedule+0x7d/0x95
[84723.234398] [<ffffffff8147baa3>] schedule_timeout+0x43/0x10b
[84723.235384] [<ffffffff810f82eb>] ? time_hardirqs_on+0x15/0x28
[84723.236426] [<ffffffff8108a23d>] ? trace_hardirqs_on+0xd/0xf
[84723.237502] [<ffffffff810af8a3>] ? read_seqcount_begin.constprop.20+0x57/0x6d
[84723.238807] [<ffffffff8108a09b>] ? trace_hardirqs_on_caller+0x16/0x1ab
[84723.242012] [<ffffffff8108a23d>] ? trace_hardirqs_on+0xd/0xf
[84723.243064] [<ffffffff810af2ad>] ? timekeeping_get_ns+0xe/0x33
[84723.244116] [<ffffffff810afa2e>] ? ktime_get+0x41/0x52
[84723.245029] [<ffffffff81477cff>] io_schedule_timeout+0xb7/0x12b
[84723.245942] [<ffffffff81477cff>] ? io_schedule_timeout+0xb7/0x12b
[84723.246596] [<ffffffff81478953>] bit_wait_io+0x39/0x45
[84723.247503] [<ffffffff81478b93>] __wait_on_bit_lock+0x49/0x8d
[84723.248540] [<ffffffff8111684f>] __lock_page+0x66/0x68
[84723.249558] [<ffffffff81081c9b>] ? autoremove_wake_function+0x3a/0x3a
[84723.250844] [<ffffffff81124a04>] lock_page+0x2c/0x2f
[84723.251871] [<ffffffff81124afc>] invalidate_inode_pages2_range+0xf5/0x2aa
[84723.253274] [<ffffffff81117c34>] ? filemap_fdatawait_range+0x12d/0x146
[84723.254757] [<ffffffff81118191>] ? filemap_fdatawrite_range+0x13/0x15
[84723.256378] [<ffffffffa05139a2>] btrfs_get_blocks_direct+0x1b0/0x664 [btrfs]
[84723.258556] [<ffffffff8119e3f9>] ? submit_page_section+0x7b/0x111
[84723.260064] [<ffffffff8119eb90>] do_blockdev_direct_IO+0x658/0xbdb
[84723.261479] [<ffffffffa05137f2>] ? btrfs_page_exists_in_range+0x1a9/0x1a9 [btrfs]
[84723.262961] [<ffffffffa050a8a6>] ? btrfs_writepage_start_hook+0xce/0xce [btrfs]
[84723.264449] [<ffffffff8119f144>] __blockdev_direct_IO+0x31/0x33
[84723.265614] [<ffffffff8119f144>] ? __blockdev_direct_IO+0x31/0x33
[84723.266769] [<ffffffffa050a8a6>] ? btrfs_writepage_start_hook+0xce/0xce [btrfs]
[84723.268264] [<ffffffffa050935d>] btrfs_direct_IO+0x1b9/0x259 [btrfs]
[84723.270954] [<ffffffffa050a8a6>] ? btrfs_writepage_start_hook+0xce/0xce [btrfs]
[84723.272465] [<ffffffff8111878c>] generic_file_direct_write+0xb3/0x128
[84723.273734] [<ffffffffa051955c>] btrfs_file_write_iter+0x228/0x404 [btrfs]
[84723.275101] [<ffffffff8116ca6f>] __vfs_write+0x7c/0xa5
[84723.276200] [<ffffffff8116cfab>] vfs_write+0xa0/0xe4
[84723.277298] [<ffffffff8116d79d>] SyS_write+0x50/0x7e
[84723.278327] [<ffffffff8147cd97>] entry_SYSCALL_64_fastpath+0x12/0x6f
[84723.279595] INFO: lockdep is turned off.
[84723.379035] INFO: task btrfs:2923 blocked for more than 120 seconds.
[84723.380323] Tainted: G W 4.3.0-rc5-btrfs-next-17+ #1
[84723.381608] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[84723.383003] btrfs D ffff88023ed75218 0 2923 2859 0x00000000
[84723.384277] ffff88001311f860 0000000000000082 ffff88001311f840 ffff88023ed75200
[84723.385748] ffff88012c6751c0 ffff880013120000 ffff88012042fe68 ffff88012042fe30
[84723.387152] ffff880221571c88 0000000000000001 ffff88001311f878 ffffffff8147856a
[84723.388620] Call Trace:
[84723.389105] [<ffffffff8147856a>] schedule+0x7d/0x95
[84723.391882] [<ffffffffa051da32>] btrfs_start_ordered_extent+0x161/0x1fa [btrfs]
[84723.393718] [<ffffffff81081c61>] ? signal_pending_state+0x31/0x31
[84723.395659] [<ffffffffa0522c5b>] __do_contiguous_readpages.constprop.21+0x81/0xdc [btrfs]
[84723.397383] [<ffffffffa050ac96>] ? btrfs_submit_direct+0x3f0/0x3f0 [btrfs]
[84723.398852] [<ffffffffa0522da3>] __extent_readpages.constprop.20+0xed/0x100 [btrfs]
[84723.400561] [<ffffffff81123f6c>] ? __lru_cache_add+0x5d/0x72
[84723.401787] [<ffffffffa0523896>] extent_readpages+0x111/0x1a7 [btrfs]
[84723.403121] [<ffffffffa050ac96>] ? btrfs_submit_direct+0x3f0/0x3f0 [btrfs]
[84723.404583] [<ffffffffa05088fa>] btrfs_readpages+0x1f/0x21 [btrfs]
[84723.406007] [<ffffffff811226df>] __do_page_cache_readahead+0x168/0x1f4
[84723.407502] [<ffffffff81122988>] ondemand_readahead+0x21d/0x22e
[84723.408937] [<ffffffff81122988>] ? ondemand_readahead+0x21d/0x22e
[84723.410487] [<ffffffff81122af1>] page_cache_sync_readahead+0x3d/0x3f
[84723.411710] [<ffffffffa0535388>] btrfs_defrag_file+0x419/0xaaf [btrfs]
[84723.413007] [<ffffffffa0531db0>] ? kzalloc+0xf/0x11 [btrfs]
[84723.414085] [<ffffffffa0535b43>] btrfs_ioctl_defrag+0x125/0x14e [btrfs]
[84723.415307] [<ffffffffa0536753>] btrfs_ioctl+0x746/0x24c6 [btrfs]
[84723.416532] [<ffffffff81087481>] ? arch_local_irq_save+0x9/0xc
[84723.417731] [<ffffffff8113ad61>] ? __might_fault+0x4c/0xa7
[84723.418699] [<ffffffff8113ad61>] ? __might_fault+0x4c/0xa7
[84723.421532] [<ffffffff8113adba>] ? __might_fault+0xa5/0xa7
[84723.422629] [<ffffffff81171139>] ? cp_new_stat+0x15d/0x174
[84723.423712] [<ffffffff8117c610>] do_vfs_ioctl+0x427/0x4e6
[84723.424801] [<ffffffff81171175>] ? SYSC_newfstat+0x25/0x2e
[84723.425968] [<ffffffff8118574d>] ? __fget_light+0x4d/0x71
[84723.427063] [<ffffffff8117c726>] SyS_ioctl+0x57/0x79
[84723.428138] [<ffffffff8147cd97>] entry_SYSCALL_64_fastpath+0x12/0x6f
Consider the following logical and physical file layout:
logical: ... [ prealloc extent A ] [ prealloc extent B ] [ extent C ] ...
4K 8K 16K
physical: ... 12853248 12857344 1103101952 ...
(= 12853248 + 4K)
Extents A and B are physically adjacent. The following diagram shows a
sequence of events that lead to the deadlock when we attempt to do a
direct IO write against the file range [4K, 16K[ and a defrag is triggered
simultaneously.
CPU 1 CPU 2
btrfs_direct_IO()
btrfs_get_blocks_direct()
creates ordered extent A, covering
the 4k prealloc extent A (range [4K, 8K[)
btrfs_defrag_file()
page_cache_sync_readahead([0K, 1M[)
btrfs_readpages()
extent_readpages()
locks all pages in the file
range [0K, 128K[ through calls
to add_to_page_cache_lru()
__do_contiguous_readpages()
finds ordered extent A
waits for it to complete
btrfs_get_blocks_direct() called again
lock_extent_direct(range [8K, 16K[)
finds a page in range [8K, 16K[ through
btrfs_page_exists_in_range()
invalidate_inode_pages2_range([8K, 16K[)
--> tries to lock pages that are already
locked by the task at CPU 2
--> our task, running __blockdev_direct_IO(),
hangs waiting to lock the pages and the
submit bio callback, btrfs_submit_direct(),
ends up never being called, resulting in the
ordered extent A never completing (because a
corresponding bio is never submitted) and
CPU 2 will wait for it forever while holding
the pages locked
---> deadlock!
Fix this by removing the page invalidation approach when attempting to
lock the range for IO from the callback btrfs_get_blocks_direct() and
falling back buffered IO. This was a rare case anyway and well behaved
applications do not mix concurrent direct IO writes with buffered reads
anyway, being a concurrent defrag the only normal case that could lead
to the deadlock.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Commit 61de718fce ("Btrfs: fix memory corruption on failure to submit
bio for direct IO") fixed problems with the error handling code after we
fail to submit a bio for direct IO. However there were 2 problems that it
did not address when the failure is due to memory allocation failures for
direct IO writes:
1) We considered that there could be only one ordered extent for the whole
IO range, which is not always true, as we can have multiple;
2) It did not set the bit BTRFS_ORDERED_IO_DONE in the ordered extent,
which can make other tasks running btrfs_wait_logged_extents() hang
forever, since they wait for that bit to be set. The general assumption
is that regardless of an error, the BTRFS_ORDERED_IO_DONE is always set
and it precedes setting the bit BTRFS_ORDERED_COMPLETE.
Fix these issues by moving part of the btrfs_endio_direct_write() handler
into a new helper function and having that new helper function called when
we fail to allocate memory to submit the bio (and its private object) for
a direct IO write.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
When a transaction is aborted, or its commit fails before writing the new
superblock and calling btrfs_finish_extent_commit(), we leak reference
counts on the block groups attached to the transaction's delete_bgs list,
because btrfs_finish_extent_commit() is never called for those two cases.
Fix this by dropping their references at btrfs_put_transaction(), which
is called when transactions are aborted (by making the transaction kthread
commit the transaction) or if their commits fail.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
During the final phase of a device replace operation, I ran into a
transaction abort that resulted in the following trace:
[23919.655368] WARNING: CPU: 10 PID: 30175 at fs/btrfs/extent-tree.c:9843 btrfs_create_pending_block_groups+0x15e/0x1ab [btrfs]()
[23919.664742] BTRFS: Transaction aborted (error -2)
[23919.665749] Modules linked in: btrfs crc32c_generic xor raid6_pq nfsd auth_rpcgss oid_registry nfs_acl nfs lockd grace fscache sunrpc loop fuse parport_pc i2c_piix4 parport psmouse acpi_cpufreq processor i2c_core evdev microcode pcspkr button serio_raw ext4 crc16 jbd2 mbcache sd_mod sg sr_mod cdrom virtio_scsi ata_generic ata_piix virtio_pci floppy virtio_ring libata e1000 virtio scsi_mod [last unloaded: btrfs]
[23919.679442] CPU: 10 PID: 30175 Comm: fsstress Not tainted 4.3.0-rc5-btrfs-next-17+ #1
[23919.682392] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.8.1-0-g4adadbd-20150316_085822-nilsson.home.kraxel.org 04/01/2014
[23919.689151] 0000000000000000 ffff8804020cbb50 ffffffff812566f4 ffff8804020cbb98
[23919.692604] ffff8804020cbb88 ffffffff8104d0a6 ffffffffa03eea69 ffff88041b678a48
[23919.694230] ffff88042ac38000 ffff88041b678930 00000000fffffffe ffff8804020cbbf0
[23919.696716] Call Trace:
[23919.698669] [<ffffffff812566f4>] dump_stack+0x4e/0x79
[23919.700597] [<ffffffff8104d0a6>] warn_slowpath_common+0x9f/0xb8
[23919.701958] [<ffffffffa03eea69>] ? btrfs_create_pending_block_groups+0x15e/0x1ab [btrfs]
[23919.703612] [<ffffffff8104d107>] warn_slowpath_fmt+0x48/0x50
[23919.705047] [<ffffffffa03eea69>] btrfs_create_pending_block_groups+0x15e/0x1ab [btrfs]
[23919.706967] [<ffffffffa0402097>] __btrfs_end_transaction+0x84/0x2dd [btrfs]
[23919.708611] [<ffffffffa0402300>] btrfs_end_transaction+0x10/0x12 [btrfs]
[23919.710099] [<ffffffffa03ef0b8>] btrfs_alloc_data_chunk_ondemand+0x121/0x28b [btrfs]
[23919.711970] [<ffffffffa0413025>] btrfs_fallocate+0x7d3/0xc6d [btrfs]
[23919.713602] [<ffffffff8108b78f>] ? lock_acquire+0x10d/0x194
[23919.714756] [<ffffffff81086dbc>] ? percpu_down_read+0x51/0x78
[23919.716155] [<ffffffff8116ef1d>] ? __sb_start_write+0x5f/0xb0
[23919.718918] [<ffffffff8116ef1d>] ? __sb_start_write+0x5f/0xb0
[23919.724170] [<ffffffff8116b579>] vfs_fallocate+0x170/0x1ff
[23919.725482] [<ffffffff8117c1d7>] ioctl_preallocate+0x89/0x9b
[23919.726790] [<ffffffff8117c5ef>] do_vfs_ioctl+0x406/0x4e6
[23919.728428] [<ffffffff81171175>] ? SYSC_newfstat+0x25/0x2e
[23919.729642] [<ffffffff8118574d>] ? __fget_light+0x4d/0x71
[23919.730782] [<ffffffff8117c726>] SyS_ioctl+0x57/0x79
[23919.731847] [<ffffffff8147cd97>] entry_SYSCALL_64_fastpath+0x12/0x6f
[23919.733330] ---[ end trace 166ef301a335832a ]---
This is due to a race between device replace and chunk allocation, which
the following diagram illustrates:
CPU 1 CPU 2
btrfs_dev_replace_finishing()
at this point
dev_replace->tgtdev->devid ==
BTRFS_DEV_REPLACE_DEVID (0ULL)
...
btrfs_start_transaction()
btrfs_commit_transaction()
btrfs_fallocate()
btrfs_alloc_data_chunk_ondemand()
btrfs_join_transaction()
--> starts a new transaction
do_chunk_alloc()
lock fs_info->chunk_mutex
btrfs_alloc_chunk()
--> creates extent map for
the new chunk with
em->bdev->map->stripes[i]->dev->devid
== X (X > 0)
--> extent map is added to
fs_info->mapping_tree
--> initial phase of bg A
allocation completes
unlock fs_info->chunk_mutex
lock fs_info->chunk_mutex
btrfs_dev_replace_update_device_in_mapping_tree()
--> iterates fs_info->mapping_tree and
replaces the device in every extent
map's map->stripes[] with
dev_replace->tgtdev, which still has
an id of 0ULL (BTRFS_DEV_REPLACE_DEVID)
btrfs_end_transaction()
btrfs_create_pending_block_groups()
--> starts final phase of
bg A creation (update device,
extent, and chunk trees, etc)
btrfs_finish_chunk_alloc()
btrfs_update_device()
--> attempts to update a device
item with ID == 0ULL
(BTRFS_DEV_REPLACE_DEVID)
which is the current ID of
bg A's
em->bdev->map->stripes[i]->dev->devid
--> doesn't find such item
returns -ENOENT
--> the device id should have been X
and not 0ULL
got -ENOENT from
btrfs_finish_chunk_alloc()
and aborts current transaction
finishes setting up the target device,
namely it sets tgtdev->devid to the value
of srcdev->devid, which is X (and X > 0)
frees the srcdev
unlock fs_info->chunk_mutex
So fix this by taking the device list mutex when processing the chunk's
extent map stripes to update the device items. This avoids getting the
wrong device id and use-after-free problems if the task finishing a
chunk allocation grabs the replaced device, which is freed while the
dev replace task is holding the device list mutex.
This happened while running fstest btrfs/071.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
prepare_pages() may end up calling prepare_uptodate_page() twice if our
write only spans a single page. But if the first call returns an error,
our page will be unlocked and its not safe to call it again.
This bug goes all the way back to 2011, and it's not something commonly
hit.
While we're here, add a more explicit check for the page being truncated
away. The bare lock_page() alone is protected only by good thoughts and
i_mutex, which we're sure to regret eventually.
Reported-by: Dave Jones <dsj@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
Dave Jones found a warning from kasan in setup_cluster_bitmaps()
==================================================================
BUG: KASAN: stack-out-of-bounds in setup_cluster_bitmap+0xc4/0x5a0 at
addr ffff88039bef6828
Read of size 8 by task nfsd/1009
page:ffffea000e6fbd80 count:0 mapcount:0 mapping: (null)
index:0x0
flags: 0x8000000000000000()
page dumped because: kasan: bad access detected
CPU: 1 PID: 1009 Comm: nfsd Tainted: G W
4.4.0-rc3-backup-debug+ #1
ffff880065647b50 000000006bb712c2 ffff88039bef6640 ffffffffa680a43e
0000004559c00000 ffff88039bef66c8 ffffffffa62638d1 ffffffffa61121c0
ffff8803a5769de8 0000000000000296 ffff8803a5769df0 0000000000046280
Call Trace:
[<ffffffffa680a43e>] dump_stack+0x4b/0x6d
[<ffffffffa62638d1>] kasan_report_error+0x501/0x520
[<ffffffffa61121c0>] ? debug_show_all_locks+0x1e0/0x1e0
[<ffffffffa6263948>] kasan_report+0x58/0x60
[<ffffffffa6814b00>] ? rb_last+0x10/0x40
[<ffffffffa66f8af4>] ? setup_cluster_bitmap+0xc4/0x5a0
[<ffffffffa6262ead>] __asan_load8+0x5d/0x70
[<ffffffffa66f8af4>] setup_cluster_bitmap+0xc4/0x5a0
[<ffffffffa66f675a>] ? setup_cluster_no_bitmap+0x6a/0x400
[<ffffffffa66fcd16>] btrfs_find_space_cluster+0x4b6/0x640
[<ffffffffa66fc860>] ? btrfs_alloc_from_cluster+0x4e0/0x4e0
[<ffffffffa66fc36e>] ? btrfs_return_cluster_to_free_space+0x9e/0xb0
[<ffffffffa702dc37>] ? _raw_spin_unlock+0x27/0x40
[<ffffffffa666a1a1>] find_free_extent+0xba1/0x1520
Andrey noticed this was because we were doing list_first_entry on a list
that might be empty. Rework the tests a bit so we don't do that.
Signed-off-by: Chris Mason <clm@fb.com>
Reprorted-by: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Reported-by: Dave Jones <dsj@fb.com>
Jan Stancek reported that I wrecked things for him by fixing things for
Vladimir :/
His report was due to an UNINTERRUPTIBLE wait getting -EINTR, which
should not be possible, however my previous patch made this possible by
unconditionally checking signal_pending().
We cannot use current->state as was done previously, because the
instruction after the store to that variable it can be changed. We must
instead pass the initial state along and use that.
Fixes: 68985633bc ("sched/wait: Fix signal handling in bit wait helpers")
Reported-by: Jan Stancek <jstancek@redhat.com>
Reported-by: Chris Mason <clm@fb.com>
Tested-by: Jan Stancek <jstancek@redhat.com>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com>
Tested-by: Chris Mason <clm@fb.com>
Reviewed-by: Paul Turner <pjt@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: tglx@linutronix.de
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: hpa@zytor.com
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Merge misc fixes from Andrew Morton:
"17 fixes"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
MIPS: fix DMA contiguous allocation
sh64: fix __NR_fgetxattr
ocfs2: fix SGID not inherited issue
mm/oom_kill.c: avoid attempting to kill init sharing same memory
drivers/base/memory.c: prohibit offlining of memory blocks with missing sections
tmpfs: fix shmem_evict_inode() warnings on i_blocks
mm/hugetlb.c: fix resv map memory leak for placeholder entries
mm: hugetlb: call huge_pte_alloc() only if ptep is null
kernel: remove stop_machine() Kconfig dependency
mm: kmemleak: mark kmemleak_init prototype as __init
mm: fix kerneldoc on mem_cgroup_replace_page
osd fs: __r4w_get_page rely on PageUptodate for uptodate
MAINTAINERS: make Vladimir co-maintainer of the memory controller
mm, vmstat: allow WQ concurrency to discover memory reclaim doesn't make any progress
mm: fix swapped Movable and Reclaimable in /proc/pagetypeinfo
memcg: fix memory.high target
mm: hugetlb: fix hugepage memory leak caused by wrong reserve count
Pull block layer fixes from Jens Axboe:
"A set of fixes for the current series. This contains:
- A bunch of fixes for lightnvm, should be the last round for this
series. From Matias and Wenwei.
- A writeback detach inode fix from Ilya, also marked for stable.
- A block (though it says SCSI) fix for an OOPS in SCSI runtime power
management.
- Module init error path fixes for null_blk from Minfei"
* 'for-linus' of git://git.kernel.dk/linux-block:
null_blk: Fix error path in module initialization
lightnvm: do not compile in debugging by default
lightnvm: prevent gennvm module unload on use
lightnvm: fix media mgr registration
lightnvm: replace req queue with nvmdev for lld
lightnvm: comments on constants
lightnvm: check mm before use
lightnvm: refactor spin_unlock in gennvm_get_blk
lightnvm: put blks when luns configure failed
lightnvm: use flags in rrpc_get_blk
block: detach bdev inode from its wb in __blkdev_put()
SCSI: Fix NULL pointer dereference in runtime PM
Commit 8f1eb48758 ("ocfs2: fix umask ignored issue") introduced an
issue, SGID of sub dir was not inherited from its parents dir. It is
because SGID is set into "inode->i_mode" in ocfs2_get_init_inode(), but
is overwritten by "mode" which don't have SGID set later.
Fixes: 8f1eb48758 ("ocfs2: fix umask ignored issue")
Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Acked-by: Srinivas Eeda <srinivas.eeda@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 42cb14b110 ("mm: migrate dirty page without
clear_page_dirty_for_io etc") simplified the migration of a PageDirty
pagecache page: one stat needs moving from zone to zone and that's about
all.
It's convenient and safest for it to shift the PageDirty bit from old
page to new, just before updating the zone stats: before copying data
and marking the new PageUptodate. This is all done while both pages are
isolated and locked, just as before; and just as before, there's a
moment when the new page is visible in the radix_tree, but not yet
PageUptodate. What's new is that it may now be briefly visible as
PageDirty before it is PageUptodate.
When I scoured the tree to see if this could cause a problem anywhere,
the only places I found were in two similar functions __r4w_get_page():
which look up a page with find_get_page() (not using page lock), then
claim it's uptodate if it's PageDirty or PageWriteback or PageUptodate.
I'm not sure whether that was right before, but now it might be wrong
(on rare occasions): only claim the page is uptodate if PageUptodate.
Or perhaps the page in question could never be migratable anyway?
Signed-off-by: Hugh Dickins <hughd@google.com>
Tested-by: Boaz Harrosh <ooo@electrozaur.com>
Cc: Benny Halevy <bhalevy@panasas.com>
Cc: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When an inconsistent space cache is detected during loading we log a
warning that users frequently mistake as instruction to invalidate the
cache manually, even though this is not required. Fix the message to
indicate that the cache will be rebuilt automatically.
Signed-off-by: Holger Hoffstätte <holger.hoffstaette@googlemail.com>
Acked-by: Filipe Manana <fdmanana@suse.com>
If we fail to allocate a new data chunk, we were jumping to the error path
without release the transaction handle we got before. Fix this by always
releasing it before doing the jump.
Fixes: 2c9fe83552 ("btrfs: Fix lost-data-profile caused by balance bg")
Signed-off-by: Filipe Manana <fdmanana@suse.com>
As of my previous change titled "Btrfs: fix scrub preventing unused block
groups from being deleted", the following warning at
extent-tree.c:btrfs_delete_unused_bgs() can be hit when we mount the a
filesysten with "-o discard":
10263 void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
10264 {
(...)
10405 if (trimming) {
10406 WARN_ON(!list_empty(&block_group->bg_list));
10407 spin_lock(&trans->transaction->deleted_bgs_lock);
10408 list_move(&block_group->bg_list,
10409 &trans->transaction->deleted_bgs);
10410 spin_unlock(&trans->transaction->deleted_bgs_lock);
10411 btrfs_get_block_group(block_group);
10412 }
(...)
This happens because scrub can now add back the block group to the list of
unused block groups (fs_info->unused_bgs). This is dangerous because we
are moving the block group from the unused block groups list to the list
of deleted block groups without holding the lock that protects the source
list (fs_info->unused_bgs_lock).
The following diagram illustrates how this happens:
CPU 1 CPU 2
cleaner_kthread()
btrfs_delete_unused_bgs()
sees bg X in list
fs_info->unused_bgs
deletes bg X from list
fs_info->unused_bgs
scrub_enumerate_chunks()
searches device tree using
its commit root
finds device extent for
block group X
gets block group X from the tree
fs_info->block_group_cache_tree
(via btrfs_lookup_block_group())
sets bg X to RO (again)
scrub_chunk(bg X)
sets bg X back to RW mode
adds bg X to the list
fs_info->unused_bgs again,
since it's still unused and
currently not in that list
sets bg X to RO mode
btrfs_remove_chunk(bg X)
--> discard is enabled and bg X
is in the fs_info->unused_bgs
list again so the warning is
triggered
--> we move it from that list into
the transaction's delete_bgs
list, but we can have another
task currently manipulating
the first list (fs_info->unused_bgs)
Fix this by using the same lock (fs_info->unused_bgs_lock) to protect both
the list of unused block groups and the list of deleted block groups. This
makes it safe and there's not much worry for more lock contention, as this
lock is seldom used and only the cleaner kthread adds elements to the list
of deleted block groups. The warning goes away too, as this was previously
an impossible case (and would have been better a BUG_ON/ASSERT) but it's
not impossible anymore.
Reproduced with fstest btrfs/073 (using MOUNT_OPTIONS="-o discard").
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Pull vfs fixes from Al Viro:
"A couple of fixes, both -stable fodder (9p one all way back to 2.6.32,
dio - to all branches where "Fix negative return from dio read beyond
eof" will end up it; it's a fixup to commit marked for -stable)"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
fix the regression from "direct-io: Fix negative return from dio read beyond eof"
9p: ->evict_inode() should kick out ->i_data, not ->i_mapping
Sure, it's better to bail out of past-the-eof read and return 0 than return
a bogus negative value on such. Only we'd better make sure we are bailing out
with 0 and not -ENOMEM...
Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
For block devices the pagecache is associated with the inode
on bdevfs, not with the aliasing ones on the mountable filesystems.
The latter have its own ->i_data empty and ->i_mapping pointing
to the (unique per major/minor) bdevfs inode. That guarantees
cache coherence between all block device inodes with the same
device number.
Eviction of an alias inode has no business trying to evict the
pages belonging to bdevfs one; moreover, ->i_mapping is only
safe to access when the thing is opened. At the time of
->evict_inode() the victim is definitely *not* opened. We are
about to kill the address space embedded into struct inode
(inode->i_data) and that's what we need to empty of any pages.
9p instance tries to empty inode->i_mapping instead, which is
both unsafe and bogus - if we have several device nodes with
the same device number in different places, closing one of them
should not try to empty the (shared) page cache.
Fortunately, other instances in the tree are OK; they are
evicting from &inode->i_data instead, as 9p one should.
Cc: stable@vger.kernel.org # v2.6.32+, ones prior to 2.6.36 need only half of that
Reported-by: "Suzuki K. Poulose" <Suzuki.Poulose@arm.com>
Tested-by: "Suzuki K. Poulose" <Suzuki.Poulose@arm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
The NFSv4.1 callback channel is currently broken because the receive
message will keep shrinking because the backchannel receive buffer size
never gets reset.
The easiest solution to this problem is instead of changing the receive
buffer, to rather adjust the copied request.
Fixes: 38b7631fbe ("nfs4: limit callback decoding to received bytes")
Cc: Benjamin Coddington <bcodding@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
some endian conversion problems with ext4 encryption, potential memory
leaks after truncate in data=journal mode, and an ocfs2 regression
caused by a jbd2 performance improvement.
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Merge tag 'ext4_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
Pull ext4 fixes from Ted Ts'o:
"Ext4 bug fixes for v4.4, including fixes for post-2038 time encodings,
some endian conversion problems with ext4 encryption, potential memory
leaks after truncate in data=journal mode, and an ocfs2 regression
caused by a jbd2 performance improvement"
* tag 'ext4_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
jbd2: fix null committed data return in undo_access
ext4: add "static" to ext4_seq_##name##_fops struct
ext4: fix an endianness bug in ext4_encrypted_follow_link()
ext4: fix an endianness bug in ext4_encrypted_zeroout()
jbd2: Fix unreclaimed pages after truncate in data=journal mode
ext4: Fix handling of extended tv_sec
Does not return any errors, nor anything from the callgraph. There's a
BUG_ON but it's a sanity check and not an error condition we could
recover from.
Signed-off-by: David Sterba <dsterba@suse.com>
Does not return any errors, nor anything from the callgraph. There's a
BUG_ON but it's a sanity check and not an error condition we could
recover from.
Signed-off-by: David Sterba <dsterba@suse.com>
Does not return any errors, nor anything from the callgraph. There's a
BUG_ON but it's a sanity check and not an error condition we could
recover from.
Signed-off-by: David Sterba <dsterba@suse.com>
Does not return any errors, nor anything from the callgraph. The branch
in end_bio_extent_writepage has been skipped since
5fd0204355 ("Btrfs: finish ordered extents in their own thread").
Signed-off-by: David Sterba <dsterba@suse.com>
