From 3dec0ba0be6a532cac949e02b853021bf6d57dad Mon Sep 17 00:00:00 2001
From: Davidlohr Bueso
Date: Fri, 12 Dec 2014 16:54:27 -0800
Subject: mm/rmap: share the i_mmap_rwsem

Similarly to the anon memory counterpart, we can share the mapping's lock
ownership as the interval tree is not modified when doing doing the walk,
only the file page.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: "Kirill A. Shutemov" <kirill@shutemov.name>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 mm/rmap.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

(limited to 'mm/rmap.c')

diff --git a/mm/rmap.c b/mm/rmap.c
index 18247f89f1a8..14ad2b3b0f54 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1690,7 +1690,8 @@ static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc)
 
 	if (!mapping)
 		return ret;
-	i_mmap_lock_write(mapping);
+
+	i_mmap_lock_read(mapping);
 	vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
 		unsigned long address = vma_address(page, vma);
 
@@ -1711,9 +1712,8 @@ static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc)
 		goto done;
 
 	ret = rwc->file_nonlinear(page, mapping, rwc->arg);
-
 done:
-	i_mmap_unlock_write(mapping);
+	i_mmap_unlock_read(mapping);
 	return ret;
 }
 
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