Due to the recursive ubi_thread implementation in the barebox, a large amount of wear-leveling can lead to a stack overflow. This was observed during extensive ubi stress tests with the linux kernel and periodic power cycles. We found that if the wear-leveling threshold is exceeded and a large amount of erase blocks need wear-leveling the stack can overflow. The hardware used to observe this was a phyCORE-i.MX 6 with 1GB NAND flash. As the kernel is perfectly capable of handling wear-leveling we can disable wear-leveling in the barebox by maxing out the threshold and removing its Kconfig option. Signed-off-by: Stefan Riedmueller <s.riedmueller@xxxxxxxxx> --- Changes in v2: - Remove threshold config completely instead of just maxing out the default --- drivers/mtd/ubi/Kconfig | 17 ----------------- drivers/mtd/ubi/build.c | 2 +- drivers/mtd/ubi/ubi.h | 11 +++++++++++ drivers/mtd/ubi/wl.c | 8 -------- 4 files changed, 12 insertions(+), 26 deletions(-) diff --git a/drivers/mtd/ubi/Kconfig b/drivers/mtd/ubi/Kconfig index 9a344082b7bb..ed2f13d14c30 100644 --- a/drivers/mtd/ubi/Kconfig +++ b/drivers/mtd/ubi/Kconfig @@ -10,23 +10,6 @@ menuconfig MTD_UBI if MTD_UBI -config MTD_UBI_WL_THRESHOLD - int "UBI wear-leveling threshold" - default 4096 - range 2 65536 - help - This parameter defines the maximum difference between the highest - erase counter value and the lowest erase counter value of eraseblocks - of UBI devices. When this threshold is exceeded, UBI starts performing - wear leveling by means of moving data from eraseblock with low erase - counter to eraseblocks with high erase counter. - - The default value should be OK for SLC NAND flashes, NOR flashes and - other flashes which have eraseblock life-cycle 100000 or more. - However, in case of MLC NAND flashes which typically have eraseblock - life-cycle less than 10000, the threshold should be lessened (e.g., - to 128 or 256, although it does not have to be power of 2). - config MTD_UBI_BEB_LIMIT int "Maximum expected bad eraseblock count per 1024 eraseblocks" default 20 diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c index 493c778c3fdb..604fe87e53b6 100644 --- a/drivers/mtd/ubi/build.c +++ b/drivers/mtd/ubi/build.c @@ -655,7 +655,7 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, ubi->vol_count - UBI_INT_VOL_COUNT, UBI_INT_VOL_COUNT, ubi->vtbl_slots); ubi_msg(ubi, "max/mean erase counter: %d/%d, WL threshold: %d, image sequence number: %u", - ubi->max_ec, ubi->mean_ec, CONFIG_MTD_UBI_WL_THRESHOLD, + ubi->max_ec, ubi->mean_ec, UBI_WL_THRESHOLD, ubi->image_seq); ubi_msg(ubi, "available PEBs: %d, total reserved PEBs: %d, PEBs reserved for bad PEB handling: %d", ubi->avail_pebs, ubi->rsvd_pebs, ubi->beb_rsvd_pebs); diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h index 922c1a3c8b49..7d07bbf19720 100644 --- a/drivers/mtd/ubi/ubi.h +++ b/drivers/mtd/ubi/ubi.h @@ -69,6 +69,17 @@ */ #define UBI_PROT_QUEUE_LEN 10 +/* + * Maximum difference between two erase counters. If this threshold is + * exceeded, the WL sub-system starts moving data from used physical + * eraseblocks with low erase counter to free physical eraseblocks with high + * erase counter. + * Extensive wear-leveling in the barebox can lead to stack overflows. Thus + * disable it by setting the threshold to the OS's max configurable value and + * leave wear-leveling to the OS. + */ +#define UBI_WL_THRESHOLD 65536 + /* The volume ID/LEB number/erase counter is unknown */ #define UBI_UNKNOWN -1 diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c index cf90ecfb2385..013ba3e1ffc7 100644 --- a/drivers/mtd/ubi/wl.c +++ b/drivers/mtd/ubi/wl.c @@ -101,14 +101,6 @@ #define WL_RESERVED_PEBS 1 /* - * Maximum difference between two erase counters. If this threshold is - * exceeded, the WL sub-system starts moving data from used physical - * eraseblocks with low erase counter to free physical eraseblocks with high - * erase counter. - */ -#define UBI_WL_THRESHOLD CONFIG_MTD_UBI_WL_THRESHOLD - -/* * When a physical eraseblock is moved, the WL sub-system has to pick the target * physical eraseblock to move to. The simplest way would be just to pick the * one with the highest erase counter. But in certain workloads this could lead -- 2.7.4 _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
