Re: [PATCH 2/6] UBI: Fastmap: Ensure that only one fastmap work is scheduled

From: Tanya Brokhman
Date: Thu Dec 04 2014 - 11:14:23 EST


On 11/24/2014 3:20 PM, Richard Weinberger wrote:
If the WL pool runs out of PEBs we schedule a fastmap write
to refill it as soon as possible.
Ensure that only one at a time is scheduled otherwise we might end in
a fastmap write storm because writing the fastmap can schedule another
write if bitflips are detected.


Reviewed-by: Tanya Brokhman <tlinder@xxxxxxxxxxxxxx>

Signed-off-by: Richard Weinberger <richard@xxxxxx>
---
drivers/mtd/ubi/ubi.h | 4 +++-
drivers/mtd/ubi/wl.c | 8 +++++++-
2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index f80ffab..04c4c05 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -427,6 +427,7 @@ struct ubi_debug_info {
* @fm_size: fastmap size in bytes
* @fm_sem: allows ubi_update_fastmap() to block EBA table changes
* @fm_work: fastmap work queue
+ * @fm_work_scheduled: non-zero if fastmap work was scheduled
*
* @used: RB-tree of used physical eraseblocks
* @erroneous: RB-tree of erroneous used physical eraseblocks
@@ -438,7 +439,7 @@ struct ubi_debug_info {
* @pq_head: protection queue head
* @wl_lock: protects the @used, @free, @pq, @pq_head, @lookuptbl, @move_from,
* @move_to, @move_to_put @erase_pending, @wl_scheduled, @works,
- * @erroneous, and @erroneous_peb_count fields
+ * @erroneous, @erroneous_peb_count, and @fm_work_scheduled fields
* @move_mutex: serializes eraseblock moves
* @work_sem: used to wait for all the scheduled works to finish and prevent
* new works from being submitted
@@ -533,6 +534,7 @@ struct ubi_device {
void *fm_buf;
size_t fm_size;
struct work_struct fm_work;
+ int fm_work_scheduled;

/* Wear-leveling sub-system's stuff */
struct rb_root used;
diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index 834f6fe..7f135df 100644
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -149,6 +149,9 @@ static void update_fastmap_work_fn(struct work_struct *wrk)
{
struct ubi_device *ubi = container_of(wrk, struct ubi_device, fm_work);
ubi_update_fastmap(ubi);
+ spin_lock(&ubi->wl_lock);
+ ubi->fm_work_scheduled = 0;
+ spin_unlock(&ubi->wl_lock);
}

/**
@@ -660,7 +663,10 @@ static struct ubi_wl_entry *get_peb_for_wl(struct ubi_device *ubi)
/* We cannot update the fastmap here because this
* function is called in atomic context.
* Let's fail here and refill/update it as soon as possible. */
- schedule_work(&ubi->fm_work);
+ if (!ubi->fm_work_scheduled) {
+ ubi->fm_work_scheduled = 1;
+ schedule_work(&ubi->fm_work);
+ }
return NULL;
} else {
pnum = pool->pebs[pool->used++];



Thanks,
Tanya Brokhman
--
Qualcomm Israel, on behalf of Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
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