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SubjectRe: [PATCH 1/1] MTD: UBI: try to avoid program data to NOR flash after erasure interrupted
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On Mon, 2013-10-28 at 04:54 +0000, Qi Wang 王起 (qiwang) wrote:
> On Sa, 2013-10-26 at 05:19 +0000, Artem Bityutskiy wrote:
> >On Thu, 2013-10-10 at 08:28 +0000, Qi Wang 王起 (qiwang) wrote:
> >> But I want to say the potential risk is if low level driver program data to
> >> this block, it will get “timeout error”. And the timeout period could be very
> >> long(almost several minutes), during this period, any operation on NOR flash
> >> cannot be accept. so program data to a erasure interrupted block isn’t a
> >> sensible action. in order to avoid program a erasure interrupted block,
> >> I suggest UBIFS can read this block before program data. the code changing as below:
> >
> >Yes, reading first sounds like a good idea. Would you please send a
> >patch implementing it?
>
> From: Qi Wang <qiwang@micron.com>
>
> nor_erase_prepare() will be called before erase a NOR flash, it will program '0'
> into a block to mark this block. But program data into a erasure interrupted block
> can cause program timtout(several minutes at most) error, could impact other
> operation on NOR flash. So UBIFS can read this block first to avoid unneeded
> program operation.
>
> This patch try to put read operation at at head of write operation in
> nor_erase_prepare(), read out the data.
> If the data is already corrupt, then no need to program any data into this block,
> just go to erase this block.
>
> Signed-off-by: Qi Wang <qiwang@qiwang@micron.com>
> ---
> diff --git a/drivers/mtd/ubi/io.c b/drivers/mtd/ubi/io.c
> index bf79def..be6ab56 100644
> --- a/drivers/mtd/ubi/io.c
> +++ b/drivers/mtd/ubi/io.c
> @@ -509,26 +509,10 @@ static int nor_erase_prepare(struct ubi_device *ubi, int pnum)
> struct ubi_vid_hdr vid_hdr;
>
> /*
> - * It is important to first invalidate the EC header, and then the VID
> - * header. Otherwise a power cut may lead to valid EC header and
> - * invalid VID header, in which case UBI will treat this PEB as
> - * corrupted and will try to preserve it, and print scary warnings.
> - */
> - addr = (loff_t)pnum * ubi->peb_size;
> - err = mtd_write(ubi->mtd, addr, 4, &written, (void *)&data);
> - if (!err) {
> - addr += ubi->vid_hdr_aloffset;
> - err = mtd_write(ubi->mtd, addr, 4, &written, (void *)&data);
> - if (!err)
> - return 0;
> - }

How about structuring the code this way:

if (EC header is good)
invalidate EC header()
if (VID header is good)
invalidate VID header()

Then you'll handle the case when only one of the headers is already
corrupted.

--
Best Regards,
Artem Bityutskiy

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