linux-kernel - [PATCH 2/2] mm/mmap: check on file instead of the rb_root_cached of its address

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Message-Id: <20200913133631.37781-2-richard.weiyang@linux.alibaba.com>
Date:   Sun, 13 Sep 2020 21:36:31 +0800
From:   Wei Yang <richard.weiyang@...ux.alibaba.com>
To:     akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Wei Yang <richard.weiyang@...ux.alibaba.com>
Subject: [PATCH 2/2] mm/mmap: check on file instead of the rb_root_cached of its address_space

In __vma_adjust(), we do the check on *root* to decide whether to adjust
the address_space. While it seems to be more meaningful to do the check
on *file* itself. This means we are adjust some data because it is a
file backed vma.

Since we seems to assume the address_space is valid if it is a file
backed vma, let's just replace *root* with *file* here.

Signed-off-by: Wei Yang <richard.weiyang@...ux.alibaba.com>
---
 mm/mmap.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 30b155098606..829897646a9c 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -823,7 +823,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
 			anon_vma_interval_tree_pre_update_vma(next);
 	}
 
-	if (root) {
+	if (file) {
 		flush_dcache_mmap_lock(mapping);
 		vma_interval_tree_remove(vma, root);
 		if (adjust_next)
@@ -844,7 +844,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
 		next->vm_pgoff += adjust_next >> PAGE_SHIFT;
 	}
 
-	if (root) {
+	if (file) {
 		if (adjust_next)
 			vma_interval_tree_insert(next, root);
 		vma_interval_tree_insert(vma, root);
@@ -896,7 +896,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
 		anon_vma_unlock_write(anon_vma);
 	}
 
-	if (root) {
+	if (file) {
 		i_mmap_unlock_write(mapping);
 		uprobe_mmap(vma);
 
-- 
2.20.1 (Apple Git-117)