linux-kernel - [PATCH] xfs: No need for inode number error injection in __xfs_dir3_data

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Message-Id: <20240924222955.346976-2-kuntal.nayak@broadcom.com>
Date: Tue, 24 Sep 2024 15:29:54 -0700
From: Kuntal Nayak <kuntal.nayak@...adcom.com>
To: leah.rumancik@...il.com,
	jwong@...nel.org,
	linux-xfs@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	gregkh@...uxfoundation.org
Cc: ajay.kaher@...adcom.com,
	alexey.makhalov@...adcom.com,
	vasavi.sirnapalli@...adcom.com,
	Dave Chinner <dchinner@...hat.com>,
	"Darrick J . Wong" <djwong@...nel.org>,
	Christoph Hellwig <hch@....de>,
	Kuntal Nayak <kuntal.nayak@...adcom.com>
Subject: [PATCH] xfs: No need for inode number error injection in __xfs_dir3_data_check

From: Dave Chinner <dchinner@...hat.com>

[ Upstream commit 39d3c0b5968b5421922e2fc939b6d6158df8ac1c ]

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@...hat.com>
Reviewed-by: Darrick J. Wong <djwong@...nel.org>
Reviewed-by: Christoph Hellwig <hch@....de>
Signed-off-by: Darrick J. Wong <djwong@...nel.org>
Signed-off-by: Kuntal Nayak <kuntal.nayak@...adcom.com>
---
 fs/xfs/libxfs/xfs_dir2_data.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/xfs/libxfs/xfs_dir2_data.c b/fs/xfs/libxfs/xfs_dir2_data.c
index 375b3edb2..e67fa086f 100644
--- a/fs/xfs/libxfs/xfs_dir2_data.c
+++ b/fs/xfs/libxfs/xfs_dir2_data.c
@@ -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;
-- 
2.39.3