Hi!
> On 20 Oct 2020, at 13:19, Vlastimil Babka <vbabka@xxxxxxx> wrote:
>
> On 10/12/20 6:09 PM, Nikita Ermakov wrote:
>> Exit from the loop over the VMA in the case when the flags
>> contain only an MS_ASYNC and start < vm_start. In this case msync()
>> would return with -ENOMEM anyway so make it return early.
>> Signed-off-by: Nikita Ermakov <sh1r4s3@xxxxxxxxxxxxxxx>
>
> AFAICS it can still return -EBUSY if there's MS_INVALIDATE and a mlocked vma. This is all subtle and I don't think we should risk breaking something for this optimization.
>
Yes, it could. But in this patch the optimization works only in the case if the flag is MS_ASYNC. If the flag is (MS_ASYNC | MS_INVALIDATE).
>> ---
>> mm/msync.c | 2 ++
>> 1 file changed, 2 insertions(+)
>> diff --git a/mm/msync.c b/mm/msync.c
>> index 69c6d2029531..ed20c3621d4c 100644
>> --- a/mm/msync.c
>> +++ b/mm/msync.c
>> @@ -69,6 +69,8 @@ SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags)
>> goto out_unlock;
>> /* Here start < vma->vm_end. */
>> if (start < vma->vm_start) {
>> + if (flags == MS_ASYNC)
>> + goto out_unlock;
>> start = vma->vm_start;
>> if (start >= end)
>> goto out_unlock;
>> base-commit: 6824a8a9b4861d7df7ee132a952bdf6f84a99cb8
>
