On 26/04/11 16:19, Arnd Bergmann wrote:
On Saturday 23 April 2011, John Stultz wrote:
From: David Ding<david.j.ding@xxxxxxxxxxxx>
CC: Chris Ball<cjb@xxxxxxxxxx>
CC: Arnd Bergmann<arnd@xxxxxxxx>
CC: Dima Zavin<dima@xxxxxxxxxxx>
Signed-off-by: Bentao Zou<bzou1@xxxxxxxxxxxx>
Signed-off-by: David Ding<david.j.ding@xxxxxxxxxxxx>
Signed-off-by: San Mehat<san@xxxxxxxxxx>
Signed-off-by: John Stultz<john.stultz@xxxxxxxxxx>
The disable_multi logic was introduced in 6a79e391 "mmc_block: ensure
all sectors that do not have errors are read" by Adrian Hunter. Maybe
he can comment on this.
My impression is that the code makes more sense without this
add-on patch, because the flag is set for exactly one request
and makes mmc_blk_issue_rw_rq issue all blocks in that request
one by one up to the first error, while after the patch,
we would read one sector, then read the remaining request at
once, fail, and read the next sector, and so on.
If the problem is transient read errors, a better solution might
be to retry the entire request before doing it one sector at a time.
Having to guess what the patch is for is pretty sad. Is writing
commit messages so hard.
The word "transient" suggests the errors might disappear, in which case
the entire read should be retried some number of times.
The big problem with reading 1 sector at a time is that it
can be quite slow (orders of magnitude slower). Possibly
this patch is aimed at that. Somewhere there is a patch to
change the retries from 1 sector at a time to 1 segment
at a time, which helps a bit. Possibly it would help to bisect
the number sectors/segments. i.e.
read error
read half of the number of sectors/segments
that were read last time (but always read at
least 1)
no read error
read all the remaining sectors/segments
This patch does the second half of that approach.
drivers/mmc/card/block.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index 61d233a..edac9ac 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -440,6 +440,8 @@ static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *req)
continue;
}
status = get_card_status(card, req);
+ } else if (disable_multi == 1) {
+ disable_multi = 0;
}
if (brq.cmd.error) {
--
1.7.3.2.146.gca209
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