From: Fox Chen <foxhlchen@gmail.com>
To: neilb@suse.de
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: [PATCH v3 07/13] docs: path-lookup: i_op->follow_link replaced with i_op->get_link
Date: Thu, 27 May 2021 17:16:12 +0800 [thread overview]
Message-ID: <20210527091618.287093-8-foxhlchen@gmail.com> (raw)
In-Reply-To: <20210527091618.287093-1-foxhlchen@gmail.com>
follow_link has been replaced by get_link() which can be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>
---
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 40b9afec4d60..4650c6427963 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
--
2.31.1
next prev parent reply other threads:[~2021-05-27 9:17 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-27 9:16 [PATCH v3 00/13] docs: path-lookup: Update pathlookup docs Fox Chen
2021-05-27 9:16 ` [PATCH v3 01/13] docs: path-lookup: update follow_managed() part Fox Chen
2021-05-27 9:16 ` [PATCH v3 02/13] docs: path-lookup: update path_to_nameidata() part Fox Chen
2021-05-27 9:16 ` [PATCH v3 03/13] docs: path-lookup: update path_mountpoint() part Fox Chen
2021-05-27 9:16 ` [PATCH v3 04/13] docs: path-lookup: update do_last() part Fox Chen
2021-05-27 9:16 ` [PATCH v3 05/13] docs: path-lookup: remove filename_mountpoint Fox Chen
2021-05-27 9:16 ` [PATCH v3 06/13] docs: path-lookup: Add macro name to symlink limit description Fox Chen
2021-05-27 9:16 ` Fox Chen [this message]
2021-05-27 9:16 ` [PATCH v3 08/13] docs: path-lookup: update i_op->put_link and cookie description Fox Chen
2021-05-27 9:16 ` [PATCH v3 09/13] docs: path-lookup: no get_link() Fox Chen
2021-05-27 9:16 ` [PATCH v3 10/13] docs: path-lookup: update WALK_GET, WALK_PUT desc Fox Chen
2021-06-17 22:31 ` NeilBrown
2021-05-27 9:16 ` [PATCH v3 11/13] docs: path-lookup: update get_link() ->follow_link description Fox Chen
2021-05-27 9:16 ` [PATCH v3 12/13] docs: path-lookup: update symlink description Fox Chen
2021-05-27 9:16 ` [PATCH v3 13/13] docs: path-lookup: use bare function() rather than literals Fox Chen
2021-06-17 22:35 ` [PATCH v3 00/13] docs: path-lookup: Update pathlookup docs NeilBrown
2021-06-18 1:00 ` Fox Chen
2021-06-18 17:39 ` Jonathan Corbet
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