mm/cma: change cma mutex to irq safe spinlock
authorMike Kravetz <mike.kravetz@oracle.com>
Wed, 5 May 2021 01:34:44 +0000 (18:34 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 5 May 2021 18:27:21 +0000 (11:27 -0700)
commit0ef7dcac998fefc4767b7f10eb3b6df150c38a4e
tree2b5662ba19fed3c83936510b8e16242b0d8b71df
parent15b8365363215da82cb019d3de0eb781c9e82564
mm/cma: change cma mutex to irq safe spinlock

Patch series "make hugetlb put_page safe for all calling contexts", v5.

This effort is the result a recent bug report [1].  Syzbot found a
potential deadlock in the hugetlb put_page/free_huge_page_path.  WARNING:
SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected Since the
free_huge_page_path already has code to 'hand off' page free requests to a
workqueue, a suggestion was proposed to make the in_irq() detection
accurate by always enabling PREEMPT_COUNT [2].  The outcome of that
discussion was that the hugetlb put_page path (free_huge_page) path should
be properly fixed and safe for all calling contexts.

[1] https://lore.kernel.org/linux-mm/000000000000f1c03b05bc43aadc@google.com/
[2] http://lkml.kernel.org/r/20210311021321.127500-1-mike.kravetz@oracle.com

This patch (of 8):

cma_release is currently a sleepable operatation because the bitmap
manipulation is protected by cma->lock mutex.  Hugetlb code which relies
on cma_release for CMA backed (giga) hugetlb pages, however, needs to be
irq safe.

The lock doesn't protect any sleepable operation so it can be changed to a
(irq aware) spin lock.  The bitmap processing should be quite fast in
typical case but if cma sizes grow to TB then we will likely need to
replace the lock by a more optimized bitmap implementation.

Link: https://lkml.kernel.org/r/20210409205254.242291-1-mike.kravetz@oracle.com
Link: https://lkml.kernel.org/r/20210409205254.242291-2-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: HORIGUCHI NAOYA <naoya.horiguchi@nec.com>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/cma.c
mm/cma.h
mm/cma_debug.c