commit 66a224023e59c01c7679fe32a41bb6bb158c2be8
author Jaegeuk Kim <jaegeuk@google.com> Tue Nov 30 10:22:39 2021 -0800
committer Randall Huang <huangrandall@google.com> Thu Dec 02 00:43:05 2021 +0000
tree 5c43237b991a6b9b19c9172e8a80b79468eb0efa
parent be77a975e623ac6ebed899fae35b48839408cef4

ANDROID: f2fs: check nr_pages for readahead

Old kernel versions have the issue, since upstream f2fs removed this flow by:
commit d4384de9eb5e ("f2fs: Remove readahead collision detection").

Bug: 206148707
Signed-off-by: Jaegeuk Kim <jaegeuk@google.com>
Change-Id: I3a95f0b436d0a5ee420f41d892401a8d79d4fe79
(cherry picked from commit a755945f812bbea48869712a1e8e81e1496c6cd2)

fs/f2fs/data.c

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 497a723..4ac20b4 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2342,6 +2342,10 @@
 	int ret = 0;
 	bool drop_ra = false;
 
+	/* this is real from f2fs_merkle_tree_readahead() in old kernel only. */
+	if (!nr_pages)
+		return 0;
+
 	map.m_pblk = 0;
 	map.m_lblk = 0;
 	map.m_len = 0;