GFS2: Stop block extents at the end of bitmaps
 

Hi,

This patch stops multiple block allocations if a nonzero
return code is received from gfs2_rbm_from_block. Without
this patch, if enough pressure is put on the file system,
you get a kernel warning quickly followed by:
BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffffa04f47e8>] gfs2_alloc_blocks+0x2c8/0x880 [gfs2]
With this patch, things run normally.

Regards,

Bob Peterson
Red Hat File Systems

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
---
diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 87ee0b7..081fba8 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -1852,8 +1852,7 @@ static void gfs2_alloc_extent(const struct gfs2_rbm *rbm, bool dinode,
block++;
while (*n < elen) {
ret = gfs2_rbm_from_block(&pos, block);
- WARN_ON(ret);
- if (gfs2_testbit(&pos) != GFS2_BLKST_FREE)
+ if (ret || gfs2_testbit(&pos) != GFS2_BLKST_FREE)
break;
gfs2_trans_add_bh(pos.rgd->rd_gl, pos.bi->bi_bh, 1);
gfs2_setbit(&pos, true, GFS2_BLKST_USED);