ocfs2: clearly handle ocfs2_grab_pages_for_write() return value

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, make the
return value handling more clear.

Link: https://lkml.kernel.org/r/20211206065051.103353-1-joseph.qi@linux.alibaba.com
Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Gang He <ghe@suse.com>
Cc: Jun Piao <piaojun@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 68d11c295dd345aa7307fd77301df44dd4b76797..498da317580a75e2e6bbb03e2f66f1a930d44216 100644 (file)
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -1799,20 +1799,20 @@ try_again:
         */
        ret = ocfs2_grab_pages_for_write(mapping, wc, wc->w_cpos, pos, len,
                                         cluster_of_pages, mmap_page);
-       if (ret && ret != -EAGAIN) {
-               mlog_errno(ret);
-               goto out_quota;
-       }
+       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;
+               }
 
-       /*
-        * 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;
+               mlog_errno(ret);
                goto out_quota;
        }