On Tue 29-06-21 15:10:24, Gabriel Krisman Bertazi wrote:
> FAN_ERROR will require an error structure to be stored per mark. But,
> since FAN_ERROR doesn't apply to inode/mount marks, it should suffice to
> only expose this information for superblock marks. Therefore, wrap this
> kind of marks into a container and plumb it for the future.
>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
...
> -static void fanotify_free_mark(struct fsnotify_mark *fsn_mark)
> +static void fanotify_free_mark(struct fsnotify_mark *mark)
> {
> - kmem_cache_free(fanotify_mark_cache, fsn_mark);
> + if (mark->flags & FSNOTIFY_MARK_FLAG_SB) {
> + struct fanotify_sb_mark *fa_mark = FANOTIFY_SB_MARK(mark);
> +
> + kmem_cache_free(fanotify_sb_mark_cache, fa_mark);
> + } else {
> + kmem_cache_free(fanotify_mark_cache, mark);
> + }
> }
Frankly, I find using mark->flags for fanotify internal distinction of mark
type somewhat ugly. Even more so because fsnotify_put_mark() could infer
the mark type information from mark->conn->type and pass it to the freeing
function. But the passing would be somewhat non-trivial so probably we can
leave that for some other day. But the fact that FSNOTIFY_MARK_FLAG_SB is
set inside fsnotify-backend specific code is a landmine waiting just for
another backend to start supporting sb marks, not set
FSNOTIFY_MARK_FLAG_SB, and some generic code depend on checking
FSNOTIFY_MARK_FLAG_SB instead of mark->conn->type.
So I see two sensible solutions:
a) Just admit this is fanotify private flag, carve out some flags from
mark->flags as backend private and have FANOTIFY_MARK_FLAG_SB in that space
(e.g. look how include/linux/buffer_head.h has flags upto BH_PrivateStart,
then e.g. include/linux/jbd2.h starts its flags from BH_PrivateStart
further).
b) Make a rule that mark connector type is also stored in mark->flags. We
have plenty of space there so why not. Then fsnotify_add_mark_locked() has
to store type into the flags.
Pick your poison :)
Honza
> const struct fsnotify_ops fanotify_fsnotify_ops = {
> diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
> index 4a5e555dc3d2..fd125a949187 100644
> --- a/fs/notify/fanotify/fanotify.h
> +++ b/fs/notify/fanotify/fanotify.h
> @@ -6,6 +6,7 @@
> #include <linux/hashtable.h>
>
> extern struct kmem_cache *fanotify_mark_cache;
> +extern struct kmem_cache *fanotify_sb_mark_cache;
> extern struct kmem_cache *fanotify_fid_event_cachep;
> extern struct kmem_cache *fanotify_path_event_cachep;
> extern struct kmem_cache *fanotify_perm_event_cachep;
> @@ -129,6 +130,18 @@ static inline void fanotify_info_copy_name(struct fanotify_info *info,
> name->name);
> }
>
> +struct fanotify_sb_mark {
> + struct fsnotify_mark fsn_mark;
> +};
> +
> +static inline
> +struct fanotify_sb_mark *FANOTIFY_SB_MARK(struct fsnotify_mark *mark)
> +{
> + WARN_ON(!(mark->flags & FSNOTIFY_MARK_FLAG_SB));
> +
> + return container_of(mark, struct fanotify_sb_mark, fsn_mark);
> +}
> +
> /*
> * Common structure for fanotify events. Concrete structs are allocated in
> * fanotify_handle_event() and freed when the information is retrieved by
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index 67b18dfe0025..a42521e140e6 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -99,6 +99,7 @@ struct ctl_table fanotify_table[] = {
> extern const struct fsnotify_ops fanotify_fsnotify_ops;
>
> struct kmem_cache *fanotify_mark_cache __read_mostly;
> +struct kmem_cache *fanotify_sb_mark_cache __read_mostly;
> struct kmem_cache *fanotify_fid_event_cachep __read_mostly;
> struct kmem_cache *fanotify_path_event_cachep __read_mostly;
> struct kmem_cache *fanotify_perm_event_cachep __read_mostly;
> @@ -915,6 +916,38 @@ static __u32 fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
> return mask & ~oldmask;
> }
>
> +static struct fsnotify_mark *fanotify_alloc_mark(struct fsnotify_group *group,
> + unsigned int type)
> +{
> + struct fanotify_sb_mark *sb_mark;
> + struct fsnotify_mark *mark;
> +
> + switch (type) {
> + case FSNOTIFY_OBJ_TYPE_SB:
> + sb_mark = kmem_cache_zalloc(fanotify_sb_mark_cache, GFP_KERNEL);
> + if (!sb_mark)
> + return NULL;
> + mark = &sb_mark->fsn_mark;
> + break;
> +
> + case FSNOTIFY_OBJ_TYPE_INODE:
> + case FSNOTIFY_OBJ_TYPE_PARENT:
> + case FSNOTIFY_OBJ_TYPE_VFSMOUNT:
> + mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
> + break;
> + default:
> + WARN_ON(1);
> + return NULL;
> + }
> +
> + fsnotify_init_mark(mark, group);
> +
> + if (type == FSNOTIFY_OBJ_TYPE_SB)
> + mark->flags |= FSNOTIFY_MARK_FLAG_SB;
> +
> + return mark;
> +}
> +
> static struct fsnotify_mark *fanotify_add_new_mark(struct fsnotify_group *group,
> fsnotify_connp_t *connp,
> unsigned int type,
> @@ -933,13 +966,12 @@ static struct fsnotify_mark *fanotify_add_new_mark(struct fsnotify_group *group,
> !inc_ucount(ucounts->ns, ucounts->uid, UCOUNT_FANOTIFY_MARKS))
> return ERR_PTR(-ENOSPC);
>
> - mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
> + mark = fanotify_alloc_mark(group, type);
> if (!mark) {
> ret = -ENOMEM;
> goto out_dec_ucounts;
> }
>
> - fsnotify_init_mark(mark, group);
> ret = fsnotify_add_mark_locked(mark, connp, type, 0, fsid);
> if (ret) {
> fsnotify_put_mark(mark);
> @@ -1497,6 +1529,8 @@ static int __init fanotify_user_setup(void)
>
> fanotify_mark_cache = KMEM_CACHE(fsnotify_mark,
> SLAB_PANIC|SLAB_ACCOUNT);
> + fanotify_sb_mark_cache = KMEM_CACHE(fanotify_sb_mark,
> + SLAB_PANIC|SLAB_ACCOUNT);
> fanotify_fid_event_cachep = KMEM_CACHE(fanotify_fid_event,
> SLAB_PANIC);
> fanotify_path_event_cachep = KMEM_CACHE(fanotify_path_event,
> diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
> index 1ce66748a2d2..c4473b467c28 100644
> --- a/include/linux/fsnotify_backend.h
> +++ b/include/linux/fsnotify_backend.h
> @@ -401,6 +401,7 @@ struct fsnotify_mark {
> #define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY 0x01
> #define FSNOTIFY_MARK_FLAG_ALIVE 0x02
> #define FSNOTIFY_MARK_FLAG_ATTACHED 0x04
> +#define FSNOTIFY_MARK_FLAG_SB 0x08
> unsigned int flags; /* flags [mark->lock] */
> };
>
> --
> 2.32.0
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
