On Fri, 10 Jul 2009, Mikulas Patocka wrote:
> Hi
>
> For me this approach looks very complex, I would be much more simple to
> hold back bios until dmeventd processes the failed mirror.
>
> This approach has redundant data structures (log and superblock) that
> could really be joined to one structure. You need an extra code to
> allocate the superblocks.
>
> Note that you also need to handle errors superblocks without loss of
> functionality (raid1 is supposed to survive failing disks) ... and it just
> increases testing time and increases possibility for other bugs.
>
>
> If someone wants to make new dm-raid1 design that wouldn't be dependent on
> dmeventd, I'm not against it, but make it from scratch without patching
> over existing code (for example, store superblocks and bitmap at the end
> of the legs like raid-145 does).
>
> Mikulas
patch to hold back bios --- untested (and not quite optimal because it
scans the "failures" list in fixed intervals), but it shows the approach.
---
drivers/md/dm-raid1.c | 10 +++++++---
drivers/md/dm-region-hash.c | 6 +-----
include/linux/dm-region-hash.h | 3 +--
3 files changed, 9 insertions(+), 10 deletions(-)
Index: linux-2.6.31-rc2-devel/drivers/md/dm-raid1.c
===================================================================
--- linux-2.6.31-rc2-devel.orig/drivers/md/dm-raid1.c 2009-07-10 14:48:19.000000000 +0200
+++ linux-2.6.31-rc2-devel/drivers/md/dm-raid1.c 2009-07-10 15:46:11.000000000 +0200
@@ -535,11 +535,11 @@ static void write_callback(unsigned long
else
uptodate = 1;
- if (unlikely(!uptodate)) {
+ if (unlikely(!uptodate) || !errors_handled(ms)) {
DMERR("All replicated volumes dead, failing I/O");
/* None of the writes succeeded, fail the I/O. */
ret = -EIO;
- } else if (errors_handled(ms)) {
+ } else {
/*
* Need to raise event. Since raising
* events can block, we need to do it in
@@ -687,8 +687,12 @@ static void do_failures(struct mirror_se
if (!ms->log_failure) {
while ((bio = bio_list_pop(failures))) {
ms->in_sync = 0;
- dm_rh_mark_nosync(ms->rh, bio, bio->bi_size, 0);
+ dm_rh_mark_nosync(ms->rh, bio);
+ spin_lock_irq(&ms->lock);
+ bio_list_add(&ms->failures, bio);
+ spin_unlock_irq(&ms->lock);
}
+ delayed_wake(ms);
return;
}
Index: linux-2.6.31-rc2-devel/drivers/md/dm-region-hash.c
===================================================================
--- linux-2.6.31-rc2-devel.orig/drivers/md/dm-region-hash.c 2009-07-10 14:54:07.000000000 +0200
+++ linux-2.6.31-rc2-devel/drivers/md/dm-region-hash.c 2009-07-10 15:45:07.000000000 +0200
@@ -392,8 +392,6 @@ static void complete_resync_work(struct
/* dm_rh_mark_nosync
* @ms
* @bio
- * @done
- * @error
*
* The bio was written on some mirror(s) but failed on other mirror(s).
* We can successfully endio the bio but should avoid the region being
@@ -401,8 +399,7 @@ static void complete_resync_work(struct
*
* This function is _not_ safe in interrupt context!
*/
-void dm_rh_mark_nosync(struct dm_region_hash *rh,
- struct bio *bio, unsigned done, int error)
+void dm_rh_mark_nosync(struct dm_region_hash *rh, struct bio *bio)
{
unsigned long flags;
struct dm_dirty_log *log = rh->log;
@@ -439,7 +436,6 @@ void dm_rh_mark_nosync(struct dm_region_
BUG_ON(!list_empty(®->list));
spin_unlock_irqrestore(&rh->region_lock, flags);
- bio_endio(bio, error);
if (recovering)
complete_resync_work(reg, 0);
}
Index: linux-2.6.31-rc2-devel/include/linux/dm-region-hash.h
===================================================================
--- linux-2.6.31-rc2-devel.orig/include/linux/dm-region-hash.h 2009-07-10 15:45:26.000000000 +0200
+++ linux-2.6.31-rc2-devel/include/linux/dm-region-hash.h 2009-07-10 15:45:36.000000000 +0200
@@ -78,8 +78,7 @@ void dm_rh_dec(struct dm_region_hash *rh
/* Delay bios on regions. */
void dm_rh_delay(struct dm_region_hash *rh, struct bio *bio);
-void dm_rh_mark_nosync(struct dm_region_hash *rh,
- struct bio *bio, unsigned done, int error);
+void dm_rh_mark_nosync(struct dm_region_hash *rh, struct bio *bio);
/*
* Region recovery control.
--
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