ext4: set FMODE_CAN_ODIRECT instead of a dummy direct_IO method

Since commit a2ad63d ("VFS: add FMODE_CAN_ODIRECT file flag") file
systems can just set the FMODE_CAN_ODIRECT flag at open time instead of
wiring up a dummy direct_IO method to indicate support for direct I/O.

Signed-off-by: Christoph Hellwig <hch@lst.de>
[RH: Rebased to upstream]
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/e5797bb597219a49043e53e4e90aa494b97dc328.1709215665.git.ritesh.list@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: Christoph Hellwig

fs/ext4/file.c

@@ -886,7 +886,7 @@ static int ext4_file_open(struct inode *inode, struct file *filp)
 	}
 
 	filp->f_mode |= FMODE_NOWAIT | FMODE_BUF_RASYNC |
-			FMODE_DIO_PARALLEL_WRITE;
+			FMODE_DIO_PARALLEL_WRITE | FMODE_CAN_ODIRECT;
 	return dquot_file_open(inode, filp);
 }
 

fs/ext4/inode.c

@@ -3530,7 +3530,6 @@ static const struct address_space_operations ext4_aops = {
 	.bmap			= ext4_bmap,
 	.invalidate_folio	= ext4_invalidate_folio,
 	.release_folio		= ext4_release_folio,
-	.direct_IO		= noop_direct_IO,
 	.migrate_folio		= buffer_migrate_folio,
 	.is_partially_uptodate  = block_is_partially_uptodate,
 	.error_remove_folio	= generic_error_remove_folio,
@@ -3547,7 +3546,6 @@ static const struct address_space_operations ext4_journalled_aops = {
 	.bmap			= ext4_bmap,
 	.invalidate_folio	= ext4_journalled_invalidate_folio,
 	.release_folio		= ext4_release_folio,
-	.direct_IO		= noop_direct_IO,
 	.migrate_folio		= buffer_migrate_folio_norefs,
 	.is_partially_uptodate  = block_is_partially_uptodate,
 	.error_remove_folio	= generic_error_remove_folio,
@@ -3564,7 +3562,6 @@ static const struct address_space_operations ext4_da_aops = {
 	.bmap			= ext4_bmap,
 	.invalidate_folio	= ext4_invalidate_folio,
 	.release_folio		= ext4_release_folio,
-	.direct_IO		= noop_direct_IO,
 	.migrate_folio		= buffer_migrate_folio,
 	.is_partially_uptodate  = block_is_partially_uptodate,
 	.error_remove_folio	= generic_error_remove_folio,
@@ -3573,7 +3570,6 @@ static const struct address_space_operations ext4_da_aops = {
 
 static const struct address_space_operations ext4_dax_aops = {
 	.writepages		= ext4_dax_writepages,
-	.direct_IO		= noop_direct_IO,
 	.dirty_folio		= noop_dirty_folio,
 	.bmap			= ext4_bmap,
 	.swap_activate		= ext4_iomap_swap_activate,