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 <swhiteho@redhat.com>
Tested-By: Abhijith Das <adas@redhat.com>

fs/gfs2/file.c

@@ -593,16 +593,12 @@ static int gfs2_fsync(struct file *file, loff_t start, loff_t end,
 		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

@@ -42,41 +42,41 @@ static void gfs2_ail_error(struct gfs2_glock *gl, const struct buffer_head *bh)
 /**
  * __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);
 }
 
 
@@ -99,13 +99,13 @@ static void gfs2_ail_empty_gl(struct gfs2_glock *gl)
 	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);
@@ -117,7 +117,7 @@ void gfs2_ail_flush(struct gfs2_glock *gl)
 	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

@@ -23,6 +23,6 @@ extern const struct gfs2_glock_operations gfs2_quota_glops;
 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

@@ -1533,7 +1533,7 @@ static void gfs2_evict_inode(struct inode *inode)
 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);