ext4: Use scoped memory APIs in ext4_da_write_begin()

Instead of setting AOP_FLAG_NOFS, use memalloc_nofs_save() and
memalloc_nofs_restore() to prevent GFP_FS allocations recursing
into the filesystem with a journal already started.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/ext4.h

@@ -3604,7 +3604,6 @@ ext4_journalled_write_inline_data(struct inode *inode,
 extern int ext4_da_write_inline_data_begin(struct address_space *mapping,
 					   struct inode *inode,
 					   loff_t pos, unsigned len,
-					   unsigned flags,
 					   struct page **pagep,
 					   void **fsdata);
 extern int ext4_try_add_inline_entry(handle_t *handle,

fs/ext4/inline.c

@@ -906,7 +906,6 @@ static int ext4_da_convert_inline_data_to_extent(struct address_space *mapping,
 int ext4_da_write_inline_data_begin(struct address_space *mapping,
 				    struct inode *inode,
 				    loff_t pos, unsigned len,
-				    unsigned flags,
 				    struct page **pagep,
 				    void **fsdata)
 {
@@ -915,6 +914,7 @@ int ext4_da_write_inline_data_begin(struct address_space *mapping,
 	struct page *page;
 	struct ext4_iloc iloc;
 	int retries = 0;
+	unsigned int flags;
 
 	ret = ext4_get_inode_loc(inode, &iloc);
 	if (ret)
@@ -931,12 +931,6 @@ int ext4_da_write_inline_data_begin(struct address_space *mapping,
 	if (ret && ret != -ENOSPC)
 		goto out_journal;
 
-	/*
-	 * We cannot recurse into the filesystem as the transaction
-	 * is already started.
-	 */
-	flags |= AOP_FLAG_NOFS;
-
 	if (ret == -ENOSPC) {
 		ext4_journal_stop(handle);
 		ret = ext4_da_convert_inline_data_to_extent(mapping,
@@ -948,7 +942,13 @@ int ext4_da_write_inline_data_begin(struct address_space *mapping,
 		goto out;
 	}
 
-	page = grab_cache_page_write_begin(mapping, 0, flags);
+	/*
+	 * We cannot recurse into the filesystem as the transaction
+	 * is already started.
+	 */
+	flags = memalloc_nofs_save();
+	page = grab_cache_page_write_begin(mapping, 0, 0);
+	memalloc_nofs_restore(flags);
 	if (!page) {
 		ret = -ENOMEM;
 		goto out_journal;

fs/ext4/inode.c

@@ -2954,8 +2954,7 @@ static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
 	trace_ext4_da_write_begin(inode, pos, len, flags);
 
 	if (ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA)) {
-		ret = ext4_da_write_inline_data_begin(mapping, inode,
-						      pos, len, flags,
+		ret = ext4_da_write_inline_data_begin(mapping, inode, pos, len,
 						      pagep, fsdata);
 		if (ret < 0)
 			return ret;