linux.git/fs/btrfs/relocation.c, branch v5.11

btrfs: reloc: fix wrong file extent type check to avoid false ENOENT

2021-01-07T16:25:05+00:00

[BUG]
There are several bug reports about recent kernel unable to relocate
certain data block groups.

Sometimes the error just goes away, but there is one reporter who can
reproduce it reliably.

The dmesg would look like:

  [438.260483] BTRFS info (device dm-10): balance: start -dvrange=34625344765952..34625344765953
  [438.269018] BTRFS info (device dm-10): relocating block group 34625344765952 flags data|raid1
  [450.439609] BTRFS info (device dm-10): found 167 extents, stage: move data extents
  [463.501781] BTRFS info (device dm-10): balance: ended with status: -2

[CAUSE]
The ENOENT error is returned from the following call chain:

  add_data_references()
  |- delete_v1_space_cache();
     |- if (!found)
	   return -ENOENT;

The variable @found is set to true if we find a data extent whose
disk bytenr matches parameter @data_bytes.

With extra debugging, the offending tree block looks like this:

  leaf bytenr = 42676709441536, data_bytenr = 34626327621632

                ctime 1567904822.739884119 (2019-09-08 03:07:02)
                mtime 0.0 (1970-01-01 01:00:00)
                otime 0.0 (1970-01-01 01:00:00)
        item 27 key (51933 EXTENT_DATA 0) itemoff 9854 itemsize 53
                generation 1517381 type 2 (prealloc)
                prealloc data disk byte 34626327621632 nr 262144 <<<
                prealloc data offset 0 nr 262144
        item 28 key (52262 ROOT_ITEM 0) itemoff 9415 itemsize 439
                generation 2618893 root_dirid 256 bytenr 42677048360960 level 3 refs 1
                lastsnap 2618893 byte_limit 0 bytes_used 5557338112 flags 0x0(none)
                uuid d0d4361f-d231-6d40-8901-fe506e4b2b53

Although item 27 has disk bytenr 34626327621632, which matches the
data_bytenr, its type is prealloc, not reg.
This makes the existing code skip that item, and return ENOENT.

[FIX]
The code is modified in commit 19b546d7a1b2 ("btrfs: relocation: Use
btrfs_find_all_leafs to locate data extent parent tree leaves"), before
that commit, we use something like

  "if (type == BTRFS_FILE_EXTENT_INLINE) continue;"

But in that offending commit, we use (type == BTRFS_FILE_EXTENT_REG),
ignoring BTRFS_FILE_EXTENT_PREALLOC.

Fix it by also checking BTRFS_FILE_EXTENT_PREALLOC.

Reported-by: Stéphane Lesimple 
Link: https://lore.kernel.org/linux-btrfs/505cabfa88575ed6dbe7cb922d8914fb@lesimple.fr
Fixes: 19b546d7a1b2 ("btrfs: relocation: Use btrfs_find_all_leafs to locate data extent parent tree leaves")
CC: stable@vger.kernel.org # 5.6+
Tested-By: Stéphane Lesimple 
Reviewed-by: Su Yue 
Signed-off-by: Qu Wenruo 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: remove inode number cache feature

2020-12-09T18:16:05+00:00

It's been deprecated since commit b547a88ea577 ("btrfs: start
deprecation of mount option inode_cache") which enumerates the reasons.

A filesystem that uses the feature (mount -o inode_cache) tracks the
inode numbers in bitmaps, that data stay on the filesystem after this
patch. The size is roughly 5MiB for 1M inodes [1], which is considered
small enough to be left there. Removal of the change can be implemented
in btrfs-progs if needed.

[1] https://lore.kernel.org/linux-btrfs/20201127145836.GZ6430@twin.jikos.cz/

Signed-off-by: Nikolay Borisov 
Reviewed-by: David Sterba 
[ update changelog ]
Signed-off-by: David Sterba

btrfs: remove err variable from do_relocation

2020-12-08T14:54:15+00:00

It simply gets assigned to 'ret' in case of errors. The flow of the
while loop is not changed by this commit since the few call sites
that 'goto next' will simply break from the loop.

Signed-off-by: Nikolay Borisov 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: eliminate err variable from merge_reloc_root

2020-12-08T14:54:15+00:00

In most cases when an error is returned from a function 'ret' is simply
assigned to 'err'. There is only one case where walk_up_reloc_tree can
return a positive value - in this case the code breaks from the loop and
ret is going to get its return value from btrfs_cow_block - either 0 or
negative. This retains the old logic of how 'err' used to be set at
this call site.

Signed-off-by: Nikolay Borisov 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: pass the owner_root and level to alloc_extent_buffer

2020-12-08T14:54:07+00:00

Now that we've plumbed all of the callers to have the owner root and the
level, plumb it down into alloc_extent_buffer().

Reviewed-by: Filipe Manana 
Signed-off-by: Josef Bacik 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: pass root owner to read_tree_block

2020-12-08T14:54:07+00:00

In order to properly set the lockdep class of a newly allocated block we
need to know the owner of the block.  For non-refcounted trees this is
straightforward, we always know in advance what tree we're reading from.
For refcounted trees we don't necessarily know, however all refcounted
trees share the same lockdep class name, tree-.

Fix all the callers of read_tree_block() to pass in the root objectid
we're using.  In places like relocation and backref we could probably
unconditionally use 0, but just in case use the root when we have it,
otherwise use 0 in the cases we don't have the root as it's going to be
a refcounted tree anyway.

This is a preparation patch for further changes.

Reviewed-by: Filipe Manana 
Signed-off-by: Josef Bacik 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: use btrfs_read_node_slot in replace_path

2020-12-08T14:54:06+00:00

We're open-coding btrfs_read_node_slot() here, replace with the helper.

Reviewed-by: Filipe Manana 
Signed-off-by: Josef Bacik 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: use btrfs_read_node_slot in do_relocation

2020-12-08T14:54:06+00:00

We're open coding btrfs_read_node_slot in do_relocation, replace this
with the proper helper.

Reviewed-by: Filipe Manana 
Signed-off-by: Josef Bacik 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: use btrfs_read_node_slot in walk_down_reloc_tree

2020-12-08T14:54:06+00:00

We do not need to call read_tree_block() here, simply use the
btrfs_read_node_slot helper.

Reviewed-by: Filipe Manana 
Signed-off-by: Josef Bacik 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: cleanup extent buffer readahead

2020-12-08T14:54:05+00:00

We're going to pass around more information when we allocate extent
buffers, in order to make that cleaner how we do readahead.  Most of the
callers have the parent node that we're getting our blockptr from, with
the sole exception of relocation which simply has the bytenr it wants to
read.

Add a helper that takes the current arguments that we need (bytenr and
gen), and add another helper for simply reading the slot out of a node.
In followup patches the helper that takes all the extra arguments will
be expanded, and the simpler helper won't need to have it's arguments
adjusted.

Reviewed-by: Filipe Manana 
Signed-off-by: Josef Bacik 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba