Patch "ocfs2: fix BUG when calculate new backup super" has been added to the 4.3-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    ocfs2: fix BUG when calculate new backup super

to the 4.3-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ocfs2-fix-bug-when-calculate-new-backup-super.patch
and it can be found in the queue-4.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 5c9ee4cbf2a945271f25b89b137f2c03bbc3be33 Mon Sep 17 00:00:00 2001
From: Joseph Qi <joseph.qi@huawei.com>
Date: Tue, 29 Dec 2015 14:54:06 -0800
Subject: ocfs2: fix BUG when calculate new backup super

From: Joseph Qi <joseph.qi@huawei.com>

commit 5c9ee4cbf2a945271f25b89b137f2c03bbc3be33 upstream.

When resizing, it firstly extends the last gd.  Once it should backup
super in the gd, it calculates new backup super and update the
corresponding value.

But it currently doesn't consider the situation that the backup super is
already done.  And in this case, it still sets the bit in gd bitmap and
then decrease from bg_free_bits_count, which leads to a corrupted gd and
trigger the BUG in ocfs2_block_group_set_bits:

    BUG_ON(le16_to_cpu(bg->bg_free_bits_count) < num_bits);

So check whether the backup super is done and then do the updates.

Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
Reviewed-by: Jiufei Xue <xuejiufei@huawei.com>
Reviewed-by: Yiwen Jiang <jiangyiwen@huawei.com>
Cc: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/ocfs2/resize.c |   15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

--- a/fs/ocfs2/resize.c
+++ b/fs/ocfs2/resize.c
@@ -54,11 +54,12 @@
 static u16 ocfs2_calc_new_backup_super(struct inode *inode,
 				       struct ocfs2_group_desc *gd,
 				       u16 cl_cpg,
+				       u16 old_bg_clusters,
 				       int set)
 {
 	int i;
 	u16 backups = 0;
-	u32 cluster;
+	u32 cluster, lgd_cluster;
 	u64 blkno, gd_blkno, lgd_blkno = le64_to_cpu(gd->bg_blkno);
 
 	for (i = 0; i < OCFS2_MAX_BACKUP_SUPERBLOCKS; i++) {
@@ -71,6 +72,12 @@ static u16 ocfs2_calc_new_backup_super(s
 		else if (gd_blkno > lgd_blkno)
 			break;
 
+		/* check if already done backup super */
+		lgd_cluster = ocfs2_blocks_to_clusters(inode->i_sb, lgd_blkno);
+		lgd_cluster += old_bg_clusters;
+		if (lgd_cluster >= cluster)
+			continue;
+
 		if (set)
 			ocfs2_set_bit(cluster % cl_cpg,
 				      (unsigned long *)gd->bg_bitmap);
@@ -99,6 +106,7 @@ static int ocfs2_update_last_group_and_i
 	u16 chain, num_bits, backups = 0;
 	u16 cl_bpc = le16_to_cpu(cl->cl_bpc);
 	u16 cl_cpg = le16_to_cpu(cl->cl_cpg);
+	u16 old_bg_clusters;
 
 	trace_ocfs2_update_last_group_and_inode(new_clusters,
 						first_new_cluster);
@@ -112,6 +120,7 @@ static int ocfs2_update_last_group_and_i
 
 	group = (struct ocfs2_group_desc *)group_bh->b_data;
 
+	old_bg_clusters = le16_to_cpu(group->bg_bits) / cl_bpc;
 	/* update the group first. */
 	num_bits = new_clusters * cl_bpc;
 	le16_add_cpu(&group->bg_bits, num_bits);
@@ -125,7 +134,7 @@ static int ocfs2_update_last_group_and_i
 				     OCFS2_FEATURE_COMPAT_BACKUP_SB)) {
 		backups = ocfs2_calc_new_backup_super(bm_inode,
 						     group,
-						     cl_cpg, 1);
+						     cl_cpg, old_bg_clusters, 1);
 		le16_add_cpu(&group->bg_free_bits_count, -1 * backups);
 	}
 
@@ -163,7 +172,7 @@ out_rollback:
 	if (ret < 0) {
 		ocfs2_calc_new_backup_super(bm_inode,
 					    group,
-					    cl_cpg, 0);
+					    cl_cpg, old_bg_clusters, 0);
 		le16_add_cpu(&group->bg_free_bits_count, backups);
 		le16_add_cpu(&group->bg_bits, -1 * num_bits);
 		le16_add_cpu(&group->bg_free_bits_count, -1 * num_bits);


Patches currently in stable-queue which might be from joseph.qi@huawei.com are

queue-4.3/ocfs2-dlm-ignore-cleaning-the-migration-mle-that-is-inuse.patch
queue-4.3/ocfs2-nfs-hangs-in-__ocfs2_cluster_lock-due-to-race-with-ocfs2_unblock_lock.patch
queue-4.3/ocfs2-fix-bug-when-calculate-new-backup-super.patch
queue-4.3/ocfs2-dlm-clear-refmap-bit-of-recovery-lock-while-doing-local-recovery-cleanup.patch