linux-kernel - [PATCH] mm: Use helper function mapping_allow

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Date:   Thu, 17 Sep 2020 07:27:36 -0400
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>, <christian.brauner@...ntu.com>,
        <mingo@...nel.org>, <peterz@...radead.org>,
        <ebiederm@...ssion.com>, <christian@...lner.me>,
        <surenb@...gle.com>, <areber@...hat.com>, <shakeelb@...gle.com>,
        <cyphar@...har.com>, <tglx@...utronix.de>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH] mm: Use helper function mapping_allow_writable()

Commit 4bb5f5d9395b ("mm: allow drivers to prevent new writable mappings")
changed i_mmap_writable from unsigned int to atomic_t and add the helper
function mapping_allow_writable() to atomic_inc i_mmap_writable. But it
forgot to use this helper function in dup_mmap() and __vma_link_file().

Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 kernel/fork.c | 2 +-
 mm/mmap.c     | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index 11ed5ac35caf..b9164b75b20c 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -558,7 +558,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
 				atomic_dec(&inode->i_writecount);
 			i_mmap_lock_write(mapping);
 			if (tmp->vm_flags & VM_SHARED)
-				atomic_inc(&mapping->i_mmap_writable);
+				mapping_allow_writable(mapping);
 			flush_dcache_mmap_lock(mapping);
 			/* insert tmp into the share list, just after mpnt */
 			vma_interval_tree_insert_after(tmp, mpnt,
diff --git a/mm/mmap.c b/mm/mmap.c
index e3a1c1b48909..ae9ef433f830 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -665,7 +665,7 @@ static void __vma_link_file(struct vm_area_struct *vma)
 		if (vma->vm_flags & VM_DENYWRITE)
 			atomic_dec(&file_inode(file)->i_writecount);
 		if (vma->vm_flags & VM_SHARED)
-			atomic_inc(&mapping->i_mmap_writable);
+			mapping_allow_writable(mapping);
 
 		flush_dcache_mmap_lock(mapping);
 		vma_interval_tree_insert(vma, &mapping->i_mmap);
-- 
2.19.1