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authorFilipe Manana <fdmanana@suse.com>2019-05-20 09:55:42 +0100
committerDavid Sterba <dsterba@suse.com>2019-05-28 18:54:10 +0200
commit6b1f72e5b82a5c2a4da4d1ebb8cc01913ddbea21 (patch)
tree68051f43aa2c4eb7b4a21595f44705ff4679b60c
parentfee13fe96529523a709d1fff487f14a5e0d56d34 (diff)
Btrfs: incremental send, fix file corruption when no-holes feature is enabled
When using the no-holes feature, if we have a file with prealloc extents with a start offset beyond the file's eof, doing an incremental send can cause corruption of the file due to incorrect hole detection. Such case requires that the prealloc extent(s) exist in both the parent and send snapshots, and that a hole is punched into the file that covers all its extents that do not cross the eof boundary. Example reproducer: $ mkfs.btrfs -f -O no-holes /dev/sdb $ mount /dev/sdb /mnt/sdb $ xfs_io -f -c "pwrite -S 0xab 0 500K" /mnt/sdb/foobar $ xfs_io -c "falloc -k 1200K 800K" /mnt/sdb/foobar $ btrfs subvolume snapshot -r /mnt/sdb /mnt/sdb/base $ btrfs send -f /tmp/base.snap /mnt/sdb/base $ xfs_io -c "fpunch 0 500K" /mnt/sdb/foobar $ btrfs subvolume snapshot -r /mnt/sdb /mnt/sdb/incr $ btrfs send -p /mnt/sdb/base -f /tmp/incr.snap /mnt/sdb/incr $ md5sum /mnt/sdb/incr/foobar 816df6f64deba63b029ca19d880ee10a /mnt/sdb/incr/foobar $ mkfs.btrfs -f /dev/sdc $ mount /dev/sdc /mnt/sdc $ btrfs receive -f /tmp/base.snap /mnt/sdc $ btrfs receive -f /tmp/incr.snap /mnt/sdc $ md5sum /mnt/sdc/incr/foobar cf2ef71f4a9e90c2f6013ba3b2257ed2 /mnt/sdc/incr/foobar --> Different checksum, because the prealloc extent beyond the file's eof confused the hole detection code and it assumed a hole starting at offset 0 and ending at the offset of the prealloc extent (1200Kb) instead of ending at the offset 500Kb (the file's size). Fix this by ensuring we never cross the file's size when issuing the write operations for a hole. Fixes: 16e7549f045d33 ("Btrfs: incompatible format change to remove hole extents") CC: stable@vger.kernel.org # 3.14+ Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
-rw-r--r--fs/btrfs/send.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index dd38dfe174df..ca30b1f06e2d 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -4999,6 +4999,12 @@ static int send_hole(struct send_ctx *sctx, u64 end)
if (offset >= sctx->cur_inode_size)
return 0;
+ /*
+ * Don't go beyond the inode's i_size due to prealloc extents that start
+ * after the i_size.
+ */
+ end = min_t(u64, end, sctx->cur_inode_size);
+
if (sctx->flags & BTRFS_SEND_FLAG_NO_FILE_DATA)
return send_update_extent(sctx, offset, end - offset);