Re: [RFC/PATCH] mtd: ubi: Free peb's synchronously for fastmap

From: Tanya Brokhman
Date: Mon Apr 07 2014 - 12:06:15 EST

On 4/7/2014 4:02 PM, Richard Weinberger wrote:
On Tue, Apr 1, 2014 at 10:01 AM, Tanya Brokhman <tlinder@xxxxxxxxxxxxxx> wrote:
At first mount it's possible that there are not enough free PEBs since
there are PEB's pending to be erased. In such scenario, fm_pool (which is
the pool from which user required PEBs are allocated) will be empty.
Try fixing the above described situation by synchronously performing
pending erase work, thus produce another free PEB.

Signed-off-by: Tatyana Brokhman <tlinder@xxxxxxxxxxxxxx>

diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index 457ead3..9a36f78 100644
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -595,10 +595,29 @@ static void refill_wl_pool(struct ubi_device *ubi)
static void refill_wl_user_pool(struct ubi_device *ubi)
struct ubi_fm_pool *pool = &ubi->fm_pool;
+ int err;

return_unused_pool_pebs(ubi, pool);

for (pool->size = 0; pool->size < pool->max_size; pool->size++) {
+ if (!ubi->free.rb_node ||
+ (ubi->free_count - ubi->beb_rsvd_pebs < 1)) {
+ /*
+ * There are no available PEBs. Try to free
+ * PEB by means of synchronous execution of
+ * pending works.
+ */
+ if (ubi->works_count == 0)
+ break;
+ spin_unlock(&ubi->wl_lock);
+ err = do_work(ubi);
+ spin_lock(&ubi->wl_lock);

This is basically what produce_free_peb() does.

Right. I didn't use t just because of the termination condition. produce_free_peb stops if there is 1 free peb. I need more then 1

+ if (err < 0)
+ break;
+ goto retry;
+ }
pool->pebs[pool->size] = __wl_get_peb(ubi);

__wl_get_peb() already calls produce_free_peb() when we run out of free PEBs.

Does your patch really fix a problem you encounter or did you find the
issue by reviewing
the code?

Yes. We encountered this issue, as described in the commit message. This is the fix. Verified and working for us.

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