[PATCH 5/6] mm: Handle read faults under the VMA lock

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>,
	linux-mm@kvack.org, Suren Baghdasaryan <surenb@google.com>
Subject: [PATCH 5/6] mm: Handle read faults under the VMA lock
Date: Wed, 27 Sep 2023 06:25:03 +0100	[thread overview]
Message-ID: <20230927052505.2855872-6-willy@infradead.org> (raw)
In-Reply-To: <20230927052505.2855872-1-willy@infradead.org>

Most file-backed faults are already handled through ->map_pages(),
but if we need to do I/O we'll come this way.  Since filemap_fault()
is now safe to be called under the VMA lock, we can handle these faults
under the VMA lock now.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 mm/memory.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 02231a9394ed..5f92126dc527 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4617,10 +4617,9 @@ static vm_fault_t do_read_fault(struct vm_fault *vmf)
 			return ret;
 	}
 
-	if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
-		vma_end_read(vmf->vma);
-		return VM_FAULT_RETRY;
-	}
+	ret = vmf_maybe_unlock_vma(vmf);
+	if (ret)
+		return ret;
 
 	ret = __do_fault(vmf);
 	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
-- 
2.40.1


