On Wednesday January 9, dan.j.williams@xxxxxxxxx wrote: > On Sun, 2007-12-30 at 10:58 -0700, dean gaudet wrote: > > i have evidence pointing to d89d87965dcbe6fe4f96a2a7e8421b3a75f634d1 > > > > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=d89d87965dcbe6fe4f96a2a7e8421b3a75f634d1 > > > > which was Neil's change in 2.6.22 for deferring generic_make_request > > until there's enough stack space for it. > > > > Commit d89d87965dcbe6fe4f96a2a7e8421b3a75f634d1 reduced stack utilization > by preventing recursive calls to generic_make_request. However the > following conditions can cause raid5 to hang until 'stripe_cache_size' is > increased: > Thanks for pursuing this guys. That explanation certainly sounds very credible. The generic_make_request_immed is a good way to confirm that we have found the bug, but I don't like it as a long term solution, as it just reintroduced the problem that we were trying to solve with the problematic commit. As you say, we could arrange that all request submission happens in raid5d and I think this is the right way to proceed. However we can still take some of the work into the thread that is submitting the IO by calling "raid5d()" at the end of make_request, like this. Can you test it please? Does it seem reasonable? Thanks, NeilBrown Signed-off-by: Neil Brown <neilb@xxxxxxx> ### Diffstat output ./drivers/md/md.c | 2 +- ./drivers/md/raid5.c | 4 +++- 2 files changed, 4 insertions(+), 2 deletions(-) diff .prev/drivers/md/md.c ./drivers/md/md.c --- .prev/drivers/md/md.c 2008-01-07 13:32:10.000000000 +1100 +++ ./drivers/md/md.c 2008-01-10 11:08:02.000000000 +1100 @@ -5774,7 +5774,7 @@ void md_check_recovery(mddev_t *mddev) if (mddev->ro) return; - if (signal_pending(current)) { + if (current == mddev->thread->tsk && signal_pending(current)) { if (mddev->pers->sync_request) { printk(KERN_INFO "md: %s in immediate safe mode\n", mdname(mddev)); diff .prev/drivers/md/raid5.c ./drivers/md/raid5.c --- .prev/drivers/md/raid5.c 2008-01-07 13:32:10.000000000 +1100 +++ ./drivers/md/raid5.c 2008-01-10 11:06:54.000000000 +1100 @@ -3432,6 +3432,7 @@ static int chunk_aligned_read(struct req } } +static void raid5d (mddev_t *mddev); static int make_request(struct request_queue *q, struct bio * bi) { @@ -3547,7 +3548,7 @@ static int make_request(struct request_q goto retry; } finish_wait(&conf->wait_for_overlap, &w); - handle_stripe(sh, NULL); + set_bit(STRIPE_HANDLE, &sh->state); release_stripe(sh); } else { /* cannot get stripe for read-ahead, just give-up */ @@ -3569,6 +3570,7 @@ static int make_request(struct request_q test_bit(BIO_UPTODATE, &bi->bi_flags) ? 0 : -EIO); } + raid5d(mddev); return 0; } - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
