linux-ext4 - [PATCH 2/2] ext4: only check dquot_initialize

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Date:   Thu,  8 Jun 2023 10:18:05 -0400
From:   "Theodore Ts'o" <tytso@....edu>
To:     Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc:     bagasdotme@...il.com, nikolas.kraetzschmar@....com, jack@...e.cz,
        "Theodore Ts'o" <tytso@....edu>
Subject: [PATCH 2/2] ext4: only check dquot_initialize_needed() when debugging

ext4_xattr_block_set() relies on its caller to call dquot_initialize()
on the inode.  To assure that this has happened there are WARN_ON
checks.  Unfortunately, this is subject to false positives if there is
an antagonist thread which is flipping the file system at high rates
between r/o and rw.  So only do the check if EXT4_XATTR_DEBUG is
enabled.

Link: https://lore.kernel.org/r/20230608044056.GA1418535@mit.edu
Signed-off-by: Theodore Ts'o <tytso@....edu>
---
 fs/ext4/xattr.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 13d7f17a9c8c..321e3a888c20 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -2056,8 +2056,9 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
 			else {
 				u32 ref;
 
+#ifdef EXT4_XATTR_DEBUG
 				WARN_ON_ONCE(dquot_initialize_needed(inode));
-
+#endif
 				/* The old block is released after updating
 				   the inode. */
 				error = dquot_alloc_block(inode,
@@ -2120,8 +2121,9 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
 			/* We need to allocate a new block */
 			ext4_fsblk_t goal, block;
 
+#ifdef EXT4_XATTR_DEBUG
 			WARN_ON_ONCE(dquot_initialize_needed(inode));
-
+#endif
 			goal = ext4_group_first_block_no(sb,
 						EXT4_I(inode)->i_block_group);
 			block = ext4_new_meta_blocks(handle, inode, goal, 0,
-- 
2.31.0