From 38c01b9605923cfdff5413e0a12e58ee8d962257 Mon Sep 17 00:00:00 2001
From: liubo <liubo2009@cn.fujitsu.com>
Date: Tue, 2 Aug 2011 02:39:03 +0000
Subject: [PATCH] Btrfs: fix a bug of balance on full multi-disk partitions
When balancing, we'll first try to shrink devices for some space,
but if it is working on a full multi-disk partition with raid protection,
we may encounter a bug, that is, while shrinking, total_bytes may be less
than bytes_used, and btrfs may allocate a dev extent that accesses out of
device's bounds.
Then we will not be able to write or read the data which stores at the end
of the device, and get the followings:
device fsid 0939f071-7ea3-46c8-95df-f176d773bfb6 devid 1 transid 10 /dev/sdb5
Btrfs detected SSD devices, enabling SSD mode
btrfs: relocating block group 476315648 flags 9
btrfs: found 4 extents
attempt to access beyond end of device
sdb5: rw=145, want=546176, limit=546147
attempt to access beyond end of device
sdb5: rw=145, want=546304, limit=546147
attempt to access beyond end of device
sdb5: rw=145, want=546432, limit=546147
attempt to access beyond end of device
sdb5: rw=145, want=546560, limit=546147
attempt to access beyond end of device
Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
---
fs/btrfs/volumes.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index a595f8775c37a..46f9a208723da 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -863,6 +863,7 @@ int find_free_dev_extent(struct btrfs_trans_handle *trans,
max_hole_start = search_start;
max_hole_size = 0;
+ hole_size = 0;
if (search_start >= search_end) {
ret = -ENOSPC;
@@ -945,7 +946,14 @@ int find_free_dev_extent(struct btrfs_trans_handle *trans,
cond_resched();
}
- hole_size = search_end- search_start;
+ /*
+ * At this point, search_start should be the end of
+ * allocated dev extents, and when shrinking the device,
+ * search_end may be smaller than search_start.
+ */
+ if (search_end > search_start)
+ hole_size = search_end - search_start;
+
if (hole_size > max_hole_size) {
max_hole_start = search_start;
max_hole_size = hole_size;
@@ -2447,9 +2455,10 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
total_avail = device->total_bytes - device->bytes_used;
else
total_avail = 0;
- /* avail is off by max(alloc_start, 1MB), but that is the same
- * for all devices, so it doesn't hurt the sorting later on
- */
+
+ /* If there is no space on this device, skip it. */
+ if (total_avail == 0)
+ continue;
ret = find_free_dev_extent(trans, device,
max_stripe_size * dev_stripes,