UBI: do not switch to R/O mode on read errors

This patch improves UBI errors handling. ATM UBI switches to
R/O mode when the WL worker fails to read the source PEB.
This means that the upper layers (e.g., UBIFS) has no
chances to unmap the erroneous PEB and fix the error.
This patch changes this behaviour and makes UBI put PEBs
like this into a separate RB-tree, thus preventing the
WL worker from hitting the same read errors again and
again.

But there is a 10% limit on a maximum amount of PEBs like this.
If there are too much of them, UBI switches to R/O mode.

Additionally, this patch teaches UBI not to panic and
switch to R/O mode if after a PEB has been copied, the
target LEB cannot be read back. Instead, now UBI cancels
the operation and schedules the target PEB for torturing.

The error paths has been tested by ingecting errors
into 'ubi_eba_copy_leb()'.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 1405b556c65..d3da6668266 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -633,6 +633,15 @@ static int io_init(struct ubi_device *ubi)
 	}
 
 	/*
+	 * Set maximum amount of physical erroneous eraseblocks to be 10%.
+	 * Erroneous PEB are those which have read errors.
+	 */
+	ubi->max_erroneous = ubi->peb_count / 10;
+	if (ubi->max_erroneous < 16)
+		ubi->max_erroneous = 16;
+	dbg_msg("max_erroneous    %d", ubi->max_erroneous);
+
+	/*
 	 * It may happen that EC and VID headers are situated in one minimal
 	 * I/O unit. In this case we can only accept this UBI image in
 	 * read-only mode.