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| author | Ian Kent <raven@themaw.net> | 2021-07-16 12:28:18 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-07-27 10:29:14 +0300 |
| commit | 895adbec302e92086359e6fd92611ac3be6d92c3 (patch) | |
| tree | f2b672c39511d1918b8ff32bfd6e8038d84c3f15 /fs/kernfs | |
| parent | bdac4d8abbfc239886103f7c6ee03abb8011a008 (diff) | |
| download | linux-895adbec302e92086359e6fd92611ac3be6d92c3.tar.xz | |
kernfs: add a revision to identify directory node changes
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.
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Ian Kent <raven@themaw.net>
Link: https://lore.kernel.org/r/162642769895.63632.8356662784964509867.stgit@web.messagingengine.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/kernfs')
| -rw-r--r-- | fs/kernfs/dir.c | 2 | ||||
| -rw-r--r-- | fs/kernfs/kernfs-internal.h | 19 |
2 files changed, 21 insertions, 0 deletions
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index 33166ec90a11..b3d1bc0f317d 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 ccc3b44f6306..c2ae58f3b202 100644 --- a/fs/kernfs/kernfs-internal.h +++ b/fs/kernfs/kernfs-internal.h @@ -81,6 +81,25 @@ 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 *parent, + struct dentry *dentry) +{ + dentry->d_time = parent->dir.rev; +} + +static inline void kernfs_inc_rev(struct kernfs_node *parent) +{ + parent->dir.rev++; +} + +static inline bool kernfs_dir_changed(struct kernfs_node *parent, + struct dentry *dentry) +{ + if (parent->dir.rev != dentry->d_time) + return true; + return false; +} + extern const struct super_operations kernfs_sops; extern struct kmem_cache *kernfs_node_cache, *kernfs_iattrs_cache; |