mm: move handling of COW faults into DAX code

Move final handling of COW faults from generic code into DAX fault
handler.  That way generic code doesn't have to be aware of
peculiarities of DAX locking so remove that knowledge and make locking
functions private to fs/dax.c.

Link: http://lkml.kernel.org/r/1479460644-25076-11-git-send-email-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 29 insertions, 32 deletions

diff --git a/fs/dax.c b/fs/dax.c
index f1dfae64b11a..e83aa4077df4 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -240,6 +240,23 @@ static void *get_unlocked_mapping_entry(struct address_space *mapping,
 	}
 }
 
+static void dax_unlock_mapping_entry(struct address_space *mapping,
+				     pgoff_t index)
+{
+	void *entry, **slot;
+
+	spin_lock_irq(&mapping->tree_lock);
+	entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
+	if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) ||
+			 !slot_locked(mapping, slot))) {
+		spin_unlock_irq(&mapping->tree_lock);
+		return;
+	}
+	unlock_slot(mapping, slot);
+	spin_unlock_irq(&mapping->tree_lock);
+	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
+}
+
 static void put_locked_mapping_entry(struct address_space *mapping,
 				     pgoff_t index, void *entry)
 {
@@ -433,22 +450,6 @@ void dax_wake_mapping_entry_waiter(struct address_space *mapping,
 		__wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
 }
 
-void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index)
-{
-	void *entry, **slot;
-
-	spin_lock_irq(&mapping->tree_lock);
-	entry = __radix_tree_lookup(&mapping->page_tree, index, NULL, &slot);
-	if (WARN_ON_ONCE(!entry || !radix_tree_exceptional_entry(entry) ||
-			 !slot_locked(mapping, slot))) {
-		spin_unlock_irq(&mapping->tree_lock);
-		return;
-	}
-	unlock_slot(mapping, slot);
-	spin_unlock_irq(&mapping->tree_lock);
-	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
-}
-
 /*
  * Delete exceptional DAX entry at @index from @mapping. Wait for radix tree
  * entry to get unlocked before deleting it.
@@ -500,10 +501,8 @@ static int dax_load_hole(struct address_space *mapping, void *entry,
 	/* This will replace locked radix tree entry with a hole page */
 	page = find_or_create_page(mapping, vmf->pgoff,
 				   vmf->gfp_mask | __GFP_ZERO);
-	if (!page) {
-		put_locked_mapping_entry(mapping, vmf->pgoff, entry);
+	if (!page)
 		return VM_FAULT_OOM;
-	}
 	vmf->page = page;
 	return VM_FAULT_LOCKED;
 }
@@ -954,7 +953,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	struct iomap iomap = { 0 };
 	unsigned flags = IOMAP_FAULT;
 	int error, major = 0;
-	int locked_status = 0;
+	int vmf_ret = 0;
 	void *entry;
 
 	/*
@@ -1007,13 +1006,11 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 
 		if (error)
 			goto finish_iomap;
-		if (!radix_tree_exceptional_entry(entry)) {
-			vmf->page = entry;
-			locked_status = VM_FAULT_LOCKED;
-		} else {
-			vmf->entry = entry;
-			locked_status = VM_FAULT_DAX_LOCKED;
-		}
+
+		__SetPageUptodate(vmf->cow_page);
+		vmf_ret = finish_fault(vmf);
+		if (!vmf_ret)
+			vmf_ret = VM_FAULT_DONE_COW;
 		goto finish_iomap;
 	}
 
@@ -1030,7 +1027,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	case IOMAP_UNWRITTEN:
 	case IOMAP_HOLE:
 		if (!(vmf->flags & FAULT_FLAG_WRITE)) {
-			locked_status = dax_load_hole(mapping, entry, vmf);
+			vmf_ret = dax_load_hole(mapping, entry, vmf);
 			break;
 		}
 		/*FALLTHRU*/
@@ -1042,7 +1039,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 
  finish_iomap:
 	if (ops->iomap_end) {
-		if (error) {
+		if (error || (vmf_ret & VM_FAULT_ERROR)) {
 			/* keep previous error */
 			ops->iomap_end(inode, pos, PAGE_SIZE, 0, flags,
 					&iomap);
@@ -1052,7 +1049,7 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 		}
 	}
  unlock_entry:
-	if (!locked_status || error)
+	if (vmf_ret != VM_FAULT_LOCKED || error)
 		put_locked_mapping_entry(mapping, vmf->pgoff, entry);
  out:
 	if (error == -ENOMEM)
@@ -1060,9 +1057,9 @@ int dax_iomap_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
 	/* -EBUSY is fine, somebody else faulted on the same PTE */
 	if (error < 0 && error != -EBUSY)
 		return VM_FAULT_SIGBUS | major;
-	if (locked_status) {
+	if (vmf_ret) {
 		WARN_ON_ONCE(error); /* -EBUSY from ops->iomap_end? */
-		return locked_status;
+		return vmf_ret;
 	}
 	return VM_FAULT_NOPAGE | major;
 }