fsnotify: srcu to protect read side of inode and vfsmount locks
Currently reading the inode->i_fsnotify_marks or
vfsmount->mnt_fsnotify_marks lists are protected by a spinlock on both the
read and the write side. This patch protects the read side of those lists
with a new single srcu.
Signed-off-by: Eric Paris <eparis@redhat.com>
diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index 4788c86..4678b41 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -144,14 +144,15 @@
{
struct fsnotify_mark *mark;
struct hlist_node *node;
+ int idx;
+
+ idx = srcu_read_lock(&fsnotify_mark_srcu);
if (!hlist_empty(&inode->i_fsnotify_marks)) {
- spin_lock(&inode->i_lock);
- hlist_for_each_entry(mark, node, &inode->i_fsnotify_marks, i.i_list) {
+ hlist_for_each_entry_rcu(mark, node, &inode->i_fsnotify_marks, i.i_list) {
if (!(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
mark->ignored_mask = 0;
}
- spin_unlock(&inode->i_lock);
}
if (data_is == FSNOTIFY_EVENT_FILE) {
@@ -159,14 +160,14 @@
mnt = ((struct file *)data)->f_path.mnt;
if (mnt && !hlist_empty(&mnt->mnt_fsnotify_marks)) {
- spin_lock(&mnt->mnt_root->d_lock);
- hlist_for_each_entry(mark, node, &mnt->mnt_fsnotify_marks, m.m_list) {
+ hlist_for_each_entry_rcu(mark, node, &mnt->mnt_fsnotify_marks, m.m_list) {
if (!(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
mark->ignored_mask = 0;
}
- spin_unlock(&mnt->mnt_root->d_lock);
}
}
+
+ srcu_read_unlock(&fsnotify_mark_srcu, idx);
}
static int send_to_group(struct fsnotify_group *group, struct inode *to_tell,
@@ -208,8 +209,10 @@
int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
const unsigned char *file_name, u32 cookie)
{
+ struct fsnotify_mark *mark;
struct fsnotify_group *group;
struct fsnotify_event *event = NULL;
+ struct hlist_node *node;
struct vfsmount *mnt = NULL;
int idx, ret = 0;
/* global tests shouldn't care about events on child only the specific event */
@@ -237,35 +240,47 @@
!needed_by_vfsmount(test_mask, mnt))
return 0;
- /*
- * SRCU!! the groups list is very very much read only and the path is
- * very hot. The VAST majority of events are not going to need to do
- * anything other than walk the list so it's crazy to pre-allocate.
- */
- idx = srcu_read_lock(&fsnotify_grp_srcu);
+ idx = srcu_read_lock(&fsnotify_mark_srcu);
if (test_mask & to_tell->i_fsnotify_mask) {
- list_for_each_entry_rcu(group, &fsnotify_inode_groups, inode_group_list) {
- if (test_mask & group->mask) {
- ret = send_to_group(group, to_tell, NULL, mask, data, data_is,
- cookie, file_name, &event);
+ hlist_for_each_entry_rcu(mark, node, &to_tell->i_fsnotify_marks, i.i_list) {
+
+ pr_debug("%s: inode_loop: mark=%p mark->mask=%x mark->ignored_mask=%x\n",
+ __func__, mark, mark->mask, mark->ignored_mask);
+
+ if (test_mask & mark->mask & ~mark->ignored_mask) {
+ group = mark->group;
+ if (!group)
+ continue;
+ ret = send_to_group(group, to_tell, NULL, mask,
+ data, data_is, cookie, file_name,
+ &event);
if (ret)
goto out;
}
}
}
- if (needed_by_vfsmount(test_mask, mnt)) {
- list_for_each_entry_rcu(group, &fsnotify_vfsmount_groups, vfsmount_group_list) {
- if (test_mask & group->mask) {
- ret = send_to_group(group, to_tell, mnt, mask, data, data_is,
- cookie, file_name, &event);
+
+ if (mnt && (test_mask & mnt->mnt_fsnotify_mask)) {
+ hlist_for_each_entry_rcu(mark, node, &mnt->mnt_fsnotify_marks, m.m_list) {
+
+ pr_debug("%s: mnt_loop: mark=%p mark->mask=%x mark->ignored_mask=%x\n",
+ __func__, mark, mark->mask, mark->ignored_mask);
+
+ if (test_mask & mark->mask & ~mark->ignored_mask) {
+ group = mark->group;
+ if (!group)
+ continue;
+ ret = send_to_group(group, to_tell, mnt, mask,
+ data, data_is, cookie, file_name,
+ &event);
if (ret)
goto out;
}
}
}
out:
- srcu_read_unlock(&fsnotify_grp_srcu, idx);
+ srcu_read_unlock(&fsnotify_mark_srcu, idx);
/*
* fsnotify_create_event() took a reference so the event can't be cleaned
* up while we are still trying to add it to lists, drop that one.
@@ -279,8 +294,14 @@
static __init int fsnotify_init(void)
{
+ int ret;
+
BUG_ON(hweight32(ALL_FSNOTIFY_EVENTS) != 23);
- return init_srcu_struct(&fsnotify_grp_srcu);
+ ret = init_srcu_struct(&fsnotify_mark_srcu);
+ if (ret)
+ panic("initializing fsnotify_mark_srcu");
+
+ return 0;
}
-subsys_initcall(fsnotify_init);
+core_initcall(fsnotify_init);