Btrfs-progs: fix restore command leaving corrupted files
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 show how to reproduce this corruption issue: $ mkfs.btrfs -f /dev/sdb3 $ mount /dev/sdb3 /mnt/btrfs $ perl -e '$d = "\x41" . ("\x00" x (1024*1024+349)); open($f,">","/mnt/btrfs/foobar"); print $f $d; close($f);' $ 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($f, "+<", "/mnt/btrfs/foobar"); seek($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 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 <fdmanana@gmail.com> Signed-off-by: David Sterba <dsterba@suse.cz> Signed-off-by: Chris Mason <chris.mason@fusionio.com>
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@ -278,6 +278,7 @@ static int copy_one_extent(struct btrfs_root *root, int fd,
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u64 bytenr;
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u64 ram_size;
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u64 disk_size;
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u64 num_bytes;
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u64 length;
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u64 size_left;
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u64 dev_bytenr;
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@ -294,7 +295,9 @@ static int copy_one_extent(struct btrfs_root *root, int fd,
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disk_size = btrfs_file_extent_disk_num_bytes(leaf, fi);
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ram_size = btrfs_file_extent_ram_bytes(leaf, fi);
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offset = btrfs_file_extent_offset(leaf, fi);
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size_left = disk_size;
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num_bytes = btrfs_file_extent_num_bytes(leaf, fi);
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size_left = num_bytes;
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bytenr += offset;
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if (offset)
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printf("offset is %Lu\n", offset);
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@ -302,7 +305,7 @@ static int copy_one_extent(struct btrfs_root *root, int fd,
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if (disk_size == 0)
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return 0;
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inbuf = malloc(disk_size);
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inbuf = malloc(size_left);
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if (!inbuf) {
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fprintf(stderr, "No memory\n");
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return -1;
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@ -357,8 +360,8 @@ again:
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goto again;
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if (compress == BTRFS_COMPRESS_NONE) {
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while (total < ram_size) {
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done = pwrite(fd, inbuf+total, ram_size-total,
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while (total < num_bytes) {
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done = pwrite(fd, inbuf+total, num_bytes-total,
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pos+total);
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if (done < 0) {
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ret = -1;
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@ -371,7 +374,7 @@ again:
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goto out;
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}
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ret = decompress(inbuf, outbuf, disk_size, &ram_size, compress);
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ret = decompress(inbuf, outbuf, num_bytes, &ram_size, compress);
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if (ret) {
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num_copies = btrfs_num_copies(&root->fs_info->mapping_tree,
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bytenr, length);
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