linux-kernel - Re: [PATCH v5] fs: introduce is_dot_or

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Message-ID: <20191211134014.GM32169@bombadil.infradead.org>
Date:   Wed, 11 Dec 2019 05:40:14 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     Gao Xiang <gaoxiang25@...wei.com>
Cc:     Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Al Viro <viro@...iv.linux.org.uk>,
        Eric Biggers <ebiggers@...nel.org>,
        "Theodore Y. Ts'o" <tytso@....edu>,
        Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <yuchao0@...wei.com>,
        Tyler Hicks <tyhicks@...onical.com>,
        linux-fsdevel@...r.kernel.org, ecryptfs@...r.kernel.org,
        linux-fscrypt@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org,
        "Darrick J. Wong" <darrick.wong@...cle.com>
Subject: Re: [PATCH v5] fs: introduce is_dot_or_dotdot helper for cleanup

On Wed, Dec 11, 2019 at 03:17:11PM +0800, Gao Xiang wrote:
> > static inline bool is_dot_or_dotdot(const unsigned char *name, size_t len)
> > {
> >         if (len >= 1 && unlikely(name[0] == '.')) {
> 
> 
> And I suggest drop "unlikely" here since files start with prefix
> '.' (plus specical ".", "..") are not as uncommon as you expected...

They absolutely are uncommon.  Even if you just consider
/home/willy/kernel/linux/.git/config, only one of those six path elements
starts with a '.'.