[PATCH] afs: Enable multipage folio support

[David Howells <dhowells@redhat.com>]

Hi Linus,

Can you apply this please?  It enables multipage folios for afs.  Support has
already been implemented in netfslib, fscache and cachefiles and in most of
afs, but I've waited for the VM side to stabilise.

Note that it does require a change to afs_write_begin() to return the correct
subpage.  This is a "temporary" change as we're working on getting rid of the
need for ->write_begin() and ->write_end() completely, at least as far as
network filesystems are concerned - but it doesn't prevent afs from making use
of the capability.

Thanks,
David
---
Enable multipage folio support for the afs filesystem.  This makes use of
Matthew Wilcox's latest folio changes.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: kafs-testing@auristor.com
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/lkml/2274528.1645833226@warthog.procyon.org.uk/
---
 fs/afs/inode.c |    2 ++
 fs/afs/write.c |    2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/afs/inode.c b/fs/afs/inode.c
index 64dab70d4a4f..6d3a3dbe4928 100644
--- a/fs/afs/inode.c
+++ b/fs/afs/inode.c
@@ -104,12 +104,14 @@ static int afs_inode_init_from_status(struct afs_operation *op,
 		inode->i_op	= &afs_file_inode_operations;
 		inode->i_fop	= &afs_file_operations;
 		inode->i_mapping->a_ops	= &afs_file_aops;
+		mapping_set_large_folios(inode->i_mapping);
 		break;
 	case AFS_FTYPE_DIR:
 		inode->i_mode	= S_IFDIR |  (status->mode & S_IALLUGO);
 		inode->i_op	= &afs_dir_inode_operations;
 		inode->i_fop	= &afs_dir_file_operations;
 		inode->i_mapping->a_ops	= &afs_dir_aops;
+		mapping_set_large_folios(inode->i_mapping);
 		break;
 	case AFS_FTYPE_SYMLINK:
 		/* Symlinks with a mode of 0644 are actually mountpoints. */
diff --git a/fs/afs/write.c b/fs/afs/write.c
index 2c885b22de34..9ebdd36eaf2f 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -91,7 +91,7 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
 			goto flush_conflicting_write;
 	}
 
-	*_page = &folio->page;
+	*_page = folio_file_page(folio, pos / PAGE_SIZE);
 	_leave(" = 0");
 	return 0;