On Mon, May 14, 2018 at 03:02:10PM +0800, Qu Wenruo wrote:
> As btrfs(5) specified:
>
> Note
> If nodatacow or nodatasum are enabled, compression is disabled.
>
> If NODATASUM or NODATACOW set, we should not compress the extent.
>
> And in fact, we have bug report about corrupted compressed extent
> leading to memory corruption in mail list.
Link please.
> Although it's mostly buggy lzo implementation causing the problem, btrfs
> still needs to be fixed to meet the specification.
That's very vague, what's the LZO bug? If the input is garbage and lzo
decompression cannot decompress it, it's not a lzo bug.
> Reported-by: James Harvey <jamespharvey20@xxxxxxxxx>
> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
> ---
> fs/btrfs/inode.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index d241285a0d2a..dbef3f404559 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -396,6 +396,14 @@ static inline int inode_need_compress(struct inode *inode, u64 start, u64 end)
> {
> struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
>
> + /*
> + * Btrfs doesn't support compression without csum or CoW.
> + * This should have the highest priority.
> + */
> + if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW ||
> + BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)
> + return 0;
This is also the wrong place to fix that, NODATASUM or NODATACOW inode
should never make it to compress_file_range (that calls
inode_need_compress).
> +
> /* force compress */
> if (btrfs_test_opt(fs_info, FORCE_COMPRESS))
> return 1;
> --
> 2.17.0
>
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