The patch titled
Subject: mm/oom_kill: allow process_mrelease to run under mmap_lock protection
has been added to the -mm tree. Its filename is
mm-oom_kill-allow-process_mrelease-to-run-under-mmap_lock-protection.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-oom_kill-allow-process_mrelease-to-run-under-mmap_lock-protection.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-oom_kill-allow-process_mrelease-to-run-under-mmap_lock-protection.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Subject: mm/oom_kill: allow process_mrelease to run under mmap_lock protection
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.
Link: https://lkml.kernel.org/r/20211124235906.14437-2-surenb@xxxxxxxxxx
Fixes: 337546e83fc7 ("mm/oom_kill.c: prevent a race between process_mrelease and exit_mmap")
Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Roman Gushchin <guro@xxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Kirill Shutemov <kirill@xxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Christian Brauner <christian@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Christian Brauner <christian.brauner@xxxxxxxxxx>
Cc: Florian Weimer <fweimer@xxxxxxxxxx>
Cc: Jan Engelhardt <jengelh@xxxxxxx>
Cc: Tim Murray <timmurray@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/oom_kill.c | 27 +++++++++++++++------------
1 file changed, 15 insertions(+), 12 deletions(-)
--- a/mm/oom_kill.c~mm-oom_kill-allow-process_mrelease-to-run-under-mmap_lock-protection
+++ a/mm/oom_kill.c
@@ -1169,15 +1169,15 @@ SYSCALL_DEFINE2(process_mrelease, int, p
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, p
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;
_
Patches currently in -mm which might be from surenb@xxxxxxxxxx are
mm-add-a-field-to-store-names-for-private-anonymous-memory-fix.patch
mm-add-anonymous-vma-name-refcounting.patch
mm-protect-free_pgtables-with-mmap_lock-write-lock-in-exit_mmap.patch
mm-oom_kill-allow-process_mrelease-to-run-under-mmap_lock-protection.patch
sysctl-change-watermark_scale_factor-max-limit-to-30%.patch
