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Subject[PATCH] fuse: fix occasional dentry leak when readdirplus is used
Date
In case d_lookup() returns a dentry with d_inode == NULL, the dentry is
not returned with dput(). This results in triggering a BUG() in
shrink_dcache_for_umount_subtree():

BUG: Dentry ...{i=0,n=...} still in use (1) [unmount of fuse fuse]

Reported-by: Justin Clift <jclift@redhat.com>
Signed-off-by: Niels de Vos <ndevos@redhat.com>

--
Reproducing the BUG() on kernels with fuse that support READDIRPLUS can
be done with the GlusterFS tests:
- http://www.gluster.org/community/documentation/index.php/Using_the_Gluster_Test_Framework

After some stressing of the VFS and fuse mountpoints, bug-860663.t will
hit the BUG(). It does not happen on running this test stand-alone.
---
fs/fuse/dir.c | 4 +++-
1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 0eda527..da67a15 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -1246,7 +1246,9 @@ static int fuse_direntplus_link(struct file *file,
if (err)
goto out;
dput(dentry);
- dentry = NULL;
+ } else if (dentry) {
+ /* this dentry does not have a d_inode, just drop it */
+ dput(dentry);
}

dentry = d_alloc(parent, &name);
--
1.7.1


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