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Date: Mon, 25 Oct 2010 00:52:34 +0800
From: Wu Fengguang <fengguang.wu@...el.com>
To: Jens Axboe <axboe@...nel.dk>
Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Torsten Kaiser <just.for.lkml@...glemail.com>,
Neil Brown <neilb@...e.de>, Rik van Riel <riel@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"Li, Shaohua" <shaohua.li@...el.com>
Subject: Re: Deadlock possibly caused by too_many_isolated.
On Fri, Oct 22, 2010 at 04:09:21PM +0800, Jens Axboe wrote:
> On 2010-10-22 10:07, Wu Fengguang wrote:
> >>> We surely need 1 set aside for each level of that stack that will
> >>> potentially consume one. 1 should be enough for the generic pool, and
> >>> then clones will use a separate pool. So md and friends should really
> >>> have a pool per device, so that stacking will always work properly.
> >>
> >> Agreed for the deadlock problem.
> >>
> >>> There should be no throughput concerns, it should purely be a safe guard
> >>> measure to prevent us deadlocking when doing IO for reclaim.
> >>
> >> It's easy to verify whether the minimal size will have negative
> >> impacts on IO throughput. In Torsten's case, increase BIO_POOL_SIZE
> >> by one and check how it performs.
> >
> > Sorry it seems simply increasing BIO_POOL_SIZE is not enough to fix
> > possible deadlocks. We need adding new mempool(s). Because when there
> > BIO_POOL_SIZE=2 and there are two concurrent reclaimers each take 1
> > reservation, they will deadlock each other when trying to take the
> > next bio at the raid1 level.
>
> Yes, plus it's not a practical solution since you don't know how deep
> the stack is. As I wrote in the initial email, each consumer needs it's
> own private mempool (and just 1 entry should suffice).
You are right. The below scratch patch adds minimal mempool code for raid1.
It passed simple stress test of resync + 3 dd writers. Although write
throughput is rather slow in my qemu, I don't observe any
temporary/permanent stuck ups.
drivers/md/raid1.c | 32 ++++++++++++++++++++++++++++----
drivers/md/raid1.h | 2 ++
fs/bio.c | 31 +++++++++++++++++++++----------
include/linux/bio.h | 2 ++
4 files changed, 53 insertions(+), 14 deletions(-)
--- linux-next.orig/drivers/md/raid1.c 2010-10-25 00:02:40.000000000 +0800
+++ linux-next/drivers/md/raid1.c 2010-10-25 00:28:16.000000000 +0800
@@ -76,6 +76,14 @@ static void r1bio_pool_free(void *r1_bio
kfree(r1_bio);
}
+static void r1_bio_destructor(struct bio *bio)
+{
+ r1bio_t *r1_bio = bio->bi_private;
+ conf_t *conf = r1_bio->mddev->private;
+
+ bio_free(bio, conf->r1_bio_set);
+}
+
#define RESYNC_BLOCK_SIZE (64*1024)
//#define RESYNC_BLOCK_SIZE PAGE_SIZE
#define RESYNC_SECTORS (RESYNC_BLOCK_SIZE >> 9)
@@ -85,6 +93,7 @@ static void r1bio_pool_free(void *r1_bio
static void * r1buf_pool_alloc(gfp_t gfp_flags, void *data)
{
struct pool_info *pi = data;
+ conf_t *conf = pi->mddev->private;
struct page *page;
r1bio_t *r1_bio;
struct bio *bio;
@@ -100,7 +109,8 @@ static void * r1buf_pool_alloc(gfp_t gfp
* Allocate bios : 1 for reading, n-1 for writing
*/
for (j = pi->raid_disks ; j-- ; ) {
- bio = bio_alloc(gfp_flags, RESYNC_PAGES);
+ bio = bio_alloc_bioset(gfp_flags, RESYNC_PAGES,
+ conf->r1_bio_set);
if (!bio)
goto out_free_bio;
r1_bio->bios[j] = bio;
@@ -386,6 +396,10 @@ static void raid1_end_write_request(stru
!test_bit(R1BIO_Degraded, &r1_bio->state),
behind);
md_write_end(r1_bio->mddev);
+ if (to_put) {
+ bio_put(to_put);
+ to_put = NULL;
+ }
raid_end_bio_io(r1_bio);
}
@@ -851,7 +865,7 @@ static int make_request(mddev_t *mddev,
}
r1_bio->read_disk = rdisk;
- read_bio = bio_clone(bio, GFP_NOIO);
+ read_bio = bio_clone_bioset(bio, GFP_NOIO, conf->r1_bio_set);
r1_bio->bios[rdisk] = read_bio;
@@ -946,7 +960,7 @@ static int make_request(mddev_t *mddev,
if (!r1_bio->bios[i])
continue;
- mbio = bio_clone(bio, GFP_NOIO);
+ mbio = bio_clone_bioset(bio, GFP_NOIO, conf->r1_bio_set);
r1_bio->bios[i] = mbio;
mbio->bi_sector = r1_bio->sector + conf->mirrors[i].rdev->data_offset;
@@ -1646,7 +1660,9 @@ static void raid1d(mddev_t *mddev)
mddev->ro ? IO_BLOCKED : NULL;
r1_bio->read_disk = disk;
bio_put(bio);
- bio = bio_clone(r1_bio->master_bio, GFP_NOIO);
+ bio = bio_clone_bioset(r1_bio->master_bio,
+ GFP_NOIO,
+ conf->r1_bio_set);
r1_bio->bios[r1_bio->read_disk] = bio;
rdev = conf->mirrors[disk].rdev;
if (printk_ratelimit())
@@ -1948,6 +1964,10 @@ static conf_t *setup_conf(mddev_t *mddev
conf->poolinfo);
if (!conf->r1bio_pool)
goto abort;
+ conf->r1_bio_set = bioset_create(mddev->raid_disks * 2, 0);
+ if (!conf->r1_bio_set)
+ goto abort;
+ conf->r1_bio_set->bio_destructor = r1_bio_destructor;
conf->poolinfo->mddev = mddev;
@@ -2012,6 +2032,8 @@ static conf_t *setup_conf(mddev_t *mddev
if (conf) {
if (conf->r1bio_pool)
mempool_destroy(conf->r1bio_pool);
+ if (conf->r1_bio_set)
+ bioset_free(conf->r1_bio_set);
kfree(conf->mirrors);
safe_put_page(conf->tmppage);
kfree(conf->poolinfo);
@@ -2121,6 +2143,8 @@ static int stop(mddev_t *mddev)
blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
if (conf->r1bio_pool)
mempool_destroy(conf->r1bio_pool);
+ if (conf->r1_bio_set)
+ bioset_free(conf->r1_bio_set);
kfree(conf->mirrors);
kfree(conf->poolinfo);
kfree(conf);
--- linux-next.orig/fs/bio.c 2010-10-25 00:02:39.000000000 +0800
+++ linux-next/fs/bio.c 2010-10-25 00:03:37.000000000 +0800
@@ -306,6 +306,7 @@ out_set:
bio->bi_flags |= idx << BIO_POOL_OFFSET;
bio->bi_max_vecs = nr_iovecs;
bio->bi_io_vec = bvl;
+ bio->bi_destructor = bs->bio_destructor;
return bio;
err_free:
@@ -340,12 +341,7 @@ static void bio_fs_destructor(struct bio
*/
struct bio *bio_alloc(gfp_t gfp_mask, int nr_iovecs)
{
- struct bio *bio = bio_alloc_bioset(gfp_mask, nr_iovecs, fs_bio_set);
-
- if (bio)
- bio->bi_destructor = bio_fs_destructor;
-
- return bio;
+ return bio_alloc_bioset(gfp_mask, nr_iovecs, fs_bio_set);
}
EXPORT_SYMBOL(bio_alloc);
@@ -460,20 +456,21 @@ void __bio_clone(struct bio *bio, struct
EXPORT_SYMBOL(__bio_clone);
/**
- * bio_clone - clone a bio
+ * bio_clone_bioset - clone a bio
* @bio: bio to clone
* @gfp_mask: allocation priority
+ * @bs: bio_set to allocate from
*
* Like __bio_clone, only also allocates the returned bio
*/
-struct bio *bio_clone(struct bio *bio, gfp_t gfp_mask)
+struct bio *
+bio_clone_bioset(struct bio *bio, gfp_t gfp_mask, struct bio_set *bs)
{
- struct bio *b = bio_alloc_bioset(gfp_mask, bio->bi_max_vecs, fs_bio_set);
+ struct bio *b = bio_alloc_bioset(gfp_mask, bio->bi_max_vecs, bs);
if (!b)
return NULL;
- b->bi_destructor = bio_fs_destructor;
__bio_clone(b, bio);
if (bio_integrity(bio)) {
@@ -489,6 +486,19 @@ struct bio *bio_clone(struct bio *bio, g
return b;
}
+EXPORT_SYMBOL(bio_clone_bioset);
+
+/**
+ * bio_clone - clone a bio
+ * @bio: bio to clone
+ * @gfp_mask: allocation priority
+ *
+ * Like __bio_clone, only also allocates the returned bio
+ */
+struct bio *bio_clone(struct bio *bio, gfp_t gfp_mask)
+{
+ return bio_clone_bioset(bio, gfp_mask, fs_bio_set);
+}
EXPORT_SYMBOL(bio_clone);
/**
@@ -1664,6 +1674,7 @@ static int __init init_bio(void)
fs_bio_set = bioset_create(BIO_POOL_SIZE, 0);
if (!fs_bio_set)
panic("bio: can't allocate bios\n");
+ fs_bio_set->bio_destructor = bio_fs_destructor;
bio_split_pool = mempool_create_kmalloc_pool(BIO_SPLIT_ENTRIES,
sizeof(struct bio_pair));
--- linux-next.orig/include/linux/bio.h 2010-10-25 00:02:40.000000000 +0800
+++ linux-next/include/linux/bio.h 2010-10-25 00:03:37.000000000 +0800
@@ -227,6 +227,7 @@ extern int bio_phys_segments(struct requ
extern void __bio_clone(struct bio *, struct bio *);
extern struct bio *bio_clone(struct bio *, gfp_t);
+extern struct bio *bio_clone_bioset(struct bio *, gfp_t, struct bio_set *);
extern void bio_init(struct bio *);
@@ -299,6 +300,7 @@ struct bio_set {
mempool_t *bio_integrity_pool;
#endif
mempool_t *bvec_pool;
+ bio_destructor_t *bio_destructor;
};
struct biovec_slab {
--- linux-next.orig/drivers/md/raid1.h 2010-10-25 00:02:40.000000000 +0800
+++ linux-next/drivers/md/raid1.h 2010-10-25 00:03:37.000000000 +0800
@@ -60,6 +60,8 @@ struct r1_private_data_s {
mempool_t *r1bio_pool;
mempool_t *r1buf_pool;
+ struct bio_set *r1_bio_set;
+
/* When taking over an array from a different personality, we store
* the new thread here until we fully activate the array.
*/
--
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