unimore/kernel-hacking-2024-linux-steffo
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xfs: No need for inode number error injection in __xfs_dir3_data_check

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We call xfs_dir_ino_validate() for every dir entry in a directory
when doing validity checking of the directory. It calls
xfs_verify_dir_ino() then emits a corruption report if bad or does
error injection if good. It is extremely costly:

  43.27%  [kernel]  [k] xfs_dir3_leaf_check_int
  10.28%  [kernel]  [k] __xfs_dir3_data_check
   6.61%  [kernel]  [k] xfs_verify_dir_ino
   4.16%  [kernel]  [k] xfs_errortag_test
   4.00%  [kernel]  [k] memcpy
   3.48%  [kernel]  [k] xfs_dir_ino_validate

7% of the cpu usage in this directory traversal workload is
xfs_dir_ino_validate() doing absolutely nothing.

We don't need error injection to simulate a bad inode numbers in the
directory structure because we can do that by fuzzing the structure
on disk.

And we don't need a corruption report, because the
__xfs_dir3_data_check() will emit one if the inode number is bad.

So just call xfs_verify_dir_ino() directly here, and get rid of all
this unnecessary overhead:

  40.30%  [kernel]  [k] xfs_dir3_leaf_check_int
  10.98%  [kernel]  [k] __xfs_dir3_data_check
   8.10%  [kernel]  [k] xfs_verify_dir_ino
   4.42%  [kernel]  [k] memcpy
   2.22%  [kernel]  [k] xfs_dir2_data_get_ftype
   1.52%  [kernel]  [k] do_raw_spin_lock

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
This commit is contained in:
Dave Chinner 2021-03-22 09:52:05 -07:00 committed by Darrick J. Wong
parent ec08c14ba2
commit 39d3c0b596
1 changed files with 1 additions and 1 deletions
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2
fs/xfs/libxfs/xfs_dir2_data.c
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@ -218,7 +218,7 @@ __xfs_dir3_data_check(
*/
if (dep->namelen == 0)
return __this_address;
if (xfs_dir_ino_validate(mp, be64_to_cpu(dep->inumber)))
if (!xfs_verify_dir_ino(mp, be64_to_cpu(dep->inumber)))
return __this_address;
if (offset + xfs_dir2_data_entsize(mp, dep->namelen) > end)
return __this_address;