From: ebiederm@xmission.com (Eric W. Biederman)
To: Ian Kent <raven@themaw.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Tejun Heo <tj@kernel.org>, Eric Sandeen <sandeen@sandeen.net>,
Fox Chen <foxhlchen@gmail.com>,
Brice Goglin <brice.goglin@gmail.com>,
Al Viro <viro@ZenIV.linux.org.uk>,
Rick Lindsley <ricklind@linux.vnet.ibm.com>,
David Howells <dhowells@redhat.com>,
Miklos Szeredi <miklos@szeredi.hu>,
Marcelo Tosatti <mtosatti@redhat.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [REPOST PATCH v4 3/5] kernfs: switch kernfs to use an rwsem
Date: Thu, 03 Jun 2021 11:59:26 -0500 [thread overview]
Message-ID: <87sg1yq3yp.fsf@disp2133> (raw)
In-Reply-To: <162218365578.34379.12523496660412609287.stgit@web.messagingengine.com> (Ian Kent's message of "Fri, 28 May 2021 14:34:15 +0800")
Ian Kent <raven@themaw.net> writes:
> The kernfs global lock restricts the ability to perform kernfs node
> lookup operations in parallel during path walks.
>
> Change the kernfs mutex to an rwsem so that, when opportunity arises,
> node searches can be done in parallel with path walk lookups.
>
> Signed-off-by: Ian Kent <raven@themaw.net>
> ---
> fs/kernfs/dir.c | 117 ++++++++++++++++++++++++-------------------
> fs/kernfs/file.c | 4 +
> fs/kernfs/inode.c | 16 +++---
> fs/kernfs/kernfs-internal.h | 5 +-
> fs/kernfs/mount.c | 12 ++--
> fs/kernfs/symlink.c | 4 +
> include/linux/kernfs.h | 2 -
> 7 files changed, 86 insertions(+), 74 deletions(-)
>
> diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
> index 5151c712f06f5..1e2e35a201dfb 100644
> --- a/fs/kernfs/dir.c
> +++ b/fs/kernfs/dir.c
> @@ -17,7 +17,7 @@
>
> #include "kernfs-internal.h"
>
> -DEFINE_MUTEX(kernfs_mutex);
> +DECLARE_RWSEM(kernfs_rwsem);
> static DEFINE_SPINLOCK(kernfs_rename_lock); /* kn->parent and ->name */
> static char kernfs_pr_cont_buf[PATH_MAX]; /* protected by rename_lock */
> static DEFINE_SPINLOCK(kernfs_idr_lock); /* root->ino_idr */
> @@ -26,10 +26,21 @@ static DEFINE_SPINLOCK(kernfs_idr_lock); /* root->ino_idr */
>
> static bool kernfs_active(struct kernfs_node *kn)
> {
> - lockdep_assert_held(&kernfs_mutex);
> return atomic_read(&kn->active) >= 0;
> }
>
> +static bool kernfs_active_write(struct kernfs_node *kn)
> +{
> + lockdep_assert_held_write(&kernfs_rwsem);
> + return kernfs_active(kn);
> +}
> +
> +static bool kernfs_active_read(struct kernfs_node *kn)
> +{
> + lockdep_assert_held_read(&kernfs_rwsem);
> + return kernfs_active(kn);
> +}
This bit is unnecessary and confusing. There is nothing read/write
about how the kernfs file is active (aka being used be a function).
Further all that is needed for correct operation is:
> static bool kernfs_active(struct kernfs_node *kn)
> {
> - lockdep_assert_held(&kernfs_mutex);
> + lockdep_assert_held(&kernfs_rwsem);
> return atomic_read(&kn->active) >= 0;
> }
Eric
next prev parent reply other threads:[~2021-06-03 16:59 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-28 6:33 [REPOST PATCH v4 0/5] kernfs: proposed locking and concurrency improvement Ian Kent
2021-05-28 6:33 ` [REPOST PATCH v4 1/5] kernfs: move revalidate to be near lookup Ian Kent
2021-06-03 14:50 ` Eric W. Biederman
2021-06-04 2:29 ` Ian Kent
2021-05-28 6:34 ` [REPOST PATCH v4 2/5] kernfs: use VFS negative dentry caching Ian Kent
2021-06-01 12:41 ` Miklos Szeredi
2021-06-02 3:44 ` Ian Kent
2021-06-02 8:58 ` Miklos Szeredi
2021-06-02 10:57 ` Ian Kent
2021-06-03 2:15 ` Ian Kent
2021-06-03 23:57 ` Ian Kent
2021-06-04 1:07 ` Ian Kent
2021-06-03 17:26 ` Eric W. Biederman
2021-06-03 18:06 ` Miklos Szeredi
2021-06-03 22:02 ` Eric W. Biederman
2021-06-04 3:14 ` Ian Kent
2021-06-04 14:28 ` Eric W. Biederman
2021-06-05 3:19 ` Ian Kent
2021-06-05 20:52 ` Eric W. Biederman
2021-05-28 6:34 ` [REPOST PATCH v4 3/5] kernfs: switch kernfs to use an rwsem Ian Kent
2021-06-01 13:11 ` Miklos Szeredi
2021-06-03 16:59 ` Eric W. Biederman [this message]
2021-05-28 6:34 ` [REPOST PATCH v4 4/5] kernfs: use i_lock to protect concurrent inode updates Ian Kent
2021-05-31 14:53 ` [kernfs] 9a658329cd: stress-ng.get.ops_per_sec 191.4% improvement kernel test robot
2021-06-01 13:18 ` [REPOST PATCH v4 4/5] kernfs: use i_lock to protect concurrent inode updates Miklos Szeredi
2021-06-02 5:41 ` Ian Kent
2021-05-28 6:34 ` [REPOST PATCH v4 5/5] kernfs: add kernfs_need_inode_refresh() Ian Kent
2021-05-28 8:56 ` [REPOST PATCH v4 0/5] kernfs: proposed locking and concurrency improvement Greg Kroah-Hartman
2021-05-28 11:56 ` Fox Chen
2021-05-30 4:44 ` Fox Chen
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