[RFC PATCH 3/8] mm/madvise: remove unnecessary checks on madvise_free_single_vma()

[Nadav Amit]

From: Nadav Amit <namit@xxxxxxxxxx>

madvise_free_single_vma() currently rechecks that the range fits within
the VMA, adapts it accordingly, and returns -EINVAL if the range is
entirely outside of the VMA.

The error-code of -EINVAL is incorrect according to the man pages (as it
should have been -ENOMEM), but anyhow the range that is provided to
madvise_free_single_vma() should always be valid. It is set correctly in
do_madvise() and then rechecked in madvise_dontneed_free() is the
mmap-lock is dropped.

Remove this check.

Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Colin Cross <ccross@xxxxxxxxxx>
Cc: Suren Baghdasarya <surenb@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Nadav Amit <namit@xxxxxxxxxx>
---
 mm/madvise.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index fe843513a4e8..17e39c70704b 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -716,14 +716,8 @@ static int madvise_free_single_vma(struct vm_area_struct *vma,
 	if (!vma_is_anonymous(vma))
 		return -EINVAL;
 
-	range.start = max(vma->vm_start, start_addr);
-	if (range.start >= vma->vm_end)
-		return -EINVAL;
-	range.end = min(vma->vm_end, end_addr);
-	if (range.end <= vma->vm_start)
-		return -EINVAL;
 	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm,
-				range.start, range.end);
+				start_addr, end_addr);
 
 	lru_add_drain();
 	tlb_gather_mmu(&tlb, mm);
-- 
2.25.1