[RFC PATCH 18/24] shared file mappings: use the vmf->range field when dropping mmap_sem

From: Michel Lespinasse <walken@google.com>
To: Peter Zijlstra <peterz@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	 Laurent Dufour <ldufour@linux.ibm.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	 Matthew Wilcox <willy@infradead.org>,
	"Liam R . Howlett" <Liam.Howlett@oracle.com>,
	 Jerome Glisse <jglisse@redhat.com>,
	Davidlohr Bueso <dave@stgolabs.net>,
	 David Rientjes <rientjes@google.com>
Cc: linux-mm <linux-mm@kvack.org>, Michel Lespinasse <walken@google.com>
Subject: [RFC PATCH 18/24] shared file mappings: use the vmf->range field when dropping mmap_sem
Date: Mon, 24 Feb 2020 12:30:51 -0800	[thread overview]
Message-ID: <20200224203057.162467-19-walken@google.com> (raw)
In-Reply-To: <20200224203057.162467-1-walken@google.com>

Modify lock_page_maybe_drop_mmap() and maybe_unlock_mmap_for_io()
to use the vmf->range field when dropping mmap_sem.

This covers dropping mmap_sem during:
- filemap_fault()
- shmem_fault()
- do_fault() write to shared file mapping
  [ through do_shared_fault and fault_dirty_shared_page() ]
- do_wp_page() write to shared file mapping
  [ through wp_page_shared() and fault_dirty_shared_page() ]

Signed-off-by: Michel Lespinasse <walken@google.com>
---
 mm/filemap.c  | 3 ++-
 mm/internal.h | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git mm/filemap.c mm/filemap.c
index 3afb5a3f0b9c..7827de7b356c 100644
--- mm/filemap.c
+++ mm/filemap.c
@@ -2364,7 +2364,8 @@ static int lock_page_maybe_drop_mmap(struct vm_fault *vmf, struct page *page,
 			 * mmap_sem here and return 0 if we don't have a fpin.
 			 */
 			if (*fpin == NULL)
-				mm_read_unlock(vmf->vma->vm_mm);
+				mm_read_range_unlock(vmf->vma->vm_mm,
+						     vmf->range);
 			return 0;
 		}
 	} else
diff --git mm/internal.h mm/internal.h
index 22f361a1e284..9bfff428c5da 100644
--- mm/internal.h
+++ mm/internal.h
@@ -382,7 +382,7 @@ static inline struct file *maybe_unlock_mmap_for_io(struct vm_fault *vmf,
 	if ((flags & (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT)) ==
 	    FAULT_FLAG_ALLOW_RETRY) {
 		fpin = get_file(vmf->vma->vm_file);
-		mm_read_unlock(vmf->vma->vm_mm);
+		mm_read_range_unlock(vmf->vma->vm_mm, vmf->range);
 	}
 	return fpin;
 }
-- 
2.25.0.341.g760bfbb309-goog


