The patch titled
Subject: fsnotify: get rid of fsnotify_destroy_mark_locked()
has been added to the -mm tree. Its filename is
fsnotify-get-rid-of-fsnotify_destroy_mark_locked.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/fsnotify-get-rid-of-fsnotify_destroy_mark_locked.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/fsnotify-get-rid-of-fsnotify_destroy_mark_locked.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Jan Kara <jack@xxxxxxxx>
Subject: fsnotify: get rid of fsnotify_destroy_mark_locked()
fsnotify_destroy_mark_locked() is subtle to use because it temporarily
releases group->mark_mutex. To avoid future problems with this function,
split it into two.
fsnotify_detach_mark() is the part that needs group->mark_mutex and
fsnotify_free_mark() is the part that must be called outside of
group->mark_mutex. This way it's much clearer what's going on and we also
avoid some pointless acquisitions of group->mark_mutex.
Signed-off-by: Jan Kara <jack@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/notify/dnotify/dnotify.c | 14 +++--
fs/notify/fanotify/fanotify_user.c | 8 ++
fs/notify/mark.c | 73 ++++++++++++++-------------
include/linux/fsnotify_backend.h | 7 +-
4 files changed, 61 insertions(+), 41 deletions(-)
diff -puN fs/notify/dnotify/dnotify.c~fsnotify-get-rid-of-fsnotify_destroy_mark_locked fs/notify/dnotify/dnotify.c
--- a/fs/notify/dnotify/dnotify.c~fsnotify-get-rid-of-fsnotify_destroy_mark_locked
+++ a/fs/notify/dnotify/dnotify.c
@@ -154,6 +154,7 @@ void dnotify_flush(struct file *filp, fl
struct dnotify_struct *dn;
struct dnotify_struct **prev;
struct inode *inode;
+ bool free = false;
inode = file_inode(filp);
if (!S_ISDIR(inode->i_mode))
@@ -182,11 +183,15 @@ void dnotify_flush(struct file *filp, fl
/* nothing else could have found us thanks to the dnotify_groups
mark_mutex */
- if (dn_mark->dn == NULL)
- fsnotify_destroy_mark_locked(fsn_mark, dnotify_group);
+ if (dn_mark->dn == NULL) {
+ fsnotify_detach_mark(fsn_mark);
+ free = true;
+ }
mutex_unlock(&dnotify_group->mark_mutex);
+ if (free)
+ fsnotify_free_mark(fsn_mark);
fsnotify_put_mark(fsn_mark);
}
@@ -362,9 +367,10 @@ out:
spin_unlock(&fsn_mark->lock);
if (destroy)
- fsnotify_destroy_mark_locked(fsn_mark, dnotify_group);
-
+ fsnotify_detach_mark(fsn_mark);
mutex_unlock(&dnotify_group->mark_mutex);
+ if (destroy)
+ fsnotify_free_mark(fsn_mark);
fsnotify_put_mark(fsn_mark);
out_err:
if (new_fsn_mark)
diff -puN fs/notify/fanotify/fanotify_user.c~fsnotify-get-rid-of-fsnotify_destroy_mark_locked fs/notify/fanotify/fanotify_user.c
--- a/fs/notify/fanotify/fanotify_user.c~fsnotify-get-rid-of-fsnotify_destroy_mark_locked
+++ a/fs/notify/fanotify/fanotify_user.c
@@ -529,8 +529,10 @@ static int fanotify_remove_vfsmount_mark
removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
&destroy_mark);
if (destroy_mark)
- fsnotify_destroy_mark_locked(fsn_mark, group);
+ fsnotify_detach_mark(fsn_mark);
mutex_unlock(&group->mark_mutex);
+ if (destroy_mark)
+ fsnotify_free_mark(fsn_mark);
fsnotify_put_mark(fsn_mark);
if (removed & real_mount(mnt)->mnt_fsnotify_mask)
@@ -557,8 +559,10 @@ static int fanotify_remove_inode_mark(st
removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
&destroy_mark);
if (destroy_mark)
- fsnotify_destroy_mark_locked(fsn_mark, group);
+ fsnotify_detach_mark(fsn_mark);
mutex_unlock(&group->mark_mutex);
+ if (destroy_mark)
+ fsnotify_free_mark(fsn_mark);
/* matches the fsnotify_find_inode_mark() */
fsnotify_put_mark(fsn_mark);
diff -puN fs/notify/mark.c~fsnotify-get-rid-of-fsnotify_destroy_mark_locked fs/notify/mark.c
--- a/fs/notify/mark.c~fsnotify-get-rid-of-fsnotify_destroy_mark_locked
+++ a/fs/notify/mark.c
@@ -122,26 +122,27 @@ u32 fsnotify_recalc_mask(struct hlist_he
}
/*
- * Any time a mark is getting freed we end up here.
- * The caller had better be holding a reference to this mark so we don't actually
- * do the final put under the mark->lock
+ * Remove mark from inode / vfsmount list, group list, drop inode reference
+ * if we got one.
+ *
+ * Must be called with group->mark_mutex held.
*/
-void fsnotify_destroy_mark_locked(struct fsnotify_mark *mark,
- struct fsnotify_group *group)
+void fsnotify_detach_mark(struct fsnotify_mark *mark)
{
struct inode *inode = NULL;
+ struct fsnotify_group *group = mark->group;
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)) {
+ if (!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
spin_unlock(&mark->lock);
return;
}
- mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
+ mark->flags &= ~FSNOTIFY_MARK_FLAG_ATTACHED;
if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) {
inode = mark->inode;
@@ -150,6 +151,12 @@ void fsnotify_destroy_mark_locked(struct
fsnotify_destroy_vfsmount_mark(mark);
else
BUG();
+ /*
+ * Note that we didn't update flags telling whether inode cares about
+ * what's happening with children. We update these flags from
+ * __fsnotify_parent() lazily when next event happens on one of our
+ * children.
+ */
list_del_init(&mark->g_list);
@@ -157,18 +164,32 @@ void fsnotify_destroy_mark_locked(struct
if (inode && (mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED))
iput(inode);
- /* release lock temporarily */
- mutex_unlock(&group->mark_mutex);
+
+ atomic_dec(&group->num_marks);
+}
+
+/*
+ * Free fsnotify mark. The freeing is actually happening from a kthread which
+ * first waits for srcu period end. Caller must have a reference to the mark
+ * or be protected by fsnotify_mark_srcu.
+ */
+void fsnotify_free_mark(struct fsnotify_mark *mark)
+{
+ struct fsnotify_group *group = mark->group;
+
+ spin_lock(&mark->lock);
+ /* something else already called this function on this mark */
+ if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
+ spin_unlock(&mark->lock);
+ return;
+ }
+ mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
+ spin_unlock(&mark->lock);
spin_lock(&destroy_lock);
list_add(&mark->g_list, &destroy_list);
spin_unlock(&destroy_lock);
wake_up(&destroy_waitq);
- /*
- * We don't necessarily have a ref on mark from caller so the above destroy
- * may have actually freed it, unless this group provides a 'freeing_mark'
- * function which must be holding a reference.
- */
/*
* Some groups like to know that marks are being freed. This is a
@@ -177,30 +198,15 @@ void fsnotify_destroy_mark_locked(struct
*/
if (group->ops->freeing_mark)
group->ops->freeing_mark(mark, group);
-
- /*
- * __fsnotify_update_child_dentry_flags(inode);
- *
- * I really want to call that, but we can't, we have no idea if the inode
- * still exists the second we drop the mark->lock.
- *
- * The next time an event arrive to this inode from one of it's children
- * __fsnotify_parent will see that the inode doesn't care about it's
- * children and will update all of these flags then. So really this
- * is just a lazy update (and could be a perf win...)
- */
-
- atomic_dec(&group->num_marks);
-
- mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
}
void fsnotify_destroy_mark(struct fsnotify_mark *mark,
struct fsnotify_group *group)
{
mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
- fsnotify_destroy_mark_locked(mark, group);
+ fsnotify_detach_mark(mark);
mutex_unlock(&group->mark_mutex);
+ fsnotify_free_mark(mark);
}
void fsnotify_destroy_marks(struct hlist_head *head, spinlock_t *lock)
@@ -342,7 +348,7 @@ int fsnotify_add_mark_locked(struct fsno
* inode->i_lock
*/
spin_lock(&mark->lock);
- mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE;
+ mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE | FSNOTIFY_MARK_FLAG_ATTACHED;
fsnotify_get_group(group);
mark->group = group;
@@ -448,8 +454,9 @@ void fsnotify_clear_marks_by_group_flags
}
mark = list_first_entry(&to_free, struct fsnotify_mark, g_list);
fsnotify_get_mark(mark);
- fsnotify_destroy_mark_locked(mark, group);
+ fsnotify_detach_mark(mark);
mutex_unlock(&group->mark_mutex);
+ fsnotify_free_mark(mark);
fsnotify_put_mark(mark);
}
}
diff -puN include/linux/fsnotify_backend.h~fsnotify-get-rid-of-fsnotify_destroy_mark_locked include/linux/fsnotify_backend.h
--- a/include/linux/fsnotify_backend.h~fsnotify-get-rid-of-fsnotify_destroy_mark_locked
+++ a/include/linux/fsnotify_backend.h
@@ -236,6 +236,7 @@ struct fsnotify_mark {
#define FSNOTIFY_MARK_FLAG_OBJECT_PINNED 0x04
#define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY 0x08
#define FSNOTIFY_MARK_FLAG_ALIVE 0x10
+#define FSNOTIFY_MARK_FLAG_ATTACHED 0x20
unsigned int flags; /* flags [mark->lock] */
void (*free_mark)(struct fsnotify_mark *mark); /* called on final put+free */
};
@@ -353,8 +354,10 @@ extern int fsnotify_add_mark_locked(stru
/* 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);
+/* detach mark from inode / mount list, group list, drop inode reference */
+extern void fsnotify_detach_mark(struct fsnotify_mark *mark);
+/* free mark */
+extern void fsnotify_free_mark(struct fsnotify_mark *mark);
/* 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 */
_
Patches currently in -mm which might be from jack@xxxxxxxx are
fsnotify-fix-oops-in-fsnotify_clear_marks_by_group_flags.patch
fs-optimize-inotify-fsnotify-code-for-unwatched-files.patch
fsnotify-document-mark-locking.patch
fsnotify-remove-mark-free_list.patch
fsnotify-get-rid-of-fsnotify_destroy_mark_locked.patch
linux-next.patch
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