summaryrefslogtreecommitdiff
path: root/0004-btrfs-send-fix-emission-of-invalid-clone-operations-within-the-same.patch
diff options
context:
space:
mode:
Diffstat (limited to '0004-btrfs-send-fix-emission-of-invalid-clone-operations-within-the-same.patch')
-rw-r--r--0004-btrfs-send-fix-emission-of-invalid-clone-operations-within-the-same.patch114
1 files changed, 114 insertions, 0 deletions
diff --git a/0004-btrfs-send-fix-emission-of-invalid-clone-operations-within-the-same.patch b/0004-btrfs-send-fix-emission-of-invalid-clone-operations-within-the-same.patch
new file mode 100644
index 0000000..496cc6f
--- /dev/null
+++ b/0004-btrfs-send-fix-emission-of-invalid-clone-operations-within-the-same.patch
@@ -0,0 +1,114 @@
+From 693469a2b9d6d27282c06ed55cb70ff648740efd Mon Sep 17 00:00:00 2001
+From: Filipe Manana <fdmanana@suse.com>
+Date: Fri, 24 Jan 2020 11:52:04 +0000
+Subject: Btrfs: send, fix emission of invalid clone operations within the same
+ file
+
+When doing an incremental send and a file has extents shared with itself
+at different file offsets, it's possible for send to emit clone operations
+that will fail at the destination because the source range goes beyond the
+file's current size. This happens when the file size has increased in the
+send snapshot, there is a hole between the shared extents and both shared
+extents are at file offsets which are greater the file's size in the
+parent snapshot.
+
+Example:
+
+ $ mkfs.btrfs -f /dev/sdb
+ $ mount /dev/sdb /mnt/sdb
+
+ $ xfs_io -f -c "pwrite -S 0xf1 0 64K" /mnt/sdb/foobar
+ $ btrfs subvolume snapshot -r /mnt/sdb /mnt/sdb/base
+ $ btrfs send -f /tmp/1.snap /mnt/sdb/base
+
+ # Create a 320K extent at file offset 512K.
+ $ xfs_io -c "pwrite -S 0xab 512K 64K" /mnt/sdb/foobar
+ $ xfs_io -c "pwrite -S 0xcd 576K 64K" /mnt/sdb/foobar
+ $ xfs_io -c "pwrite -S 0xef 640K 64K" /mnt/sdb/foobar
+ $ xfs_io -c "pwrite -S 0x64 704K 64K" /mnt/sdb/foobar
+ $ xfs_io -c "pwrite -S 0x73 768K 64K" /mnt/sdb/foobar
+
+ # Clone part of that 320K extent into a lower file offset (192K).
+ # This file offset is greater than the file's size in the parent
+ # snapshot (64K). Also the clone range is a bit behind the offset of
+ # the 320K extent so that we leave a hole between the shared extents.
+ $ xfs_io -c "reflink /mnt/sdb/foobar 448K 192K 192K" /mnt/sdb/foobar
+
+ $ btrfs subvolume snapshot -r /mnt/sdb /mnt/sdb/incr
+ $ btrfs send -p /mnt/sdb/base -f /tmp/2.snap /mnt/sdb/incr
+
+ $ mkfs.btrfs -f /dev/sdc
+ $ mount /dev/sdc /mnt/sdc
+
+ $ btrfs receive -f /tmp/1.snap /mnt/sdc
+ $ btrfs receive -f /tmp/2.snap /mnt/sdc
+ ERROR: failed to clone extents to foobar: Invalid argument
+
+The problem is that after processing the extent at file offset 192K, send
+does not issue a write operation full of zeroes for the hole between that
+extent and the extent starting at file offset 520K (hole range from 384K
+to 512K), this is because the hole is at an offset larger the size of the
+file in the parent snapshot (384K > 64K). As a consequence the field
+'cur_inode_next_write_offset' of the send context remains with a value of
+384K when we start to process the extent at file offset 512K, which is the
+value set after processing the extent at offset 192K.
+
+This screws up the lookup of possible extents to clone because due to an
+incorrect value of 'cur_inode_next_write_offset' we can now consider
+extents for cloning, in the same inode, that lie beyond the current size
+of the file in the receiver of the send stream. Also, when checking if
+an extent in the same file can be used for cloning, we must also check
+that not only its start offset doesn't start at or beyond the current eof
+of the file in the receiver but that the source range doesn't go beyond
+current eof, that is we must check offset + length does not cross the
+current eof, as that makes clone operations fail with -EINVAL.
+
+So fix this by updating 'cur_inode_next_write_offset' whenever we start
+processing an extent and checking an extent's offset and length when
+considering it for cloning operations.
+
+A test case for fstests follows soon.
+
+Fixes: 11f2069c113e02 ("Btrfs: send, allow clone operations within the same file")
+Signed-off-by: Filipe Manana <fdmanana@suse.com>
+Reviewed-by: Josef Bacik <josef@toxicpanda.com>
+---
+ fs/btrfs/send.c | 15 ++++++++++++++-
+ 1 file changed, 14 insertions(+), 1 deletion(-)
+
+diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
+index 091e5bc8c7ea..0b42dac8a35f 100644
+--- a/fs/btrfs/send.c
++++ b/fs/btrfs/send.c
+@@ -1269,7 +1269,8 @@ static int __iterate_backrefs(u64 ino, u64 offset, u64 root, void *ctx_)
+ * destination of the stream.
+ */
+ if (ino == bctx->cur_objectid &&
+- offset >= bctx->sctx->cur_inode_next_write_offset)
++ offset + bctx->extent_len >
++ bctx->sctx->cur_inode_next_write_offset)
+ return 0;
+ }
+
+@@ -5804,6 +5805,18 @@ static int process_extent(struct send_ctx *sctx,
+ }
+ }
+
++ /*
++ * There might be a hole between the end of the last processed extent
++ * and this extent, and we may have not sent a write operation for that
++ * hole because it was not needed (range is beyond eof in the parent
++ * snapshot). So adjust the next write offset to the offset of this
++ * extent, as we want to make sure we don't do mistakes when checking if
++ * we can clone this extent from some other offset in this inode or when
++ * detecting if we need to issue a truncate operation when finishing the
++ * processing this inode.
++ */
++ sctx->cur_inode_next_write_offset = key->offset;
++
+ ret = find_extent_clone(sctx, path, key->objectid, key->offset,
+ sctx->cur_inode_size, &found_clone);
+ if (ret != -ENOENT && ret < 0)
+--
+cgit v1.2.1-1-g437b
+