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    SubjectRE: [PATCH 03/14] d_path: regularize handling of root dentry in __dentry_path()
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    > -----Original Message-----
    > From: Al Viro <viro@ftp.linux.org.uk> On Behalf Of Al Viro
    > Sent: Wednesday, May 19, 2021 8:49 AM
    > To: Linus Torvalds <torvalds@linux-foundation.org>
    > Cc: Justin He <Justin.He@arm.com>; Petr Mladek <pmladek@suse.com>; Steven
    > Rostedt <rostedt@goodmis.org>; Sergey Senozhatsky
    > <senozhatsky@chromium.org>; Andy Shevchenko
    > <andriy.shevchenko@linux.intel.com>; Rasmus Villemoes
    > <linux@rasmusvillemoes.dk>; Jonathan Corbet <corbet@lwn.net>; Heiko
    > Carstens <hca@linux.ibm.com>; Vasily Gorbik <gor@linux.ibm.com>; Christian
    > Borntraeger <borntraeger@de.ibm.com>; Eric W . Biederman
    > <ebiederm@xmission.com>; Darrick J. Wong <darrick.wong@oracle.com>; Peter
    > Zijlstra (Intel) <peterz@infradead.org>; Ira Weiny <ira.weiny@intel.com>;
    > Eric Biggers <ebiggers@google.com>; Ahmed S. Darwish
    > <a.darwish@linutronix.de>; open list:DOCUMENTATION <linux-
    > doc@vger.kernel.org>; Linux Kernel Mailing List <linux-
    > kernel@vger.kernel.org>; linux-s390 <linux-s390@vger.kernel.org>; linux-
    > fsdevel <linux-fsdevel@vger.kernel.org>
    > Subject: [PATCH 03/14] d_path: regularize handling of root dentry in
    > __dentry_path()
    >
    > All path-forming primitives boil down to sequence of prepend_name()
    > on dentries encountered along the way toward root. Each time we prepend
    > / + dentry name to the buffer. Normally that does exactly what we want,
    > but there's a corner case when we don't call prepend_name() at all (in case
    > of __dentry_path() that happens if we are given root dentry). We obviously
    > want to end up with "/", rather than "", so this corner case needs to be
    > handled.
    >
    > __dentry_path() used to manually put '/' in the end of buffer before
    > doing anything else, to be overwritten by the first call of prepend_name()
    > if one happens and to be left in place if we don't call prepend_name() at
    > all. That required manually checking that we had space in the buffer
    > (prepend_name() and prepend() take care of such checks themselves) and lead
    > to clumsy keeping track of return value.
    >
    > A better approach is to check if the main loop has added anything
    > into the buffer and prepend "/" if it hasn't. A side benefit of using
    > prepend()
    > is that it does the right thing if we'd already run out of buffer, making
    > the overflow-handling logics simpler.
    >
    > Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
    Reviewed-by: Jia He <justin.he@arm.com>


    --
    Cheers,
    Justin (Jia He)


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