[PATCH 08/10] mm/mremap: share the i_mmap_rwsem

From: Davidlohr Bueso
Date: Thu Oct 30 2014 - 15:42:27 EST


As per the comment in move_ptes(), we only require taking the
anon vma and i_mmap locks to ensure that rmap will always observe
either the old or new ptes, in the case of need_rmap_lock=true.
No modifications to the tree itself, thus share the i_mmap_rwsem.

Signed-off-by: Davidlohr Bueso <dbueso@xxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
mm/mremap.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/mremap.c b/mm/mremap.c
index c929324..09bd644 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -119,7 +119,7 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
if (need_rmap_locks) {
if (vma->vm_file) {
mapping = vma->vm_file->f_mapping;
- i_mmap_lock_write(mapping);
+ i_mmap_lock_read(mapping);
}
if (vma->anon_vma) {
anon_vma = vma->anon_vma;
@@ -156,7 +156,7 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
if (anon_vma)
anon_vma_unlock_read(anon_vma);
if (mapping)
- i_mmap_unlock_write(mapping);
+ i_mmap_unlock_read(mapping);
}

#define LATENCY_LIMIT (64 * PAGE_SIZE)
--
1.8.4.5

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