On Tuesday February 6, [email protected] wrote:
>
> This patch should fix the worst of the offences, but I'd like to
> experiment and think a bit more before I submit it to stable.
> And probably test it too - as yet I have only compile and brain
> tested.
Ok, I've experimented and tested and now I know what was causing the
double-unlock.
The following patch is suitable for 2.6.20.1 and mainline. There is
room for a bit more improvement, but only for performance, not
correctness. I'll look into that later.
Thanks,
NeilBrown
------------------------------------
Fix various bugs with aligned reads in RAID5.
It is possible for raid5 to be sent a bio that is too big
for an underlying device. So if it is a READ that we
pass stright down to a device, it will fail and confuse
RAID5.
So in 'chunk_aligned_read' we check that the bio fits within the
parameters for the target device and if it doesn't fit, fall back
on reading through the stripe cache and making lots of one-page
requests.
Note that this is the earliest time we can check against the device
because earlier we don't have a lock on the device, so it could change
underneath us.
Also, the code for handling a retry through the cache when a read
fails has not been tested and was badly broken. This patch fixes that
code.
Signed-off-by: Neil Brown <[email protected]>
### Diffstat output
./drivers/md/raid5.c | 42 +++++++++++++++++++++++++++++++++++++++---
1 file changed, 39 insertions(+), 3 deletions(-)
diff .prev/drivers/md/raid5.c ./drivers/md/raid5.c
--- .prev/drivers/md/raid5.c 2007-02-02 14:17:55.000000000 +1100
+++ ./drivers/md/raid5.c 2007-02-06 19:19:01.000000000 +1100
@@ -2570,7 +2570,7 @@ static struct bio *remove_bio_from_retry
}
bi = conf->retry_read_aligned_list;
if(bi) {
- conf->retry_read_aligned = bi->bi_next;
+ conf->retry_read_aligned_list = bi->bi_next;
bi->bi_next = NULL;
bi->bi_phys_segments = 1; /* biased count of active stripes */
bi->bi_hw_segments = 0; /* count of processed stripes */
@@ -2619,6 +2619,27 @@ static int raid5_align_endio(struct bio
return 0;
}
+static int bio_fits_rdev(struct bio *bi)
+{
+ request_queue_t *q = bdev_get_queue(bi->bi_bdev);
+
+ if ((bi->bi_size>>9) > q->max_sectors)
+ return 0;
+ blk_recount_segments(q, bi);
+ if (bi->bi_phys_segments > q->max_phys_segments ||
+ bi->bi_hw_segments > q->max_hw_segments)
+ return 0;
+
+ if (q->merge_bvec_fn)
+ /* it's too hard to apply the merge_bvec_fn at this stage,
+ * just just give up
+ */
+ return 0;
+
+ return 1;
+}
+
+
static int chunk_aligned_read(request_queue_t *q, struct bio * raid_bio)
{
mddev_t *mddev = q->queuedata;
@@ -2665,6 +2686,13 @@ static int chunk_aligned_read(request_qu
align_bi->bi_flags &= ~(1 << BIO_SEG_VALID);
align_bi->bi_sector += rdev->data_offset;
+ if (!bio_fits_rdev(align_bi)) {
+ /* too big in some way */
+ bio_put(align_bi);
+ rdev_dec_pending(rdev, mddev);
+ return 0;
+ }
+
spin_lock_irq(&conf->device_lock);
wait_event_lock_irq(conf->wait_for_stripe,
conf->quiesce == 0,
@@ -3055,7 +3083,9 @@ static int retry_aligned_read(raid5_con
last_sector = raid_bio->bi_sector + (raid_bio->bi_size>>9);
for (; logical_sector < last_sector;
- logical_sector += STRIPE_SECTORS, scnt++) {
+ logical_sector += STRIPE_SECTORS,
+ sector += STRIPE_SECTORS,
+ scnt++) {
if (scnt < raid_bio->bi_hw_segments)
/* already done this stripe */
@@ -3071,7 +3101,13 @@ static int retry_aligned_read(raid5_con
}
set_bit(R5_ReadError, &sh->dev[dd_idx].flags);
- add_stripe_bio(sh, raid_bio, dd_idx, 0);
+ if (!add_stripe_bio(sh, raid_bio, dd_idx, 0)) {
+ release_stripe(sh);
+ raid_bio->bi_hw_segments = scnt;
+ conf->retry_read_aligned = raid_bio;
+ return handled;
+ }
+
handle_stripe(sh, NULL);
release_stripe(sh);
handled++;
-
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