Contributors: 8
Author Tokens Token Proportion Commits Commit Proportion
Javier González 2353 69.66% 24 53.33%
Hans Holmberg 927 27.44% 10 22.22%
Matias Björling 63 1.87% 5 11.11%
Igor Konopko 24 0.71% 2 4.44%
Heiner Litz 8 0.24% 1 2.22%
Dan Carpenter 1 0.03% 1 2.22%
Christoph Hellwig 1 0.03% 1 2.22%
Kent Overstreet 1 0.03% 1 2.22%
Total 3378 45 


// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2016 CNEX Labs
 * Initial release: Javier Gonzalez <javier@cnexlabs.com>
 *                  Matias Bjorling <matias@cnexlabs.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * pblk-write.c - pblk's write path from write buffer to media
 */

#include "pblk.h"
#include "pblk-trace.h"

static unsigned long pblk_end_w_bio(struct pblk *pblk, struct nvm_rq *rqd,
				    struct pblk_c_ctx *c_ctx)
{
	struct bio *original_bio;
	struct pblk_rb *rwb = &pblk->rwb;
	unsigned long ret;
	int i;

	for (i = 0; i < c_ctx->nr_valid; i++) {
		struct pblk_w_ctx *w_ctx;
		int pos = c_ctx->sentry + i;
		int flags;

		w_ctx = pblk_rb_w_ctx(rwb, pos);
		flags = READ_ONCE(w_ctx->flags);

		if (flags & PBLK_FLUSH_ENTRY) {
			flags &= ~PBLK_FLUSH_ENTRY;
			/* Release flags on context. Protect from writes */
			smp_store_release(&w_ctx->flags, flags);

#ifdef CONFIG_NVM_PBLK_DEBUG
			atomic_dec(&rwb->inflight_flush_point);
#endif
		}

		while ((original_bio = bio_list_pop(&w_ctx->bios)))
			bio_endio(original_bio);
	}

	if (c_ctx->nr_padded)
		pblk_bio_free_pages(pblk, rqd->bio, c_ctx->nr_valid,
							c_ctx->nr_padded);

#ifdef CONFIG_NVM_PBLK_DEBUG
	atomic_long_add(rqd->nr_ppas, &pblk->sync_writes);
#endif

	ret = pblk_rb_sync_advance(&pblk->rwb, c_ctx->nr_valid);

	bio_put(rqd->bio);
	pblk_free_rqd(pblk, rqd, PBLK_WRITE);

	return ret;
}

static unsigned long pblk_end_queued_w_bio(struct pblk *pblk,
					   struct nvm_rq *rqd,
					   struct pblk_c_ctx *c_ctx)
{
	list_del(&c_ctx->list);
	return pblk_end_w_bio(pblk, rqd, c_ctx);
}

static void pblk_complete_write(struct pblk *pblk, struct nvm_rq *rqd,
				struct pblk_c_ctx *c_ctx)
{
	struct pblk_c_ctx *c, *r;
	unsigned long flags;
	unsigned long pos;

#ifdef CONFIG_NVM_PBLK_DEBUG
	atomic_long_sub(c_ctx->nr_valid, &pblk->inflight_writes);
#endif
	pblk_up_rq(pblk, c_ctx->lun_bitmap);

	pos = pblk_rb_sync_init(&pblk->rwb, &flags);
	if (pos == c_ctx->sentry) {
		pos = pblk_end_w_bio(pblk, rqd, c_ctx);

retry:
		list_for_each_entry_safe(c, r, &pblk->compl_list, list) {
			rqd = nvm_rq_from_c_ctx(c);
			if (c->sentry == pos) {
				pos = pblk_end_queued_w_bio(pblk, rqd, c);
				goto retry;
			}
		}
	} else {
		WARN_ON(nvm_rq_from_c_ctx(c_ctx) != rqd);
		list_add_tail(&c_ctx->list, &pblk->compl_list);
	}
	pblk_rb_sync_end(&pblk->rwb, &flags);
}

/* Map remaining sectors in chunk, starting from ppa */
static void pblk_map_remaining(struct pblk *pblk, struct ppa_addr *ppa,
		int rqd_ppas)
{
	struct pblk_line *line;
	struct ppa_addr map_ppa = *ppa;
	__le64 addr_empty = cpu_to_le64(ADDR_EMPTY);
	__le64 *lba_list;
	u64 paddr;
	int done = 0;
	int n = 0;

	line = pblk_ppa_to_line(pblk, *ppa);
	lba_list = emeta_to_lbas(pblk, line->emeta->buf);

	spin_lock(&line->lock);

	while (!done)  {
		paddr = pblk_dev_ppa_to_line_addr(pblk, map_ppa);

		if (!test_and_set_bit(paddr, line->map_bitmap))
			line->left_msecs--;

		if (n < rqd_ppas && lba_list[paddr] != addr_empty)
			line->nr_valid_lbas--;

		lba_list[paddr] = addr_empty;

		if (!test_and_set_bit(paddr, line->invalid_bitmap))
			le32_add_cpu(line->vsc, -1);

		done = nvm_next_ppa_in_chk(pblk->dev, &map_ppa);

		n++;
	}

	line->w_err_gc->has_write_err = 1;
	spin_unlock(&line->lock);
}

static void pblk_prepare_resubmit(struct pblk *pblk, unsigned int sentry,
				  unsigned int nr_entries)
{
	struct pblk_rb *rb = &pblk->rwb;
	struct pblk_rb_entry *entry;
	struct pblk_line *line;
	struct pblk_w_ctx *w_ctx;
	struct ppa_addr ppa_l2p;
	int flags;
	unsigned int i;

	spin_lock(&pblk->trans_lock);
	for (i = 0; i < nr_entries; i++) {
		entry = &rb->entries[pblk_rb_ptr_wrap(rb, sentry, i)];
		w_ctx = &entry->w_ctx;

		/* Check if the lba has been overwritten */
		if (w_ctx->lba != ADDR_EMPTY) {
			ppa_l2p = pblk_trans_map_get(pblk, w_ctx->lba);
			if (!pblk_ppa_comp(ppa_l2p, entry->cacheline))
				w_ctx->lba = ADDR_EMPTY;
		}

		/* Mark up the entry as submittable again */
		flags = READ_ONCE(w_ctx->flags);
		flags |= PBLK_WRITTEN_DATA;
		/* Release flags on write context. Protect from writes */
		smp_store_release(&w_ctx->flags, flags);

		/* Decrease the reference count to the line as we will
		 * re-map these entries
		 */
		line = pblk_ppa_to_line(pblk, w_ctx->ppa);
		atomic_dec(&line->sec_to_update);
		kref_put(&line->ref, pblk_line_put);
	}
	spin_unlock(&pblk->trans_lock);
}

static void pblk_queue_resubmit(struct pblk *pblk, struct pblk_c_ctx *c_ctx)
{
	struct pblk_c_ctx *r_ctx;

	r_ctx = kzalloc(sizeof(struct pblk_c_ctx), GFP_KERNEL);
	if (!r_ctx)
		return;

	r_ctx->lun_bitmap = NULL;
	r_ctx->sentry = c_ctx->sentry;
	r_ctx->nr_valid = c_ctx->nr_valid;
	r_ctx->nr_padded = c_ctx->nr_padded;

	spin_lock(&pblk->resubmit_lock);
	list_add_tail(&r_ctx->list, &pblk->resubmit_list);
	spin_unlock(&pblk->resubmit_lock);

#ifdef CONFIG_NVM_PBLK_DEBUG
	atomic_long_add(c_ctx->nr_valid, &pblk->recov_writes);
#endif
}

static void pblk_submit_rec(struct work_struct *work)
{
	struct pblk_rec_ctx *recovery =
			container_of(work, struct pblk_rec_ctx, ws_rec);
	struct pblk *pblk = recovery->pblk;
	struct nvm_rq *rqd = recovery->rqd;
	struct pblk_c_ctx *c_ctx = nvm_rq_to_pdu(rqd);
	struct ppa_addr *ppa_list = nvm_rq_to_ppa_list(rqd);

	pblk_log_write_err(pblk, rqd);

	pblk_map_remaining(pblk, ppa_list, rqd->nr_ppas);
	pblk_queue_resubmit(pblk, c_ctx);

	pblk_up_rq(pblk, c_ctx->lun_bitmap);
	if (c_ctx->nr_padded)
		pblk_bio_free_pages(pblk, rqd->bio, c_ctx->nr_valid,
							c_ctx->nr_padded);
	bio_put(rqd->bio);
	pblk_free_rqd(pblk, rqd, PBLK_WRITE);
	mempool_free(recovery, &pblk->rec_pool);

	atomic_dec(&pblk->inflight_io);
	pblk_write_kick(pblk);
}


static void pblk_end_w_fail(struct pblk *pblk, struct nvm_rq *rqd)
{
	struct pblk_rec_ctx *recovery;

	recovery = mempool_alloc(&pblk->rec_pool, GFP_ATOMIC);
	if (!recovery) {
		pblk_err(pblk, "could not allocate recovery work\n");
		return;
	}

	recovery->pblk = pblk;
	recovery->rqd = rqd;

	INIT_WORK(&recovery->ws_rec, pblk_submit_rec);
	queue_work(pblk->close_wq, &recovery->ws_rec);
}

static void pblk_end_io_write(struct nvm_rq *rqd)
{
	struct pblk *pblk = rqd->private;
	struct pblk_c_ctx *c_ctx = nvm_rq_to_pdu(rqd);

	if (rqd->error) {
		pblk_end_w_fail(pblk, rqd);
		return;
	} else {
		if (trace_pblk_chunk_state_enabled())
			pblk_check_chunk_state_update(pblk, rqd);
#ifdef CONFIG_NVM_PBLK_DEBUG
		WARN_ONCE(rqd->bio->bi_status, "pblk: corrupted write error\n");
#endif
	}

	pblk_complete_write(pblk, rqd, c_ctx);
	atomic_dec(&pblk->inflight_io);
}

static void pblk_end_io_write_meta(struct nvm_rq *rqd)
{
	struct pblk *pblk = rqd->private;
	struct pblk_g_ctx *m_ctx = nvm_rq_to_pdu(rqd);
	struct pblk_line *line = m_ctx->private;
	struct pblk_emeta *emeta = line->emeta;
	struct ppa_addr *ppa_list = nvm_rq_to_ppa_list(rqd);
	int sync;

	pblk_up_chunk(pblk, ppa_list[0]);

	if (rqd->error) {
		pblk_log_write_err(pblk, rqd);
		pblk_err(pblk, "metadata I/O failed. Line %d\n", line->id);
		line->w_err_gc->has_write_err = 1;
	} else {
		if (trace_pblk_chunk_state_enabled())
			pblk_check_chunk_state_update(pblk, rqd);
	}

	sync = atomic_add_return(rqd->nr_ppas, &emeta->sync);
	if (sync == emeta->nr_entries)
		pblk_gen_run_ws(pblk, line, NULL, pblk_line_close_ws,
						GFP_ATOMIC, pblk->close_wq);

	pblk_free_rqd(pblk, rqd, PBLK_WRITE_INT);

	atomic_dec(&pblk->inflight_io);
}

static int pblk_alloc_w_rq(struct pblk *pblk, struct nvm_rq *rqd,
			   unsigned int nr_secs, nvm_end_io_fn(*end_io))
{
	/* Setup write request */
	rqd->opcode = NVM_OP_PWRITE;
	rqd->nr_ppas = nr_secs;
	rqd->is_seq = 1;
	rqd->private = pblk;
	rqd->end_io = end_io;

	return pblk_alloc_rqd_meta(pblk, rqd);
}

static int pblk_setup_w_rq(struct pblk *pblk, struct nvm_rq *rqd,
			   struct ppa_addr *erase_ppa)
{
	struct pblk_line_meta *lm = &pblk->lm;
	struct pblk_line *e_line = pblk_line_get_erase(pblk);
	struct pblk_c_ctx *c_ctx = nvm_rq_to_pdu(rqd);
	unsigned int valid = c_ctx->nr_valid;
	unsigned int padded = c_ctx->nr_padded;
	unsigned int nr_secs = valid + padded;
	unsigned long *lun_bitmap;
	int ret;

	lun_bitmap = kzalloc(lm->lun_bitmap_len, GFP_KERNEL);
	if (!lun_bitmap)
		return -ENOMEM;
	c_ctx->lun_bitmap = lun_bitmap;

	ret = pblk_alloc_w_rq(pblk, rqd, nr_secs, pblk_end_io_write);
	if (ret) {
		kfree(lun_bitmap);
		return ret;
	}

	if (likely(!e_line || !atomic_read(&e_line->left_eblks)))
		ret = pblk_map_rq(pblk, rqd, c_ctx->sentry, lun_bitmap,
							valid, 0);
	else
		ret = pblk_map_erase_rq(pblk, rqd, c_ctx->sentry, lun_bitmap,
							valid, erase_ppa);

	return ret;
}

static int pblk_calc_secs_to_sync(struct pblk *pblk, unsigned int secs_avail,
				  unsigned int secs_to_flush)
{
	int secs_to_sync;

	secs_to_sync = pblk_calc_secs(pblk, secs_avail, secs_to_flush, true);

#ifdef CONFIG_NVM_PBLK_DEBUG
	if ((!secs_to_sync && secs_to_flush)
			|| (secs_to_sync < 0)
			|| (secs_to_sync > secs_avail && !secs_to_flush)) {
		pblk_err(pblk, "bad sector calculation (a:%d,s:%d,f:%d)\n",
				secs_avail, secs_to_sync, secs_to_flush);
	}
#endif

	return secs_to_sync;
}

int pblk_submit_meta_io(struct pblk *pblk, struct pblk_line *meta_line)
{
	struct nvm_tgt_dev *dev = pblk->dev;
	struct nvm_geo *geo = &dev->geo;
	struct pblk_line_mgmt *l_mg = &pblk->l_mg;
	struct pblk_line_meta *lm = &pblk->lm;
	struct pblk_emeta *emeta = meta_line->emeta;
	struct ppa_addr *ppa_list;
	struct pblk_g_ctx *m_ctx;
	struct bio *bio;
	struct nvm_rq *rqd;
	void *data;
	u64 paddr;
	int rq_ppas = pblk->min_write_pgs;
	int id = meta_line->id;
	int rq_len;
	int i, j;
	int ret;

	rqd = pblk_alloc_rqd(pblk, PBLK_WRITE_INT);

	m_ctx = nvm_rq_to_pdu(rqd);
	m_ctx->private = meta_line;

	rq_len = rq_ppas * geo->csecs;
	data = ((void *)emeta->buf) + emeta->mem;

	bio = pblk_bio_map_addr(pblk, data, rq_ppas, rq_len,
					l_mg->emeta_alloc_type, GFP_KERNEL);
	if (IS_ERR(bio)) {
		pblk_err(pblk, "failed to map emeta io");
		ret = PTR_ERR(bio);
		goto fail_free_rqd;
	}
	bio->bi_iter.bi_sector = 0; /* internal bio */
	bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
	rqd->bio = bio;

	ret = pblk_alloc_w_rq(pblk, rqd, rq_ppas, pblk_end_io_write_meta);
	if (ret)
		goto fail_free_bio;

	ppa_list = nvm_rq_to_ppa_list(rqd);
	for (i = 0; i < rqd->nr_ppas; ) {
		spin_lock(&meta_line->lock);
		paddr = __pblk_alloc_page(pblk, meta_line, rq_ppas);
		spin_unlock(&meta_line->lock);
		for (j = 0; j < rq_ppas; j++, i++, paddr++)
			ppa_list[i] = addr_to_gen_ppa(pblk, paddr, id);
	}

	spin_lock(&l_mg->close_lock);
	emeta->mem += rq_len;
	if (emeta->mem >= lm->emeta_len[0])
		list_del(&meta_line->list);
	spin_unlock(&l_mg->close_lock);

	pblk_down_chunk(pblk, ppa_list[0]);

	ret = pblk_submit_io(pblk, rqd);
	if (ret) {
		pblk_err(pblk, "emeta I/O submission failed: %d\n", ret);
		goto fail_rollback;
	}

	return NVM_IO_OK;

fail_rollback:
	pblk_up_chunk(pblk, ppa_list[0]);
	spin_lock(&l_mg->close_lock);
	pblk_dealloc_page(pblk, meta_line, rq_ppas);
	list_add(&meta_line->list, &meta_line->list);
	spin_unlock(&l_mg->close_lock);
fail_free_bio:
	bio_put(bio);
fail_free_rqd:
	pblk_free_rqd(pblk, rqd, PBLK_WRITE_INT);
	return ret;
}

static inline bool pblk_valid_meta_ppa(struct pblk *pblk,
				       struct pblk_line *meta_line,
				       struct nvm_rq *data_rqd)
{
	struct nvm_tgt_dev *dev = pblk->dev;
	struct nvm_geo *geo = &dev->geo;
	struct pblk_c_ctx *data_c_ctx = nvm_rq_to_pdu(data_rqd);
	struct pblk_line *data_line = pblk_line_get_data(pblk);
	struct ppa_addr ppa, ppa_opt;
	u64 paddr;
	int pos_opt;

	/* Schedule a metadata I/O that is half the distance from the data I/O
	 * with regards to the number of LUNs forming the pblk instance. This
	 * balances LUN conflicts across every I/O.
	 *
	 * When the LUN configuration changes (e.g., due to GC), this distance
	 * can align, which would result on metadata and data I/Os colliding. In
	 * this case, modify the distance to not be optimal, but move the
	 * optimal in the right direction.
	 */
	paddr = pblk_lookup_page(pblk, meta_line);
	ppa = addr_to_gen_ppa(pblk, paddr, 0);
	ppa_opt = addr_to_gen_ppa(pblk, paddr + data_line->meta_distance, 0);
	pos_opt = pblk_ppa_to_pos(geo, ppa_opt);

	if (test_bit(pos_opt, data_c_ctx->lun_bitmap) ||
				test_bit(pos_opt, data_line->blk_bitmap))
		return true;

	if (unlikely(pblk_ppa_comp(ppa_opt, ppa)))
		data_line->meta_distance--;

	return false;
}

static struct pblk_line *pblk_should_submit_meta_io(struct pblk *pblk,
						    struct nvm_rq *data_rqd)
{
	struct pblk_line_meta *lm = &pblk->lm;
	struct pblk_line_mgmt *l_mg = &pblk->l_mg;
	struct pblk_line *meta_line;

	spin_lock(&l_mg->close_lock);
	if (list_empty(&l_mg->emeta_list)) {
		spin_unlock(&l_mg->close_lock);
		return NULL;
	}
	meta_line = list_first_entry(&l_mg->emeta_list, struct pblk_line, list);
	if (meta_line->emeta->mem >= lm->emeta_len[0]) {
		spin_unlock(&l_mg->close_lock);
		return NULL;
	}
	spin_unlock(&l_mg->close_lock);

	if (!pblk_valid_meta_ppa(pblk, meta_line, data_rqd))
		return NULL;

	return meta_line;
}

static int pblk_submit_io_set(struct pblk *pblk, struct nvm_rq *rqd)
{
	struct ppa_addr erase_ppa;
	struct pblk_line *meta_line;
	int err;

	pblk_ppa_set_empty(&erase_ppa);

	/* Assign lbas to ppas and populate request structure */
	err = pblk_setup_w_rq(pblk, rqd, &erase_ppa);
	if (err) {
		pblk_err(pblk, "could not setup write request: %d\n", err);
		return NVM_IO_ERR;
	}

	meta_line = pblk_should_submit_meta_io(pblk, rqd);

	/* Submit data write for current data line */
	err = pblk_submit_io(pblk, rqd);
	if (err) {
		pblk_err(pblk, "data I/O submission failed: %d\n", err);
		return NVM_IO_ERR;
	}

	if (!pblk_ppa_empty(erase_ppa)) {
		/* Submit erase for next data line */
		if (pblk_blk_erase_async(pblk, erase_ppa)) {
			struct pblk_line *e_line = pblk_line_get_erase(pblk);
			struct nvm_tgt_dev *dev = pblk->dev;
			struct nvm_geo *geo = &dev->geo;
			int bit;

			atomic_inc(&e_line->left_eblks);
			bit = pblk_ppa_to_pos(geo, erase_ppa);
			WARN_ON(!test_and_clear_bit(bit, e_line->erase_bitmap));
		}
	}

	if (meta_line) {
		/* Submit metadata write for previous data line */
		err = pblk_submit_meta_io(pblk, meta_line);
		if (err) {
			pblk_err(pblk, "metadata I/O submission failed: %d",
					err);
			return NVM_IO_ERR;
		}
	}

	return NVM_IO_OK;
}

static void pblk_free_write_rqd(struct pblk *pblk, struct nvm_rq *rqd)
{
	struct pblk_c_ctx *c_ctx = nvm_rq_to_pdu(rqd);
	struct bio *bio = rqd->bio;

	if (c_ctx->nr_padded)
		pblk_bio_free_pages(pblk, bio, c_ctx->nr_valid,
							c_ctx->nr_padded);
}

static int pblk_submit_write(struct pblk *pblk, int *secs_left)
{
	struct bio *bio;
	struct nvm_rq *rqd;
	unsigned int secs_avail, secs_to_sync, secs_to_com;
	unsigned int secs_to_flush, packed_meta_pgs;
	unsigned long pos;
	unsigned int resubmit;

	*secs_left = 0;

	spin_lock(&pblk->resubmit_lock);
	resubmit = !list_empty(&pblk->resubmit_list);
	spin_unlock(&pblk->resubmit_lock);

	/* Resubmit failed writes first */
	if (resubmit) {
		struct pblk_c_ctx *r_ctx;

		spin_lock(&pblk->resubmit_lock);
		r_ctx = list_first_entry(&pblk->resubmit_list,
					struct pblk_c_ctx, list);
		list_del(&r_ctx->list);
		spin_unlock(&pblk->resubmit_lock);

		secs_avail = r_ctx->nr_valid;
		pos = r_ctx->sentry;

		pblk_prepare_resubmit(pblk, pos, secs_avail);
		secs_to_sync = pblk_calc_secs_to_sync(pblk, secs_avail,
				secs_avail);

		kfree(r_ctx);
	} else {
		/* If there are no sectors in the cache,
		 * flushes (bios without data) will be cleared on
		 * the cache threads
		 */
		secs_avail = pblk_rb_read_count(&pblk->rwb);
		if (!secs_avail)
			return 0;

		secs_to_flush = pblk_rb_flush_point_count(&pblk->rwb);
		if (!secs_to_flush && secs_avail < pblk->min_write_pgs_data)
			return 0;

		secs_to_sync = pblk_calc_secs_to_sync(pblk, secs_avail,
					secs_to_flush);
		if (secs_to_sync > pblk->max_write_pgs) {
			pblk_err(pblk, "bad buffer sync calculation\n");
			return 0;
		}

		secs_to_com = (secs_to_sync > secs_avail) ?
			secs_avail : secs_to_sync;
		pos = pblk_rb_read_commit(&pblk->rwb, secs_to_com);
	}

	packed_meta_pgs = (pblk->min_write_pgs - pblk->min_write_pgs_data);
	bio = bio_alloc(GFP_KERNEL, secs_to_sync + packed_meta_pgs);

	bio->bi_iter.bi_sector = 0; /* internal bio */
	bio_set_op_attrs(bio, REQ_OP_WRITE, 0);

	rqd = pblk_alloc_rqd(pblk, PBLK_WRITE);
	rqd->bio = bio;

	if (pblk_rb_read_to_bio(&pblk->rwb, rqd, pos, secs_to_sync,
								secs_avail)) {
		pblk_err(pblk, "corrupted write bio\n");
		goto fail_put_bio;
	}

	if (pblk_submit_io_set(pblk, rqd))
		goto fail_free_bio;

#ifdef CONFIG_NVM_PBLK_DEBUG
	atomic_long_add(secs_to_sync, &pblk->sub_writes);
#endif

	*secs_left = 1;
	return 0;

fail_free_bio:
	pblk_free_write_rqd(pblk, rqd);
fail_put_bio:
	bio_put(bio);
	pblk_free_rqd(pblk, rqd, PBLK_WRITE);

	return -EINTR;
}

int pblk_write_ts(void *data)
{
	struct pblk *pblk = data;
	int secs_left;
	int write_failure = 0;

	while (!kthread_should_stop()) {
		if (!write_failure) {
			write_failure = pblk_submit_write(pblk, &secs_left);

			if (secs_left)
				continue;
		}
		set_current_state(TASK_INTERRUPTIBLE);
		io_schedule();
	}

	return 0;
}