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From:   Josef Bacik <josef@toxicpanda.com>
To:     kernel-team@fb.com, hannes@cmpxchg.org,
        linux-kernel@vger.kernel.org, tj@kernel.org, david@fromorbit.com,
        akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org,
        linux-btrfs@vger.kernel.org, riel@fb.com, linux-mm@kvack.org
Subject: [PATCH 6/7] mm: allow ->page_mkwrite to do retries
Date:   Thu, 18 Oct 2018 16:23:17 -0400
Message-Id: <20181018202318.9131-7-josef@toxicpanda.com>
In-Reply-To: <20181018202318.9131-1-josef@toxicpanda.com>
References: <20181018202318.9131-1-josef@toxicpanda.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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@toxicpanda.com>
---
 mm/memory.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 433075f722ea..c5e81edd94f9 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