* + mm-mremap-fix-memory-account-on-do_munmap-failure.patch added to -mm tree
@ 2021-07-20 23:28 akpm
2021-07-21 12:51 ` Dmitry Safonov
0 siblings, 1 reply; 3+ messages in thread
From: akpm @ 2021-07-20 23:28 UTC (permalink / raw)
To: mm-commits, weiyongjun1, wangkefeng.wang, 0x7f454c46, chenwandun
The patch titled
Subject: mm/mremap: fix memory account on do_munmap() failure
has been added to the -mm tree. Its filename is
mm-mremap-fix-memory-account-on-do_munmap-failure.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-mremap-fix-memory-account-on-do_munmap-failure.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-mremap-fix-memory-account-on-do_munmap-failure.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/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: Chen Wandun <chenwandun@huawei.com>
Subject: mm/mremap: fix memory account on do_munmap() failure
mremap will account the delta between new_len and old_len in
vma_to_resize, and then call move_vma when expanding an existing memory
mapping. In function move_vma, there are two scenarios when calling
do_munmap:
1. move_page_tables from old_addr to new_addr success
2. move_page_tables from old_addr to new_addr fail
In first scenario, it should account old_len if do_munmap fail, because
the delta has already been accounted.
In second scenario, new_addr/new_len will assign to old_addr/old_len if
move_page_table fail, so do_munmap is try to unmap new_addr actually, if
do_munmap fail, it should account the new_len, because error code will be
return from move_vma, and delta will be unaccounted. What'more, because
of new_len == old_len, so account old_len also is OK.
In summary, account old_len will be correct if do_munmap fail.
Link: https://lkml.kernel.org/r/20210717101942.120607-1-chenwandun@huawei.com
Fixes: 51df7bcb6151 ("mm/mremap: account memory on do_munmap() failure")
Signed-off-by: Chen Wandun <chenwandun@huawei.com>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/mremap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/mremap.c~mm-mremap-fix-memory-account-on-do_munmap-failure
+++ a/mm/mremap.c
@@ -686,7 +686,7 @@ static unsigned long move_vma(struct vm_
if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) {
/* OOM: unable to split vma, just get accounts right */
if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP))
- vm_acct_memory(new_len >> PAGE_SHIFT);
+ vm_acct_memory(old_len >> PAGE_SHIFT);
excess = 0;
}
_
Patches currently in -mm which might be from chenwandun@huawei.com are
mm-mremap-fix-memory-account-on-do_munmap-failure.patch
mm-vmalloc-fix-wrong-behavior-in-vread.patch
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: + mm-mremap-fix-memory-account-on-do_munmap-failure.patch added to -mm tree
2021-07-20 23:28 + mm-mremap-fix-memory-account-on-do_munmap-failure.patch added to -mm tree akpm
@ 2021-07-21 12:51 ` Dmitry Safonov
0 siblings, 0 replies; 3+ messages in thread
From: Dmitry Safonov @ 2021-07-21 12:51 UTC (permalink / raw)
To: akpm, mm-commits, weiyongjun1, wangkefeng.wang, chenwandun
On 7/21/21 12:28 AM, akpm@linux-foundation.org wrote:
> The patch titled
> Subject: mm/mremap: fix memory account on do_munmap() failure
> has been added to the -mm tree. Its filename is
> mm-mremap-fix-memory-account-on-do_munmap-failure.patch
>
> This patch should soon appear at
> https://ozlabs.org/~akpm/mmots/broken-out/mm-mremap-fix-memory-account-on-do_munmap-failure.patch
> and later at
> https://ozlabs.org/~akpm/mmotm/broken-out/mm-mremap-fix-memory-account-on-do_munmap-failure.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/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: Chen Wandun <chenwandun@huawei.com>
> Subject: mm/mremap: fix memory account on do_munmap() failure
>
> mremap will account the delta between new_len and old_len in
> vma_to_resize, and then call move_vma when expanding an existing memory
> mapping. In function move_vma, there are two scenarios when calling
> do_munmap:
>
> 1. move_page_tables from old_addr to new_addr success
> 2. move_page_tables from old_addr to new_addr fail
>
> In first scenario, it should account old_len if do_munmap fail, because
> the delta has already been accounted.
>
> In second scenario, new_addr/new_len will assign to old_addr/old_len if
> move_page_table fail, so do_munmap is try to unmap new_addr actually, if
> do_munmap fail, it should account the new_len, because error code will be
> return from move_vma, and delta will be unaccounted. What'more, because
> of new_len == old_len, so account old_len also is OK.
>
> In summary, account old_len will be correct if do_munmap fail.
>
> Link: https://lkml.kernel.org/r/20210717101942.120607-1-chenwandun@huawei.com
> Fixes: 51df7bcb6151 ("mm/mremap: account memory on do_munmap() failure")
> Signed-off-by: Chen Wandun <chenwandun@huawei.com>
> Cc: Dmitry Safonov <0x7f454c46@gmail.com>
> Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
> Cc: Wei Yongjun <weiyongjun1@huawei.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Nice catch!
> ---
>
> mm/mremap.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- a/mm/mremap.c~mm-mremap-fix-memory-account-on-do_munmap-failure
> +++ a/mm/mremap.c
> @@ -686,7 +686,7 @@ static unsigned long move_vma(struct vm_
> if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) {
> /* OOM: unable to split vma, just get accounts right */
> if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP))
> - vm_acct_memory(new_len >> PAGE_SHIFT);
> + vm_acct_memory(old_len >> PAGE_SHIFT);
> excess = 0;
> }
>
But now as you noticed the accounting in vma_to_resize(), I can't help
but see that accounting for MREMAP_DONTUNMAP seems to have been broken
from the beginning. Either we should also hack around this way:
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -605,7 +605,12 @@ static unsigned long move_vma(struct vm_area_struct
*vma,
return err;
if (unlikely(flags & MREMAP_DONTUNMAP && vm_flags & VM_ACCOUNT)) {
- if (security_vm_enough_memory_mm(mm, new_len >> PAGE_SHIFT))
+ /*
+ * new_len >= old_len, VMA shrinking is not in this path.
+ * (new_len - old_len) is already charged in vma_to_resize()
+ * So, charge old_len instead of new_len.
+ */
+ if (security_vm_enough_memory_mm(mm, old_len >> PAGE_SHIFT))
return -ENOMEM;
}
@@ -614,7 +619,7 @@ static unsigned long move_vma(struct vm_area_struct
*vma,
&need_rmap_locks);
if (!new_vma) {
if (unlikely(flags & MREMAP_DONTUNMAP && vm_flags & VM_ACCOUNT))
- vm_unacct_memory(new_len >> PAGE_SHIFT);
+ vm_unacct_memory(old_len >> PAGE_SHIFT);
return -ENOMEM;
}
--->8---
But I hate what's going on here.
That's disgusting, let's not account/unaccount memory for
vma_to_resize(), I've sent an alternative patch:
https://lore.kernel.org/lkml/20210721124949.517217-1-dima@arista.com/
Thanks,
Dmitry
^ permalink raw reply [flat|nested] 3+ messages in thread
* + mm-mremap-fix-memory-account-on-do_munmap-failure.patch added to -mm tree
@ 2021-07-22 4:28 akpm
0 siblings, 0 replies; 3+ messages in thread
From: akpm @ 2021-07-22 4:28 UTC (permalink / raw)
To: mm-commits, weiyongjun1, wangkefeng.wang, dima, chenwandun
The patch titled
Subject: mm/mremap: fix memory account on do_munmap() failure
has been added to the -mm tree. Its filename is
mm-mremap-fix-memory-account-on-do_munmap-failure.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-mremap-fix-memory-account-on-do_munmap-failure.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-mremap-fix-memory-account-on-do_munmap-failure.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/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: Chen Wandun <chenwandun@huawei.com>
Subject: mm/mremap: fix memory account on do_munmap() failure
mremap will account the delta between new_len and old_len in
vma_to_resize, and then call move_vma when expanding an existing memory
mapping. In function move_vma, there are two scenarios when calling
do_munmap:
1. move_page_tables from old_addr to new_addr success
2. move_page_tables from old_addr to new_addr fail
In first scenario, it should account old_len if do_munmap fail, because
the delta has already been accounted.
In second scenario, new_addr/new_len will assign to old_addr/old_len if
move_page_table fail, so do_munmap is try to unmap new_addr actually, if
do_munmap fail, it should account the new_len, because error code will be
return from move_vma, and delta will be unaccounted. What'more, because
of new_len == old_len, so account old_len also is OK.
In summary, account old_len will be correct if do_munmap fail.
Link: https://lkml.kernel.org/r/20210717101942.120607-1-chenwandun@huawei.com
Fixes: 51df7bcb6151 ("mm/mremap: account memory on do_munmap() failure")
Signed-off-by: Chen Wandun <chenwandun@huawei.com>
Acked-by: Dmitry Safonov <dima@arista.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/mremap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/mremap.c~mm-mremap-fix-memory-account-on-do_munmap-failure
+++ a/mm/mremap.c
@@ -686,7 +686,7 @@ static unsigned long move_vma(struct vm_
if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) {
/* OOM: unable to split vma, just get accounts right */
if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP))
- vm_acct_memory(new_len >> PAGE_SHIFT);
+ vm_acct_memory(old_len >> PAGE_SHIFT);
excess = 0;
}
_
Patches currently in -mm which might be from chenwandun@huawei.com are
mm-mremap-fix-memory-account-on-do_munmap-failure.patch
mm-vmalloc-fix-wrong-behavior-in-vread.patch
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-07-20 23:28 + mm-mremap-fix-memory-account-on-do_munmap-failure.patch added to -mm tree akpm
2021-07-21 12:51 ` Dmitry Safonov
2021-07-22 4:28 akpm
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