On 02/09/2017 05:18 AM, Damien Le Moal wrote:
> 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. Write requests are processed using a
> combination of on-disk buffering using the device conventional zones,
> allowing any random write access to be safely executed, or direct in-place
> processing for requests aligned on a zone sequential write pointer position.
> A background reclaim process ensures that some 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 an FS) remain stored in
> conventional zones, resulting in no apparent write overhead.
>
[ .. ]
> +/*
> + * CRC32
> + */
> +static u32 dmz_sb_crc32(u32 crc, const void *buf, size_t length)
> +{
> + unsigned char *p = (unsigned char *)buf;
> + int i;
> +
> +#define CRCPOLY_LE 0xedb88320
> +
> + while (length--) {
> + crc ^= *p++;
> + for (i = 0; i < 8; i++)
> + crc = (crc >> 1) ^ ((crc & 1) ? CRCPOLY_LE : 0);
> + }
> +
> + return crc;
> +}
> +
Why do you insist on your own CRC32 implementations?
Don't we have enough already?
[ .. ]
> +/*
> + * Write blocks.
> + */
> +static int dmz_reclaim_write(struct dm_zoned_target *dzt,
> + struct dm_zone *zone,
> + struct dm_zoned_ioreg **ioregs,
> + unsigned int nr_ioregs)
> +{
> + struct dm_zoned_ioreg *ioreg;
> + sector_t chunk_block;
> + int i, ret = 0;
> +
> + for (i = 0; i < nr_ioregs; i++) {
> +
> + ioreg = ioregs[i];
> +
> + /* Wait for the read I/O to complete */
> + wait_for_completion_io(&ioreg->wait);
> +
> + if (ret || ioreg->err) {
> + if (ret == 0)
> + ret = ioreg->err;
> + dmz_reclaim_free_ioreg(ioreg);
> + ioregs[i] = NULL;
> + continue;
> + }
> +
> + chunk_block = ioreg->chunk_block;
> +
> + dmz_dev_debug(dzt,
> + "Reclaim: Write %s zone %u, block %llu+%u\n",
> + dmz_is_rnd(zone) ? "RND" : "SEQ",
> + dmz_id(dzt, zone),
> + (unsigned long long)chunk_block,
> + ioreg->nr_blocks);
> +
> + /*
> + * If we are writing in a sequential zones,
> + * we must make sure that writes are sequential. So
> + * fill up any eventual hole between writes.
> + */
> + if (dmz_is_seq(zone)) {
> + ret = dmz_reclaim_align_wp(dzt, zone, chunk_block);
> + if (ret)
> + break;
> + }
> +
> + /* Do write */
> + dmz_reclaim_submit_ioreg(dzt, zone, ioreg, REQ_OP_WRITE);
> + wait_for_completion_io(&ioreg->wait);
> +
> + ret = ioreg->err;
> + if (ret) {
> + dmz_dev_err(dzt, "Reclaim: Write failed\n");
> + } else {
> + if (dmz_is_seq(zone))
> + zone->wp_block += ioreg->nr_blocks;
> + ret = dmz_validate_blocks(dzt, zone, chunk_block,
> + ioreg->nr_blocks);
> + }
> +
> + ioregs[i] = NULL;
> + dmz_reclaim_free_ioreg(ioreg);
> +
> + }
> +
> + return ret;
> +}
> +
> +/*
> + * Move valid blocks of src_zone into dst_zone.
> + */
> +static int dmz_reclaim_copy_zone(struct dm_zoned_target *dzt,
> + struct dm_zone *src_zone,
> + struct dm_zone *dst_zone)
> +{
> + struct dm_zoned_ioreg *ioregs[DMZ_RECLAIM_MAX_IOREGS];
> + struct dm_zoned_ioreg *ioreg;
> + sector_t chunk_block = 0;
> + sector_t first_block, end_block;
> + int nr_ioregs = 0, i, ret;
> +
> + if (dmz_is_seq(src_zone))
> + end_block = src_zone->wp_block;
> + else
> + end_block = dzt->zone_nr_blocks;
> +
> + while (chunk_block < end_block) {
> +
> + /* Read valid regions from source zone */
> + nr_ioregs = 0;
> + first_block = chunk_block;
> + while (nr_ioregs < DMZ_RECLAIM_MAX_IOREGS &&
> + chunk_block < end_block) {
> +
> + ioreg = dmz_reclaim_read(dzt, src_zone, chunk_block);
> + if (IS_ERR(ioreg)) {
> + ret = PTR_ERR(ioreg);
> + goto err;
> + }
> + if (!ioreg)
> + break;
> +
> + chunk_block = ioreg->chunk_block + ioreg->nr_blocks;
> + ioregs[nr_ioregs] = ioreg;
> + nr_ioregs++;
> +
> + }
> +
> + /* Are we done ? */
> + if (!nr_ioregs)
> + break;
> +
> + /* Write in destination zone */
> + ret = dmz_reclaim_write(dzt, dst_zone, ioregs, nr_ioregs);
> + if (ret != 0) {
> + dmz_invalidate_blocks(dzt, dst_zone,
> + first_block,
> + end_block - first_block);
> + goto err;
> + }
> +
> + }
> +
> + return 0;
> +
> +err:
> + for (i = 0; i < nr_ioregs; i++) {
> + ioreg = ioregs[i];
> + if (ioreg) {
> + wait_for_completion_io(&ioreg->wait);
> + dmz_reclaim_free_ioreg(ioreg);
> + }
> + }
> +
> + return ret;
> +}
> +
Have you looked at using dm-kcopyd for doing the reclaim?
What's inhibiting you from using it?
Cheers,
Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
h...@suse.de +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
