linux-kernel - Re: [PATCH] btrfs: Accept and ignore compression level for lzo

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Message-ID: <a637a576-f107-4d05-84c8-280b133e925a@gmx.com>
Date: Fri, 22 Aug 2025 17:57:49 +0930
From: Qu Wenruo <quwenruo.btrfs@....com>
To: Calvin Owens <calvin@...nvd.org>, linux-kernel@...r.kernel.org
Cc: linux-btrfs@...r.kernel.org, Daniel Vacek <neelx@...e.com>,
 David Sterba <dsterba@...e.com>, Josef Bacik <josef@...icpanda.com>,
 Chris Mason <clm@...com>
Subject: Re: [PATCH] btrfs: Accept and ignore compression level for lzo



在 2025/8/22 17:15, Calvin Owens 写道:
> The compression level is meaningless for lzo, but before commit
> 3f093ccb95f30 ("btrfs: harden parsing of compression mount options"),
> it was silently ignored if passed.

Since LZO doesn't support compression level, why providing a level 
parameter in the first place?

I think it's time for those users to properly update their mount options.

> 
> After that commit, passing a level with lzo fails to mount:
> 
>      BTRFS error: unrecognized compression value lzo:1
> 
> Restore the old behavior, in case any users were relying on it.
> 
> Fixes: 3f093ccb95f30 ("btrfs: harden parsing of compression mount options")
> Signed-off-by: Calvin Owens <calvin@...nvd.org>
> ---
>   fs/btrfs/super.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index a262b494a89f..7ee35038c7fb 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -299,7 +299,7 @@ static int btrfs_parse_compress(struct btrfs_fs_context *ctx,
>   		btrfs_set_opt(ctx->mount_opt, COMPRESS);
>   		btrfs_clear_opt(ctx->mount_opt, NODATACOW);
>   		btrfs_clear_opt(ctx->mount_opt, NODATASUM);
> -	} else if (btrfs_match_compress_type(string, "lzo", false)) {
> +	} else if (btrfs_match_compress_type(string, "lzo", true)) {
>   		ctx->compress_type = BTRFS_COMPRESS_LZO;
>   		ctx->compress_level = 0;
>   		btrfs_set_opt(ctx->mount_opt, COMPRESS);