linux-kernel - Re: [PATCH v2 03/12] docs: path-lookup: update path

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Date:   Mon, 19 Apr 2021 11:03:51 +1000
From:   NeilBrown <neilb@...e.de>
To:     Fox Chen <foxhlchen@...il.com>
Cc:     Fox Chen <foxhlchen@...il.com>, corbet@....net,
        vegard.nossum@...cle.com, viro@...iv.linux.org.uk,
        rdunlap@...radead.org, grandmaster@...klimov.de,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        gregkh@...uxfoundation.org
Subject: Re: [PATCH v2 03/12] docs: path-lookup: update path_mountpoint() part

On Tue, Mar 16 2021, Fox Chen wrote:

> path_mountpoint() doesn't exist anymore. Have been folded
> into path_lookup_at when flag is set with LOOKUP_MOUNTPOINT.
> Check commit: commit 161aff1d93abf0e ("LOOKUP_MOUNTPOINT: fold
> path_mountpointat() into path_lookupat()")
>
> Signed-off-by: Fox Chen <foxhlchen@...il.com>
> ---
>  Documentation/filesystems/path-lookup.rst | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/Documentation/filesystems/path-lookup.rst b/Documentation/filesystems/path-lookup.rst
> index a29d714431a3..b6a301b78121 100644
> --- a/Documentation/filesystems/path-lookup.rst
> +++ b/Documentation/filesystems/path-lookup.rst
> @@ -472,7 +472,7 @@ Handling the final component
>  ``nd->last_type`` to refer to the final component of the path.  It does
>  not call ``walk_component()`` that last time.  Handling that final
>  component remains for the caller to sort out. Those callers are
> -``path_lookupat()``, ``path_parentat()``, ``path_mountpoint()`` and
> +``path_lookupat()``, ``path_parentat()`` and
>  ``path_openat()`` each of which handles the differing requirements of
>  different system calls.
>  
> @@ -488,12 +488,10 @@ perform their operation.
>  object is wanted such as by ``stat()`` or ``chmod()``.  It essentially just
>  calls ``walk_component()`` on the final component through a call to
>  ``lookup_last()``.  ``path_lookupat()`` returns just the final dentry.
> -
> -``path_mountpoint()`` handles the special case of unmounting which must
> -not try to revalidate the mounted filesystem.  It effectively
> -contains, through a call to ``mountpoint_last()``, an alternate
> -implementation of ``lookup_slow()`` which skips that step.  This is
> -important when unmounting a filesystem that is inaccessible, such as
> +It is worth noting that when flag ``LOOKUP_MOUNTPOINT`` is set,
> +``path_lookupat()`` will unset LOOKUP_JUMPED in nameidata so that in the further

I would say "subsequent" rather than "further".

Either way:
 Reviewed-by: NeilBrown <neilb@...e.de>

Thanks,
NeilBrown


> +path traversal ``d_weak_revalidate()`` won't be called.
> +This is important when unmounting a filesystem that is inaccessible, such as
>  one provided by a dead NFS server.
>  
>  Finally ``path_openat()`` is used for the ``open()`` system call; it
> -- 
> 2.30.2

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