linux-kernel - [PATCH 8/9] mm: allow ->page

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Date:   Wed, 26 Sep 2018 17:08:55 -0400
From:   Josef Bacik <josef@...icpanda.com>
To:     kernel-team@...com, linux-kernel@...r.kernel.org,
        hannes@...xchg.org, tj@...nel.org, linux-fsdevel@...r.kernel.org,
        akpm@...ux-foundation.org, riel@...hat.com, linux-mm@...ck.org,
        linux-btrfs@...r.kernel.org
Subject: [PATCH 8/9] mm: allow ->page_mkwrite to do retries

Before we didn't set the retry flag on our vm_fault.  We want to allow
file systems to drop the mmap_sem if they so choose, so set this flag
and deal with VM_FAULT_RETRY appropriately.

Signed-off-by: Josef Bacik <josef@...icpanda.com>
---
 mm/memory.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 6f8abde84986..821435855177 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2384,11 +2384,13 @@ static vm_fault_t do_page_mkwrite(struct vm_fault *vmf)
 	unsigned int old_flags = vmf->flags;
 
 	vmf->flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
+	vmf->flags |= old_flags & FAULT_FLAG_ALLOW_RETRY;
 
 	ret = vmf->vma->vm_ops->page_mkwrite(vmf);
 	/* Restore original flags so that caller is not surprised */
 	vmf->flags = old_flags;
-	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))
+	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE |
+			    VM_FAULT_RETRY)))
 		return ret;
 	if (unlikely(!(ret & VM_FAULT_LOCKED))) {
 		lock_page(page);
@@ -2683,7 +2685,8 @@ static vm_fault_t wp_page_shared(struct vm_fault *vmf)
 		pte_unmap_unlock(vmf->pte, vmf->ptl);
 		tmp = do_page_mkwrite(vmf);
 		if (unlikely(!tmp || (tmp &
-				      (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
+				      (VM_FAULT_ERROR | VM_FAULT_NOPAGE |
+				       VM_FAULT_RETRY)))) {
 			put_page(vmf->page);
 			return tmp;
 		}
@@ -3716,7 +3719,8 @@ static vm_fault_t do_shared_fault(struct vm_fault *vmf)
 		unlock_page(vmf->page);
 		tmp = do_page_mkwrite(vmf);
 		if (unlikely(!tmp ||
-				(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
+				(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE |
+					VM_FAULT_RETRY)))) {
 			put_page(vmf->page);
 			return tmp;
 		}
-- 
2.14.3