From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f182.google.com ([209.85.212.182]:36802 "EHLO mail-wi0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753948Ab3GJPnk (ORCPT ); Wed, 10 Jul 2013 11:43:40 -0400 Received: by mail-wi0-f182.google.com with SMTP id m6so6488716wiv.3 for ; Wed, 10 Jul 2013 08:43:39 -0700 (PDT) From: Filipe David Borba Manana To: linux-btrfs@vger.kernel.org Cc: Filipe David Borba Manana Subject: [PATCH] Btrfs-progs: fix restore command leaving corrupted files Date: Wed, 10 Jul 2013 16:43:26 +0100 Message-Id: <1373471006-20994-1-git-send-email-fdmanana@gmail.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: When there are files that have parts shared with snapshots, the restore command was incorrectly restoring them, as it was not taking into account the offset and number of bytes fields from the file extent item. Besides leaving the recovered file corrupt, it was also inneficient as it read and wrote more data than needed (with each extent copy overwriting portions of the one previously written). The following steps and small C program show how to reproduce this corruption issue: $ mkfs.btrfs -f /dev/sdb3 $ mount /dev/sdb3 /mnt/btrfs $ ./write_file /mnt/btrfs/foobar $ du -b /mnt/btrfs/foobar 1048926 /mnt/btrfs/foobar $ md5sum /mnt/btrfs/foobar f9f778f3a7410c40e4ed104a3a63c3c4 /mnt/btrfs/foobar $ btrfs subvolume snapshot /mnt/btrfs /mnt/btrfs/my_snap $ perl -e 'open($f, "+<", "/dev/btrfs/foobar"); seek($f, 4096, 0); print $f "\xff"; close($f);' $ md5sum /mnt/btrfs/foobar b983fcefd4622a03a78936484c40272b /mnt/btrfs/foobar $ umount /mnt/btrfs $ btrfs restore /dev/sdb3 /tmp/copy $ du -b /tmp/copy/foobar 1048926 /tmp/copy/foobar $ md5sum /tmp/copy/foobar 88db338cbc1c44dfabae083f1ce642d5 /tmp/copy/foobar $ od -t x1 -j 8192 -N 4 /tmp/copy/foobar 0020000 41 00 00 00 0020004 $ mount /dev/sdb3 /mnt/btrfs $ od -t x1 -j 8192 -N 4 /mnt/btrfs/foobar 0020000 00 00 00 00 0020004 $ md5sum /mnt/btrfs/foobar b983fcefd4622a03a78936484c40272b /mnt/btrfs/foobar $ cat write_file.c: int main(int argc, char *argv[]) { int fd; unsigned char buf[BUF_SIZE]; if (argc < 2) { fprintf(stderr, "Use: %s filepath\n", argv[0]); return 1; } fd = open(argv[1], O_CREAT | O_WRONLY | O_TRUNC, S_IRWXU); assert(fd >= 0); memset(buf, 0, BUF_SIZE); buf[0] = 65; assert(write(fd, buf, BUF_SIZE) == BUF_SIZE); assert(close(fd) == 0); return 0; } Tested this change with zlib, lzo compression and file sizes larger than 1GiB, and found no regression or other corruption issues (so far at least). Signed-off-by: Filipe David Borba Manana --- cmds-restore.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/cmds-restore.c b/cmds-restore.c index e48df40..9688599 100644 --- a/cmds-restore.c +++ b/cmds-restore.c @@ -272,6 +272,7 @@ static int copy_one_extent(struct btrfs_root *root, int fd, u64 bytenr; u64 ram_size; u64 disk_size; + u64 num_bytes; u64 length; u64 size_left; u64 dev_bytenr; @@ -288,7 +289,9 @@ static int copy_one_extent(struct btrfs_root *root, int fd, disk_size = btrfs_file_extent_disk_num_bytes(leaf, fi); ram_size = btrfs_file_extent_ram_bytes(leaf, fi); offset = btrfs_file_extent_offset(leaf, fi); - size_left = disk_size; + num_bytes = btrfs_file_extent_num_bytes(leaf, fi); + size_left = num_bytes; + bytenr += offset; if (offset) printf("offset is %Lu\n", offset); @@ -296,7 +299,7 @@ static int copy_one_extent(struct btrfs_root *root, int fd, if (disk_size == 0) return 0; - inbuf = malloc(disk_size); + inbuf = malloc(size_left); if (!inbuf) { fprintf(stderr, "No memory\n"); return -1; @@ -351,8 +354,8 @@ again: goto again; if (compress == BTRFS_COMPRESS_NONE) { - while (total < ram_size) { - done = pwrite(fd, inbuf+total, ram_size-total, + while (total < num_bytes) { + done = pwrite(fd, inbuf+total, num_bytes-total, pos+total); if (done < 0) { ret = -1; @@ -365,7 +368,7 @@ again: goto out; } - ret = decompress(inbuf, outbuf, disk_size, &ram_size, compress); + ret = decompress(inbuf, outbuf, num_bytes, &ram_size, compress); if (ret) { num_copies = btrfs_num_copies(&root->fs_info->mapping_tree, bytenr, length); -- 1.7.9.5