fs: remove noop_set_page_dirty()

Use __set_page_dirty_no_writeback() instead. This will set the dirty bit
on the page, which will be used to avoid calling set_page_dirty() in the
future. It will have no effect on actually writing the page back, as the
pages are not on any LRU lists.

[[e-mail]: export __set_page_dirty_no_writeback() to modules]

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
Cc: Al Viro <[e-mail]>
Cc: Christoph Hellwig <[e-mail]>
Cc: Dan Williams <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Cc: Jan Kara <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/dax/device.c

···
 }
 
 static const struct address_space_operations dev_dax_aops = {
-	.set_page_dirty		= noop_set_page_dirty,
+	.set_page_dirty		= __set_page_dirty_no_writeback,
 	.invalidatepage		= noop_invalidatepage,
 };
 

fs/ext2/inode.c

···
 static const struct address_space_operations ext2_dax_aops = {
 	.writepages		= ext2_dax_writepages,
 	.direct_IO		= noop_direct_IO,
-	.set_page_dirty		= noop_set_page_dirty,
+	.set_page_dirty		= __set_page_dirty_no_writeback,
 	.invalidatepage		= noop_invalidatepage,
 };
 

fs/ext4/inode.c

···
 static const struct address_space_operations ext4_dax_aops = {
 	.writepages		= ext4_dax_writepages,
 	.direct_IO		= noop_direct_IO,
-	.set_page_dirty		= noop_set_page_dirty,
+	.set_page_dirty		= __set_page_dirty_no_writeback,
 	.bmap			= ext4_bmap,
 	.invalidatepage		= noop_invalidatepage,
 	.swap_activate		= ext4_iomap_swap_activate,

fs/fuse/dax.c

···
 static const struct address_space_operations fuse_dax_file_aops  = {
 	.writepages	= fuse_dax_writepages,
 	.direct_IO	= noop_direct_IO,
-	.set_page_dirty	= noop_set_page_dirty,
+	.set_page_dirty	= __set_page_dirty_no_writeback,
 	.invalidatepage	= noop_invalidatepage,
 };
 

fs/libfs.c

···
 }
 EXPORT_SYMBOL(noop_fsync);
 
-int noop_set_page_dirty(struct page *page)
-{
-	/*
-	 * Unlike __set_page_dirty_no_writeback that handles dirty page
-	 * tracking in the page object, dax does all dirty tracking in
-	 * the inode address_space in response to mkwrite faults. In the
-	 * dax case we only need to worry about potentially dirty CPU
-	 * caches, not dirty page cache pages to write back.
-	 *
-	 * This callback is defined to prevent fallback to
-	 * __set_page_dirty_buffers() in set_page_dirty().
-	 */
-	return 0;
-}
-EXPORT_SYMBOL_GPL(noop_set_page_dirty);
-
 void noop_invalidatepage(struct page *page, unsigned int offset,
 		unsigned int length)
 {

fs/xfs/xfs_aops.c

···
 const struct address_space_operations xfs_dax_aops = {
 	.writepages		= xfs_dax_writepages,
 	.direct_IO		= noop_direct_IO,
-	.set_page_dirty		= noop_set_page_dirty,
+	.set_page_dirty		= __set_page_dirty_no_writeback,
 	.invalidatepage		= noop_invalidatepage,
 	.swap_activate		= xfs_iomap_swapfile_activate,
 };

include/linux/fs.h

···
 extern void simple_recursive_removal(struct dentry *,
                               void (*callback)(struct dentry *));
 extern int noop_fsync(struct file *, loff_t, loff_t, int);
-extern int noop_set_page_dirty(struct page *page);
 extern void noop_invalidatepage(struct page *page, unsigned int offset,
 		unsigned int length);
 extern ssize_t noop_direct_IO(struct kiocb *iocb, struct iov_iter *iter);

mm/page-writeback.c

···
 		return !TestSetPageDirty(page);
 	return 0;
 }
+EXPORT_SYMBOL(__set_page_dirty_no_writeback);
 
 /*
  * Helper function for set_page_dirty family.