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Date: Mon, 22 Dec 2008 13:29:06 +0200
From: Adrian Hunter <ext-adrian.hunter@...ia.com>
To: Pierre Ossman <drzeus@...eus.cx>
CC: LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] mmc_block: ensure all sectors that do not have errors
are read
Pierre Ossman wrote:
> On Fri, 05 Dec 2008 13:09:11 +0200
> Adrian Hunter <ext-adrian.hunter@...ia.com> wrote:
>
>> @@ -281,6 +289,16 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
>> brq.data.sg = mq->sg;
>> brq.data.sg_len = mmc_queue_map_sg(mq);
>>
>> + /*
>> + * Some drivers expect the sg list to be the same size as the
>> + * request, which it won't be if we have fallen back to do
>> + * one sector at a time.
>> + */
>> + if (disable_multi) {
>> + brq.data.sg->length = 512;
>> + brq.data.sg_len = 1;
>> + }
>> +
>> mmc_queue_bounce_pre(mq);
>>
>> mmc_wait_for_req(card->host, &brq.mrq);
>
> Unfortunately, there is no guarantee that the sg list will be sector
> aligned.
OK. I am curious though - do you know anywhere in the kernel that actually
does submit I/O in buffers that are not aligned to 512?
> Look at the code removed in f3eb0aaa02 for how to handle this
> properly.
>
> Other than that, the patch looks ready to go.
>
> Rgds
From: Adrian Hunter <ext-adrian.hunter@...ia.com>
Subject: [PATCH] mmc_block: ensure all sectors that do not have errors are read
If a card encounters an ECC error while reading a sector it will
timeout. Instead of reporting the entire I/O request as having
an error, redo the I/O one sector at a time so that all readable
sectors are provided to the upper layers.
Signed-off-by: Adrian Hunter <ext-adrian.hunter@...ia.com>
---
drivers/mmc/card/block.c | 76 +++++++++++++++++++++++++++++++++++----------
1 files changed, 59 insertions(+), 17 deletions(-)
diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index 2998112..679b489 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -231,7 +231,7 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
struct mmc_blk_data *md = mq->data;
struct mmc_card *card = md->queue.card;
struct mmc_blk_request brq;
- int ret = 1;
+ int ret = 1, disable_multi = 0;
mmc_claim_host(card->host);
@@ -253,6 +253,14 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
brq.stop.flags = MMC_RSP_SPI_R1B | MMC_RSP_R1B | MMC_CMD_AC;
brq.data.blocks = req->nr_sectors;
+ /*
+ * After a read error, we redo the request one sector at a time
+ * in order to accurately determine which sectors can be read
+ * successfully.
+ */
+ if (disable_multi && brq.data.blocks > 1)
+ brq.data.blocks = 1;
+
if (brq.data.blocks > 1) {
/* SPI multiblock writes terminate using a special
* token, not a STOP_TRANSMISSION request.
@@ -281,6 +289,25 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
brq.data.sg = mq->sg;
brq.data.sg_len = mmc_queue_map_sg(mq);
+ /*
+ * Adjust the sg list so it is the same size as the
+ * request.
+ */
+ if (brq.data.blocks != req->nr_sectors) {
+ int i, data_size = brq.data.blocks << 9;
+ struct scatterlist *sg;
+
+ for_each_sg(brq.data.sg, sg, brq.data.sg_len, i) {
+ data_size -= sg->length;
+ if (data_size <= 0) {
+ sg->length += data_size;
+ i++;
+ break;
+ }
+ }
+ brq.data.sg_len = i;
+ }
+
mmc_queue_bounce_pre(mq);
mmc_wait_for_req(card->host, &brq.mrq);
@@ -292,8 +319,16 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
* until later as we need to wait for the card to leave
* programming mode even when things go wrong.
*/
- if (brq.cmd.error || brq.data.error || brq.stop.error)
+ if (brq.cmd.error || brq.data.error || brq.stop.error) {
+ if (brq.data.blocks > 1 && rq_data_dir(req) == READ) {
+ /* Redo read one sector at a time */
+ printk(KERN_WARNING "%s: retrying using single "
+ "block read\n", req->rq_disk->disk_name);
+ disable_multi = 1;
+ continue;
+ }
status = get_card_status(card, req);
+ }
if (brq.cmd.error) {
printk(KERN_ERR "%s: error %d sending read/write "
@@ -350,8 +385,20 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
#endif
}
- if (brq.cmd.error || brq.data.error || brq.stop.error)
+ if (brq.cmd.error || brq.stop.error || brq.data.error) {
+ if (rq_data_dir(req) == READ) {
+ /*
+ * After an error, we redo I/O one sector at a
+ * time, so we only reach here after trying to
+ * read a single sector.
+ */
+ spin_lock_irq(&md->lock);
+ ret = __blk_end_request(req, -EIO, brq.data.blksz);
+ spin_unlock_irq(&md->lock);
+ continue;
+ }
goto cmd_err;
+ }
/*
* A block was successfully transferred.
@@ -373,25 +420,20 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
* If the card is not SD, we can still ok written sectors
* as reported by the controller (which might be less than
* the real number of written sectors, but never more).
- *
- * For reads we just fail the entire chunk as that should
- * be safe in all cases.
*/
- if (rq_data_dir(req) != READ) {
- if (mmc_card_sd(card)) {
- u32 blocks;
+ if (mmc_card_sd(card)) {
+ u32 blocks;
- blocks = mmc_sd_num_wr_blocks(card);
- if (blocks != (u32)-1) {
- spin_lock_irq(&md->lock);
- ret = __blk_end_request(req, 0, blocks << 9);
- spin_unlock_irq(&md->lock);
- }
- } else {
+ blocks = mmc_sd_num_wr_blocks(card);
+ if (blocks != (u32)-1) {
spin_lock_irq(&md->lock);
- ret = __blk_end_request(req, 0, brq.data.bytes_xfered);
+ ret = __blk_end_request(req, 0, blocks << 9);
spin_unlock_irq(&md->lock);
}
+ } else {
+ spin_lock_irq(&md->lock);
+ ret = __blk_end_request(req, 0, brq.data.bytes_xfered);
+ spin_unlock_irq(&md->lock);
}
mmc_release_host(card->host);
--
1.5.4.3
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