[PATCH 8/9] mm: allow ->page_mkwrite to do retries

[Josef Bacik]

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 <jo...@toxicpanda.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