[v2,0/3] btrfs-progs: image: make restored image file to be properly enlarged

Message

Qu Wenruo April 29, 2021, 9:06 a.m. UTC

Recent kernel will refuse to mount restored image, even the source fs is
empty:
 # mkfs.btrfs -f /dev/test/test
 # btrfs-image /dev/test/test /tmp/dump
 # btrfs-image -r /tmp/dump ~/test.img
 # mount ~/test.img /mnt/btrfs
 mount: /mnt/btrfs: wrong fs type, bad option, bad superblock on /dev/loop0, missing codepage or helper program, or other error.
 # dmesg -t | tail -n 7
 loop0: detected capacity change from 10592 to 0
 BTRFS info (device loop0): disk space caching is enabled
 BTRFS info (device loop0): has skinny extents
 BTRFS info (device loop0): flagging fs with big metadata feature
 BTRFS error (device loop0): device total_bytes should be at most 5423104 but found 10737418240
 BTRFS error (device loop0): failed to read chunk tree: -22
 BTRFS error (device loop0): open_ctree failed

This is triggered by a recent kernel commit 3a160a933111 ("btrfs: drop never met disk total
bytes check in verify_one_dev_extent").

But the root cause is, we didn't enlarge the output file if the source
image only contains single device.

This bug won't affect restore to block device, or the destination file
is already large enough.

This patchset will fix the problem, and with new test case to detect
such problem.

Also remove one dead code exposed during the development.

Changelog:
v2:
- Comments word change
- Only enlarge the file when the target file is smaller than expected
  device size
- Change the prefix of the 1st patch
  From "btrfs" to "btrfs-progs"

Qu Wenruo (3):
  btrfs-progs: image: remove the dead stat() call
  btrfs-progs: image: enlarge the output file if no tree modification is
    needed for restore
  btrfs-progs: misc-tests: add test to ensure the restored image can be
    mounted

 image/main.c                                  | 51 ++++++++++++++++---
 .../048-image-restore-mount/test.sh           | 20 ++++++++
 2 files changed, 63 insertions(+), 8 deletions(-)
 create mode 100755 tests/misc-tests/048-image-restore-mount/test.sh

Comments

David Sterba April 29, 2021, 7:54 p.m. UTC | #1

On Thu, Apr 29, 2021 at 05:06:55PM +0800, Qu Wenruo wrote:
> Recent kernel will refuse to mount restored image, even the source fs is
> empty:
>  # mkfs.btrfs -f /dev/test/test
>  # btrfs-image /dev/test/test /tmp/dump
>  # btrfs-image -r /tmp/dump ~/test.img
>  # mount ~/test.img /mnt/btrfs
>  mount: /mnt/btrfs: wrong fs type, bad option, bad superblock on /dev/loop0, missing codepage or helper program, or other error.
>  # dmesg -t | tail -n 7
>  loop0: detected capacity change from 10592 to 0
>  BTRFS info (device loop0): disk space caching is enabled
>  BTRFS info (device loop0): has skinny extents
>  BTRFS info (device loop0): flagging fs with big metadata feature
>  BTRFS error (device loop0): device total_bytes should be at most 5423104 but found 10737418240
>  BTRFS error (device loop0): failed to read chunk tree: -22
>  BTRFS error (device loop0): open_ctree failed
> 
> This is triggered by a recent kernel commit 3a160a933111 ("btrfs: drop never met disk total
> bytes check in verify_one_dev_extent").
> 
> But the root cause is, we didn't enlarge the output file if the source
> image only contains single device.
> 
> This bug won't affect restore to block device, or the destination file
> is already large enough.
> 
> This patchset will fix the problem, and with new test case to detect
> such problem.
> 
> Also remove one dead code exposed during the development.
> 
> Changelog:
> v2:
> - Comments word change
> - Only enlarge the file when the target file is smaller than expected
>   device size
> - Change the prefix of the 1st patch
>   From "btrfs" to "btrfs-progs"
> 
> Qu Wenruo (3):
>   btrfs-progs: image: remove the dead stat() call
>   btrfs-progs: image: enlarge the output file if no tree modification is
>     needed for restore
>   btrfs-progs: misc-tests: add test to ensure the restored image can be
>     mounted

Added to devel, thanks.