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Sat, 26 Sep 2026 14:22:14 -0700 (PDT) Message-ID: <18af260e-b53e-4156-a6a3-e34d9b3b6293@suse.com> Date: Sun, 27 Sep 2026 06:52:09 +0930 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] btrfs: use strstarts() and str_has_prefix() for prefix checks To: George Hu Cc: dsterba@suse.com, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, mason@kernel.org References: <20260926122217.22759-1-integral@archlinux.org> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=wqu@suse.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNGFF1IFdlbnJ1byA8d3F1QHN1c2UuY29tPsLAlAQTAQgAPgIbAwULCQgHAgYVCAkKCwIE FgIDAQIeAQIXgBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJqqw0NBQkUl/JeAAoJEMI9kfOh Jf6o/xYH/3AaWnGSq58XnY/T3/YYjr6g+TUZxa7MPyiYTELNpNlvmNlbtbAL0nW0LNvkeiqf SmYA+xkwY4RbxnZYQK0H5iv2w1eqa9qqFZb4bIBRmTapu26GEEkpad0W0ZhoSPMO8bV2Bwkf YdtPZQLaeUKvHZqNqBKnmtRLQj2Cgy3kuXX3bEGvWjzUOxPUSCj/S++JWBewMdMBPT62vZM0 3156gfn5mHA94s2p+NFJoWkERY+JPTMu9NISkpD7yuGhXN88qd/aqD0RrlhxvKsrQogdPwn9 vP18FGG3CRlHtOvOLVoY5NKSOWTDc+o+8t2XEETFTGbKYTcqeTzi4SxhvBLtTinOwE0EWdWB rwEIAKpT62HgSzL9zwGe+WIUCMB+nOEjXAfvoUPUwk+YCEDcOdfkkM5FyBoJs8TCEuPXGXBO Cl5P5B8OYYnkHkGWutAVlUTV8KESOIm/KJIA7jJA+Ss9VhMjtePfgWexw+P8itFRSRrrwyUf E+0WcAevblUi45LjWWZgpg3A80tHP0iToOZ5MbdYk7YFBE29cDSleskfV80ZKxFv6koQocq0 vXzTfHvXNDELAuH7Ms/WJcdUzmPyBf3Oq6mKBBH8J6XZc9LjjNZwNbyvsHSrV5bgmu/THX2n g/3be+iqf6OggCiy3I1NSMJ5KtR0q2H2Nx2Vqb1fYPOID8McMV9Ll6rh8S8AEQEAAcLAfAQY AQgAJgIbDBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXWBBQkQ/lrSAAoJEMI9kfOhJf6o cakH+QHwDszsoYvmrNq36MFGgvAHRjdlrHRBa4A1V1kzd4kOUokongcrOOgHY9yfglcvZqlJ qfa4l+1oxs1BvCi29psteQTtw+memmcGruKi+YHD7793zNCMtAtYidDmQ2pWaLfqSaryjlzR /3tBWMyvIeWZKURnZbBzWRREB7iWxEbZ014B3gICqZPDRwwitHpH8Om3eZr7ygZck6bBa4MU o1XgbZcspyCGqu1xF/bMAY2iCDcq6ULKQceuKkbeQ8qxvt9hVxJC2W3lHq8dlK1pkHPDg9wO JoAXek8MF37R8gpLoGWl41FIUb3hFiu3zhDDvslYM4BmzI18QgQTQnotJH8= In-Reply-To: <20260926122217.22759-1-integral@archlinux.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2026/9/26 21:52, George Hu 写道: > Replace strncmp() prefix checks with strstarts() when only a boolean result > is needed, and with str_has_prefix() when the prefix length is needed after > a successful match. > > This makes prefix checks clearer and more concise. > > Signed-off-by: George Hu > --- > V1 -> V2: > - Avoid replacing strncmp() with strstarts() when the parameter is > not NUL terminated > - Revise subject > > fs/btrfs/super.c | 5 ++--- > fs/btrfs/xattr.c | 3 +-- > 2 files changed, 3 insertions(+), 5 deletions(-) > > diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c > index ddb620ac241b..287cdc45bef8 100644 > --- a/fs/btrfs/super.c > +++ b/fs/btrfs/super.c > @@ -263,10 +263,9 @@ static const struct fs_parameter_spec btrfs_fs_parameters[] = { > > static bool btrfs_match_compress_type(const char *string, const char *type, bool may_have_level) > { > - const int len = strlen(type); > + const size_t len = str_has_prefix(string, type); > > - return (strncmp(string, type, len) == 0) && > - ((may_have_level && string[len] == ':') || string[len] == '\0'); > + return len && ((may_have_level && string[len] == ':') || string[len] == '\0'); For this call site, both strings are NUL terminated so there is no problem about accessing beyond boundary. But to be honest, I don't think this improves the readability. I still have to check what str_has_prefix() really returns to understand the code, as the function is not a common helper and just by the name I don't get what if it will return. > } > > static int btrfs_parse_compress(struct btrfs_fs_context *ctx, > diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c > index ab55d10bd71f..9011d8096e2d 100644 > --- a/fs/btrfs/xattr.c > +++ b/fs/btrfs/xattr.c > @@ -239,8 +239,7 @@ int btrfs_setxattr_trans(struct inode *inode, const char *name, > * block_rsv of the handle and trigger a warning for the start > * case. > */ > - ASSERT(strncmp(name, XATTR_SECURITY_PREFIX, > - XATTR_SECURITY_PREFIX_LEN) == 0); > + ASSERT(strstarts(name, XATTR_SECURITY_PREFIX)); @name is not NUL-terminated, thus even the old code is not safe. The only thing saving us here is that we should have a security XATTR passed in, thus the name must have the "security." prefix and not cause access-beyond-boundary. Again, I do not think it's a good idea to use strstarts() with any non-NUL-terminated strings. > trans = current->journal_info; > } >