linux-kernel - Re: [PATCH v2 12/12] docs: path-lookup: update symlink description

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Date:   Mon, 19 Apr 2021 10:34:54 +0800
From:   Fox Chen <foxhlchen@...il.com>
To:     NeilBrown <neilb@...e.de>
Cc:     Jonathan Corbet <corbet@....net>, vegard.nossum@...cle.com,
        Al Viro <viro@...iv.linux.org.uk>, rdunlap@...radead.org,
        grandmaster@...klimov.de, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v2 12/12] docs: path-lookup: update symlink description

On Mon, Apr 19, 2021 at 9:59 AM NeilBrown <neilb@...e.de> wrote:
>
> On Tue, Mar 16 2021, Fox Chen wrote:
>
> > instead of lookup_real()/vfs_create(), i_op->lookup() and
> > i_op->create() will be called directly.
> >
> > update vfs_open() logic
> >
> > should_follow_link is merged into lookup_last() or open_last_lookup()
> > which returns symlink name instead of an integer.
> >
> > Signed-off-by: Fox Chen <foxhlchen@...il.com>
> > ---
> >  Documentation/filesystems/path-lookup.rst | 13 ++++++-------
> >  1 file changed, 6 insertions(+), 7 deletions(-)
> >
> > diff --git a/Documentation/filesystems/path-lookup.rst b/Documentation/filesystems/path-lookup.rst
> > index eef6e9f68fba..adbc714740c2 100644
> > --- a/Documentation/filesystems/path-lookup.rst
> > +++ b/Documentation/filesystems/path-lookup.rst
> > @@ -1202,16 +1202,15 @@ the code.
> >     it.  If the file was found in the dcache, then ``vfs_open()`` is used for
> >     this.  If not, then ``lookup_open()`` will either call ``atomic_open()`` (if
> >     the filesystem provides it) to combine the final lookup with the open, or
> > -   will perform the separate ``lookup_real()`` and ``vfs_create()`` steps
> > +   will perform the separate ``i_op->lookup()`` and ``i_op->create()`` steps
> >     directly.  In the later case the actual "open" of this newly found or
> >     created file will be performed by ``vfs_open()``, just as if the name
> >     were found in the dcache.
> >
> >  2. ``vfs_open()`` can fail with ``-EOPENSTALE`` if the cached information
> > -   wasn't quite current enough.  Rather than restarting the lookup from
> > -   the top with ``LOOKUP_REVAL`` set, ``lookup_open()`` is called instead,
> > -   giving the filesystem a chance to resolve small inconsistencies.
> > -   If that doesn't work, only then is the lookup restarted from the top.
> > +   wasn't quite current enough.  If it's in RCU-walk -ECHILD will be returned
> > +   otherwise will return -ESTALE.  When -ESTALE is returned, the caller may
>
> "otherwise -ESTALE is returned".
> If you don't like repeating "is returned", then maybe:
>   "... -ECHILD will be returned, otherwise the result is -ESTALE".
>
>
> > +   retry with LOOKUP_REVAL flag set.
> >
> >  3. An open with O_CREAT **does** follow a symlink in the final component,
> >     unlike other creation system calls (like ``mkdir``).  So the sequence::
> > @@ -1221,8 +1220,8 @@ the code.
> >
> >     will create a file called ``/tmp/bar``.  This is not permitted if
> >     ``O_EXCL`` is set but otherwise is handled for an O_CREAT open much
> > -   like for a non-creating open: ``should_follow_link()`` returns ``1``, and
> > -   so does ``do_last()`` so that ``trailing_symlink()`` gets called and the
> > +   like for a non-creating open: ``lookup_last()`` or ``open_last_lookup()``
> > +   returns a non ``Null`` value, and ``link_path_walk()`` gets called and the
>
> "NULL", not "Null".
>
> This those changes,
>  Reviewed-by: NeilBrown <neilb@...e.de>
>
> Thanks for a lot of all these improvements!! and apologies for the delay
> in the review.

Thanks for the review, I will fix them and send the next version back.


> Thanks,
> NeilBrown
>
>
> >     open process continues on the symlink that was found.
> >
> >  Updating the access time
> > --
> > 2.30.2


thanks,
fox