From: NeilBrown <neilb@suse.de>
To: Fox Chen <foxhlchen@gmail.com>,
corbet@lwn.net, vegard.nossum@oracle.com,
viro@zeniv.linux.org.uk, rdunlap@infradead.org,
grandmaster@al2klimov.de
Cc: Fox Chen <foxhlchen@gmail.com>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 07/12] docs: path-lookup: i_op->follow_link replaced with i_op->get_link
Date: Thu, 28 Jan 2021 14:53:40 +1100 [thread overview]
Message-ID: <8735ylhg3f.fsf@notabene.neil.brown.name> (raw)
In-Reply-To: <20210126072443.33066-8-foxhlchen@gmail.com>
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On Tue, Jan 26 2021, Fox Chen wrote:
> follow_link has been replaced by get_link() which can be
> called in RCU mode.
>
> see commit: 6b2553918d8b4e6de9853fd6315bec7271a2e592
>
> Signed-off-by: Fox Chen <foxhlchen@gmail.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 25d2a5a59f45..0a362849b26f 100644
> --- a/Documentation/filesystems/path-lookup.rst
> +++ b/Documentation/filesystems/path-lookup.rst
> @@ -1062,13 +1062,11 @@ filesystem cannot successfully get a reference in RCU-walk mode, it
> must return ``-ECHILD`` and ``unlazy_walk()`` will be called to return to
> REF-walk mode in which the filesystem is allowed to sleep.
>
> -The place for all this to happen is the ``i_op->follow_link()`` inode
> -method. In the present mainline code this is never actually called in
> -RCU-walk mode as the rewrite is not quite complete. It is likely that
> -in a future release this method will be passed an ``inode`` pointer when
> -called in RCU-walk mode so it both (1) knows to be careful, and (2) has the
> -validated pointer. Much like the ``i_op->permission()`` method we
> -looked at previously, ``->follow_link()`` would need to be careful that
> +The place for all this to happen is the ``i_op->get_link()`` inode
> +method. This is called both in RCU-walk and REF-walk. In RCU-walk the
> +``dentry*`` argument is NULL, ``->get_link()`` can return -ECHILD to drop
> +RCU-walk. Much like the ``i_op->permission()`` method we
The phrase "drop RCU-walk" isn't consistent with the rest of the text.
It talks about "dropping down to REF-walk", so you could write "dropping
out of RCU-walk", but not just "dropping RCU-walk".
NeilBrown
> +looked at previously, ``->get_link()`` would need to be careful that
> all the data structures it references are safe to be accessed while
> holding no counted reference, only the RCU lock. Though getting a
> reference with ``->follow_link()`` is not yet done in RCU-walk mode, the
> --
> 2.30.0
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next prev parent reply other threads:[~2021-01-28 4:14 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-26 7:24 [PATCH 00/12] docs: path-lookup: Update pathlookup docs Fox Chen
2021-01-26 7:24 ` [PATCH 01/12] docs: path-lookup: update follow_managed() part Fox Chen
2021-01-26 14:03 ` Greg KH
2021-01-27 1:11 ` Fox Chen
2021-01-28 3:20 ` NeilBrown
2021-01-26 7:24 ` [PATCH 02/12] docs: path-lookup: update path_to_nameidata() parth Fox Chen
2021-01-28 3:24 ` NeilBrown
2021-01-26 7:24 ` [PATCH 03/12] docs: path-lookup: update path_mountpoint() part Fox Chen
2021-01-28 3:28 ` NeilBrown
2021-01-26 7:24 ` [PATCH 04/12] docs: path-lookup: update do_last() part Fox Chen
2021-01-28 3:50 ` NeilBrown
2021-01-26 7:24 ` [PATCH 05/12] docs: path-lookup: remove filename_mountpoint Fox Chen
2021-01-26 7:24 ` [PATCH 06/12] docs: path-lookup: Add macro name to symlink limit description Fox Chen
2021-01-26 7:24 ` [PATCH 07/12] docs: path-lookup: i_op->follow_link replaced with i_op->get_link Fox Chen
2021-01-28 3:53 ` NeilBrown [this message]
2021-01-26 7:24 ` [PATCH 08/12] docs: path-lookup: update i_op->put_link and cookie description Fox Chen
2021-01-28 3:50 ` NeilBrown
2021-01-26 7:24 ` [PATCH 09/12] docs: path-lookup: no get_link() Fox Chen
2021-01-26 7:24 ` [PATCH 10/12] docs: path-lookup: update WALK_GET, WALK_PUT desc Fox Chen
2021-01-26 7:24 ` [PATCH 11/12] docs: path-lookup: update get_link() ->follow_link description Fox Chen
2021-01-26 7:24 ` [PATCH 12/12] docs: path-lookup: update symlink description Fox Chen
2021-01-26 7:30 ` [PATCH 00/12] docs: path-lookup: Update pathlookup docs Fox Chen
2021-01-26 20:31 ` Jonathan Corbet
2021-01-28 1:23 ` Fox Chen
2021-01-28 3:58 ` NeilBrown
2021-01-29 1:29 ` Fox Chen
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