linux-kernel - [RFC v2 02/10] mm: Remove nest locking operation with mmap

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Message-Id: <1495624801-8063-3-git-send-email-ldufour@linux.vnet.ibm.com>
Date:   Wed, 24 May 2017 13:19:53 +0200
From:   Laurent Dufour <ldufour@...ux.vnet.ibm.com>
To:     linux-mm@...ck.org
Cc:     Davidlohr Bueso <dave@...olabs.net>, akpm@...ux-foundation.org,
        Jan Kara <jack@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Michal Hocko <mhocko@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Andi Kleen <andi@...stfloor.org>, haren@...ux.vnet.ibm.com,
        aneesh.kumar@...ux.vnet.ibm.com, khandual@...ux.vnet.ibm.com,
        paulmck@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org
Subject: [RFC v2 02/10] mm: Remove nest locking operation with mmap_sem

The range locking framework doesn't yet provide nest locking
operation.

Once the range locking API while provide nested operation support,
this patch will have to be reviewed.

Signed-off-by: Laurent Dufour <ldufour@...ux.vnet.ibm.com>
---
 mm/mmap.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mm/mmap.c b/mm/mmap.c
index f82741e199c0..87c8625ae91d 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3284,7 +3284,11 @@ static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
 		 * The LSB of head.next can't change from under us
 		 * because we hold the mm_all_locks_mutex.
 		 */
+#ifndef CONFIG_MEM_RANGE_LOCK
 		down_write_nest_lock(&anon_vma->root->rwsem, &mm->mmap_sem);
+#else
+		down_write(&anon_vma->root->rwsem);
+#endif
 		/*
 		 * We can safely modify head.next after taking the
 		 * anon_vma->root->rwsem. If some other vma in this mm shares
@@ -3314,7 +3318,11 @@ static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
 		 */
 		if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
 			BUG();
+#ifndef CONFIG_MEM_RANGE_LOCK
 		down_write_nest_lock(&mapping->i_mmap_rwsem, &mm->mmap_sem);
+#else
+		down_write(&mapping->i_mmap_rwsem);
+#endif
 	}
 }
 
-- 
2.7.4