[PATCH 3.2 35/70] ocfs2: fix BUG when calculate new backup super

[Ben Hutchings <ben@decadent.org.uk>]

3.2.76-rc1 review patch.  If anyone has any objections, please let me know.

------------------

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>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 fs/ocfs2/resize.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

--- a/fs/ocfs2/resize.c
+++ b/fs/ocfs2/resize.c
@@ -56,11 +56,12 @@ static u16 ocfs2_calc_new_backup_super(s
 				       int new_clusters,
 				       u32 first_new_cluster,
 				       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++) {
@@ -73,6 +74,12 @@ 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);
@@ -101,6 +108,7 @@ 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);
@@ -114,6 +122,7 @@ 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);
@@ -129,7 +138,7 @@ static int ocfs2_update_last_group_and_i
 						     group,
 						     new_clusters,
 						     first_new_cluster,
-						     cl_cpg, 1);
+						     cl_cpg, old_bg_clusters, 1);
 		le16_add_cpu(&group->bg_free_bits_count, -1 * backups);
 	}
 
@@ -169,7 +178,7 @@ out_rollback:
 					    group,
 					    new_clusters,
 					    first_new_cluster,
-					    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);