[PATCH] Btrfs: fix lost i_size update after cloning inline extent

[PATCH] Btrfs: fix lost i_size update after cloning inline extent

[fdmanana]

From: Filipe Manana <fdmanana@suse.com>

When not using the NO_HOLES feature we were not marking the destination's
file range as written after cloning an inline extent into it. This can
lead to a data loss if the current destination file size is smaller than
the source file's size.

Example:

  $ mkfs.btrfs -f -O ^no-holes /dev/sdc
  $ mount /mnt/sdc /mnt

  $ echo "hello world" > /mnt/foo
  $ cp --reflink=always /mnt/foo /mnt/bar
  $ rm -f /mnt/foo
  $ umount /mnt

  $ mount /mnt/sdc /mnt
  $ cat /mnt/bar
  $
  $ stat -c %s /mnt/bar
  0

  # -> the file is empty, since we deleted foo, the data lost is forever

Fix that by calling btrfs_inode_set_file_extent_range() after cloning an
inline extent.

A test case for fstests will follow soon.

Fixes: 9ddc959e802bf ("btrfs: use the file extent tree infrastructure")
Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
 fs/btrfs/reflink.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/btrfs/reflink.c b/fs/btrfs/reflink.c
index d1973141d3bb..040009d1cc31 100644
--- a/fs/btrfs/reflink.c
+++ b/fs/btrfs/reflink.c
@@ -264,6 +264,7 @@ static int clone_copy_inline_extent(struct inode *dst,
 			    size);
 	inode_add_bytes(dst, datal);
 	set_bit(BTRFS_INODE_NEEDS_FULL_SYNC, &BTRFS_I(dst)->runtime_flags);
+	ret = btrfs_inode_set_file_extent_range(BTRFS_I(dst), 0, aligned_end);
 out:
 	if (!ret && !trans) {
 		/*
-- 
2.11.0

Re: [PATCH] Btrfs: fix lost i_size update after cloning inline extent

[Filipe Manana]

On Sat, Apr 4, 2020 at 9:21 PM <fdmanana@kernel.org> wrote:
>
> From: Filipe Manana <fdmanana@suse.com>
>
> When not using the NO_HOLES feature we were not marking the destination's
> file range as written after cloning an inline extent into it. This can
> lead to a data loss if the current destination file size is smaller than
> the source file's size.
>
> Example:
>
>   $ mkfs.btrfs -f -O ^no-holes /dev/sdc
>   $ mount /mnt/sdc /mnt
>
>   $ echo "hello world" > /mnt/foo
>   $ cp --reflink=always /mnt/foo /mnt/bar
>   $ rm -f /mnt/foo
>   $ umount /mnt
>
>   $ mount /mnt/sdc /mnt
>   $ cat /mnt/bar
>   $
>   $ stat -c %s /mnt/bar
>   0
>
>   # -> the file is empty, since we deleted foo, the data lost is forever
>
> Fix that by calling btrfs_inode_set_file_extent_range() after cloning an
> inline extent.
>
> A test case for fstests will follow soon.
>
> Fixes: 9ddc959e802bf ("btrfs: use the file extent tree infrastructure")
> Signed-off-by: Filipe Manana <fdmanana@suse.com>

Reported-by: Johannes Hirte <johannes.hirte@datenkhaos.de>
Link: https://lore.kernel.org/linux-btrfs/20200404193846.GA432065@latitude/
Tested-by: Johannes Hirte <johannes.hirte@datenkhaos.de>

> ---
>  fs/btrfs/reflink.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/fs/btrfs/reflink.c b/fs/btrfs/reflink.c
> index d1973141d3bb..040009d1cc31 100644
> --- a/fs/btrfs/reflink.c
> +++ b/fs/btrfs/reflink.c
> @@ -264,6 +264,7 @@ static int clone_copy_inline_extent(struct inode *dst,
>                             size);
>         inode_add_bytes(dst, datal);
>         set_bit(BTRFS_INODE_NEEDS_FULL_SYNC, &BTRFS_I(dst)->runtime_flags);
> +       ret = btrfs_inode_set_file_extent_range(BTRFS_I(dst), 0, aligned_end);
>  out:
>         if (!ret && !trans) {
>                 /*
> --
> 2.11.0
>

Re: [PATCH] Btrfs: fix lost i_size update after cloning inline extent

[David Sterba]

On Mon, Apr 06, 2020 at 11:51:20AM +0100, Filipe Manana wrote:
> On Sat, Apr 4, 2020 at 9:21 PM <fdmanana@kernel.org> wrote:
> >
> > From: Filipe Manana <fdmanana@suse.com>
> >
> > When not using the NO_HOLES feature we were not marking the destination's
> > file range as written after cloning an inline extent into it. This can
> > lead to a data loss if the current destination file size is smaller than
> > the source file's size.
> >
> > Example:
> >
> >   $ mkfs.btrfs -f -O ^no-holes /dev/sdc
> >   $ mount /mnt/sdc /mnt
> >
> >   $ echo "hello world" > /mnt/foo
> >   $ cp --reflink=always /mnt/foo /mnt/bar
> >   $ rm -f /mnt/foo
> >   $ umount /mnt
> >
> >   $ mount /mnt/sdc /mnt
> >   $ cat /mnt/bar
> >   $
> >   $ stat -c %s /mnt/bar
> >   0
> >
> >   # -> the file is empty, since we deleted foo, the data lost is forever
> >
> > Fix that by calling btrfs_inode_set_file_extent_range() after cloning an
> > inline extent.
> >
> > A test case for fstests will follow soon.
> >
> > Fixes: 9ddc959e802bf ("btrfs: use the file extent tree infrastructure")
> > Signed-off-by: Filipe Manana <fdmanana@suse.com>
> 
> Reported-by: Johannes Hirte <johannes.hirte@datenkhaos.de>
> Link: https://lore.kernel.org/linux-btrfs/20200404193846.GA432065@latitude/
> Tested-by: Johannes Hirte <johannes.hirte@datenkhaos.de>

Thanks, added to misc-next.