Messages in this thread | | | From | Miklos Szeredi <> | Date | Fri, 11 Jun 2021 14:49:43 +0200 | Subject | Re: [PATCH v6 2/7] kernfs: add a revision to identify directory node changes |
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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?
You could just reduce that to a WARN_ON, or remove the conditions altogether then.
Thanks, Miklos
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