Merge tag 'gfs2-v6.4-rc4-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2

Pull gfs2 fix from Andreas Gruenbacher:

 - Don't get stuck writing page onto itself under direct I/O

* tag 'gfs2-v6.4-rc4-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2:
  gfs2: Don't get stuck writing page onto itself under direct I/O

1 files changed, 14 insertions, 3 deletions

diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index 300844f50dcd..cb62c8f07d1e 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -784,9 +784,13 @@ static inline bool should_fault_in_pages(struct iov_iter *i,
 	if (!user_backed_iter(i))
 		return false;
 
+	/*
+	 * Try to fault in multiple pages initially.  When that doesn't result
+	 * in any progress, fall back to a single page.
+	 */
 	size = PAGE_SIZE;
 	offs = offset_in_page(iocb->ki_pos);
-	if (*prev_count != count || !*window_size) {
+	if (*prev_count != count) {
 		size_t nr_dirtied;
 
 		nr_dirtied = max(current->nr_dirtied_pause -
@@ -870,6 +874,7 @@ static ssize_t gfs2_file_direct_write(struct kiocb *iocb, struct iov_iter *from,
 	struct gfs2_inode *ip = GFS2_I(inode);
 	size_t prev_count = 0, window_size = 0;
 	size_t written = 0;
+	bool enough_retries;
 	ssize_t ret;
 
 	/*
@@ -913,11 +918,17 @@ retry:
 	if (ret > 0)
 		written = ret;
 
+	enough_retries = prev_count == iov_iter_count(from) &&
+			 window_size <= PAGE_SIZE;
 	if (should_fault_in_pages(from, iocb, &prev_count, &window_size)) {
 		gfs2_glock_dq(gh);
 		window_size -= fault_in_iov_iter_readable(from, window_size);
-		if (window_size)
-			goto retry;
+		if (window_size) {
+			if (!enough_retries)
+				goto retry;
+			/* fall back to buffered I/O */
+			ret = 0;
+		}
 	}
 out_unlock:
 	if (gfs2_holder_queued(gh))