GFS2: Fix AIL flush issue during fsync

Unfortunately, it is not enough to just ignore locked buffers during
the AIL flush from fsync. We need to be able to ignore all buffers
which are locked, dirty or pinned at this stage as they might have
been added subsequent to the log flush earlier in the fsync function.

In addition, this means that we no longer need to rely on i_mutex to
keep out writes during fsync, so we can, as a side-effect, remove
that protection too.

Signed-off-by: Steven Whitehouse <[e-mail]>
Tested-By: Abhijith Das <[e-mail]>

fs/gfs2/file.c

···
 		sync_state &= ~I_DIRTY_SYNC;
 
 	if (sync_state) {
-		mutex_lock(&inode->i_mutex);
 		ret = sync_inode_metadata(inode, 1);
-		if (ret) {
-			mutex_unlock(&inode->i_mutex);
+		if (ret)
 			return ret;
-		}
 		if (gfs2_is_jdata(ip))
 			filemap_write_and_wait(mapping);
-		gfs2_ail_flush(ip->i_gl);
-		mutex_unlock(&inode->i_mutex);
+		gfs2_ail_flush(ip->i_gl, 1);
 	}
 
 	if (mapping->nrpages)

fs/gfs2/glops.c

···
 /**
  * __gfs2_ail_flush - remove all buffers for a given lock from the AIL
  * @gl: the glock
+ * @fsync: set when called from fsync (not all buffers will be clean)
  *
  * None of the buffers should be dirty, locked, or pinned.
  */
 
-static void __gfs2_ail_flush(struct gfs2_glock *gl, unsigned long b_state)
+static void __gfs2_ail_flush(struct gfs2_glock *gl, bool fsync)
 {
 	struct gfs2_sbd *sdp = gl->gl_sbd;
 	struct list_head *head = &gl->gl_ail_list;
-	struct gfs2_bufdata *bd;
+	struct gfs2_bufdata *bd, *tmp;
 	struct buffer_head *bh;
+	const unsigned long b_state = (1UL << BH_Dirty)|(1UL << BH_Pinned)|(1UL << BH_Lock);
 	sector_t blocknr;
 
+	gfs2_log_lock(sdp);
 	spin_lock(&sdp->sd_ail_lock);
-	while (!list_empty(head)) {
-		bd = list_entry(head->next, struct gfs2_bufdata,
-				bd_ail_gl_list);
+	list_for_each_entry_safe(bd, tmp, head, bd_ail_gl_list) {
 		bh = bd->bd_bh;
-		blocknr = bh->b_blocknr;
-		if (bh->b_state & b_state)
+		if (bh->b_state & b_state) {
+			if (fsync)
+				continue;
 			gfs2_ail_error(gl, bh);
+		}
+		blocknr = bh->b_blocknr;
 		bh->b_private = NULL;
 		gfs2_remove_from_ail(bd); /* drops ref on bh */
-		spin_unlock(&sdp->sd_ail_lock);
 
 		bd->bd_bh = NULL;
 		bd->bd_blkno = blocknr;
 
-		gfs2_log_lock(sdp);
 		gfs2_trans_add_revoke(sdp, bd);
-		gfs2_log_unlock(sdp);
-
-		spin_lock(&sdp->sd_ail_lock);
 	}
-	gfs2_assert_withdraw(sdp, !atomic_read(&gl->gl_ail_count));
+	BUG_ON(!fsync && atomic_read(&gl->gl_ail_count));
 	spin_unlock(&sdp->sd_ail_lock);
+	gfs2_log_unlock(sdp);
 }
 
 
···
 	BUG_ON(current->journal_info);
 	current->journal_info = &tr;
 
-	__gfs2_ail_flush(gl, (1ul << BH_Dirty)|(1ul << BH_Pinned)|(1ul << BH_Lock));
+	__gfs2_ail_flush(gl, 0);
 
 	gfs2_trans_end(sdp);
 	gfs2_log_flush(sdp, NULL);
 }
 
-void gfs2_ail_flush(struct gfs2_glock *gl)
+void gfs2_ail_flush(struct gfs2_glock *gl, bool fsync)
 {
 	struct gfs2_sbd *sdp = gl->gl_sbd;
 	unsigned int revokes = atomic_read(&gl->gl_ail_count);
···
 	ret = gfs2_trans_begin(sdp, 0, revokes);
 	if (ret)
 		return;
-	__gfs2_ail_flush(gl, (1ul << BH_Dirty)|(1ul << BH_Pinned));
+	__gfs2_ail_flush(gl, fsync);
 	gfs2_trans_end(sdp);
 	gfs2_log_flush(sdp, NULL);
 }

fs/gfs2/glops.h

···
 extern const struct gfs2_glock_operations gfs2_journal_glops;
 extern const struct gfs2_glock_operations *gfs2_glops_list[];
 
-extern void gfs2_ail_flush(struct gfs2_glock *gl);
+extern void gfs2_ail_flush(struct gfs2_glock *gl, bool fsync);
 
 #endif /* __GLOPS_DOT_H__ */

fs/gfs2/super.c

···
 out_truncate:
 	gfs2_log_flush(sdp, ip->i_gl);
 	write_inode_now(inode, 1);
-	gfs2_ail_flush(ip->i_gl);
+	gfs2_ail_flush(ip->i_gl, 0);
 
 	/* Case 2 starts here */
 	error = gfs2_trans_begin(sdp, 0, sdp->sd_jdesc->jd_blocks);