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Fri, 22 Aug 2025 03:20:51 -0700 (PDT) Received: from saltykitkat.localnet ([156.246.92.146]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-32515451214sm2091157a91.19.2025.08.22.03.20.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 22 Aug 2025 03:20:50 -0700 (PDT) From: Sun YangKai To: calvin@wbinvd.org Cc: clm@fb.com, dsterba@suse.com, josef@toxicpanda.com, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, neelx@suse.com, quwenruo.btrfs@gmx.com Subject: Re: [PATCH] btrfs: Accept and ignore compression level for lzo Date: Fri, 22 Aug 2025 18:20:44 +0800 Message-ID: <2022221.PYKUYFuaPT@saltykitkat> In-Reply-To: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" > The compression level is meaningless for lzo, but before commit > 3f093ccb95f30 ("btrfs: harden parsing of compression mount options"), > it was silently ignored if passed. > > 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 > --- > > 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); > > -- > 2.47.2 A possible improvement would be to emit a warning in btrfs_match_compress_type() when @may_have_level is false but a level is still provided. And the warning message can be something like "Providing a compression level for {compression_type} is not supported, the level is ignored." This way: 1. users receive a clearer hint about what happened, 2. existing setups relying on this behavior continue to work, 3. the @may_have_level semantics remain consistent.