From: Tejun Heo <tj@kernel.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: Julia Lawall <julia.lawall@lip6.fr>,
kbuild-all@lists.01.org, linux-kernel@vger.kernel.org,
kernel-team@fb.com, linux-block@vger.kernel.org
Subject: [PATCH block/for-linus] blkcg: Fix multiple bugs in blkcg_activate_policy()
Date: Tue, 15 Oct 2019 09:03:47 -0700 [thread overview]
Message-ID: <20191015160347.GM18794@devbig004.ftw2.facebook.com> (raw)
In-Reply-To: <07cbc404-65db-b236-9ae2-558197b8cdb6@kernel.dk>
blkcg_activate_policy() has the following bugs.
* cf09a8ee19ad ("blkcg: pass @q and @blkcg into
blkcg_pol_alloc_pd_fn()") added @blkcg to ->pd_alloc_fn(); however,
blkcg_activate_policy() ends up using pd's allocated for the root
blkcg for all preallocations, so ->pd_init_fn() for non-root blkcgs
can be passed in pd's which are allocated for the root blkcg.
For blk-iocost, this means that ->pd_init_fn() can write beyond the
end of the allocated object as it determines the length of the flex
array at the end based on the blkcg's nesting level.
* Each pd is initialized as they get allocated. If alloc fails, the
policy will get freed with pd's initialized on it.
* After the above partial failure, the partial pds are not freed.
This patch fixes all the above issues by
* Restructuring blkcg_activate_policy() so that alloc and init passes
are separate. Init takes place only after all allocs succeeded and
on failure all allocated pds are freed.
* Unifying and fixing the cleanup of the remaining pd_prealloc.
Signed-off-by: Tejun Heo <tj@kernel.org>
Fixes: cf09a8ee19ad ("blkcg: pass @q and @blkcg into blkcg_pol_alloc_pd_fn()")
---
block/blk-cgroup.c | 69 +++++++++++++++++++++++++++++++++++++++--------------
1 file changed, 51 insertions(+), 18 deletions(-)
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1362,7 +1362,7 @@ int blkcg_activate_policy(struct request
const struct blkcg_policy *pol)
{
struct blkg_policy_data *pd_prealloc = NULL;
- struct blkcg_gq *blkg;
+ struct blkcg_gq *blkg, *pinned_blkg = NULL;
int ret;
if (blkcg_policy_enabled(q, pol))
@@ -1370,49 +1370,82 @@ int blkcg_activate_policy(struct request
if (queue_is_mq(q))
blk_mq_freeze_queue(q);
-pd_prealloc:
- if (!pd_prealloc) {
- pd_prealloc = pol->pd_alloc_fn(GFP_KERNEL, q, &blkcg_root);
- if (!pd_prealloc) {
- ret = -ENOMEM;
- goto out_bypass_end;
- }
- }
-
+retry:
spin_lock_irq(&q->queue_lock);
- /* blkg_list is pushed at the head, reverse walk to init parents first */
+ /* blkg_list is pushed at the head, reverse walk to allocate parents first */
list_for_each_entry_reverse(blkg, &q->blkg_list, q_node) {
struct blkg_policy_data *pd;
if (blkg->pd[pol->plid])
continue;
- pd = pol->pd_alloc_fn(GFP_NOWAIT | __GFP_NOWARN, q, &blkcg_root);
- if (!pd)
- swap(pd, pd_prealloc);
+ /* If prealloc matches, use it; otherwise try GFP_NOWAIT */
+ if (blkg == pinned_blkg) {
+ pd = pd_prealloc;
+ pd_prealloc = NULL;
+ } else {
+ pd = pol->pd_alloc_fn(GFP_NOWAIT | __GFP_NOWARN, q,
+ blkg->blkcg);
+ }
+
if (!pd) {
+ /*
+ * GFP_NOWAIT failed. Free the existing one and
+ * prealloc for @blkg w/ GFP_KERNEL.
+ */
+ if (pinned_blkg)
+ blkg_put(pinned_blkg);
+ blkg_get(blkg);
+ pinned_blkg = blkg;
+
spin_unlock_irq(&q->queue_lock);
- goto pd_prealloc;
+
+ if (pd_prealloc)
+ pol->pd_free_fn(pd_prealloc);
+ pd_prealloc = pol->pd_alloc_fn(GFP_KERNEL, q,
+ blkg->blkcg);
+ if (pd_prealloc)
+ goto retry;
+ else
+ goto enomem;
}
blkg->pd[pol->plid] = pd;
pd->blkg = blkg;
pd->plid = pol->plid;
- if (pol->pd_init_fn)
- pol->pd_init_fn(pd);
}
+ /* all allocated, init in the same order */
+ if (pol->pd_init_fn)
+ list_for_each_entry_reverse(blkg, &q->blkg_list, q_node)
+ pol->pd_init_fn(blkg->pd[pol->plid]);
+
__set_bit(pol->plid, q->blkcg_pols);
ret = 0;
spin_unlock_irq(&q->queue_lock);
-out_bypass_end:
+out:
if (queue_is_mq(q))
blk_mq_unfreeze_queue(q);
+ if (pinned_blkg)
+ blkg_put(pinned_blkg);
if (pd_prealloc)
pol->pd_free_fn(pd_prealloc);
return ret;
+
+enomem:
+ /* alloc failed, nothing's initialized yet, free everything */
+ spin_lock_irq(&q->queue_lock);
+ list_for_each_entry(blkg, &q->blkg_list, q_node) {
+ if (blkg->pd[pol->plid]) {
+ pol->pd_free_fn(blkg->pd[pol->plid]);
+ blkg->pd[pol->plid] = NULL;
+ }
+ }
+ spin_unlock_irq(&q->queue_lock);
+ ret = -ENOMEM;
+ goto out;
}
EXPORT_SYMBOL_GPL(blkcg_activate_policy);
next prev parent reply other threads:[~2019-10-15 16:03 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <alpine.DEB.2.21.1910151232480.2818@hadrien>
2019-10-15 15:48 ` [PATCH block/for-linus] blkcg: fix botched pd_prealloc error handling in blkcg_activate_policy() Tejun Heo
2019-10-15 15:52 ` Jens Axboe
2019-10-15 16:03 ` Tejun Heo [this message]
2019-10-15 16:13 ` [PATCH block/for-linus] blkcg: Fix multiple bugs " Jens Axboe
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20191015160347.GM18794@devbig004.ftw2.facebook.com \
--to=tj@kernel.org \
--cc=axboe@kernel.dk \
--cc=julia.lawall@lip6.fr \
--cc=kbuild-all@lists.01.org \
--cc=kernel-team@fb.com \
--cc=linux-block@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).