GFS2: filesystem hang caused by incorrect lock order

This patch fixes a deadlock in GFS2 where two processes are trying
to reclaim an unlinked dinode:
One holds the inode glock and calls gfs2_lookup_by_inum trying to look
up the inode, which it can't, due to I_FREEING.  The other has set
I_FREEING from vfs and is at the beginning of gfs2_delete_inode
waiting for the glock, which is held by the first.  The solution is to
add a new non_block parameter to the gfs2_iget function that causes it
to return -ENOENT if the inode is being freed.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index 5b2cb8132f6..b9f28e66dad 100644
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -1327,7 +1327,8 @@ static void gfs2_evict_inode(struct inode *inode)
         if (inode->i_nlink || (sb->s_flags & MS_RDONLY))
                 goto out;
 
-        error = gfs2_glock_nq_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &gh);
+        /* Must not read inode block until block type has been verified */
+        error = gfs2_glock_nq_init(ip->i_gl, LM_ST_EXCLUSIVE, GL_SKIP, &gh);
         if (unlikely(error)) {
                 gfs2_glock_dq_uninit(&ip->i_iopen_gh);
                 goto out;
@@ -1337,6 +1338,12 @@ static void gfs2_evict_inode(struct inode *inode)
         if (error)
                 goto out_truncate;
 
+        if (test_bit(GIF_INVALID, &ip->i_flags)) {
+                error = gfs2_inode_refresh(ip);
+                if (error)
+                        goto out_truncate;
+        }
+
         ip->i_iopen_gh.gh_flags |= GL_NOCACHE;
         gfs2_glock_dq_wait(&ip->i_iopen_gh);
         gfs2_holder_reinit(LM_ST_EXCLUSIVE, LM_FLAG_TRY_1CB | GL_NOCACHE, &ip->i_iopen_gh);