From: Charan Teja Kalla <quic_charante@quicinc.com>
To: Michal Hocko <mhocko@suse.com>
Cc: <akpm@linux-foundation.org>, <minchan@kernel.org>,
<surenb@google.com>, <vbabka@suse.cz>, <rientjes@google.com>,
<nadav.amit@gmail.com>, <edgararriaga@google.com>,
<linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] Revert "mm: madvise: skip unmapped vma holes passed to process_madvise"
Date: Thu, 24 Mar 2022 19:33:56 +0530 [thread overview]
Message-ID: <d69a9b5a-7421-5a7d-9e5f-06b062769315@quicinc.com> (raw)
In-Reply-To: <Yjxoha4PLlKjEayl@dhcp22.suse.cz>
Thanks Michal.
On 3/24/2022 6:18 PM, Michal Hocko wrote:
> On Wed 23-03-22 20:54:09, Charan Teja Kalla wrote:
>> This reverts commit 08095d6310a7 ("mm: madvise: skip unmapped vma holes
>> passed to process_madvise") as process_madvise() fails to return exact
>> processed bytes at other cases too. As an example: if the
>> process_madvise() hits mlocked pages after processing some initial bytes
>> passed in [start, end), it just returns EINVAL though some bytes are
>> processed. Thus making an exception only for ENOMEM is partially fixing
>> the problem of returning the proper advised bytes.
>>
>> Thus revert this patch and return proper bytes advised, if there any,
>> for all the error types in the following patch.
>
> I do agree with the revert. I am not sure the above really is a proper
> justification though. 08095d6310a7 was changing one (arguably) dubious
> semantic by another one without a proper justification and wider
> consensus which I would expect from a patch which changes an existing
> semantic. Not to mention it being marked for stable tree.
Thanks for pointing this out. Since 08095d6310a7 is marked for stable
tree, doing the same for this change.
Cc: <stable@vger.kernel.org> # 5.10+
>
> But let's not nit pick on that now. Let's send this revert ASAP and use
> some more time to discuss the semantic and whether any change is really
> required.
>
>> Signed-off-by: Charan Teja Kalla <quic_charante@quicinc.com>
>
> Acked-by: Michal Hocko <mhocko@suse.com>
>
Thanks for the quick ack.
>> ---
>> mm/madvise.c | 9 +--------
>> 1 file changed, 1 insertion(+), 8 deletions(-)
>>
>> diff --git a/mm/madvise.c b/mm/madvise.c
>> index 39b712f..0d8fd17 100644
>> --- a/mm/madvise.c
>> +++ b/mm/madvise.c
>> @@ -1433,16 +1433,9 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
>>
>> while (iov_iter_count(&iter)) {
>> iovec = iov_iter_iovec(&iter);
>> - /*
>> - * do_madvise returns ENOMEM if unmapped holes are present
>> - * in the passed VMA. process_madvise() is expected to skip
>> - * unmapped holes passed to it in the 'struct iovec' list
>> - * and not fail because of them. Thus treat -ENOMEM return
>> - * from do_madvise as valid and continue processing.
>> - */
>> ret = do_madvise(mm, (unsigned long)iovec.iov_base,
>> iovec.iov_len, behavior);
>> - if (ret < 0 && ret != -ENOMEM)
>> + if (ret < 0)
>> break;
>> iov_iter_advance(&iter, iovec.iov_len);
>> }
>> --
>> 2.7.4
>
next prev parent reply other threads:[~2022-03-24 14:04 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-23 15:24 [PATCH 0/2] mm: madvise: return exact bytes advised with process_madvise under error Charan Teja Kalla
2022-03-23 15:24 ` [PATCH 1/2] Revert "mm: madvise: skip unmapped vma holes passed to process_madvise" Charan Teja Kalla
2022-03-24 12:48 ` Michal Hocko
2022-03-24 14:03 ` Charan Teja Kalla [this message]
2022-03-23 15:24 ` [PATCH 2/2] mm: madvise: return exact bytes advised with process_madvise under error Charan Teja Kalla
2022-03-24 13:14 ` Michal Hocko
2022-03-24 15:45 ` Charan Teja Kalla
2022-03-25 0:46 ` Minchan Kim
2022-03-25 0:48 ` Minchan Kim
2022-03-25 8:02 ` Michal Hocko
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