[PATCH] UBI: add ubi_err() to report the failure of leb read

[hujianyang]

If an error occur while reading from PEBs, for example, an ECC error,
ubi_io_read() will print some error messages. But it's not enough for
debugging. These messages don't show the mapping info for a read from
UBIFS layer.

Although UBIFS will soon print its error messages after catching the
return value from UBI layer,  multi-path reading will confuse the
relationship between LEBs and PEBs showed by these messages.

This patch adds an ubi_err() to report reading errors in the function
ubi_eba_read_leb(). The mapping info of LEB and PEB is showed by
this error message.

Signed-off-by: hujianyang <hujianyang at huawei.com>
---
 drivers/mtd/ubi/eba.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
index b698534..b4e69e1 100644
--- a/drivers/mtd/ubi/eba.c
+++ b/drivers/mtd/ubi/eba.c
@@ -477,6 +477,8 @@ out_free:
 	ubi_free_vid_hdr(ubi, vid_hdr);
 out_unlock:
 	leb_read_unlock(ubi, vol_id, lnum);
+	ubi_err(ubi, "err %d while reading %d bytes from offset %d of LEB %d:%d, PEB %d",
+		err, len, offset, vol_id, lnum, pnum);
 	return err;
 }

-- 
1.6.0.2