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authorJan Kara <jack@suse.cz>2020-02-24 12:52:17 +0100
committerJan Kara <jack@suse.cz>2020-02-26 13:14:27 +0100
commitbc36dfffd5f3f19edcf85954d93eb0bc45875c37 (patch)
tree725b67fb30346bf312326d501eefbfff53a29c98 /fs
parentf8788d86ab28f61f7b46eb6be375f8a726783636 (diff)
ext2: Silence lockdep warning about reclaim under xattr_sem
Lockdep complains about a chain: sb_internal#2 --> &ei->xattr_sem#2 --> fs_reclaim and shrink_dentry_list -> ext2_evict_inode -> ext2_xattr_delete_inode -> down_write(ei->xattr_sem) creating a locking cycle in the reclaim path. This is however a false positive because when we are in ext2_evict_inode() we are the only holder of the inode reference and nobody else should touch xattr_sem of that inode. So we cannot ever block on acquiring the xattr_sem in the reclaim path. Silence the lockdep warning by using down_write_trylock() in ext2_xattr_delete_inode() to not create false locking dependency. Reported-by: "J. R. Okajima" <hooanon05g@gmail.com> Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com> Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'fs')
-rw-r--r--fs/ext2/xattr.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c
index 0456bc990b5e..9ad07c7ef0b3 100644
--- a/fs/ext2/xattr.c
+++ b/fs/ext2/xattr.c
@@ -790,7 +790,15 @@ ext2_xattr_delete_inode(struct inode *inode)
struct buffer_head *bh = NULL;
struct ext2_sb_info *sbi = EXT2_SB(inode->i_sb);
- down_write(&EXT2_I(inode)->xattr_sem);
+ /*
+ * We are the only ones holding inode reference. The xattr_sem should
+ * better be unlocked! We could as well just not acquire xattr_sem at
+ * all but this makes the code more futureproof. OTOH we need trylock
+ * here to avoid false-positive warning from lockdep about reclaim
+ * circular dependency.
+ */
+ if (WARN_ON_ONCE(!down_write_trylock(&EXT2_I(inode)->xattr_sem)))
+ return;
if (!EXT2_I(inode)->i_file_acl)
goto cleanup;