Merge tag 'netfs-fixes-20210621' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull netfs fixes from David Howells:
 "This contains patches to fix netfs_write_begin() and afs_write_end()
  in the following ways:

  (1) In netfs_write_begin(), extract the decision about whether to skip
      a page out to its own helper and have that clear around the region
      to be written, but not clear that region. This requires the
      filesystem to patch it up afterwards if the hole doesn't get
      completely filled.

  (2) Use offset_in_thp() in (1) rather than manually calculating the
      offset into the page.

  (3) Due to (1), afs_write_end() now needs to handle short data write
      into the page by generic_perform_write(). I've adopted an
      analogous approach to ceph of just returning 0 in this case and
      letting the caller go round again.

  It also adds a note that (in the future) the len parameter may extend
  beyond the page allocated. This is because the page allocation is
  deferred to write_begin() and that gets to decide what size of THP to
  allocate."

Jeff Layton points out:
 "The netfs fix in particular fixes a data corruption bug in cephfs"

* tag 'netfs-fixes-20210621' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  netfs: fix test for whether we can skip read when writing beyond EOF
  afs: Fix afs_write_end() to handle short writes

1 files changed, 9 insertions, 2 deletions

diff --git a/fs/afs/write.c b/fs/afs/write.c
index e9ccaa3baf2e..3104b62c2082 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -118,6 +118,15 @@ int afs_write_end(struct file *file, struct address_space *mapping,
 	_enter("{%llx:%llu},{%lx}",
 	       vnode->fid.vid, vnode->fid.vnode, page->index);
 
+	if (!PageUptodate(page)) {
+		if (copied < len) {
+			copied = 0;
+			goto out;
+		}
+
+		SetPageUptodate(page);
+	}
+
 	if (copied == 0)
 		goto out;
 
@@ -132,8 +141,6 @@ int afs_write_end(struct file *file, struct address_space *mapping,
 		write_sequnlock(&vnode->cb_lock);
 	}
 
-	ASSERT(PageUptodate(page));
-
 	if (PagePrivate(page)) {
 		priv = page_private(page);
 		f = afs_page_dirty_from(page, priv);