NFS: Fix a potential race between umount and nfs_access_cache_shrinker()
Thanks to Yawei Niu for spotting the race.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 5ca762d..476cb0f 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1694,13 +1694,19 @@
restart:
spin_lock(&nfs_access_lru_lock);
list_for_each_entry(nfsi, &nfs_access_lru_list, access_cache_inode_lru) {
+ struct rw_semaphore *s_umount;
struct inode *inode;
if (nr_to_scan-- == 0)
break;
- inode = igrab(&nfsi->vfs_inode);
- if (inode == NULL)
+ s_umount = &nfsi->vfs_inode.i_sb->s_umount;
+ if (!down_read_trylock(s_umount))
continue;
+ inode = igrab(&nfsi->vfs_inode);
+ if (inode == NULL) {
+ up_read(s_umount);
+ continue;
+ }
spin_lock(&inode->i_lock);
if (list_empty(&nfsi->access_cache_entry_lru))
goto remove_lru_entry;
@@ -1719,6 +1725,7 @@
spin_unlock(&inode->i_lock);
spin_unlock(&nfs_access_lru_lock);
iput(inode);
+ up_read(s_umount);
goto restart;
}
spin_unlock(&nfs_access_lru_lock);