The patch titled
Subject: cgroups: forbid pre_destroy() callback failures
has been added to the -mm tree. Its filename is
cgroups-forbid-pre_destroy-callback-to-fail.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** 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: Michal Hocko <mhocko@xxxxxxx>
Subject: cgroups: forbid pre_destroy() callback failures
Now that the mem_cgroup_pre_destroy() callback doesn't fail (other than a
race with a task attach resp. child group appears) finally we can safely
move on and forbid all the callbacks from failing.
The last missing piece is moving cgroup_call_pre_destroy() after
cgroup_clear_css_refs() so that css_tryget() fails so no new charges for
the memcg can happen.
We cannot, however, move cgroup_call_pre_destroy right after because we
cannot call mem_cgroup_pre_destroy with the cgroup_lock held (see 3fa59dfb
cgroup: fix potential deadlock in pre_destroy) so we have to move it after
the lock is released.
Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Glauber Costa <glommer@xxxxxxxxxxxxx>
Cc: Li Zefan <lizefan@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Balbir Singh <bsingharora@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/cgroup.c | 30 +++++++++---------------------
1 file changed, 9 insertions(+), 21 deletions(-)
diff -puN kernel/cgroup.c~cgroups-forbid-pre_destroy-callback-to-fail kernel/cgroup.c
--- a/kernel/cgroup.c~cgroups-forbid-pre_destroy-callback-to-fail
+++ a/kernel/cgroup.c
@@ -858,7 +858,7 @@ static struct inode *cgroup_new_inode(um
* Call subsys's pre_destroy handler.
* This is called before css refcnt check.
*/
-static int cgroup_call_pre_destroy(struct cgroup *cgrp)
+static void cgroup_call_pre_destroy(struct cgroup *cgrp)
{
struct cgroup_subsys *ss;
int ret = 0;
@@ -867,15 +867,8 @@ static int cgroup_call_pre_destroy(struc
if (!ss->pre_destroy)
continue;
- ret = ss->pre_destroy(cgrp);
- if (ret) {
- /* ->pre_destroy() failure is being deprecated */
- WARN_ON_ONCE(!ss->__DEPRECATED_clear_css_refs);
- break;
- }
+ BUG_ON(ss->pre_destroy(cgrp));
}
-
- return ret;
}
static void cgroup_diput(struct dentry *dentry, struct inode *inode)
@@ -4282,7 +4275,6 @@ again:
mutex_unlock(&cgroup_mutex);
return -EBUSY;
}
- mutex_unlock(&cgroup_mutex);
/*
* In general, subsystem has no css->refcnt after pre_destroy(). But
@@ -4295,17 +4287,6 @@ again:
*/
set_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
- /*
- * Call pre_destroy handlers of subsys. Notify subsystems
- * that rmdir() request comes.
- */
- ret = cgroup_call_pre_destroy(cgrp);
- if (ret) {
- clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
- return ret;
- }
-
- mutex_lock(&cgroup_mutex);
parent = cgrp->parent;
if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
@@ -4327,6 +4308,7 @@ again:
return -EINTR;
goto again;
}
+
/* NO css_tryget() can success after here. */
finish_wait(&cgroup_rmdir_waitq, &wait);
clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
@@ -4365,6 +4347,12 @@ again:
spin_unlock(&cgrp->event_list_lock);
mutex_unlock(&cgroup_mutex);
+
+ /*
+ * Call pre_destroy handlers of subsys. Notify subsystems
+ * that rmdir() request comes.
+ */
+ cgroup_call_pre_destroy(cgrp);
return 0;
}
_
Patches currently in -mm which might be from mhocko@xxxxxxx are
thp-clean-up-__collapse_huge_page_isolate.patch
thp-clean-up-__collapse_huge_page_isolate-v2.patch
mm-introduce-mm_find_pmd.patch
mm-introduce-mm_find_pmd-fix.patch
thp-introduce-hugepage_vma_check.patch
thp-cleanup-introduce-mk_huge_pmd.patch
memory-hotplug-allocate-zones-pcp-before-onlining-pages-fix.patch
memcg-split-mem_cgroup_force_empty-into-reclaiming-and-reparenting-parts.patch
memcg-root_cgroup-cannot-reach-mem_cgroup_move_parent.patch
memcg-simplify-mem_cgroup_force_empty_list-error-handling.patch
cgroups-forbid-pre_destroy-callback-to-fail.patch
memcg-make-mem_cgroup_reparent_charges-non-failing.patch
hugetlb-do-not-fail-in-hugetlb_cgroup_pre_destroy.patch
drop_caches-add-some-documentation-and-info-messsge.patch
drop_caches-add-some-documentation-and-info-messsge-checkpatch-fixes.patch
mm-memblock-reduce-overhead-in-binary-search.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
