[PATCH 08/10] fsnotify: introduce locked versions of fsnotify_add_mark() and fsnotify_remove_mark()
Stefan Bader
stefan.bader at canonical.com
Mon Apr 16 18:47:28 UTC 2012
On 16.04.2012 20:02, Andy Whitcroft wrote:
> From: Lino Sanfilippo <LinoSanfilippo at gmx.de>
>
> This patch introduces fsnotify_add_mark_locked() and fsnotify_remove_mark_locked()
> which are essentially the same as fsnotify_add_mark() and fsnotify_remove_mark() but
> assume that the caller has already taken the groups mark mutex.
>
> Signed-off-by: Lino Sanfilippo <LinoSanfilippo at gmx.de>
> Signed-off-by: Eric Paris <eparis at redhat.com>
>
> (cherry-picked from commit fb634e66bbe4119fe5074ecf89630cdb361041d6 git://git.infradead.org/users/eparis/notify.git)
> BugLink: http://bugs.launchpad.net/bugs/922906
> Signed-off-by: Andy Whitcroft <apw at canonical.com>
> ---
> fs/notify/mark.c | 42 +++++++++++++++++++++++++++-----------
> include/linux/fsnotify_backend.h | 4 ++++
> 2 files changed, 34 insertions(+), 12 deletions(-)
>
> diff --git a/fs/notify/mark.c b/fs/notify/mark.c
> index 716b7e2..37962c7 100644
> --- a/fs/notify/mark.c
> +++ b/fs/notify/mark.c
> @@ -122,18 +122,18 @@ EXPORT_SYMBOL(fsnotify_put_mark);
> * The caller had better be holding a reference to this mark so we don't actually
> * do the final put under the mark->lock
> */
> -void fsnotify_destroy_mark(struct fsnotify_mark *mark,
> - struct fsnotify_group *group)
> +void fsnotify_destroy_mark_locked(struct fsnotify_mark *mark,
> + struct fsnotify_group *group)
> {
> struct inode *inode = NULL;
>
> - mutex_lock(&group->mark_mutex);
> + BUG_ON(!mutex_is_locked(&group->mark_mutex));
> +
> spin_lock(&mark->lock);
>
> /* something else already called this function on this mark */
> if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
> spin_unlock(&mark->lock);
> - mutex_unlock(&group->mark_mutex);
> return;
> }
>
> @@ -150,6 +150,8 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark,
> list_del_init(&mark->g_list);
>
> spin_unlock(&mark->lock);
> +
> + /* release lock temporarily */
> mutex_unlock(&group->mark_mutex);
>
> spin_lock(&destroy_lock);
Hm, not necessarily means anything, but here the lock is temporarily dropped
while the next patch sort of seems to assume iteration over a list is save
because the lock is held over the iteration...
> @@ -185,6 +187,16 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark,
> */
>
> atomic_dec(&group->num_marks);
> +
> + mutex_lock(&group->mark_mutex);
> +}
> +
> +void fsnotify_destroy_mark(struct fsnotify_mark *mark,
> + struct fsnotify_group *group)
> +{
> + mutex_lock(&group->mark_mutex);
> + fsnotify_destroy_mark_locked(mark, group);
> + mutex_unlock(&group->mark_mutex);
> }
> EXPORT_SYMBOL(fsnotify_destroy_mark);
>
> @@ -210,14 +222,15 @@ void fsnotify_set_mark_ignored_mask_locked(struct fsnotify_mark *mark, __u32 mas
> * These marks may be used for the fsnotify backend to determine which
> * event types should be delivered to which group.
> */
> -int fsnotify_add_mark(struct fsnotify_mark *mark,
> - struct fsnotify_group *group, struct inode *inode,
> - struct vfsmount *mnt, int allow_dups)
> +int fsnotify_add_mark_locked(struct fsnotify_mark *mark,
> + struct fsnotify_group *group, struct inode *inode,
> + struct vfsmount *mnt, int allow_dups)
> {
> int ret = 0;
>
> BUG_ON(inode && mnt);
> BUG_ON(!inode && !mnt);
> + BUG_ON(!mutex_is_locked(&group->mark_mutex));
>
> /*
> * LOCKING ORDER!!!!
> @@ -225,8 +238,6 @@ int fsnotify_add_mark(struct fsnotify_mark *mark,
> * mark->lock
> * inode->i_lock
> */
> - mutex_lock(&group->mark_mutex);
> -
> spin_lock(&mark->lock);
> mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE;
>
> @@ -252,8 +263,6 @@ int fsnotify_add_mark(struct fsnotify_mark *mark,
> fsnotify_set_mark_mask_locked(mark, mark->mask);
> spin_unlock(&mark->lock);
>
> - mutex_unlock(&group->mark_mutex);
> -
> if (inode)
> __fsnotify_update_child_dentry_flags(inode);
>
> @@ -266,7 +275,6 @@ err:
> atomic_dec(&group->num_marks);
>
> spin_unlock(&mark->lock);
> - mutex_unlock(&group->mark_mutex);
>
> spin_lock(&destroy_lock);
> list_add(&mark->destroy_list, &destroy_list);
> @@ -277,6 +285,16 @@ err:
> }
> EXPORT_SYMBOL(fsnotify_add_mark);
>
> +int fsnotify_add_mark(struct fsnotify_mark *mark, struct fsnotify_group *group,
> + struct inode *inode, struct vfsmount *mnt, int allow_dups)
> +{
> + int ret;
> + mutex_lock(&group->mark_mutex);
> + ret = fsnotify_add_mark_locked(mark, group, inode, mnt, allow_dups);
> + mutex_unlock(&group->mark_mutex);
> + return ret;
> +}
> +
> /*
> * clear any marks in a group in which mark->flags & flags is true
> */
> diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
> index 5b33a85..4f205fa 100644
> --- a/include/linux/fsnotify_backend.h
> +++ b/include/linux/fsnotify_backend.h
> @@ -408,9 +408,13 @@ extern void fsnotify_set_mark_mask_locked(struct fsnotify_mark *mark, __u32 mask
> /* attach the mark to both the group and the inode */
> extern int fsnotify_add_mark(struct fsnotify_mark *mark, struct fsnotify_group *group,
> struct inode *inode, struct vfsmount *mnt, int allow_dups);
> +extern int fsnotify_add_mark_locked(struct fsnotify_mark *mark, struct fsnotify_group *group,
> + struct inode *inode, struct vfsmount *mnt, int allow_dups);
> /* given a group and a mark, flag mark to be freed when all references are dropped */
> extern void fsnotify_destroy_mark(struct fsnotify_mark *mark,
> struct fsnotify_group *group);
> +extern void fsnotify_destroy_mark_locked(struct fsnotify_mark *mark,
> + struct fsnotify_group *group);
> /* run all the marks in a group, and clear all of the vfsmount marks */
> extern void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group);
> /* run all the marks in a group, and clear all of the inode marks */
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