/*

 * CDDL HEADER START

 *

 * The contents of this file are subject to the terms of the

 * Common Development and Distribution License (the "License").

 * You may not use this file except in compliance with the License.

 *

 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE

 * or http://www.opensolaris.org/os/licensing.

 * See the License for the specific language governing permissions

 * and limitations under the License.

 *

 * When distributing Covered Code, include this CDDL HEADER in each

 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.

 * If applicable, add the following below this CDDL HEADER, with the

 * fields enclosed by brackets "[]" replaced with your own identifying

 * information: Portions Copyright [yyyy] [name of copyright owner]

 *

 * CDDL HEADER END

 */

/*

 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.

 * Use is subject to license terms.

 */

#pragma ident	"%Z%%M%	%I%	%E% SMI"

#include <sys/zfs_context.h>

#include <sys/spa.h>

#include <sys/vdev_impl.h>

#include <sys/zio.h>

#include <sys/fs/zfs.h>

/*

 * Virtual device vector for mirroring.

 */

typedef struct mirror_map {

	int	mm_error;

	short	mm_tried;

	short	mm_skipped;

} mirror_map_t;

static mirror_map_t *

vdev_mirror_map_alloc(zio_t *zio)

{

	zio->io_vsd = kmem_zalloc(zio->io_vd->vdev_children *

	    sizeof (mirror_map_t), KM_SLEEP);

	return (zio->io_vsd);

}

static void

vdev_mirror_map_free(zio_t *zio)

{

	kmem_free(zio->io_vsd,

	    zio->io_vd->vdev_children * sizeof (mirror_map_t));

	zio->io_vsd = NULL;

}

static int

vdev_mirror_open(vdev_t *vd, uint64_t *asize, uint64_t *ashift)

{

	vdev_t *cvd;

	uint64_t c;

	int numerrors = 0;

	int ret, lasterror = 0;

	if (vd->vdev_children == 0) {

		vd->vdev_stat.vs_aux = VDEV_AUX_BAD_LABEL;

		return (EINVAL);

	}

	for (c = 0; c < vd->vdev_children; c++) {

		cvd = vd->vdev_child[c];

		if ((ret = vdev_open(cvd)) != 0) {

			lasterror = ret;

			numerrors++;

			continue;

		}

		*asize = MIN(*asize - 1, cvd->vdev_asize - 1) + 1;

		*ashift = cvd->vdev_ashift;

	}

	if (numerrors == vd->vdev_children) {

		vd->vdev_stat.vs_aux = VDEV_AUX_NO_REPLICAS;

		return (lasterror);

	}

	return (0);

}

static void

vdev_mirror_close(vdev_t *vd)

{

	uint64_t c;

	for (c = 0; c < vd->vdev_children; c++)

		vdev_close(vd->vdev_child[c]);

}

static void

vdev_mirror_child_done(zio_t *zio)

{

	mirror_map_t *mm = zio->io_private;

	mm->mm_error = zio->io_error;

	mm->mm_tried = 1;

	mm->mm_skipped = 0;

}

static void

vdev_mirror_scrub_done(zio_t *zio)

{

	mirror_map_t *mm = zio->io_private;

	if (zio->io_error == 0) {

		zio_t *pio = zio->io_parent;

		mutex_enter(&pio->io_lock);

		bcopy(zio->io_data, pio->io_data, pio->io_size);

		mutex_exit(&pio->io_lock);

	}

	zio_buf_free(zio->io_data, zio->io_size);

	mm->mm_error = zio->io_error;

	mm->mm_tried = 1;

	mm->mm_skipped = 0;

}

/*

 * Try to find a child whose DTL doesn't contain the block we want to read.

 * If we can't, try the read on any vdev we haven't already tried.

 */

static int

vdev_mirror_child_select(zio_t *zio)

{

	mirror_map_t *mm = zio->io_vsd;

	vdev_t *vd = zio->io_vd;

	vdev_t *cvd;

	uint64_t txg = zio->io_txg;

	int i, c;

	ASSERT(zio->io_bp == NULL || zio->io_bp->blk_birth == txg);

	/*

	 * Select the child we'd like to read from absent any errors.

	 * The current policy is to alternate sides at 8M granularity.

	 * XXX -- investigate other policies for read distribution.

	 */

	c = (zio->io_offset >> (SPA_MAXBLOCKSHIFT + 6)) % vd->vdev_children;

	/*

	 * If this is a replacing vdev, always try child 0 (the source) first.

	 */

	if (vd->vdev_ops == &vdev_replacing_ops)

		c = 0;

	/*

	 * Try to find a child whose DTL doesn't contain the block to read.

	 * If a child is known to be completely inaccessible (indicated by

	 * vdev_is_dead() returning B_TRUE), don't even try.

	 */

	for (i = 0; i < vd->vdev_children; i++, c++) {

		if (c >= vd->vdev_children)

			c = 0;

		if (mm[c].mm_tried || mm[c].mm_skipped)

			continue;

		cvd = vd->vdev_child[c];

		if (vdev_is_dead(cvd)) {

			mm[c].mm_error = ENXIO;

			mm[c].mm_tried = 1;	/* don't even try */

			mm[c].mm_skipped = 1;

			continue;

		}

		if (!vdev_dtl_contains(&cvd->vdev_dtl_map, txg, 1))

			return (c);

		mm[c].mm_error = ESTALE;

		mm[c].mm_skipped = 1;

	}

	/*

	 * Every device is either missing or has this txg in its DTL.

	 * If we don't have any sibling replicas to consult, look for

	 * any child we haven't already tried before giving up.

	 */

	if (vd == vd->vdev_top || vd->vdev_parent->vdev_children <= 1) {

		for (c = 0; c < vd->vdev_children; c++) {

			if (!mm[c].mm_tried)

				return (c);

		}

	}

	/*

	 * Every child failed.  There's no place left to look.

	 */

	return (-1);

}

static void

vdev_mirror_io_start(zio_t *zio)

{

	vdev_t *vd = zio->io_vd;

	mirror_map_t *mm;

	int c, children;

	mm = vdev_mirror_map_alloc(zio);

	if (zio->io_type == ZIO_TYPE_READ) {

		if ((zio->io_flags & ZIO_FLAG_SCRUB) &&

		    vd->vdev_ops != &vdev_replacing_ops) {

			/*

			 * For scrubbing reads we need to allocate a read

			 * buffer for each child and issue reads to all

			 * children.  If any child succeeds, it will copy its

			 * data into zio->io_data in vdev_mirror_scrub_done.

			 */

			for (c = 0; c < vd->vdev_children; c++) {

				zio_nowait(zio_vdev_child_io(zio, zio->io_bp,

				    vd->vdev_child[c], zio->io_offset,

				    zio_buf_alloc(zio->io_size), zio->io_size,

				    zio->io_type, zio->io_priority,

				    ZIO_FLAG_CANFAIL, vdev_mirror_scrub_done,

				    &mm[c]));

			}

			zio_wait_children_done(zio);

			return;

		}

		/*

		 * For normal reads just pick one child.

		 */

		c = vdev_mirror_child_select(zio);

		children = (c >= 0);

	} else {

		ASSERT(zio->io_type == ZIO_TYPE_WRITE);

		/*

		 * If this is a resilvering I/O to a replacing vdev,

		 * only the last child should be written -- unless the

		 * first child happens to have a DTL entry here as well.

		 * All other writes go to all children.

		 */

		if ((zio->io_flags & ZIO_FLAG_RESILVER) &&

		    vd->vdev_ops == &vdev_replacing_ops &&

		    !vdev_dtl_contains(&vd->vdev_child[0]->vdev_dtl_map,

		    zio->io_txg, 1)) {

			c = vd->vdev_children - 1;

			children = 1;

		} else {

			c = 0;

			children = vd->vdev_children;

		}

	}

	while (children--) {

		zio_nowait(zio_vdev_child_io(zio, zio->io_bp,

		    vd->vdev_child[c], zio->io_offset, zio->io_data,

		    zio->io_size, zio->io_type, zio->io_priority,

		    ZIO_FLAG_CANFAIL, vdev_mirror_child_done, &mm[c]));

		c++;

	}

	zio_wait_children_done(zio);

}

static void

vdev_mirror_io_done(zio_t *zio)

{

	vdev_t *vd = zio->io_vd;

	vdev_t *cvd;

	mirror_map_t *mm = zio->io_vsd;

	int c;

	int good_copies = 0;

	int unexpected_errors = 0;

	ASSERT(mm != NULL);

	zio->io_error = 0;

	zio->io_numerrors = 0;

	for (c = 0; c < vd->vdev_children; c++) {

		if (mm[c].mm_tried && mm[c].mm_error == 0) {

			good_copies++;

			continue;

		}

		/*

		 * We preserve any EIOs because those may be worth retrying;

		 * whereas ECKSUM and ENXIO are more likely to be persistent.

		 */

		if (mm[c].mm_error) {

			if (zio->io_error != EIO)

				zio->io_error = mm[c].mm_error;

			if (!mm[c].mm_skipped)

				unexpected_errors++;

			zio->io_numerrors++;

		}

	}

	if (zio->io_type == ZIO_TYPE_WRITE) {

		/*

		 * XXX -- for now, treat partial writes as success.

		 */

		/* XXPOLICY */

		if (good_copies != 0)

			zio->io_error = 0;

		ASSERT(mm != NULL);

		vdev_mirror_map_free(zio);

		zio_next_stage(zio);

		return;

	}

	ASSERT(zio->io_type == ZIO_TYPE_READ);

	/*

	 * If we don't have a good copy yet, keep trying other children.

	 */

	/* XXPOLICY */

	if (good_copies == 0 && (c = vdev_mirror_child_select(zio)) != -1) {

		ASSERT(c >= 0 && c < vd->vdev_children);

		cvd = vd->vdev_child[c];

		dprintf("%s: retrying i/o (err=%d) on child %s\n",

		    vdev_description(zio->io_vd), zio->io_error,

		    vdev_description(cvd));

		zio->io_error = 0;

		zio_vdev_io_redone(zio);

		zio_nowait(zio_vdev_child_io(zio, zio->io_bp, cvd,

		    zio->io_offset, zio->io_data, zio->io_size,

		    ZIO_TYPE_READ, zio->io_priority, ZIO_FLAG_CANFAIL,

		    vdev_mirror_child_done, &mm[c]));

		zio_wait_children_done(zio);

		return;

	}

	/* XXPOLICY */

	if (good_copies)

		zio->io_error = 0;

	else

		ASSERT(zio->io_error != 0);

	if (good_copies && (spa_mode & FWRITE) &&

	    (unexpected_errors || (zio->io_flags & ZIO_FLAG_RESILVER))) {

		/*

		 * Use the good data we have in hand to repair damaged children.

		 */

		for (c = 0; c < vd->vdev_children; c++) {

			/*

			 * Don't rewrite known good children.

			 * Not only is it unnecessary, it could

			 * actually be harmful: if the system lost

			 * power while rewriting the only good copy,

			 * there would be no good copies left!

			 */

			cvd = vd->vdev_child[c];

			if (mm[c].mm_error == 0) {

				if (mm[c].mm_tried)

					continue;

				if (!vdev_dtl_contains(&cvd->vdev_dtl_map,

				    zio->io_txg, 1))

					continue;

				mm[c].mm_error = ESTALE;

			}

			dprintf("%s resilvered %s @ 0x%llx error %d\n",

			    vdev_description(vd),

			    vdev_description(cvd),

			    zio->io_offset, mm[c].mm_error);

			zio_nowait(zio_vdev_child_io(zio, zio->io_bp, cvd,

			    zio->io_offset, zio->io_data, zio->io_size,

			    ZIO_TYPE_WRITE, zio->io_priority,

			    ZIO_FLAG_IO_REPAIR | ZIO_FLAG_CANFAIL |

			    ZIO_FLAG_DONT_PROPAGATE, NULL, NULL));

		}

	}

	vdev_mirror_map_free(zio);

	zio_next_stage(zio);

}

static void

vdev_mirror_state_change(vdev_t *vd, int faulted, int degraded)

{

	if (faulted == vd->vdev_children)

		vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,

		    VDEV_AUX_NO_REPLICAS);

	else if (degraded + faulted != 0)

		vdev_set_state(vd, B_FALSE, VDEV_STATE_DEGRADED, VDEV_AUX_NONE);

	else

		vdev_set_state(vd, B_FALSE, VDEV_STATE_HEALTHY, VDEV_AUX_NONE);

}

vdev_ops_t vdev_mirror_ops = {

	vdev_mirror_open,

	vdev_mirror_close,

	vdev_default_asize,

	vdev_mirror_io_start,

	vdev_mirror_io_done,

	vdev_mirror_state_change,

	VDEV_TYPE_MIRROR,	/* name of this vdev type */

	B_FALSE			/* not a leaf vdev */

};

vdev_ops_t vdev_replacing_ops = {

	vdev_mirror_open,

	vdev_mirror_close,

	vdev_default_asize,

	vdev_mirror_io_start,

	vdev_mirror_io_done,

	vdev_mirror_state_change,

	VDEV_TYPE_REPLACING,	/* name of this vdev type */

	B_FALSE			/* not a leaf vdev */

};