From 1375cb65e87b327a8dd4f920c3e3d837fb40e9c2 Mon Sep 17 00:00:00 2001
From: Dave Chinner <dchinner@redhat.com>
Date: Tue, 9 Oct 2012 14:50:52 +1100
Subject: [PATCH] xfs: growfs: don't read garbage for new secondary superblocks
When updating new secondary superblocks in a growfs operation, the
superblock buffer is read from the newly grown region of the
underlying device. This is not guaranteed to be zero, so violates
the underlying assumption that the unused parts of superblocks are
zero filled. Get a new buffer for these secondary superblocks to
ensure that the unused regions are zero filled correctly.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
---
fs/xfs/xfs_fsops.c | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
index c25b094efbf7..4beaede43277 100644
--- a/fs/xfs/xfs_fsops.c
+++ b/fs/xfs/xfs_fsops.c
@@ -399,9 +399,26 @@ xfs_growfs_data_private(
/* update secondary superblocks. */
for (agno = 1; agno < nagcount; agno++) {
- error = xfs_trans_read_buf(mp, NULL, mp->m_ddev_targp,
+ error = 0;
+ /*
+ * new secondary superblocks need to be zeroed, not read from
+ * disk as the contents of the new area we are growing into is
+ * completely unknown.
+ */
+ if (agno < oagcount) {
+ error = xfs_trans_read_buf(mp, NULL, mp->m_ddev_targp,
XFS_AGB_TO_DADDR(mp, agno, XFS_SB_BLOCK(mp)),
XFS_FSS_TO_BB(mp, 1), 0, &bp);
+ } else {
+ bp = xfs_trans_get_buf(NULL, mp->m_ddev_targp,
+ XFS_AGB_TO_DADDR(mp, agno, XFS_SB_BLOCK(mp)),
+ XFS_FSS_TO_BB(mp, 1), 0);
+ if (bp)
+ xfs_buf_zero(bp, 0, BBTOB(bp->b_length));
+ else
+ error = ENOMEM;
+ }
+
if (error) {
xfs_warn(mp,
"error %d reading secondary superblock for ag %d",
@@ -423,7 +440,7 @@ xfs_growfs_data_private(
break; /* no point in continuing */
}
}
- return 0;
+ return error;
error0:
xfs_trans_cancel(tp, XFS_TRANS_ABORT);
--
2.20.1