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authorDamien Le Moal <damien.lemoal@wdc.com>2017-06-07 15:55:39 +0900
committerMike Snitzer <snitzer@redhat.com>2017-06-19 11:05:20 -0400
commit3b1a94c88b798d4f3bd1a5b61f5c8fb9d987c242 (patch)
tree173fcaced4dffd3e7d334a2992e40a9466747b91 /drivers/md/dm-zoned-reclaim.c
parentb73c67c2cbb0004e6da9720a167fe42e31f7a6e8 (diff)
dm zoned: drive-managed zoned block device target
The dm-zoned device mapper target provides transparent write access to zoned block devices (ZBC and ZAC compliant block devices). dm-zoned hides to the device user (a file system or an application doing raw block device accesses) any constraint imposed on write requests by the device, equivalent to a drive-managed zoned block device model. Write requests are processed using a combination of on-disk buffering using the device conventional zones and direct in-place processing for requests aligned to a zone sequential write pointer position. A background reclaim process implemented using dm_kcopyd_copy ensures that conventional zones are always available for executing unaligned write requests. The reclaim process overhead is minimized by managing buffer zones in a least-recently-written order and first targeting the oldest buffer zones. Doing so, blocks under regular write access (such as metadata blocks of a file system) remain stored in conventional zones, resulting in no apparent overhead. dm-zoned implementation focus on simplicity and on minimizing overhead (CPU, memory and storage overhead). For a 14TB host-managed disk with 256 MB zones, dm-zoned memory usage per disk instance is at most about 3 MB and as little as 5 zones will be used internally for storing metadata and performing buffer zone reclaim operations. This is achieved using zone level indirection rather than a full block indirection system for managing block movement between zones. dm-zoned primary target is host-managed zoned block devices but it can also be used with host-aware device models to mitigate potential device-side performance degradation due to excessive random writing. Zoned block devices can be formatted and checked for use with the dm-zoned target using the dmzadm utility available at: https://github.com/hgst/dm-zoned-tools Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Reviewed-by: Hannes Reinecke <hare@suse.com> Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com> [Mike Snitzer partly refactored Damien's original work to cleanup the code] Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md/dm-zoned-reclaim.c')
-rw-r--r--drivers/md/dm-zoned-reclaim.c570
1 files changed, 570 insertions, 0 deletions
diff --git a/drivers/md/dm-zoned-reclaim.c b/drivers/md/dm-zoned-reclaim.c
new file mode 100644
index 000000000000..05c0a126f5c8
--- /dev/null
+++ b/drivers/md/dm-zoned-reclaim.c
@@ -0,0 +1,570 @@
+/*
+ * Copyright (C) 2017 Western Digital Corporation or its affiliates.
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm-zoned.h"
+
+#include <linux/module.h>
+
+#define DM_MSG_PREFIX "zoned reclaim"
+
+struct dmz_reclaim {
+ struct dmz_metadata *metadata;
+ struct dmz_dev *dev;
+
+ struct delayed_work work;
+ struct workqueue_struct *wq;
+
+ struct dm_kcopyd_client *kc;
+ struct dm_kcopyd_throttle kc_throttle;
+ int kc_err;
+
+ unsigned long flags;
+
+ /* Last target access time */
+ unsigned long atime;
+};
+
+/*
+ * Reclaim state flags.
+ */
+enum {
+ DMZ_RECLAIM_KCOPY,
+};
+
+/*
+ * Number of seconds of target BIO inactivity to consider the target idle.
+ */
+#define DMZ_IDLE_PERIOD (10UL * HZ)
+
+/*
+ * Percentage of unmapped (free) random zones below which reclaim starts
+ * even if the target is busy.
+ */
+#define DMZ_RECLAIM_LOW_UNMAP_RND 30
+
+/*
+ * Percentage of unmapped (free) random zones above which reclaim will
+ * stop if the target is busy.
+ */
+#define DMZ_RECLAIM_HIGH_UNMAP_RND 50
+
+/*
+ * Align a sequential zone write pointer to chunk_block.
+ */
+static int dmz_reclaim_align_wp(struct dmz_reclaim *zrc, struct dm_zone *zone,
+ sector_t block)
+{
+ struct dmz_metadata *zmd = zrc->metadata;
+ sector_t wp_block = zone->wp_block;
+ unsigned int nr_blocks;
+ int ret;
+
+ if (wp_block == block)
+ return 0;
+
+ if (wp_block > block)
+ return -EIO;
+
+ /*
+ * Zeroout the space between the write
+ * pointer and the requested position.
+ */
+ nr_blocks = block - wp_block;
+ ret = blkdev_issue_zeroout(zrc->dev->bdev,
+ dmz_start_sect(zmd, zone) + dmz_blk2sect(wp_block),
+ dmz_blk2sect(nr_blocks), GFP_NOFS, false);
+ if (ret) {
+ dmz_dev_err(zrc->dev,
+ "Align zone %u wp %llu to %llu (wp+%u) blocks failed %d",
+ dmz_id(zmd, zone), (unsigned long long)wp_block,
+ (unsigned long long)block, nr_blocks, ret);
+ return ret;
+ }
+
+ zone->wp_block = block;
+
+ return 0;
+}
+
+/*
+ * dm_kcopyd_copy end notification.
+ */
+static void dmz_reclaim_kcopy_end(int read_err, unsigned long write_err,
+ void *context)
+{
+ struct dmz_reclaim *zrc = context;
+
+ if (read_err || write_err)
+ zrc->kc_err = -EIO;
+ else
+ zrc->kc_err = 0;
+
+ clear_bit_unlock(DMZ_RECLAIM_KCOPY, &zrc->flags);
+ smp_mb__after_atomic();
+ wake_up_bit(&zrc->flags, DMZ_RECLAIM_KCOPY);
+}
+
+/*
+ * Copy valid blocks of src_zone into dst_zone.
+ */
+static int dmz_reclaim_copy(struct dmz_reclaim *zrc,
+ struct dm_zone *src_zone, struct dm_zone *dst_zone)
+{
+ struct dmz_metadata *zmd = zrc->metadata;
+ struct dmz_dev *dev = zrc->dev;
+ struct dm_io_region src, dst;
+ sector_t block = 0, end_block;
+ sector_t nr_blocks;
+ sector_t src_zone_block;
+ sector_t dst_zone_block;
+ unsigned long flags = 0;
+ int ret;
+
+ if (dmz_is_seq(src_zone))
+ end_block = src_zone->wp_block;
+ else
+ end_block = dev->zone_nr_blocks;
+ src_zone_block = dmz_start_block(zmd, src_zone);
+ dst_zone_block = dmz_start_block(zmd, dst_zone);
+
+ if (dmz_is_seq(dst_zone))
+ set_bit(DM_KCOPYD_WRITE_SEQ, &flags);
+
+ while (block < end_block) {
+ /* Get a valid region from the source zone */
+ ret = dmz_first_valid_block(zmd, src_zone, &block);
+ if (ret <= 0)
+ return ret;
+ nr_blocks = ret;
+
+ /*
+ * If we are writing in a sequential zone, we must make sure
+ * that writes are sequential. So Zeroout any eventual hole
+ * between writes.
+ */
+ if (dmz_is_seq(dst_zone)) {
+ ret = dmz_reclaim_align_wp(zrc, dst_zone, block);
+ if (ret)
+ return ret;
+ }
+
+ src.bdev = dev->bdev;
+ src.sector = dmz_blk2sect(src_zone_block + block);
+ src.count = dmz_blk2sect(nr_blocks);
+
+ dst.bdev = dev->bdev;
+ dst.sector = dmz_blk2sect(dst_zone_block + block);
+ dst.count = src.count;
+
+ /* Copy the valid region */
+ set_bit(DMZ_RECLAIM_KCOPY, &zrc->flags);
+ ret = dm_kcopyd_copy(zrc->kc, &src, 1, &dst, flags,
+ dmz_reclaim_kcopy_end, zrc);
+ if (ret)
+ return ret;
+
+ /* Wait for copy to complete */
+ wait_on_bit_io(&zrc->flags, DMZ_RECLAIM_KCOPY,
+ TASK_UNINTERRUPTIBLE);
+ if (zrc->kc_err)
+ return zrc->kc_err;
+
+ block += nr_blocks;
+ if (dmz_is_seq(dst_zone))
+ dst_zone->wp_block = block;
+ }
+
+ return 0;
+}
+
+/*
+ * Move valid blocks of dzone buffer zone into dzone (after its write pointer)
+ * and free the buffer zone.
+ */
+static int dmz_reclaim_buf(struct dmz_reclaim *zrc, struct dm_zone *dzone)
+{
+ struct dm_zone *bzone = dzone->bzone;
+ sector_t chunk_block = dzone->wp_block;
+ struct dmz_metadata *zmd = zrc->metadata;
+ int ret;
+
+ dmz_dev_debug(zrc->dev,
+ "Chunk %u, move buf zone %u (weight %u) to data zone %u (weight %u)",
+ dzone->chunk, dmz_id(zmd, bzone), dmz_weight(bzone),
+ dmz_id(zmd, dzone), dmz_weight(dzone));
+
+ /* Flush data zone into the buffer zone */
+ ret = dmz_reclaim_copy(zrc, bzone, dzone);
+ if (ret < 0)
+ return ret;
+
+ dmz_lock_flush(zmd);
+
+ /* Validate copied blocks */
+ ret = dmz_merge_valid_blocks(zmd, bzone, dzone, chunk_block);
+ if (ret == 0) {
+ /* Free the buffer zone */
+ dmz_invalidate_blocks(zmd, bzone, 0, zrc->dev->zone_nr_blocks);
+ dmz_lock_map(zmd);
+ dmz_unmap_zone(zmd, bzone);
+ dmz_unlock_zone_reclaim(dzone);
+ dmz_free_zone(zmd, bzone);
+ dmz_unlock_map(zmd);
+ }
+
+ dmz_unlock_flush(zmd);
+
+ return 0;
+}
+
+/*
+ * Merge valid blocks of dzone into its buffer zone and free dzone.
+ */
+static int dmz_reclaim_seq_data(struct dmz_reclaim *zrc, struct dm_zone *dzone)
+{
+ unsigned int chunk = dzone->chunk;
+ struct dm_zone *bzone = dzone->bzone;
+ struct dmz_metadata *zmd = zrc->metadata;
+ int ret = 0;
+
+ dmz_dev_debug(zrc->dev,
+ "Chunk %u, move data zone %u (weight %u) to buf zone %u (weight %u)",
+ chunk, dmz_id(zmd, dzone), dmz_weight(dzone),
+ dmz_id(zmd, bzone), dmz_weight(bzone));
+
+ /* Flush data zone into the buffer zone */
+ ret = dmz_reclaim_copy(zrc, dzone, bzone);
+ if (ret < 0)
+ return ret;
+
+ dmz_lock_flush(zmd);
+
+ /* Validate copied blocks */
+ ret = dmz_merge_valid_blocks(zmd, dzone, bzone, 0);
+ if (ret == 0) {
+ /*
+ * Free the data zone and remap the chunk to
+ * the buffer zone.
+ */
+ dmz_invalidate_blocks(zmd, dzone, 0, zrc->dev->zone_nr_blocks);
+ dmz_lock_map(zmd);
+ dmz_unmap_zone(zmd, bzone);
+ dmz_unmap_zone(zmd, dzone);
+ dmz_unlock_zone_reclaim(dzone);
+ dmz_free_zone(zmd, dzone);
+ dmz_map_zone(zmd, bzone, chunk);
+ dmz_unlock_map(zmd);
+ }
+
+ dmz_unlock_flush(zmd);
+
+ return 0;
+}
+
+/*
+ * Move valid blocks of the random data zone dzone into a free sequential zone.
+ * Once blocks are moved, remap the zone chunk to the sequential zone.
+ */
+static int dmz_reclaim_rnd_data(struct dmz_reclaim *zrc, struct dm_zone *dzone)
+{
+ unsigned int chunk = dzone->chunk;
+ struct dm_zone *szone = NULL;
+ struct dmz_metadata *zmd = zrc->metadata;
+ int ret;
+
+ /* Get a free sequential zone */
+ dmz_lock_map(zmd);
+ szone = dmz_alloc_zone(zmd, DMZ_ALLOC_RECLAIM);
+ dmz_unlock_map(zmd);
+ if (!szone)
+ return -ENOSPC;
+
+ dmz_dev_debug(zrc->dev,
+ "Chunk %u, move rnd zone %u (weight %u) to seq zone %u",
+ chunk, dmz_id(zmd, dzone), dmz_weight(dzone),
+ dmz_id(zmd, szone));
+
+ /* Flush the random data zone into the sequential zone */
+ ret = dmz_reclaim_copy(zrc, dzone, szone);
+
+ dmz_lock_flush(zmd);
+
+ if (ret == 0) {
+ /* Validate copied blocks */
+ ret = dmz_copy_valid_blocks(zmd, dzone, szone);
+ }
+ if (ret) {
+ /* Free the sequential zone */
+ dmz_lock_map(zmd);
+ dmz_free_zone(zmd, szone);
+ dmz_unlock_map(zmd);
+ } else {
+ /* Free the data zone and remap the chunk */
+ dmz_invalidate_blocks(zmd, dzone, 0, zrc->dev->zone_nr_blocks);
+ dmz_lock_map(zmd);
+ dmz_unmap_zone(zmd, dzone);
+ dmz_unlock_zone_reclaim(dzone);
+ dmz_free_zone(zmd, dzone);
+ dmz_map_zone(zmd, szone, chunk);
+ dmz_unlock_map(zmd);
+ }
+
+ dmz_unlock_flush(zmd);
+
+ return 0;
+}
+
+/*
+ * Reclaim an empty zone.
+ */
+static void dmz_reclaim_empty(struct dmz_reclaim *zrc, struct dm_zone *dzone)
+{
+ struct dmz_metadata *zmd = zrc->metadata;
+
+ dmz_lock_flush(zmd);
+ dmz_lock_map(zmd);
+ dmz_unmap_zone(zmd, dzone);
+ dmz_unlock_zone_reclaim(dzone);
+ dmz_free_zone(zmd, dzone);
+ dmz_unlock_map(zmd);
+ dmz_unlock_flush(zmd);
+}
+
+/*
+ * Find a candidate zone for reclaim and process it.
+ */
+static void dmz_reclaim(struct dmz_reclaim *zrc)
+{
+ struct dmz_metadata *zmd = zrc->metadata;
+ struct dm_zone *dzone;
+ struct dm_zone *rzone;
+ unsigned long start;
+ int ret;
+
+ /* Get a data zone */
+ dzone = dmz_get_zone_for_reclaim(zmd);
+ if (!dzone)
+ return;
+
+ start = jiffies;
+
+ if (dmz_is_rnd(dzone)) {
+ if (!dmz_weight(dzone)) {
+ /* Empty zone */
+ dmz_reclaim_empty(zrc, dzone);
+ ret = 0;
+ } else {
+ /*
+ * Reclaim the random data zone by moving its
+ * valid data blocks to a free sequential zone.
+ */
+ ret = dmz_reclaim_rnd_data(zrc, dzone);
+ }
+ rzone = dzone;
+
+ } else {
+ struct dm_zone *bzone = dzone->bzone;
+ sector_t chunk_block = 0;
+
+ ret = dmz_first_valid_block(zmd, bzone, &chunk_block);
+ if (ret < 0)
+ goto out;
+
+ if (ret == 0 || chunk_block >= dzone->wp_block) {
+ /*
+ * The buffer zone is empty or its valid blocks are
+ * after the data zone write pointer.
+ */
+ ret = dmz_reclaim_buf(zrc, dzone);
+ rzone = bzone;
+ } else {
+ /*
+ * Reclaim the data zone by merging it into the
+ * buffer zone so that the buffer zone itself can
+ * be later reclaimed.
+ */
+ ret = dmz_reclaim_seq_data(zrc, dzone);
+ rzone = dzone;
+ }
+ }
+out:
+ if (ret) {
+ dmz_unlock_zone_reclaim(dzone);
+ return;
+ }
+
+ (void) dmz_flush_metadata(zrc->metadata);
+
+ dmz_dev_debug(zrc->dev, "Reclaimed zone %u in %u ms",
+ dmz_id(zmd, rzone), jiffies_to_msecs(jiffies - start));
+}
+
+/*
+ * Test if the target device is idle.
+ */
+static inline int dmz_target_idle(struct dmz_reclaim *zrc)
+{
+ return time_is_before_jiffies(zrc->atime + DMZ_IDLE_PERIOD);
+}
+
+/*
+ * Test if reclaim is necessary.
+ */
+static bool dmz_should_reclaim(struct dmz_reclaim *zrc)
+{
+ struct dmz_metadata *zmd = zrc->metadata;
+ unsigned int nr_rnd = dmz_nr_rnd_zones(zmd);
+ unsigned int nr_unmap_rnd = dmz_nr_unmap_rnd_zones(zmd);
+ unsigned int p_unmap_rnd = nr_unmap_rnd * 100 / nr_rnd;
+
+ /* Reclaim when idle */
+ if (dmz_target_idle(zrc) && nr_unmap_rnd < nr_rnd)
+ return true;
+
+ /* If there are still plenty of random zones, do not reclaim */
+ if (p_unmap_rnd >= DMZ_RECLAIM_HIGH_UNMAP_RND)
+ return false;
+
+ /*
+ * If the percentage of unmappped random zones is low,
+ * reclaim even if the target is busy.
+ */
+ return p_unmap_rnd <= DMZ_RECLAIM_LOW_UNMAP_RND;
+}
+
+/*
+ * Reclaim work function.
+ */
+static void dmz_reclaim_work(struct work_struct *work)
+{
+ struct dmz_reclaim *zrc = container_of(work, struct dmz_reclaim, work.work);
+ struct dmz_metadata *zmd = zrc->metadata;
+ unsigned int nr_rnd, nr_unmap_rnd;
+ unsigned int p_unmap_rnd;
+
+ if (!dmz_should_reclaim(zrc)) {
+ mod_delayed_work(zrc->wq, &zrc->work, DMZ_IDLE_PERIOD);
+ return;
+ }
+
+ /*
+ * We need to start reclaiming random zones: set up zone copy
+ * throttling to either go fast if we are very low on random zones
+ * and slower if there are still some free random zones to avoid
+ * as much as possible to negatively impact the user workload.
+ */
+ nr_rnd = dmz_nr_rnd_zones(zmd);
+ nr_unmap_rnd = dmz_nr_unmap_rnd_zones(zmd);
+ p_unmap_rnd = nr_unmap_rnd * 100 / nr_rnd;
+ if (dmz_target_idle(zrc) || p_unmap_rnd < DMZ_RECLAIM_LOW_UNMAP_RND / 2) {
+ /* Idle or very low percentage: go fast */
+ zrc->kc_throttle.throttle = 100;
+ } else {
+ /* Busy but we still have some random zone: throttle */
+ zrc->kc_throttle.throttle = min(75U, 100U - p_unmap_rnd / 2);
+ }
+
+ dmz_dev_debug(zrc->dev,
+ "Reclaim (%u): %s, %u%% free rnd zones (%u/%u)",
+ zrc->kc_throttle.throttle,
+ (dmz_target_idle(zrc) ? "Idle" : "Busy"),
+ p_unmap_rnd, nr_unmap_rnd, nr_rnd);
+
+ dmz_reclaim(zrc);
+
+ dmz_schedule_reclaim(zrc);
+}
+
+/*
+ * Initialize reclaim.
+ */
+int dmz_ctr_reclaim(struct dmz_dev *dev, struct dmz_metadata *zmd,
+ struct dmz_reclaim **reclaim)
+{
+ struct dmz_reclaim *zrc;
+ int ret;
+
+ zrc = kzalloc(sizeof(struct dmz_reclaim), GFP_KERNEL);
+ if (!zrc)
+ return -ENOMEM;
+
+ zrc->dev = dev;
+ zrc->metadata = zmd;
+ zrc->atime = jiffies;
+
+ /* Reclaim kcopyd client */
+ zrc->kc = dm_kcopyd_client_create(&zrc->kc_throttle);
+ if (IS_ERR(zrc->kc)) {
+ ret = PTR_ERR(zrc->kc);
+ zrc->kc = NULL;
+ goto err;
+ }
+
+ /* Reclaim work */
+ INIT_DELAYED_WORK(&zrc->work, dmz_reclaim_work);
+ zrc->wq = alloc_ordered_workqueue("dmz_rwq_%s", WQ_MEM_RECLAIM,
+ dev->name);
+ if (!zrc->wq) {
+ ret = -ENOMEM;
+ goto err;
+ }
+
+ *reclaim = zrc;
+ queue_delayed_work(zrc->wq, &zrc->work, 0);
+
+ return 0;
+err:
+ if (zrc->kc)
+ dm_kcopyd_client_destroy(zrc->kc);
+ kfree(zrc);
+
+ return ret;
+}
+
+/*
+ * Terminate reclaim.
+ */
+void dmz_dtr_reclaim(struct dmz_reclaim *zrc)
+{
+ cancel_delayed_work_sync(&zrc->work);
+ destroy_workqueue(zrc->wq);
+ dm_kcopyd_client_destroy(zrc->kc);
+ kfree(zrc);
+}
+
+/*
+ * Suspend reclaim.
+ */
+void dmz_suspend_reclaim(struct dmz_reclaim *zrc)
+{
+ cancel_delayed_work_sync(&zrc->work);
+}
+
+/*
+ * Resume reclaim.
+ */
+void dmz_resume_reclaim(struct dmz_reclaim *zrc)
+{
+ queue_delayed_work(zrc->wq, &zrc->work, DMZ_IDLE_PERIOD);
+}
+
+/*
+ * BIO accounting.
+ */
+void dmz_reclaim_bio_acc(struct dmz_reclaim *zrc)
+{
+ zrc->atime = jiffies;
+}
+
+/*
+ * Start reclaim if necessary.
+ */
+void dmz_schedule_reclaim(struct dmz_reclaim *zrc)
+{
+ if (dmz_should_reclaim(zrc))
+ mod_delayed_work(zrc->wq, &zrc->work, 0);
+}
+