On Thu, Nov 24 2016, Song Liu wrote:
> 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 an extra page to
> disk_info. When alloc_page fails, handle_stripe() trys to use these
> pages. When these pages are used by other stripe (R5C_EXTRA_PAGE_IN_USE),
> the stripe is added to delayed_list.
>
> Signed-off-by: Song Liu <songliubraving@xxxxxx>
Reviewed-by: NeilBrown <neilb@xxxxxxxx>
Thanks,
NeilBrown
> ---
> drivers/md/raid5-cache.c | 27 ++++++++++++++++-
> drivers/md/raid5.c | 78 ++++++++++++++++++++++++++++++++++++++++--------
> drivers/md/raid5.h | 6 ++++
> 3 files changed, 98 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
> index 8cb79fc..818874d 100644
> --- a/drivers/md/raid5-cache.c
> +++ b/drivers/md/raid5-cache.c
> @@ -2334,15 +2334,40 @@ int r5c_try_caching_write(struct r5conf *conf,
> */
> void r5c_release_extra_page(struct stripe_head *sh)
> {
> + struct r5conf *conf = sh->raid_conf;
> int i;
> + bool using_disk_info_extra_page;
> +
> + using_disk_info_extra_page =
> + sh->dev[0].orig_page == conf->disks[0].extra_page;
>
> 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;
> - put_page(p);
> + if (!using_disk_info_extra_page)
> + put_page(p);
> }
> +
> + if (using_disk_info_extra_page) {
> + clear_bit(R5C_EXTRA_PAGE_IN_USE, &conf->cache_state);
> + md_wakeup_thread(conf->mddev->thread);
> + }
> +}
> +
> +void r5c_use_extra_page(struct stripe_head *sh)
> +{
> + struct r5conf *conf = sh->raid_conf;
> + int i;
> + struct r5dev *dev;
> +
> + for (i = sh->disks; i--; ) {
> + dev = &sh->dev[i];
> + if (dev->orig_page != dev->page)
> + put_page(dev->orig_page);
> + dev->orig_page = conf->disks[i].extra_page;
> + }
> }
>
> /*
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index dbab8c7..db909b9 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++) {
> @@ -2253,10 +2256,24 @@ static int resize_stripes(struct r5conf *conf, int newsize)
> */
> ndisks = kzalloc(newsize * sizeof(struct disk_info), GFP_NOIO);
> if (ndisks) {
> - for (i=0; i<conf->raid_disks; i++)
> + for (i = 0; i < conf->pool_size; i++)
> ndisks[i] = conf->disks[i];
> - kfree(conf->disks);
> - conf->disks = ndisks;
> +
> + for (i = conf->pool_size; i < newsize; i++) {
> + ndisks[i].extra_page = alloc_page(GFP_NOIO);
> + if (!ndisks[i].extra_page)
> + err = -ENOMEM;
> + }
> +
> + if (err) {
> + for (i = conf->pool_size; i < newsize; i++)
> + if (ndisks[i].extra_page)
> + put_page(ndisks[i].extra_page);
> + kfree(ndisks);
> + } else {
> + kfree(conf->disks);
> + conf->disks = ndisks;
> + }
> } else
> err = -ENOMEM;
>
> @@ -3580,10 +3597,10 @@ 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 +3666,32 @@ 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
> + * disk_info->extra_page
> + */
> + if (!test_and_set_bit(R5C_EXTRA_PAGE_IN_USE,
> + &conf->cache_state)) {
> + r5c_use_extra_page(sh);
> + break;
> + }
> +
> + /* extra_page in use, 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 +3767,7 @@ 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 +4583,12 @@ 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;
> + }
> }
> }
>
> @@ -6458,6 +6500,8 @@ static void raid5_free_percpu(struct r5conf *conf)
>
> static void free_conf(struct r5conf *conf)
> {
> + int i;
> +
> if (conf->log)
> r5l_exit_log(conf->log);
> if (conf->shrinker.nr_deferred)
> @@ -6466,6 +6510,9 @@ static void free_conf(struct r5conf *conf)
> free_thread_groups(conf);
> shrink_stripes(conf);
> raid5_free_percpu(conf);
> + for (i = 0; i < conf->pool_size; i++)
> + if (conf->disks[i].extra_page)
> + put_page(conf->disks[i].extra_page);
> kfree(conf->disks);
> kfree(conf->stripe_hashtbl);
> kfree(conf);
> @@ -6612,9 +6659,16 @@ static struct r5conf *setup_conf(struct mddev *mddev)
>
> conf->disks = kzalloc(max_disks * sizeof(struct disk_info),
> GFP_KERNEL);
> +
> if (!conf->disks)
> goto abort;
>
> + for (i = 0; i < max_disks; i++) {
> + conf->disks[i].extra_page = alloc_page(GFP_KERNEL);
> + if (!conf->disks[i].extra_page)
> + goto abort;
> + }
> +
> conf->mddev = mddev;
>
> if ((conf->stripe_hashtbl = kzalloc(PAGE_SIZE, GFP_KERNEL)) == NULL)
> diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
> index d13fe45..ed8e136 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 */
> @@ -439,6 +440,7 @@ enum {
>
> struct disk_info {
> struct md_rdev *rdev, *replacement;
> + struct page *extra_page; /* extra page to use in prexor */
> };
>
> /*
> @@ -559,6 +561,9 @@ enum r5_cache_state {
> * only process stripes that are already
> * occupying the log
> */
> + R5C_EXTRA_PAGE_IN_USE, /* a stripe is using disk_info.extra_page
> + * for prexor
> + */
> };
>
> struct r5conf {
> @@ -765,6 +770,7 @@ 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(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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