diff options
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.patch | 114 |
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 + |