RMW of r5c write back cache uses an extra page to store old data for
prexor. handle_stripe_dirtying() allocates this page by calling
alloc_page(). However, alloc_page() may fail.
To handle alloc_page() failures, this patch adds a small mempool
in r5l_log. When alloc_page fails, handle_stripe() trys to use pages
from the mempool. When the mempool is in use, the stripe is added
to delayed_list.
Signed-off-by: Song Liu <songliubraving@xxxxxx>
---
drivers/md/raid5-cache.c | 43 +++++++++++++++++++++++++++++++++++++++++++
drivers/md/raid5.c | 47 ++++++++++++++++++++++++++++++++++++++---------
drivers/md/raid5.h | 8 ++++++++
3 files changed, 89 insertions(+), 9 deletions(-)
diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 8cb79fc..9406c39 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -162,6 +162,9 @@ struct r5l_log {
/* to submit async io_units, to fulfill ordering of flush */
struct work_struct deferred_io_work;
+
+ /* to handle alloc_page() failures in handle_stripe_dirtying() */
+ mempool_t *extra_page_pool;
};
/*
@@ -2334,15 +2337,48 @@ int r5c_try_caching_write(struct r5conf *conf,
*/
void r5c_release_extra_page(struct stripe_head *sh)
{
+ struct r5conf *conf = sh->raid_conf;
+ struct r5l_log *log = conf->log;
int i;
+ bool using_extra_page_pool;
+
+ using_extra_page_pool = test_and_clear_bit(
+ STRIPE_R5C_EXTRA_PAGE, &sh->state);
for (i = sh->disks; i--; )
if (sh->dev[i].page != sh->dev[i].orig_page) {
struct page *p = sh->dev[i].orig_page;
sh->dev[i].orig_page = sh->dev[i].page;
+ if (using_extra_page_pool)
+ mempool_free(p, log->extra_page_pool);
+ else
+ put_page(p);
+ }
+
+ if (using_extra_page_pool)
+ clear_bit(R5C_EXTRA_PAGE_IN_USE, &conf->cache_state);
+}
+
+void r5c_use_extra_page_pool(struct stripe_head *sh)
+{
+ struct r5l_log *log = sh->raid_conf->log;
+ int i;
+ struct r5dev *dev;
+ struct page *p;
+
+ for (i = sh->disks; i--; ) {
+ dev = &sh->dev[i];
+ if (dev->orig_page != dev->page) {
+ p = dev->orig_page;
+ dev->orig_page = dev->page;
put_page(p);
}
+ dev->orig_page = mempool_alloc(log->extra_page_pool,
+ GFP_ATOMIC);
+ BUG_ON(!dev->orig_page);
+ }
+ set_bit(STRIPE_R5C_EXTRA_PAGE, &sh->state);
}
/*
@@ -2581,6 +2617,10 @@ int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev)
if (!log->meta_pool)
goto out_mempool;
+ log->extra_page_pool = mempool_create_page_pool(conf->raid_disks, 0);
+ if (!log->extra_page_pool)
+ goto extra_page_pool;
+
log->reclaim_thread = md_register_thread(r5l_reclaim_thread,
log->rdev->mddev, "reclaim");
if (!log->reclaim_thread)
@@ -2611,6 +2651,8 @@ int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev)
error:
md_unregister_thread(&log->reclaim_thread);
reclaim_thread:
+ mempool_destroy(log->extra_page_pool);
+extra_page_pool:
mempool_destroy(log->meta_pool);
out_mempool:
bioset_free(log->bs);
@@ -2626,6 +2668,7 @@ int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev)
void r5l_exit_log(struct r5l_log *log)
{
md_unregister_thread(&log->reclaim_thread);
+ mempool_destroy(log->extra_page_pool);
mempool_destroy(log->meta_pool);
bioset_free(log->bs);
mempool_destroy(log->io_pool);
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index dbab8c7..9d20849 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -876,6 +876,8 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
if (!test_bit(STRIPE_R5C_CACHING, &sh->state)) {
/* writing out phase */
+ if (s->waiting_extra_page)
+ return;
if (r5l_write_stripe(conf->log, sh) == 0)
return;
} else { /* caching phase */
@@ -2007,6 +2009,7 @@ static struct stripe_head *alloc_stripe(struct kmem_cache *sc, gfp_t gfp,
INIT_LIST_HEAD(&sh->batch_list);
INIT_LIST_HEAD(&sh->lru);
INIT_LIST_HEAD(&sh->r5c);
+ INIT_LIST_HEAD(&sh->log_list);
atomic_set(&sh->count, 1);
sh->log_start = MaxSector;
for (i = 0; i < disks; i++) {
@@ -3580,10 +3583,10 @@ static void handle_stripe_clean_event(struct r5conf *conf,
break_stripe_batch_list(head_sh, STRIPE_EXPAND_SYNC_FLAGS);
}
-static void handle_stripe_dirtying(struct r5conf *conf,
- struct stripe_head *sh,
- struct stripe_head_state *s,
- int disks)
+static int handle_stripe_dirtying(struct r5conf *conf,
+ struct stripe_head *sh,
+ struct stripe_head_state *s,
+ int disks)
{
int rmw = 0, rcw = 0, i;
sector_t recovery_cp = conf->mddev->recovery_cp;
@@ -3649,12 +3652,32 @@ static void handle_stripe_dirtying(struct r5conf *conf,
dev->page == dev->orig_page &&
!test_bit(R5_LOCKED, &sh->dev[sh->pd_idx].flags)) {
/* alloc page for prexor */
- dev->orig_page = alloc_page(GFP_NOIO);
+ struct page *p = alloc_page(GFP_NOIO);
+
+ if (p) {
+ dev->orig_page = p;
+ continue;
+ }
- /* will handle failure in a later patch*/
- BUG_ON(!dev->orig_page);
+ /*
+ * alloc_page() failed, try use
+ * log->extra_page_pool
+ */
+ if (!test_and_set_bit(R5C_EXTRA_PAGE_IN_USE,
+ &conf->cache_state)) {
+ r5c_use_extra_page_pool(sh);
+ break;
+ }
+
+ /* extra_page_pool busy, add to delayed_list */
+ set_bit(STRIPE_DELAYED, &sh->state);
+ s->waiting_extra_page = 1;
+ return -EAGAIN;
}
+ }
+ for (i = disks; i--; ) {
+ struct r5dev *dev = &sh->dev[i];
if ((dev->towrite ||
i == sh->pd_idx || i == sh->qd_idx ||
test_bit(R5_InJournal, &dev->flags)) &&
@@ -3730,6 +3753,7 @@ static void handle_stripe_dirtying(struct r5conf *conf,
(s->locked == 0 && (rcw == 0 || rmw == 0) &&
!test_bit(STRIPE_BIT_DELAY, &sh->state)))
schedule_reconstruction(sh, s, rcw == 0, 0);
+ return 0;
}
static void handle_parity_checks5(struct r5conf *conf, struct stripe_head *sh,
@@ -4545,8 +4569,12 @@ static void handle_stripe(struct stripe_head *sh)
if (ret == -EAGAIN ||
/* stripe under reclaim: !caching && injournal */
(!test_bit(STRIPE_R5C_CACHING, &sh->state) &&
- s.injournal > 0))
- handle_stripe_dirtying(conf, sh, &s, disks);
+ s.injournal > 0)) {
+ ret = handle_stripe_dirtying(conf, sh, &s,
+ disks);
+ if (ret == -EAGAIN)
+ goto finish;
+ }
}
}
@@ -6612,6 +6640,7 @@ static struct r5conf *setup_conf(struct mddev *mddev)
conf->disks = kzalloc(max_disks * sizeof(struct disk_info),
GFP_KERNEL);
+
if (!conf->disks)
goto abort;
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index d13fe45..fad19eb 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -276,6 +276,7 @@ struct stripe_head_state {
struct md_rdev *blocked_rdev;
int handle_bad_blocks;
int log_failed;
+ int waiting_extra_page;
};
/* Flags for struct r5dev.flags */
@@ -377,6 +378,9 @@ enum {
* in conf->r5c_full_stripe_list)
*/
STRIPE_R5C_PREFLUSH, /* need to flush journal device */
+ STRIPE_R5C_EXTRA_PAGE, /* extra orig_page of this stripe is allocated
+ * from extra_page_pool
+ */
};
#define STRIPE_EXPAND_SYNC_FLAGS \
@@ -559,6 +563,9 @@ enum r5_cache_state {
* only process stripes that are already
* occupying the log
*/
+ R5C_EXTRA_PAGE_IN_USE, /* a stripe is using the pages in
+ * r5l_log.extra_page_pool for prexor
+ */
};
struct r5conf {
@@ -765,6 +772,7 @@ extern void
r5c_finish_stripe_write_out(struct r5conf *conf, struct stripe_head *sh,
struct stripe_head_state *s);
extern void r5c_release_extra_page(struct stripe_head *sh);
+extern void r5c_use_extra_page_pool(struct stripe_head *sh);
extern void r5l_wake_reclaim(struct r5l_log *log, sector_t space);
extern void r5c_handle_cached_data_endio(struct r5conf *conf,
struct stripe_head *sh, int disks, struct bio_list *return_bi);
--
2.9.3
--
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