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.
---
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
