From: Suren Baghdasaryan <surenb@google.com>
To: akpm@linux-foundation.org
Cc: mhocko@kernel.org, mhocko@suse.com, rientjes@google.com,
willy@infradead.org, hannes@cmpxchg.org, guro@fb.com,
riel@surriel.com, minchan@kernel.org, kirill@shutemov.name,
aarcange@redhat.com, christian@brauner.io, hch@infradead.org,
oleg@redhat.com, david@redhat.com, jannh@google.com,
shakeelb@google.com, luto@kernel.org,
christian.brauner@ubuntu.com, fweimer@redhat.com,
jengelh@inai.de, timmurray@google.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, kernel-team@android.com,
surenb@google.com
Subject: [PATCH v2 2/2] mm/oom_kill: allow process_mrelease to run under mmap_lock protection
Date: Wed, 24 Nov 2021 15:59:06 -0800 [thread overview]
Message-ID: <20211124235906.14437-2-surenb@google.com> (raw)
In-Reply-To: <20211124235906.14437-1-surenb@google.com>
With exit_mmap holding mmap_write_lock during free_pgtables call,
process_mrelease does not need to elevate mm->mm_users in order to
prevent exit_mmap from destrying pagetables while __oom_reap_task_mm
is walking the VMA tree. The change prevents process_mrelease from
calling the last mmput, which can lead to waiting for IO completion
in exit_aio.
Fixes: 337546e83fc7 ("mm/oom_kill.c: prevent a race between process_mrelease and exit_mmap")
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
mm/oom_kill.c | 27 +++++++++++++++------------
1 file changed, 15 insertions(+), 12 deletions(-)
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 1ddabefcfb5a..67780386f478 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -1169,15 +1169,15 @@ SYSCALL_DEFINE2(process_mrelease, int, pidfd, unsigned int, flags)
goto put_task;
}
- if (mmget_not_zero(p->mm)) {
- mm = p->mm;
- if (task_will_free_mem(p))
- reap = true;
- else {
- /* Error only if the work has not been done already */
- if (!test_bit(MMF_OOM_SKIP, &mm->flags))
- ret = -EINVAL;
- }
+ mm = p->mm;
+ mmgrab(mm);
+
+ if (task_will_free_mem(p))
+ reap = true;
+ else {
+ /* Error only if the work has not been done already */
+ if (!test_bit(MMF_OOM_SKIP, &mm->flags))
+ ret = -EINVAL;
}
task_unlock(p);
@@ -1188,13 +1188,16 @@ SYSCALL_DEFINE2(process_mrelease, int, pidfd, unsigned int, flags)
ret = -EINTR;
goto drop_mm;
}
- if (!__oom_reap_task_mm(mm))
+ /*
+ * Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure
+ * possible change in exit_mmap is seen
+ */
+ if (!test_bit(MMF_OOM_SKIP, &mm->flags) && !__oom_reap_task_mm(mm))
ret = -EAGAIN;
mmap_read_unlock(mm);
drop_mm:
- if (mm)
- mmput(mm);
+ mmdrop(mm);
put_task:
put_task_struct(task);
return ret;
--
2.34.0.rc2.393.gf8c9666880-goog
next prev parent reply other threads:[~2021-11-24 23:59 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-24 23:59 [PATCH v2 1/2] mm: protect free_pgtables with mmap_lock write lock in exit_mmap Suren Baghdasaryan
2021-11-24 23:59 ` Suren Baghdasaryan [this message]
2021-11-29 11:23 ` Michal Hocko
2021-12-06 18:35 ` Suren Baghdasaryan
2021-12-06 18:52 ` Matthew Wilcox
2021-12-07 10:03 ` Michal Hocko
2021-12-07 10:09 ` Michal Hocko
2021-12-07 16:50 ` Suren Baghdasaryan
2021-12-07 21:54 ` Suren Baghdasaryan
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