On Monday, October 31, 2011 11:01:47 am Peter Holm wrote:
> Author: pho
> Date: Mon Oct 31 15:01:47 2011
> New Revision: 226967
> URL: http://svn.freebsd.org/changeset/base/226967
>
> Log:
> The kern_renameat() looks up the fvp using the DELETE flag, which causes
> the removal of the name cache entry for fvp.
>
> Reported by: Anton Yuzhaninov <citrin citrin ru>
> In collaboration with: kib
> MFC after: 1 week
>
> Modified:
> head/sys/ufs/ufs/ufs_vnops.c
So I ran into this at work recently, and even this fix applied I was still
seeing rename()'s that were seemingly not taking effect. After getting some
extra KTR traces, I figured out that the same purge needs to be applied to the
destination vnode. Specifically, the issue I ran into was that was renaming
'foo' to 'bar', but lookups for 'bar' were still returning the old file. The
reason was that a lookup after the namei(RENAME) of the destination while
ufs_rename() had its locks dropped was readding the name cache entry for
'bar', and then a cache_lookup() of 'bar' would return the old vnode as long
as that vnode was valid (e.g. if it had a link in another location, or other
processes had an open file descriptor for it). I'm currently testing the
patch below:
Index: ufs/ufs/ufs_vnops.c
===================================================================
--- ufs/ufs/ufs_vnops.c (revision 225498)
+++ ufs/ufs/ufs_vnops.c (working copy)
@@ -1519,8 +1539,15 @@
* ufs_lookup_ino() and then VFS_VGET(), another thread might do a
* normal lookup of the from name just before the VFS_VGET() call,
* causing the cache entry to be re-instantiated.
+ *
+ * The same issue also applies to tvp if it exists as
+ * otherwise we may have a stale name cache entry for the new
+ * name that references the old i-node if it has other links
+ * or open file descriptors.
*/
cache_purge(fvp);
+ if (tvp)
+ cache_purge(tvp);
unlockout:
vput(fdvp);
Index: fs/tmpfs/tmpfs_vnops.c
===================================================================
--- fs/tmpfs/tmpfs_vnops.c (revision 225498)
+++ fs/tmpfs/tmpfs_vnops.c (working copy)
@@ -1090,6 +1090,8 @@
tmpfs_free_dirent(VFS_TO_TMPFS(tvp->v_mount), de, TRUE);
}
cache_purge(fvp);
+ if (tvp != NULL)
+ cache_purge(tvp);
error = 0;
--
John Baldwin
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