fs: don't use igrab() while holding i_lock

Fix the incorrect use of igrab() inside the i_lock in NFS and Ceph‥

If we are already holding the i_lock, we have a reference to the
inode so we can safely use ihold() to gain an extra reference. This
avoids hangs due to lock recursion on the i_lock now that the
inode_lock is gone and igrab() uses the i_lock itself.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Cc: Ryan Mallon <ryan@bluewatersys.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index ab1bf5bb021f..a6804f704d9d 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -590,7 +590,8 @@ nfs4_get_open_state(struct inode *inode, struct nfs4_state_owner *owner)
                 state->owner = owner;
                 atomic_inc(&owner->so_count);
                 list_add(&state->inode_states, &nfsi->open_states);
-                state->inode = igrab(inode);
+                ihold(inode);
+                state->inode = inode;
                 spin_unlock(&inode->i_lock);
                 /* Note: The reclaim code dictates that we add stateless
                  * and read-only stateids to the end of the list */