[PATCH v2] mtd: ubi: eba.c: fix return value overwrite issue in try_write_vid_and_data()

[Wang YanQing]

The commit 2d78aee426d8 ("UBI: simplify LEB write and atomic LEB change code")
adds helper function, try_write_vid_and_data(), to simplify the code, but this
helper function has bug, it will return 0 (success) when ubi_io_write_vid_hdr()
or the ubi_io_write_data() return error number (-EIO, etc), because the return
value of ubi_wl_put_peb() will overwrite the original return value.

This issue will cause unexpected data loss issue, because the caller of this
function and UBIFS willn't know the data is lost.

Fixes: 2d78aee426d8 ("UBI: simplify LEB write and atomic LEB change code")

Signed-off-by: Wang YanQing <udknight@xxxxxxxxx>
---
 Changes v1-v2:
 1: add error code in warning message, suggested by Zhihao Cheng
 
 drivers/mtd/ubi/eba.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
index 09c408c..4e1d807 100644
--- a/drivers/mtd/ubi/eba.c
+++ b/drivers/mtd/ubi/eba.c
@@ -946,7 +946,7 @@ static int try_write_vid_and_data(struct ubi_volume *vol, int lnum,
 				  int offset, int len)
 {
 	struct ubi_device *ubi = vol->ubi;
-	int pnum, opnum, err, vol_id = vol->vol_id;
+	int pnum, opnum, err, err2, vol_id = vol->vol_id;
 
 	pnum = ubi_wl_get_peb(ubi);
 	if (pnum < 0) {
@@ -981,10 +981,19 @@ static int try_write_vid_and_data(struct ubi_volume *vol, int lnum,
 out_put:
 	up_read(&ubi->fm_eba_sem);
 
-	if (err && pnum >= 0)
-		err = ubi_wl_put_peb(ubi, vol_id, lnum, pnum, 1);
-	else if (!err && opnum >= 0)
-		err = ubi_wl_put_peb(ubi, vol_id, lnum, opnum, 0);
+	if (err && pnum >= 0) {
+		err2 = ubi_wl_put_peb(ubi, vol_id, lnum, pnum, 1);
+		if (err2) {
+			ubi_warn(ubi, "failed to return physical eraseblock %d, error %d",
+				 pnum, err2);
+		}
+	} else if (!err && opnum >= 0) {
+		err2 = ubi_wl_put_peb(ubi, vol_id, lnum, opnum, 0);
+		if (err2) {
+			ubi_warn(ubi, "failed to return physical eraseblock %d, error %d",
+				 opnum, err2);
+		}
+	}
 
 	return err;
 }
-- 
1.8.5.6.2.g3d8a54e.dirty