ocfs2: clearly handle ocfs2_grab_pages_for_write() return value

Commit Message

Joseph Qi Dec. 6, 2021, 6:36 a.m. UTC

ocfs2_grab_pages_for_write() may return -EAGAIN if write context type is
mmap and it could not lock the target page. In this case, we exit with
no error and no target page. And then trigger the caller page_mkwrite()
to retry.
Since there are other caller types, e.g. buffer and direct io, so make
the return value handling more clearly.

Reported-by: Dan Carpenter <[e-mail]>
Signed-off-by: Joseph Qi <[e-mail]>
---
 fs/ocfs2/aops.c | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

Patch

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 68d11c295dd3..f983f982b321 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -1799,22 +1799,23 @@  int ocfs2_write_begin_nolock(struct address_space *mapping,
 	 */
 	ret = ocfs2_grab_pages_for_write(mapping, wc, wc->w_cpos, pos, len,
 					 cluster_of_pages, mmap_page);
-	if (ret && ret != -EAGAIN) {
+	if (ret) {
+		/*
+		 * ocfs2_grab_pages_for_write() returns -EAGAIN if it could not lock
+		 * the target page. In this case, we exit with no error and no target
+		 * page. This will trigger the caller, page_mkwrite(), to re-try
+		 * the operation.
+		 */
+		if (type == OCFS2_WRITE_MMAP && ret == -EAGAIN) {
+			BUG_ON(wc->w_target_page);
+			ret = 0;
+			goto out_quota;
+		}
+
 		mlog_errno(ret);
 		goto out_quota;
 	}
 
-	/*
-	 * ocfs2_grab_pages_for_write() returns -EAGAIN if it could not lock
-	 * the target page. In this case, we exit with no error and no target
-	 * page. This will trigger the caller, page_mkwrite(), to re-try
-	 * the operation.
-	 */
-	if (ret == -EAGAIN) {
-		BUG_ON(wc->w_target_page);
-		ret = 0;
-		goto out_quota;
-	}
 
 	ret = ocfs2_write_cluster_by_desc(mapping, data_ac, meta_ac, wc, pos,
 					  len);