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Message-ID: <bcbb928cda44551c8587f4967289f4d060f03646.camel@themaw.net>
Date: Fri, 04 Jun 2021 10:29:21 +0800
From: Ian Kent <raven@...maw.net>
To: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Tejun Heo <tj@...nel.org>, Eric Sandeen <sandeen@...deen.net>,
Fox Chen <foxhlchen@...il.com>,
Brice Goglin <brice.goglin@...il.com>,
Al Viro <viro@...IV.linux.org.uk>,
Rick Lindsley <ricklind@...ux.vnet.ibm.com>,
David Howells <dhowells@...hat.com>,
Miklos Szeredi <miklos@...redi.hu>,
Marcelo Tosatti <mtosatti@...hat.com>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [REPOST PATCH v4 1/5] kernfs: move revalidate to be near lookup
On Thu, 2021-06-03 at 09:50 -0500, Eric W. Biederman wrote:
> Ian Kent <raven@...maw.net> writes:
>
> > While the dentry operation kernfs_dop_revalidate() is grouped with
> > dentry type functions it also has a strong affinity to the inode
> > operation ->lookup().
> >
> > In order to take advantage of the VFS negative dentry caching that
> > can be used to reduce path lookup overhead on non-existent paths it
> > will need to call kernfs_find_ns(). So, to avoid a forward
> > declaration,
> > move it to be near kernfs_iop_lookup().
> >
> > There's no functional change from this patch.
>
> Does this patch compile independently?
Doubt it.
>
> During the code movement kernfs_active is replaced
> by kernfs_active_read which does not exist yet.
Oops, that was a consequence of reordering the series which I
didn't catch.
I'll fix that when I post a v5 which I'm going to have to do.
Thanks for looking at this Eric,
Ian
>
> Eric
>
> > Signed-off-by: Ian Kent <raven@...maw.net>
> > ---
> > fs/kernfs/dir.c | 86 ++++++++++++++++++++++++++++---------------
> > ------------
> > 1 file changed, 43 insertions(+), 43 deletions(-)
> >
> > diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
> > index 7e0e62deab53c..4c69e2af82dac 100644
> > --- a/fs/kernfs/dir.c
> > +++ b/fs/kernfs/dir.c
> > @@ -548,49 +548,6 @@ void kernfs_put(struct kernfs_node *kn)
> > }
> > EXPORT_SYMBOL_GPL(kernfs_put);
> >
> > -static int kernfs_dop_revalidate(struct dentry *dentry, unsigned
> > int flags)
> > -{
> > - struct kernfs_node *kn;
> > -
> > - if (flags & LOOKUP_RCU)
> > - return -ECHILD;
> > -
> > - /* Always perform fresh lookup for negatives */
> > - if (d_really_is_negative(dentry))
> > - goto out_bad_unlocked;
> > -
> > - kn = kernfs_dentry_node(dentry);
> > - mutex_lock(&kernfs_mutex);
> > -
> > - /* The kernfs node has been deactivated */
> > - if (!kernfs_active(kn))
> > - goto out_bad;
> > -
> > - /* The kernfs node has been moved? */
> > - if (kernfs_dentry_node(dentry->d_parent) != kn->parent)
> > - goto out_bad;
> > -
> > - /* The kernfs node has been renamed */
> > - if (strcmp(dentry->d_name.name, kn->name) != 0)
> > - goto out_bad;
> > -
> > - /* The kernfs node has been moved to a different namespace
> > */
> > - if (kn->parent && kernfs_ns_enabled(kn->parent) &&
> > - kernfs_info(dentry->d_sb)->ns != kn->ns)
> > - goto out_bad;
> > -
> > - mutex_unlock(&kernfs_mutex);
> > - return 1;
> > -out_bad:
> > - mutex_unlock(&kernfs_mutex);
> > -out_bad_unlocked:
> > - return 0;
> > -}
> > -
> > -const struct dentry_operations kernfs_dops = {
> > - .d_revalidate = kernfs_dop_revalidate,
> > -};
> > -
> > /**
> > * kernfs_node_from_dentry - determine kernfs_node associated with
> > a dentry
> > * @dentry: the dentry in question
> > @@ -1073,6 +1030,49 @@ struct kernfs_node
> > *kernfs_create_empty_dir(struct kernfs_node *parent,
> > return ERR_PTR(rc);
> > }
> >
> > +static int kernfs_dop_revalidate(struct dentry *dentry, unsigned
> > int flags)
> > +{
> > + struct kernfs_node *kn;
> > +
> > + if (flags & LOOKUP_RCU)
> > + return -ECHILD;
> > +
> > + /* Always perform fresh lookup for negatives */
> > + if (d_really_is_negative(dentry))
> > + goto out_bad_unlocked;
> > +
> > + kn = kernfs_dentry_node(dentry);
> > + mutex_lock(&kernfs_mutex);
> > +
> > + /* The kernfs node has been deactivated */
> > + if (!kernfs_active_read(kn))
> > + goto out_bad;
> > +
> > + /* The kernfs node has been moved? */
> > + if (kernfs_dentry_node(dentry->d_parent) != kn->parent)
> > + goto out_bad;
> > +
> > + /* The kernfs node has been renamed */
> > + if (strcmp(dentry->d_name.name, kn->name) != 0)
> > + goto out_bad;
> > +
> > + /* The kernfs node has been moved to a different namespace
> > */
> > + if (kn->parent && kernfs_ns_enabled(kn->parent) &&
> > + kernfs_info(dentry->d_sb)->ns != kn->ns)
> > + goto out_bad;
> > +
> > + mutex_unlock(&kernfs_mutex);
> > + return 1;
> > +out_bad:
> > + mutex_unlock(&kernfs_mutex);
> > +out_bad_unlocked:
> > + return 0;
> > +}
> > +
> > +const struct dentry_operations kernfs_dops = {
> > + .d_revalidate = kernfs_dop_revalidate,
> > +};
> > +
> > static struct dentry *kernfs_iop_lookup(struct inode *dir,
> > struct dentry *dentry,
> > unsigned int flags)
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