gfs2: gl_object races fix

Function glock_clear_object() checks if the specified glock is still
pointing at the right object and clears the gl_object pointer.  To
handle the case of incompletely constructed inodes, glock_clear_object()
also allows gl_object to be NULL.

However, in the teardown case, when iget_failed() is called and the
inode is removed from the inode hash, by the time we get to the
glock_clear_object() calls in gfs2_put_super() and its helpers, we don't
have exclusion against concurrent gfs2_inode_lookup() and
gfs2_create_inode() calls, and the inode and iopen glocks may already be
pointing at another inode, so the checks in glock_clear_object() are
incorrect.

To better handle this case, always completely disassociate an inode from
its glocks before tearing it down.  In addition, get rid of a duplicate
glock_clear_object() call in gfs2_evict_inode().  That way,
glock_clear_object() will only ever be called when the glock points at
the current inode, and the NULL check in glock_clear_object() can be
removed.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 524f3c9..2868e97 100644 (file)
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -883,6 +883,7 @@ void glock_set_object(struct gfs2_glock *gl, void *object)
 /**
  * glock_clear_object - clear the gl_object field of a glock
  * @gl: the glock
+ * @object: object the glock currently points at
  */
 void glock_clear_object(struct gfs2_glock *gl, void *object)
 {
@@ -892,8 +893,7 @@ void glock_clear_object(struct gfs2_glock *gl, void *object)
        prev_object = gl->gl_object;
        gl->gl_object = NULL;
        spin_unlock(&gl->gl_lockref.lock);
-       if (gfs2_assert_warn(gl->gl_name.ln_sbd,
-                            prev_object == object || prev_object == NULL)) {
+       if (gfs2_assert_warn(gl->gl_name.ln_sbd, prev_object == object)) {
                pr_warn("glock=%u/%llx\n",
                        gl->gl_name.ln_type,
                        (unsigned long long)gl->gl_name.ln_number);

diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 614db30..c76fdb8 100644 (file)
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -225,6 +225,10 @@ fail:
                gfs2_glock_dq_uninit(&ip->i_iopen_gh);
        if (gfs2_holder_initialized(&i_gh))
                gfs2_glock_dq_uninit(&i_gh);
+       if (ip->i_gl) {
+               gfs2_glock_put(ip->i_gl);
+               ip->i_gl = NULL;
+       }
        iget_failed(inode);
        return ERR_PTR(error);
 }
@@ -816,6 +820,10 @@ fail_gunlock3:
 fail_gunlock2:
        gfs2_glock_put(io_gl);
 fail_free_inode:
+       if (ip->i_gl) {
+               gfs2_glock_put(ip->i_gl);
+               ip->i_gl = NULL;
+       }
        gfs2_rs_deltree(&ip->i_res);
        gfs2_qa_put(ip);
 fail_free_acls:

diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index 999cc14..de99505 100644 (file)
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -1401,10 +1401,8 @@ static void gfs2_evict_inode(struct inode *inode)
        if (gfs2_rs_active(&ip->i_res))
                gfs2_rs_deltree(&ip->i_res);
 
-       if (gfs2_holder_initialized(&gh)) {
-               glock_clear_object(ip->i_gl, ip);
+       if (gfs2_holder_initialized(&gh))
                gfs2_glock_dq_uninit(&gh);
-       }
        if (ret && ret != GLR_TRYFAILED && ret != -EROFS)
                fs_warn(sdp, "gfs2_evict_inode: %d\n", ret);
 out: