[RFC PATCH 75/76] afs: Make afs_write_begin() return the THP subpage

[David Howells <dhowells@xxxxxxxxxx>]

generic_perform_write() can't handle a THP, so we have to return the
subpage of that THP from afs_write_begin() and then convert it back into
the head on entry to afs_write_end().

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---

 fs/afs/write.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/afs/write.c b/fs/afs/write.c
index bab110c00abd..a88c6ae71868 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -81,7 +81,7 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
 			goto flush_conflicting_write;
 	}
 
-	*_page = page;
+	*_page = find_subpage(page, pos / PAGE_SIZE);
 	_leave(" = 0");
 	return 0;
 
@@ -110,9 +110,10 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
  */
 int afs_write_end(struct file *file, struct address_space *mapping,
 		  loff_t pos, unsigned len, unsigned copied,
-		  struct page *page, void *fsdata)
+		  struct page *subpage, void *fsdata)
 {
 	struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
+	struct page *page = thp_head(subpage);
 	unsigned long priv;
 	unsigned int f, from = pos & (thp_size(page) - 1);
 	unsigned int t, to = from + copied;