Neil,
We're chasing a case where the raid1 code gets stuck during resync. Nate
is able to reproduce it much more reliably than me - so attaching his
reproducing script. Basically run it on an existing raid1 with internal
bitmap on rotating disk.
Nate was able to bisect it to 79ef3a8aa1cb1523cc231c9a90a278333c21f761,
the original iobarrier rewrite patch, and it can be reproduced in
current Linus' top of trunk a794b4f3292160bb3fd0f1f90ec8df454e3b17b3.
In Nate's analysis it hangs in raise_barrier():
static void raise_barrier(struct r1conf *conf, sector_t sector_nr)
{
spin_lock_irq(&conf->resync_lock);
/* Wait until no block IO is waiting */
wait_event_lock_irq(conf->wait_barrier, !conf->nr_waiting,
conf->resync_lock);
/* block any new IO from starting */
conf->barrier++;
conf->next_resync = sector_nr;
/* For these conditions we must wait:
* A: while the array is in frozen state
* B: while barrier >= RESYNC_DEPTH, meaning resync reach
* the max count which allowed.
* C: next_resync + RESYNC_SECTORS > start_next_window, meaning
* next resync will reach to the window which normal bios are
* handling.
* D: while there are any active requests in the current window.
*/
wait_event_lock_irq(conf->wait_barrier,
!conf->array_frozen &&
conf->barrier < RESYNC_DEPTH &&
conf->current_window_requests == 0 &&
(conf->start_next_window >=
conf->next_resync + RESYNC_SECTORS),
conf->resync_lock);
crash> r1conf 0xffff882028f3e600 | grep -e array_frozen -e barrier -e start_next_window -e next_resync
barrier = 0x1, (conf->barrier < RESYNC_DEPTH)
array_frozen = 0x0, (!conf->array_frozen)
next_resync = 0x3000,
start_next_window = 0x3000,
ie. next_resync == start_next_window, which will never wake up since
start_next_window is smaller than next_resync + RESYNC_SECTORS.
Have you seen anything like this?
Cheers,
Jes
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