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Subject: [PATCH 56/67] afs: Make afs_write_begin() return the THP subpage
From:   David Howells <dhowells@redhat.com>
To:     linux-cachefs@redhat.com
Cc:     dhowells@redhat.com, Trond Myklebust <trondmy@hammerspace.com>,
        Anna Schumaker <anna.schumaker@netapp.com>,
        Steve French <sfrench@samba.org>,
        Dominique Martinet <asmadeus@codewreck.org>,
        Jeff Layton <jlayton@redhat.com>,
        Matthew Wilcox <willy@infradead.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Omar Sandoval <osandov@osandov.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org,
        linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org,
        v9fs-developer@lists.sourceforge.net,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Date:   Mon, 18 Oct 2021 16:05:32 +0100
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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@redhat.com>
---

 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 281f0e93e2c6..5cd417e95029 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -90,7 +90,7 @@ 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;
 
@@ -120,9 +120,10 @@ 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 = offset_in_thp(page, pos);
 	unsigned int t, to = from + copied;