Hi Neil,
I hope you are doing better after the flu. Maybe you find some time
to explain the following codings in raid5.c to me. At least one of
the patchs seems to be signed off by you. The RAID5 I'm using has
default settings.
1) Generally speaking of md_wakup_thread() calls. Does it make
any sense to call them the from within raid5d()? Or when being
implemented at locations that might be called from the
make_request() path too - for simplicity no further caller destinction
was programmed.
1) In case of a single direct I/O writer to the /dev/md0 device the
following coding will always fire the md_wakeup_thread(). That
is one reason for alternating raid5d loops one with data to
process and the next without. Is that corner case wanted?
static void handle_stripe(struct stripe_head *sh)
...
ops_run_io(sh, &s);
if (s.dec_preread_active) {
/* We delay this until after ops_run_io so that if make_request
* is waiting on a flush, it won't continue until the writes
* have actually been submitted.
*/
atomic_dec(&conf->preread_active_stripes);
if (atomic_read(&conf->preread_active_stripes) <
IO_THRESHOLD)
md_wakeup_thread(conf->mddev->thread); */
}
2) The wakeup_thread() in the following preread path seems
to be unnecesary or will a double call wake the thread twice?
void do_release_stripe(struct r5conf *conf, struct stripe_head *sh,
struct list_head *temp_inactive_list, int mstwake)
{
BUG_ON(!list_empty(&sh->lru));
BUG_ON(atomic_read(&conf->active_stripes)==0);
if (test_bit(STRIPE_HANDLE, &sh->state)) {
if (test_bit(STRIPE_DELAYED, &sh->state) &&
!test_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
list_add_tail(&sh->lru, &conf->delayed_list);
if (atomic_read(&conf->preread_active_stripes)
< IO_THRESHOLD)
md_wakeup_thread(conf->mddev->thread);
} else if (test_bit(STRIPE_BIT_DELAY, &sh->state) &&
...
}
md_wakeup_thread(conf->mddev->thread);
...
Thanks in advance.
Markus****************************************************************************
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