From: Ian Kent <raven@themaw.net>
To: Miklos Szeredi <miklos@szeredi.hu>
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>,
Marcelo Tosatti <mtosatti@redhat.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Carlos Maiolino <cmaiolino@redhat.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v6 2/7] kernfs: add a revision to identify directory node changes
Date: Fri, 11 Jun 2021 20:56:18 +0800 [thread overview]
Message-ID: <03f6e366fb4ebb56b15541d53eda461a55d3d38e.camel@themaw.net> (raw)
In-Reply-To: <CAJfpeguzPEy+UAcyT4tcpvYxeTwB+64yxRw8Sh7UBROBuafYdw@mail.gmail.com>
On Fri, 2021-06-11 at 14:49 +0200, Miklos Szeredi wrote:
> On Wed, 9 Jun 2021 at 10:50, Ian Kent <raven@themaw.net> wrote:
> >
> > Add a revision counter to kernfs directory nodes so it can be used
> > to detect if a directory node has changed during negative dentry
> > revalidation.
> >
> > There's an assumption that sizeof(unsigned long) <= sizeof(pointer)
> > on all architectures and as far as I know that assumption holds.
> >
> > So adding a revision counter to the struct kernfs_elem_dir variant
> > of
> > the kernfs_node type union won't increase the size of the
> > kernfs_node
> > struct. This is because struct kernfs_elem_dir is at least
> > sizeof(pointer) smaller than the largest union variant. It's
> > tempting
> > to make the revision counter a u64 but that would increase the size
> > of
> > kernfs_node on archs where sizeof(pointer) is smaller than the
> > revision
> > counter.
> >
> > Signed-off-by: Ian Kent <raven@themaw.net>
> > ---
> > fs/kernfs/dir.c | 2 ++
> > fs/kernfs/kernfs-internal.h | 23 +++++++++++++++++++++++
> > include/linux/kernfs.h | 5 +++++
> > 3 files changed, 30 insertions(+)
> >
> > diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
> > index 33166ec90a112..b3d1bc0f317d0 100644
> > --- a/fs/kernfs/dir.c
> > +++ b/fs/kernfs/dir.c
> > @@ -372,6 +372,7 @@ static int kernfs_link_sibling(struct
> > kernfs_node *kn)
> > /* successfully added, account subdir number */
> > if (kernfs_type(kn) == KERNFS_DIR)
> > kn->parent->dir.subdirs++;
> > + kernfs_inc_rev(kn->parent);
> >
> > return 0;
> > }
> > @@ -394,6 +395,7 @@ static bool kernfs_unlink_sibling(struct
> > kernfs_node *kn)
> >
> > if (kernfs_type(kn) == KERNFS_DIR)
> > kn->parent->dir.subdirs--;
> > + kernfs_inc_rev(kn->parent);
> >
> > rb_erase(&kn->rb, &kn->parent->dir.children);
> > RB_CLEAR_NODE(&kn->rb);
> > diff --git a/fs/kernfs/kernfs-internal.h b/fs/kernfs/kernfs-
> > internal.h
> > index ccc3b44f6306f..b4e7579e04799 100644
> > --- a/fs/kernfs/kernfs-internal.h
> > +++ b/fs/kernfs/kernfs-internal.h
> > @@ -81,6 +81,29 @@ static inline struct kernfs_node
> > *kernfs_dentry_node(struct dentry *dentry)
> > return d_inode(dentry)->i_private;
> > }
> >
> > +static inline void kernfs_set_rev(struct kernfs_node *kn,
> > + struct dentry *dentry)
> > +{
> > + if (kernfs_type(kn) == KERNFS_DIR)
> > + dentry->d_time = kn->dir.rev;
> > +}
> > +
> > +static inline void kernfs_inc_rev(struct kernfs_node *kn)
> > +{
> > + if (kernfs_type(kn) == KERNFS_DIR)
> > + kn->dir.rev++;
> > +}
> > +
> > +static inline bool kernfs_dir_changed(struct kernfs_node *kn,
> > + struct dentry *dentry)
> > +{
> > + if (kernfs_type(kn) == KERNFS_DIR) {
>
> Aren't these always be called on a KERNFS_DIR node?
Yes they are.
>
> You could just reduce that to a WARN_ON, or remove the conditions
> altogether then.
I was tempted to not use the check, a WARN_ON sounds better than
removing the check, I'll do that in a v7.
Thanks
Ian
next prev parent reply other threads:[~2021-06-11 12:56 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-09 8:49 [PATCH v6 0/7] kernfs: proposed locking and concurrency improvement Ian Kent
2021-06-09 8:49 ` [PATCH v6 1/7] kernfs: move revalidate to be near lookup Ian Kent
2021-06-11 12:45 ` Miklos Szeredi
2021-06-09 8:49 ` [PATCH v6 2/7] kernfs: add a revision to identify directory node changes Ian Kent
2021-06-11 12:49 ` Miklos Szeredi
2021-06-11 12:56 ` Ian Kent [this message]
2021-06-11 13:11 ` Greg Kroah-Hartman
2021-06-11 13:31 ` Ian Kent
2021-06-11 14:05 ` Greg Kroah-Hartman
2021-06-11 14:16 ` Ian Kent
2021-06-09 8:50 ` [PATCH v6 3/7] kernfs: use VFS negative dentry caching Ian Kent
2021-06-11 13:07 ` Miklos Szeredi
2021-06-12 0:47 ` Ian Kent
2021-06-12 1:48 ` Al Viro
2021-06-13 1:16 ` Ian Kent
2021-06-12 0:07 ` Al Viro
2021-06-12 0:43 ` Ian Kent
2021-06-12 1:08 ` Ian Kent
2021-06-12 1:51 ` Al Viro
2021-06-13 1:57 ` Ian Kent
2021-06-09 8:50 ` [PATCH v6 4/7] kernfs: switch kernfs to use an rwsem Ian Kent
2021-06-11 13:10 ` Miklos Szeredi
2021-06-12 1:24 ` Al Viro
2021-06-09 8:51 ` [PATCH v6 5/7] kernfs: use i_lock to protect concurrent inode updates Ian Kent
2021-06-11 13:11 ` Miklos Szeredi
2021-06-12 1:45 ` Al Viro
2021-06-13 1:31 ` Ian Kent
2021-06-14 1:32 ` Ian Kent
2021-06-14 6:52 ` Ian Kent
2021-06-14 7:16 ` Ian Kent
2021-06-09 8:52 ` [PATCH v6 6/7] kernfs: add kernfs_need_inode_refresh() Ian Kent
2021-06-11 13:13 ` Miklos Szeredi
2021-06-09 8:52 ` [PATCH v6 7/7] kernfs: dont call d_splice_alias() under kernfs node lock Ian Kent
2021-06-11 13:14 ` Miklos Szeredi
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