From: NeilBrown <neilb@suse.de>
To: Fox Chen <foxhlchen@gmail.com>
Cc: Fox Chen <foxhlchen@gmail.com>,
corbet@lwn.net, vegard.nossum@oracle.com,
viro@zeniv.linux.org.uk, rdunlap@infradead.org,
grandmaster@al2klimov.de, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org
Subject: Re: [PATCH v2 07/12] docs: path-lookup: i_op->follow_link replaced with i_op->get_link
Date: Mon, 19 Apr 2021 11:28:14 +1000 [thread overview]
Message-ID: <871rb72hch.fsf@notabene.neil.brown.name> (raw)
In-Reply-To: <20210316054727.25655-8-foxhlchen@gmail.com>
[-- Attachment #1: Type: text/plain, Size: 2100 bytes --]
On Tue, Mar 16 2021, Fox Chen wrote:
> follow_link has been replaced by get_link() which can be
> called in RCU mode.
>
> see commit: commit 6b2553918d8b ("replace ->follow_link() with
> new method that could stay in RCU mode")
>
> Signed-off-by: Fox Chen <foxhlchen@gmail.com>
Reviewed-By: NeilBrown <neilb@suse.de>
Thanks,
NeilBrown
> ---
> 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 af5c20fecfef..e6b6c43ff0f6 100644
> --- a/Documentation/filesystems/path-lookup.rst
> +++ b/Documentation/filesystems/path-lookup.rst
> @@ -1060,13 +1060,11 @@ 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 out of
> +RCU-walk. Much like the ``i_op->permission()`` method we
> +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
> --
> 2.30.2
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 853 bytes --]
next prev parent reply other threads:[~2021-04-19 1:28 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-16 5:47 [PATCH v2 00/12] docs: path-lookup: Update pathlookup docs Fox Chen
2021-03-16 5:47 ` [PATCH v2 01/12] docs: path-lookup: update follow_managed() part Fox Chen
2021-04-19 0:52 ` NeilBrown
2021-04-19 2:17 ` Matthew Wilcox
2021-04-19 2:33 ` Fox Chen
2021-04-19 3:25 ` Matthew Wilcox
2021-04-19 3:33 ` Fox Chen
2021-04-19 19:22 ` Jonathan Corbet
2021-04-20 1:12 ` Fox Chen
2021-03-16 5:47 ` [PATCH v2 02/12] docs: path-lookup: update path_to_nameidata() part Fox Chen
2021-04-19 1:00 ` NeilBrown
2021-03-16 5:47 ` [PATCH v2 03/12] docs: path-lookup: update path_mountpoint() part Fox Chen
2021-04-19 1:03 ` NeilBrown
2021-03-16 5:47 ` [PATCH v2 04/12] docs: path-lookup: update do_last() part Fox Chen
2021-04-19 1:17 ` NeilBrown
2021-03-16 5:47 ` [PATCH v2 05/12] docs: path-lookup: remove filename_mountpoint Fox Chen
2021-04-19 1:20 ` NeilBrown
2021-03-16 5:47 ` [PATCH v2 06/12] docs: path-lookup: Add macro name to symlink limit description Fox Chen
2021-04-19 1:22 ` NeilBrown
2021-03-16 5:47 ` [PATCH v2 07/12] docs: path-lookup: i_op->follow_link replaced with i_op->get_link Fox Chen
2021-04-19 1:28 ` NeilBrown [this message]
2021-03-16 5:47 ` [PATCH v2 08/12] docs: path-lookup: update i_op->put_link and cookie description Fox Chen
2021-04-19 1:37 ` NeilBrown
2021-03-16 5:47 ` [PATCH v2 09/12] docs: path-lookup: no get_link() Fox Chen
2021-04-19 1:41 ` NeilBrown
2021-03-16 5:47 ` [PATCH v2 10/12] docs: path-lookup: update WALK_GET, WALK_PUT desc Fox Chen
2021-04-19 1:47 ` NeilBrown
2021-03-16 5:47 ` [PATCH v2 11/12] docs: path-lookup: update get_link() ->follow_link description Fox Chen
2021-04-19 1:54 ` NeilBrown
2021-03-16 5:47 ` [PATCH v2 12/12] docs: path-lookup: update symlink description Fox Chen
2021-04-19 1:59 ` NeilBrown
2021-04-19 2:34 ` Fox Chen
2021-04-13 21:18 ` [PATCH v2 00/12] docs: path-lookup: Update pathlookup docs Jonathan Corbet
2021-04-13 22:26 ` NeilBrown
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=871rb72hch.fsf@notabene.neil.brown.name \
--to=neilb@suse.de \
--cc=corbet@lwn.net \
--cc=foxhlchen@gmail.com \
--cc=grandmaster@al2klimov.de \
--cc=gregkh@linuxfoundation.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=rdunlap@infradead.org \
--cc=vegard.nossum@oracle.com \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).