Pull btrfs fix from David Sterba:
 "One more fix for a problem with snapshot of a newly created subvolume
  that can lead to inconsistent data under some circumstances. Kernel
  6.5 added a performance optimization to skip transaction commit for
  subvolume creation but this could end up with newer data on disk but
  not linked to other structures.

  The fix itself is an added condition, the rest of the patch is a
  parameter added to several functions"

* tag 'for-6.6-rc7-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: fix unwritten extent buffer after snapshotting a new subvolume

When creating a snapshot of a subvolume that was created in the current
transaction, we can end up not persisting a dirty extent buffer that is
referenced by the snapshot, resulting in IO errors due to checksum failures
when trying to read the extent buffer later from disk. A sequence of steps
that leads to this is the following:

1) At ioctl.c:create_subvol() we allocate an extent buffer, with logical
   address 36007936, for the leaf/root of a new subvolume that has an ID
   of 291. We mark the extent buffer as dirty, and at this point the
   subvolume tree has a single node/leaf which is also its root (level 0);

2) We no longer commit the transaction used to create the subvolume at
   create_subvol(). We used to, but that was recently removed in
   commit 1b53e51a4a8f ("btrfs: don't commit transaction for every subvol
   create");

3) The transaction used to create the subvolume has an ID of 33, so the
   extent buffer 36007936 has a generation of 33;

4) Several updates happen to subvolume 291 during transaction 33, several
   files created and its tree height changes from 0 to 1, so we end up with
   a new root at level 1 and the extent buffer 36007936 is now a leaf of
   that new root node, which is extent buffer 36048896.

   The commit root remains as 36007936, since we are still at transaction
   33;

5) Creation of a snapshot of subvolume 291, with an ID of 292, starts at
   ioctl.c:create_snapshot(). This triggers a commit of transaction 33 and
   we end up at transaction.c:create_pending_snapshot(), in the critical
   section of a transaction commit.

   There we COW the root of subvolume 291, which is extent buffer 36048896.
   The COW operation returns extent buffer 36048896, since there's no need
   to COW because the extent buffer was created in this transaction and it
   was not written yet.

   The we call btrfs_copy_root() against the root node 36048896. During
   this operation we allocate a new extent buffer to turn into the root
   node of the snapshot, copy the contents of the root node 36048896 into
   this snapshot root extent buffer, set the owner to 292 (the ID of the
   snapshot), etc, and then we call btrfs_inc_ref(). This will create a
   delayed reference for each leaf pointed by the root node with a
   reference root of 292 - this includes a reference for the leaf
   36007936.

   After that we set the bit BTRFS_ROOT_FORCE_COW in the root's state.

   Then we call btrfs_insert_dir_item(), to create the directory entry in
   in the tree of subvolume 291 that points to the snapshot. This ends up
   needing to modify leaf 36007936 to insert the respective directory
   items. Because the bit BTRFS_ROOT_FORCE_COW is set for the root's state,
   we need to COW the leaf. We end up at btrfs_force_cow_block() and then
   at update_ref_for_cow().

   At update_ref_for_cow() we call btrfs_block_can_be_shared() which
   returns false, despite the fact the leaf 36007936 is shared - the
   subvolume's root and the snapshot's root point to that leaf. The
   reason that it incorrectly returns false is because the commit root
   of the subvolume is extent buffer 36007936 - it was the initial root
   of the subvolume when we created it. So btrfs_block_can_be_shared()
   which has the following logic:

   int btrfs_block_can_be_shared(struct btrfs_root *root,
                                 struct extent_buffer *buf)
   {
       if (test_bit(BTRFS_ROOT_SHAREABLE, &root->state) &&
           buf != root->node && buf != root->commit_root &&
           (btrfs_header_generation(buf) <=
            btrfs_root_last_snapshot(&root->root_item) ||
            btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC)))
               return 1;

       return 0;
   }

   Returns false (0) since 'buf' (extent buffer 36007936) matches the
   root's commit root.

   As a result, at update_ref_for_cow(), we don't check for the number
   of references for extent buffer 36007936, we just assume it's not
   shared and therefore that it has only 1 reference, so we set the local
   variable 'refs' to 1.

   Later on, in the final if-else statement at update_ref_for_cow():

   static noinline int update_ref_for_cow(struct btrfs_trans_handle *trans,
                                          struct btrfs_root *root,
                                          struct extent_buffer *buf,
                                          struct extent_buffer *cow,
                                          int *last_ref)
   {
      (...)
      if (refs > 1) {
          (...)
      } else {
          (...)
          btrfs_clear_buffer_dirty(trans, buf);
          *last_ref = 1;
      }
   }

   So we mark the extent buffer 36007936 as not dirty, and as a result
   we don't write it to disk later in the transaction commit, despite the
   fact that the snapshot's root points to it.

   Attempting to access the leaf or dumping the tree for example shows
   that the extent buffer was not written:

   $ btrfs inspect-internal dump-tree -t 292 /dev/sdb
   btrfs-progs v6.2.2
   file tree key (292 ROOT_ITEM 33)
   node 36110336 level 1 items 2 free space 119 generation 33 owner 292
   node 36110336 flags 0x1(WRITTEN) backref revision 1
   checksum stored a8103e3e
   checksum calced a8103e3e
   fs uuid 90c9a46f-ae9f-4626-9aff-0cbf3e2e3a79
   chunk uuid e8c9c885-78f4-4d31-85fe-89e5f5fd4a07
           key (256 INODE_ITEM 0) block 36007936 gen 33
           key (257 EXTENT_DATA 0) block 36052992 gen 33
   checksum verify failed on 36007936 wanted 0x00000000 found 0x86005f29
   checksum verify failed on 36007936 wanted 0x00000000 found 0x86005f29
   total bytes 107374182400
   bytes used 38572032
   uuid 90c9a46f-ae9f-4626-9aff-0cbf3e2e3a79

   The respective on disk region is full of zeroes as the device was
   trimmed at mkfs time.

   Obviously 'btrfs check' also detects and complains about this:

   $ btrfs check /dev/sdb
   Opening filesystem to check...
   Checking filesystem on /dev/sdb
   UUID: 90c9a46f-ae9f-4626-9aff-0cbf3e2e3a79
   generation: 33 (33)
   [1/7] checking root items
   [2/7] checking extents
   checksum verify failed on 36007936 wanted 0x00000000 found 0x86005f29
   checksum verify failed on 36007936 wanted 0x00000000 found 0x86005f29
   checksum verify failed on 36007936 wanted 0x00000000 found 0x86005f29
   bad tree block 36007936, bytenr mismatch, want=36007936, have=0
   owner ref check failed [36007936 4096]
   ERROR: errors found in extent allocation tree or chunk allocation
   [3/7] checking free space tree
   [4/7] checking fs roots
   checksum verify failed on 36007936 wanted 0x00000000 found 0x86005f29
   checksum verify failed on 36007936 wanted 0x00000000 found 0x86005f29
   checksum verify failed on 36007936 wanted 0x00000000 found 0x86005f29
   bad tree block 36007936, bytenr mismatch, want=36007936, have=0
   The following tree block(s) is corrupted in tree 292:
        tree block bytenr: 36110336, level: 1, node key: (256, 1, 0)
   root 292 root dir 256 not found
   ERROR: errors found in fs roots
   found 38572032 bytes used, error(s) found
   total csum bytes: 16048
   total tree bytes: 1265664
   total fs tree bytes: 1118208
   total extent tree bytes: 65536
   btree space waste bytes: 562598
   file data blocks allocated: 65978368
    referenced 36569088

Fix this by updating btrfs_block_can_be_shared() to consider that an
extent buffer may be shared if it matches the commit root and if its
generation matches the current transaction's generation.

This can be reproduced with the following script:

   $ cat test.sh
   #!/bin/bash

   MNT=/mnt/sdi
   DEV=/dev/sdi

   # Use a filesystem with a 64K node size so that we have the same node
   # size on every machine regardless of its page size (on x86_64 default
   # node size is 16K due to the 4K page size, while on PPC it's 64K by
   # default). This way we can make sure we are able to create a btree for
   # the subvolume with a height of 2.
   mkfs.btrfs -f -n 64K $DEV
   mount $DEV $MNT

   btrfs subvolume create $MNT/subvol

   # Create a few empty files on the subvolume, this bumps its btree
   # height to 2 (root node at level 1 and 2 leaves).
   for ((i = 1; i <= 300; i++)); do
       echo -n > $MNT/subvol/file_$i
   done

   btrfs subvolume snapshot -r $MNT/subvol $MNT/subvol/snap

   umount $DEV

   btrfs check $DEV

Running it on a 6.5 kernel (or any 6.6-rc kernel at the moment):

   $ ./test.sh
   Create subvolume '/mnt/sdi/subvol'
   Create a readonly snapshot of '/mnt/sdi/subvol' in '/mnt/sdi/subvol/snap'
   Opening filesystem to check...
   Checking filesystem on /dev/sdi
   UUID: bbdde2ff-7d02-45ca-8a73-3c36f23755a1
   [1/7] checking root items
   [2/7] checking extents
   parent transid verify failed on 30539776 wanted 7 found 5
   parent transid verify failed on 30539776 wanted 7 found 5
   parent transid verify failed on 30539776 wanted 7 found 5
   Ignoring transid failure
   owner ref check failed [30539776 65536]
   ERROR: errors found in extent allocation tree or chunk allocation
   [3/7] checking free space tree
   [4/7] checking fs roots
   parent transid verify failed on 30539776 wanted 7 found 5
   Ignoring transid failure
   Wrong key of child node/leaf, wanted: (256, 1, 0), have: (2, 132, 0)
   Wrong generation of child node/leaf, wanted: 5, have: 7
   root 257 root dir 256 not found
   ERROR: errors found in fs roots
   found 917504 bytes used, error(s) found
   total csum bytes: 0
   total tree bytes: 851968
   total fs tree bytes: 393216
   total extent tree bytes: 65536
   btree space waste bytes: 736550
   file data blocks allocated: 0
    referenced 0

A test case for fstests will follow soon.

Fixes: 1b53e51a4a8f ("btrfs: don't commit transaction for every subvol create")
CC: stable@vger.kernel.org # 6.5+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Pull btrfs fix from David Sterba:
 "Fix a bug in chunk size decision that could lead to suboptimal
  placement and filling patterns"

* tag 'for-6.6-rc6-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: fix stripe length calculation for non-zoned data chunk allocation

Commit f6fca3917b4d "btrfs: store chunk size in space-info struct"
broke data chunk allocations on non-zoned multi-device filesystems when
using default chunk_size.  Commit 5da431b71d4b "btrfs: fix the max chunk
size and stripe length calculation" partially fixed that, and this patch
completes the fix for that case.

After commit f6fca3917b4d and 5da431b71d4b, the sequence of events for
a data chunk allocation on a non-zoned filesystem is:

        1.  btrfs_create_chunk calls init_alloc_chunk_ctl, which copies
        space_info->chunk_size (default 10 GiB) to ctl->max_stripe_len
        unmodified.  Before f6fca3917b4d, ctl->max_stripe_len value was
        1 GiB for non-zoned data chunks and not configurable.

        2.  btrfs_create_chunk calls gather_device_info which consumes
        and produces more fields of chunk_ctl.

        3.  gather_device_info multiplies ctl->max_stripe_len by
        ctl->dev_stripes (which is 1 in all cases except dup)
        and calls find_free_dev_extent with that number as num_bytes.

        4.  find_free_dev_extent locates the first dev_extent hole on
        a device which is at least as large as num_bytes.  With default
        max_chunk_size from f6fca3917b4d, it finds the first hole which is
        longer than 10 GiB, or the largest hole if that hole is shorter
        than 10 GiB.  This is different from the pre-f6fca3917b4d
        behavior, where num_bytes is 1 GiB, and find_free_dev_extent
        may choose a different hole.

        5.  gather_device_info repeats step 4 with all devices to find
        the first or largest dev_extent hole that can be allocated on
        each device.

        6.  gather_device_info sorts the device list by the hole size
        on each device, using total unallocated space on each device to
        break ties, then returns to btrfs_create_chunk with the list.

        7.  btrfs_create_chunk calls decide_stripe_size_regular.

        8.  decide_stripe_size_regular finds the largest stripe_len that
        fits across the first nr_devs device dev_extent holes that were
        found by gather_device_info (and satisfies other constraints
        on stripe_len that are not relevant here).

        9.  decide_stripe_size_regular caps the length of the stripe it
        computed at 1 GiB.  This cap appeared in 5da431b71d4b to correct
        one of the other regressions introduced in f6fca3917b4d.

        10.  btrfs_create_chunk creates a new chunk with the above
        computed size and number of devices.

At step 4, gather_device_info() has found a location where stripe up to
10 GiB in length could be allocated on several devices, and selected
which devices should have a dev_extent allocated on them, but at step
9, only 1 GiB of the space that was found on each device can be used.
This mismatch causes new suboptimal chunk allocation cases that did not
occur in pre-f6fca3917b4d kernels.

Consider a filesystem using raid1 profile with 3 devices.  After some
balances, device 1 has 10x 1 GiB unallocated space, while devices 2
and 3 have 1x 10 GiB unallocated space, i.e. the same total amount of
space, but distributed across different numbers of dev_extent holes.
For visualization, let's ignore all the chunks that were allocated before
this point, and focus on the remaining holes:

        Device 1:  [_] [_] [_] [_] [_] [_] [_] [_] [_] [_] (10x 1 GiB unallocated)
        Device 2:  [__________] (10 GiB contig unallocated)
        Device 3:  [__________] (10 GiB contig unallocated)

Before f6fca3917b4d, the allocator would fill these optimally by
allocating chunks with dev_extents on devices 1 and 2 ([12]), 1 and 3
([13]), or 2 and 3 ([23]):

        [after 0 chunk allocations]
        Device 1:  [_] [_] [_] [_] [_] [_] [_] [_] [_] [_] (10 GiB)
        Device 2:  [__________] (10 GiB)
        Device 3:  [__________] (10 GiB)

        [after 1 chunk allocation]
        Device 1:  [12] [_] [_] [_] [_] [_] [_] [_] [_] [_]
        Device 2:  [12] [_________] (9 GiB)
        Device 3:  [__________] (10 GiB)

        [after 2 chunk allocations]
        Device 1:  [12] [13] [_] [_] [_] [_] [_] [_] [_] [_] (8 GiB)
        Device 2:  [12] [_________] (9 GiB)
        Device 3:  [13] [_________] (9 GiB)

        [after 3 chunk allocations]
        Device 1:  [12] [13] [12] [_] [_] [_] [_] [_] [_] [_] (7 GiB)
        Device 2:  [12] [12] [________] (8 GiB)
        Device 3:  [13] [_________] (9 GiB)

        [...]

        [after 12 chunk allocations]
        Device 1:  [12] [13] [12] [13] [12] [13] [12] [13] [_] [_] (2 GiB)
        Device 2:  [12] [12] [23] [23] [12] [12] [23] [23] [__] (2 GiB)
        Device 3:  [13] [13] [23] [23] [13] [23] [13] [23] [__] (2 GiB)

        [after 13 chunk allocations]
        Device 1:  [12] [13] [12] [13] [12] [13] [12] [13] [12] [_] (1 GiB)
        Device 2:  [12] [12] [23] [23] [12] [12] [23] [23] [12] [_] (1 GiB)
        Device 3:  [13] [13] [23] [23] [13] [23] [13] [23] [__] (2 GiB)

        [after 14 chunk allocations]
        Device 1:  [12] [13] [12] [13] [12] [13] [12] [13] [12] [13] (full)
        Device 2:  [12] [12] [23] [23] [12] [12] [23] [23] [12] [_] (1 GiB)
        Device 3:  [13] [13] [23] [23] [13] [23] [13] [23] [13] [_] (1 GiB)

        [after 15 chunk allocations]
        Device 1:  [12] [13] [12] [13] [12] [13] [12] [13] [12] [13] (full)
        Device 2:  [12] [12] [23] [23] [12] [12] [23] [23] [12] [23] (full)
        Device 3:  [13] [13] [23] [23] [13] [23] [13] [23] [13] [23] (full)

This allocates all of the space with no waste.  The sorting function used
by gather_device_info considers free space holes above 1 GiB in length
to be equal to 1 GiB, so once find_free_dev_extent locates a sufficiently
long hole on each device, all the holes appear equal in the sort, and the
comparison falls back to sorting devices by total free space.  This keeps
usable space on each device equal so they can all be filled completely.

After f6fca3917b4d, the allocator prefers the devices with larger holes
over the devices with more free space, so it makes bad allocation choices:

        [after 1 chunk allocation]
        Device 1:  [_] [_] [_] [_] [_] [_] [_] [_] [_] [_] (10 GiB)
        Device 2:  [23] [_________] (9 GiB)
        Device 3:  [23] [_________] (9 GiB)

        [after 2 chunk allocations]
        Device 1:  [_] [_] [_] [_] [_] [_] [_] [_] [_] [_] (10 GiB)
        Device 2:  [23] [23] [________] (8 GiB)
        Device 3:  [23] [23] [________] (8 GiB)

        [after 3 chunk allocations]
        Device 1:  [_] [_] [_] [_] [_] [_] [_] [_] [_] [_] (10 GiB)
        Device 2:  [23] [23] [23] [_______] (7 GiB)
        Device 3:  [23] [23] [23] [_______] (7 GiB)

        [...]

        [after 9 chunk allocations]
        Device 1:  [_] [_] [_] [_] [_] [_] [_] [_] [_] [_] (10 GiB)
        Device 2:  [23] [23] [23] [23] [23] [23] [23] [23] [23] [_] (1 GiB)
        Device 3:  [23] [23] [23] [23] [23] [23] [23] [23] [23] [_] (1 GiB)

        [after 10 chunk allocations]
        Device 1:  [12] [_] [_] [_] [_] [_] [_] [_] [_] [_] (9 GiB)
        Device 2:  [23] [23] [23] [23] [23] [23] [23] [23] [12] (full)
        Device 3:  [23] [23] [23] [23] [23] [23] [23] [23] [_] (1 GiB)

        [after 11 chunk allocations]
        Device 1:  [12] [13] [_] [_] [_] [_] [_] [_] [_] [_] (8 GiB)
        Device 2:  [23] [23] [23] [23] [23] [23] [23] [23] [12] (full)
        Device 3:  [23] [23] [23] [23] [23] [23] [23] [23] [13] (full)

No further allocations are possible, with 8 GiB wasted (4 GiB of data
space).  The sort in gather_device_info now considers free space in
holes longer than 1 GiB to be distinct, so it will prefer devices 2 and
3 over device 1 until all but 1 GiB is allocated on devices 2 and 3.
At that point, with only 1 GiB unallocated on every device, the largest
hole length on each device is equal at 1 GiB, so the sort finally moves
to ordering the devices with the most free space, but by this time it
is too late to make use of the free space on device 1.

Note that it's possible to contrive a case where the pre-f6fca3917b4d
allocator fails the same way, but these cases generally have extensive
dev_extent fragmentation as a precondition (e.g. many holes of 768M
in length on one device, and few holes 1 GiB in length on the others).
With the regression in f6fca3917b4d, bad chunk allocation can occur even
under optimal conditions, when all dev_extent holes are exact multiples
of stripe_len in length, as in the example above.

Also note that post-f6fca3917b4d kernels do treat dev_extent holes
larger than 10 GiB as equal, so the bad behavior won't show up on a
freshly formatted filesystem; however, as the filesystem ages and fills
up, and holes ranging from 1 GiB to 10 GiB in size appear, the problem
can show up as a failure to balance after adding or removing devices,
or an unexpected shortfall in available space due to unequal allocation.

To fix the regression and make data chunk allocation work
again, set ctl->max_stripe_len back to the original SZ_1G, or
space_info->chunk_size if that's smaller (the latter can happen if the
user set space_info->chunk_size to less than 1 GiB via sysfs, or it's
a 32 MiB system chunk with a hardcoded chunk_size and stripe_len).

While researching the background of the earlier commits, I found that an
identical fix was already proposed at:

  https://lore.kernel.org/linux-btrfs/de83ac46-a4a3-88d3-85ce-255b7abc5249@gmx.com/

The previous review missed one detail:  ctl->max_stripe_len is used
before decide_stripe_size_regular() is called, when it is too late for
the changes in that function to have any effect.  ctl->max_stripe_len is
not used directly by decide_stripe_size_regular(), but the parameter
does heavily influence the per-device free space data presented to
the function.

Fixes: f6fca3917b4d ("btrfs: store chunk size in space-info struct")
CC: stable@vger.kernel.org # 6.1+
Link: https://lore.kernel.org/linux-btrfs/20231007051421.19657-1-ce3g8jdj@umail.furryterror.org/
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
Signed-off-by: David Sterba <dsterba@suse.com>

Pull btrfs fixes from David Sterba:
 "A revert of recent mount option parsing fix, this breaks mounts with
  security options.

  The second patch is a flexible array annotation"

* tag 'for-6.6-rc5-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: add __counted_by for struct btrfs_delayed_item and use struct_size()
  Revert "btrfs: reject unknown mount options early"

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time via CONFIG_UBSAN_BOUNDS (for
array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

While there, use struct_size() helper, instead of the open-coded
version, to calculate the size for the allocation of the whole
flexible structure, including of course, the flexible-array member.

This code was found with the help of Coccinelle, and audited and
fixed manually.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

This reverts commit 5f521494cc73520ffac18ede0758883b9aedd018.

The patch breaks mounts with security mount options like

  $ mount -o context=system_u:object_r:root_t:s0 /dev/sdX /mn
  mount: /mnt: wrong fs type, bad option, bad superblock on /dev/sdX, missing codepage or helper program, ...

We cannot reject all unknown options in btrfs_parse_subvol_options() as
intended, the security options can be present at this point and it's not
possible to enumerate them in a future proof way. This means unknown
mount options are silently accepted like before when the filesystem is
mounted with either -o subvol=/path or as followup mounts of the same
device.

Reported-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com
Signed-off-by: David Sterba <dsterba@suse.com>

Pull btrfs fixes from David Sterba:

 - reject unknown mount options

 - adjust transaction abort error message level

 - fix one more build warning with -Wmaybe-uninitialized

 - proper error handling in several COW-related cases

* tag 'for-6.6-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: error out when reallocating block for defrag using a stale transaction
  btrfs: error when COWing block from a root that is being deleted
  btrfs: error out when COWing block using a stale transaction
  btrfs: always print transaction aborted messages with an error level
  btrfs: reject unknown mount options early
  btrfs: fix some -Wmaybe-uninitialized warnings in ioctl.c

At btrfs_realloc_node() we have these checks to verify we are not using a
stale transaction (a past transaction with an unblocked state or higher),
and the only thing we do is to trigger two WARN_ON(). This however is a
critical problem, highly unexpected and if it happens it's most likely due
to a bug, so we should error out and turn the fs into error state so that
such issue is much more easily noticed if it's triggered.

The problem is critical because in btrfs_realloc_node() we COW tree blocks,
and using such stale transaction will lead to not persisting the extent
buffers used for the COW operations, as allocating tree block adds the
range of the respective extent buffers to the ->dirty_pages iotree of the
transaction, and a stale transaction, in the unlocked state or higher,
will not flush dirty extent buffers anymore, therefore resulting in not
persisting the tree block and resource leaks (not cleaning the dirty_pages
iotree for example).

So do the following changes:

1) Return -EUCLEAN if we find a stale transaction;

2) Turn the fs into error state, with error -EUCLEAN, so that no
   transaction can be committed, and generate a stack trace;

3) Combine both conditions into a single if statement, as both are related
   and have the same error message;

4) Mark the check as unlikely, since this is not expected to ever happen.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

At btrfs_cow_block() we check if the block being COWed belongs to a root
that is being deleted and if so we log an error message. However this is
an unexpected case and it indicates a bug somewhere, so we should return
an error and abort the transaction. So change this in the following ways:

1) Abort the transaction with -EUCLEAN, so that if the issue ever happens
   it can easily be noticed;

2) Change the logged message level from error to critical, and change the
   message itself to print the block's logical address and the ID of the
   root;

3) Return -EUCLEAN to the caller;

4) As this is an unexpected scenario, that should never happen, mark the
   check as unlikely, allowing the compiler to potentially generate better
   code.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>