ext4: Use scoped memory APIs in ext4_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

@@ -3591,7 +3591,6 @@ extern int ext4_readpage_inline(struct inode *inode, struct page *page);
 extern int ext4_try_to_write_inline_data(struct address_space *mapping,
 					 struct inode *inode,
 					 loff_t pos, unsigned len,
-					 unsigned flags,
 					 struct page **pagep);
 extern int ext4_write_inline_data_end(struct inode *inode,
 				      loff_t pos, unsigned len,

fs/ext4/inline.c

@@ -527,13 +527,13 @@ int ext4_readpage_inline(struct inode *inode, struct page *page)
 }
 
 static int ext4_convert_inline_data_to_extent(struct address_space *mapping,
-					      struct inode *inode,
-					      unsigned flags)
+					      struct inode *inode)
 {
 	int ret, needed_blocks, no_expand;
 	handle_t *handle = NULL;
 	int retries = 0, sem_held = 0;
 	struct page *page = NULL;
+	unsigned int flags;
 	unsigned from, to;
 	struct ext4_iloc iloc;
 
@@ -562,9 +562,9 @@ static int ext4_convert_inline_data_to_extent(struct address_space *mapping,
 
 	/* We cannot recurse into the filesystem as the transaction is already
 	 * started */
-	flags |= AOP_FLAG_NOFS;
-
-	page = grab_cache_page_write_begin(mapping, 0, flags);
+	flags = memalloc_nofs_save();
+	page = grab_cache_page_write_begin(mapping, 0, 0);
+	memalloc_nofs_restore(flags);
 	if (!page) {
 		ret = -ENOMEM;
 		goto out;
@@ -649,11 +649,11 @@ static int ext4_convert_inline_data_to_extent(struct address_space *mapping,
 int ext4_try_to_write_inline_data(struct address_space *mapping,
 				  struct inode *inode,
 				  loff_t pos, unsigned len,
-				  unsigned flags,
 				  struct page **pagep)
 {
 	int ret;
 	handle_t *handle;
+	unsigned int flags;
 	struct page *page;
 	struct ext4_iloc iloc;
 
@@ -691,9 +691,9 @@ int ext4_try_to_write_inline_data(struct address_space *mapping,
 	if (ret)
 		goto out;
 
-	flags |= AOP_FLAG_NOFS;
-
-	page = grab_cache_page_write_begin(mapping, 0, flags);
+	flags = memalloc_nofs_save();
+	page = grab_cache_page_write_begin(mapping, 0, 0);
+	memalloc_nofs_restore(flags);
 	if (!page) {
 		ret = -ENOMEM;
 		goto out;
@@ -727,8 +727,7 @@ int ext4_try_to_write_inline_data(struct address_space *mapping,
 	brelse(iloc.bh);
 	return ret;
 convert:
-	return ext4_convert_inline_data_to_extent(mapping,
-						  inode, flags);
+	return ext4_convert_inline_data_to_extent(mapping, inode);
 }
 
 int ext4_write_inline_data_end(struct inode *inode, loff_t pos, unsigned len,

fs/ext4/inode.c

@@ -1156,7 +1156,7 @@ static int ext4_write_begin(struct file *file, struct address_space *mapping,
 
 	if (ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA)) {
 		ret = ext4_try_to_write_inline_data(mapping, inode, pos, len,
-						    flags, pagep);
+						    pagep);
 		if (ret < 0)
 			return ret;
 		if (ret == 1)