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NFS: Fix a potential race between umount and nfs_access_cache_shrinker()

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Thanks to Yawei Niu for spotting the race.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Trond Myklebust 2008-01-25 16:38:17 -05:00
parent e6f8107595
commit 6f23e3872c
1 changed files with 9 additions and 2 deletions
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11
fs/nfs/dir.c
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@ -1694,13 +1694,19 @@ int nfs_access_cache_shrinker(int nr_to_scan, gfp_t gfp_mask)
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 @@ remove_lru_entry:
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);