We've had some users hitting what used to be a BUG() in
shink_dcache_for_umount() but is now a printk:
BUG: Dentry ffff880066676000{i=20007,n=foobar} still in use (1) [unmount of nfs4 0:39]
VFS: Busy inodes after unmount of 0:39. Self-destruct in 5 seconds. Have a nice day...
The users don't like that very much.
I've spotted a dentry leak in the rare case where d_add_unique() finds an
alias on open and we swap the open context's dentry. I'm pretty sure we
shouldn't be doing another dget() there. I can reliably reproduce it with
this bit of bash:
mkdir -p /exports/dir{1,2}
exportfs -o rw localhost:/exports
mount -t nfs -ov4.1 localhost:/ /mnt/localhost
(sleep 2) > /mnt/localhost/dir1/foobar &
waitpid="$!"
sleep 1
mv /exports/dir{1,2}/foobar
echo A > /mnt/localhost/dir2/foobar
stat /mnt/localhost/dir1/foobar 2> /dev/null
mv /exports/dir{2,1}/foobar
echo A > /mnt/localhost/dir1/foobar
wait $waitpid
umount /mnt/localhost
Ben
Version 2:
This version corrects for the case where the dentry returned is the same as
the ctx->dentry, even though that is quite impossible. There's no need to
check if the returned dentry differs from ctx->dentry, so get rid of the
check.
8<---------------------------------------------------------------------
In the case where d_add_unique() finds an appropriate alias to use it will
have already incremented the reference count. An additional dget() to swap
the open context's dentry is unnecessary and will leak a reference.
Signed-off-by: Benjamin Coddington <bcodding@xxxxxxxxxx>
---
fs/nfs/nfs4proc.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 4bfc33a..1488159 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -2466,9 +2466,9 @@ static int _nfs4_open_and_get_state(struct nfs4_opendata *opendata,
dentry = d_add_unique(dentry, igrab(state->inode));
if (dentry == NULL) {
dentry = opendata->dentry;
- } else if (dentry != ctx->dentry) {
+ } else {
dput(ctx->dentry);
- ctx->dentry = dget(dentry);
+ ctx->dentry = dentry;
}
nfs_set_verifier(dentry,
nfs_save_change_attribute(d_inode(opendata->dir)));
--
1.7.1
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