RE: [PATCH 02/14] d_path: saner calling conventions for __dentry_path()

[Justin He]

> -----Original Message-----
> From: Justin He
> Sent: Friday, June 25, 2021 5:33 PM
> To: Al Viro <viro@xxxxxxxxxxxxxxxxxx>; Linus Torvalds <torvalds@linux-
> foundation.org>
> Cc: Petr Mladek <pmladek@xxxxxxxx>; Steven Rostedt <rostedt@xxxxxxxxxxx>;
> Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>; Andy Shevchenko
> <andriy.shevchenko@xxxxxxxxxxxxxxx>; Rasmus Villemoes
> <linux@xxxxxxxxxxxxxxxxxx>; Jonathan Corbet <corbet@xxxxxxx>; Heiko
> Carstens <hca@xxxxxxxxxxxxx>; Vasily Gorbik <gor@xxxxxxxxxxxxx>; Christian
> Borntraeger <borntraeger@xxxxxxxxxx>; Eric W . Biederman
> <ebiederm@xxxxxxxxxxxx>; Darrick J. Wong <darrick.wong@xxxxxxxxxx>; Peter
> Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>; Ira Weiny <ira.weiny@xxxxxxxxx>;
> Eric Biggers <ebiggers@xxxxxxxxxx>; Ahmed S. Darwish
> <a.darwish@xxxxxxxxxxxxx>; open list:DOCUMENTATION <linux-
> doc@xxxxxxxxxxxxxxx>; Linux Kernel Mailing List <linux-
> kernel@xxxxxxxxxxxxxxx>; linux-s390 <linux-s390@xxxxxxxxxxxxxxx>; linux-
> fsdevel <linux-fsdevel@xxxxxxxxxxxxxxx>
> Subject: RE: [PATCH 02/14] d_path: saner calling conventions for
> __dentry_path()
> 
> Hi Al
> 
> > -----Original Message-----
> > From: Al Viro <viro@xxxxxxxxxxxxxxxx> On Behalf Of Al Viro
> > Sent: Wednesday, May 19, 2021 8:49 AM
> > To: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> > Cc: Justin He <Justin.He@xxxxxxx>; Petr Mladek <pmladek@xxxxxxxx>; Steven
> > Rostedt <rostedt@xxxxxxxxxxx>; Sergey Senozhatsky
> > <senozhatsky@xxxxxxxxxxxx>; Andy Shevchenko
> > <andriy.shevchenko@xxxxxxxxxxxxxxx>; Rasmus Villemoes
> > <linux@xxxxxxxxxxxxxxxxxx>; Jonathan Corbet <corbet@xxxxxxx>; Heiko
> > Carstens <hca@xxxxxxxxxxxxx>; Vasily Gorbik <gor@xxxxxxxxxxxxx>;
> Christian
> > Borntraeger <borntraeger@xxxxxxxxxx>; Eric W . Biederman
> > <ebiederm@xxxxxxxxxxxx>; Darrick J. Wong <darrick.wong@xxxxxxxxxx>; Peter
> > Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>; Ira Weiny <ira.weiny@xxxxxxxxx>;
> > Eric Biggers <ebiggers@xxxxxxxxxx>; Ahmed S. Darwish
> > <a.darwish@xxxxxxxxxxxxx>; open list:DOCUMENTATION <linux-
> > doc@xxxxxxxxxxxxxxx>; Linux Kernel Mailing List <linux-
> > kernel@xxxxxxxxxxxxxxx>; linux-s390 <linux-s390@xxxxxxxxxxxxxxx>; linux-
> > fsdevel <linux-fsdevel@xxxxxxxxxxxxxxx>
> > Subject: [PATCH 02/14] d_path: saner calling conventions for
> __dentry_path()
> >
> > 1) lift NUL-termination into the callers
> > 2) pass pointer to the end of buffer instead of that to beginning.
> >
> > (1) allows to simplify dentry_path() - we don't need to play silly
> > games with restoring the leading / of "//deleted" after __dentry_path()
> > would've overwritten it with NUL.
> >
> > We also do not need to check if (either) prepend() in there fails -
> > if the buffer is not large enough, we'll end with negative buflen
> > after prepend() and __dentry_path() will return the right value
> > (ERR_PTR(-ENAMETOOLONG)) just fine.
> >
> > Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> > ---
> >  fs/d_path.c | 33 +++++++++++++--------------------
> >  1 file changed, 13 insertions(+), 20 deletions(-)
> >
> > diff --git a/fs/d_path.c b/fs/d_path.c
> > index 01df5dfa1f88..1a1cf05e7780 100644
> > --- a/fs/d_path.c
> > +++ b/fs/d_path.c
> > @@ -326,22 +326,21 @@ char *simple_dname(struct dentry *dentry, char
> > *buffer, int buflen)
> >  /*
> >   * Write full pathname from the root of the filesystem into the buffer.
> >   */
> I suggest adding the comments to remind NUL terminator should be prepended
> before invoking __dentry_path()
> 
Except for my suggestion about adding comments

Reviewed-by: Jia He <justin.he@xxxxxxx>