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Commit 00356bd5 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: clean up cgroup_serial_nr_cursor 



cgroup_serial_nr_cursor was created atomic64_t because I thought it
was never gonna used for anything other than assigning unique numbers
to cgroups and didn't want to worry about synchronization; however,
now we're using it as an event-stamp to distinguish cgroups created
before and after certain point which assumes that it's protected by
cgroup_mutex.

Let's make it clear by making it a u64.  Also, rename it to
cgroup_serial_nr_next and make it point to the next nr to allocate so
that where it's pointing to is clear and more conventional.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
parent e8c82d20

kernel/cgroup.c

+8 −7
Original line number Diff line number Diff line
@@ -203,9 +203,10 @@ static struct cgroup_name root_cgroup_name = { .name = "/" }; 
 * guarantees cgroups with bigger numbers are newer than those with smaller

 * numbers.  Also, as cgroups are always appended to the parent's

 * ->children list, it guarantees that sibling cgroups are always sorted in

 * the ascending serial number order on the list.

 * the ascending serial number order on the list.  Protected by

 * cgroup_mutex.

 */

static atomic64_t cgroup_serial_nr_cursor = ATOMIC64_INIT(0);

static u64 cgroup_serial_nr_next = 1;



/* This flag indicates whether tasks in the fork and exit paths should

 * check for fork/exit handlers to call. This avoids us having to do
@@ -2803,7 +2804,7 @@ static void cgroup_cfts_commit(struct cgroup_subsys *ss, 
	struct super_block *sb = ss->root->sb;

	struct dentry *prev = NULL;

	struct inode *inode;

	u64 update_upto;

	u64 update_before;



	/* %NULL @cfts indicates abort and don't bother if @ss isn't attached */

	if (!cfts || ss->root == &rootnode ||
@@ -2815,9 +2816,9 @@ static void cgroup_cfts_commit(struct cgroup_subsys *ss, 
	/*

	 * All cgroups which are created after we drop cgroup_mutex will

	 * have the updated set of files, so we only need to update the

	 * cgroups created before the current @cgroup_serial_nr_cursor.

	 * cgroups created before the current @cgroup_serial_nr_next.

	 */

	update_upto = atomic64_read(&cgroup_serial_nr_cursor);

	update_before = cgroup_serial_nr_next;



	mutex_unlock(&cgroup_mutex);
@@ -2844,7 +2845,7 @@ static void cgroup_cfts_commit(struct cgroup_subsys *ss, 


		mutex_lock(&inode->i_mutex);

		mutex_lock(&cgroup_mutex);

		if (cgrp->serial_nr <= update_upto && !cgroup_is_dead(cgrp))

		if (cgrp->serial_nr < update_before && !cgroup_is_dead(cgrp))

			cgroup_addrm_files(cgrp, ss, cfts, is_add);

		mutex_unlock(&cgroup_mutex);

		mutex_unlock(&inode->i_mutex);
@@ -4327,7 +4328,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry, 
		goto err_free_all;

	lockdep_assert_held(&dentry->d_inode->i_mutex);



	cgrp->serial_nr = atomic64_inc_return(&cgroup_serial_nr_cursor);

	cgrp->serial_nr = cgroup_serial_nr_next++;



	/* allocation complete, commit to creation */

	list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);