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afs: Only update d_fsdata if different in afs_d_revalidate() 

In the in-kernel afs filesystem, d_fsdata is set with the data version of
the parent directory.  afs_d_revalidate() will update this to the current
directory version, but it shouldn't do this if it the value it read from
d_fsdata is the same as no lock is held and cmpxchg() is not used.

Fix the code to only change the value if it is different from the current
directory version.

Fixes: 260a980317 ("[AFS]: Add "directory write" support.")
Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells 2019-07-30 14:38:51 +01:00
parent 37c0bbb332
commit 5dc84855b0
1 changed files with 2 additions and 1 deletions
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3
fs/afs/dir.c
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@ -1017,7 +1017,7 @@ static int afs_d_revalidate(struct dentry *dentry, unsigned int flags)
dir_version = (long)dir->status.data_version;
de_version = (long)dentry->d_fsdata;
if (de_version == dir_version)
goto out_valid;
goto out_valid_noupdate;
dir_version = (long)dir->invalid_before;
if (de_version - dir_version >= 0)
@ -1081,6 +1081,7 @@ static int afs_d_revalidate(struct dentry *dentry, unsigned int flags)
out_valid:
dentry->d_fsdata = (void *)dir_version;
out_valid_noupdate:
dput(parent);
key_put(key);
_leave(" = 1 [valid]");