From: Eric Biggers <ebiggers@kernel.org>
To: Tiezhu Yang <yangtiezhu@loongson.cn>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
"Theodore Y. Ts'o" <tytso@mit.edu>,
Jaegeuk Kim <jaegeuk@kernel.org>, Chao Yu <yuchao0@huawei.com>,
Tyler Hicks <tyhicks@canonical.com>,
linux-fsdevel@vger.kernel.org, ecryptfs@vger.kernel.org,
linux-fscrypt@vger.kernel.org,
linux-f2fs-devel@lists.sourceforge.net,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5] fs: introduce is_dot_or_dotdot helper for cleanup
Date: Tue, 10 Dec 2019 18:48:58 -0800 [thread overview]
Message-ID: <20191211024858.GB732@sol.localdomain> (raw)
In-Reply-To: <1576030801-8609-1-git-send-email-yangtiezhu@loongson.cn>
On Wed, Dec 11, 2019 at 10:20:01AM +0800, Tiezhu Yang wrote:
> diff --git a/include/linux/namei.h b/include/linux/namei.h
> index 7fe7b87..0fd9315 100644
> --- a/include/linux/namei.h
> +++ b/include/linux/namei.h
> @@ -92,4 +92,14 @@ retry_estale(const long error, const unsigned int flags)
> return error == -ESTALE && !(flags & LOOKUP_REVAL);
> }
>
> +static inline bool is_dot_or_dotdot(const unsigned char *name, size_t len)
> +{
> + if (unlikely(name[0] == '.')) {
> + if (len == 1 || (len == 2 && name[1] == '.'))
> + return true;
> + }
> +
> + return false;
> +}
> +
> #endif /* _LINUX_NAMEI_H */
I had suggested adding a len >= 1 check to handle the empty name case correctly.
What I had in mind was
static inline bool is_dot_or_dotdot(const unsigned char *name, size_t len)
{
if (len >= 1 && unlikely(name[0] == '.')) {
if (len < 2 || (len == 2 && name[1] == '.'))
return true;
}
return false;
}
As is, you're proposing that it always dereference the first byte even when
len=0, which seems like a bad idea for a shared helper function. Did you check
whether it's okay for all the existing callers? fscrypt_fname_disk_to_usr() is
called from 6 places, did you check all of them?
How about keeping the existing optimized code for the hot path in fs/namei.c
(i.e. not using the helper function), while having the helper function do the
extra check to handle len=0 correctly?
- Eric
next prev parent reply other threads:[~2019-12-11 2:49 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-11 2:20 [PATCH v5] fs: introduce is_dot_or_dotdot helper for cleanup Tiezhu Yang
2019-12-11 2:48 ` Eric Biggers [this message]
2019-12-11 3:59 ` Tiezhu Yang
2019-12-11 4:47 ` Al Viro
2019-12-11 6:38 ` Tiezhu Yang
2019-12-11 7:17 ` Gao Xiang
2019-12-11 13:40 ` Matthew Wilcox
2019-12-11 14:41 ` Gao Xiang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20191211024858.GB732@sol.localdomain \
--to=ebiggers@kernel.org \
--cc=ecryptfs@vger.kernel.org \
--cc=jaegeuk@kernel.org \
--cc=linux-f2fs-devel@lists.sourceforge.net \
--cc=linux-fscrypt@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=tyhicks@canonical.com \
--cc=tytso@mit.edu \
--cc=viro@zeniv.linux.org.uk \
--cc=yangtiezhu@loongson.cn \
--cc=yuchao0@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).