[mirror_zfs-debian.git] / module / zfs / vdev_mirror.c

/*
 * 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 2010 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#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_child {
	vdev_t		*mc_vd;
	uint64_t	mc_offset;
	int		mc_error;
	uint8_t		mc_tried;
	uint8_t		mc_skipped;
	uint8_t		mc_speculative;
} mirror_child_t;

typedef struct mirror_map {
	int		mm_children;
	int		mm_replacing;
	int		mm_preferred;
	int		mm_root;
	mirror_child_t	mm_child[1];
} mirror_map_t;

int vdev_mirror_shift = 21;

static void
vdev_mirror_map_free(zio_t *zio)
{
	mirror_map_t *mm = zio->io_vsd;

	kmem_free(mm, offsetof(mirror_map_t, mm_child[mm->mm_children]));
}

static const zio_vsd_ops_t vdev_mirror_vsd_ops = {
	vdev_mirror_map_free,
	zio_vsd_default_cksum_report
};

static mirror_map_t *
vdev_mirror_map_alloc(zio_t *zio)
{
	mirror_map_t *mm = NULL;
	mirror_child_t *mc;
	vdev_t *vd = zio->io_vd;
	int c, d;

	if (vd == NULL) {
		dva_t *dva = zio->io_bp->blk_dva;
		spa_t *spa = zio->io_spa;

		c = BP_GET_NDVAS(zio->io_bp);

		mm = kmem_zalloc(offsetof(mirror_map_t, mm_child[c]), KM_SLEEP);
		mm->mm_children = c;
		mm->mm_replacing = B_FALSE;
		mm->mm_preferred = spa_get_random(c);
		mm->mm_root = B_TRUE;

		/*
		 * Check the other, lower-index DVAs to see if they're on
		 * the same vdev as the child we picked.  If they are, use
		 * them since they are likely to have been allocated from
		 * the primary metaslab in use at the time, and hence are
		 * more likely to have locality with single-copy data.
		 */
		for (c = mm->mm_preferred, d = c - 1; d >= 0; d--) {
			if (DVA_GET_VDEV(&dva[d]) == DVA_GET_VDEV(&dva[c]))
				mm->mm_preferred = d;
		}

		for (c = 0; c < mm->mm_children; c++) {
			mc = &mm->mm_child[c];

			mc->mc_vd = vdev_lookup_top(spa, DVA_GET_VDEV(&dva[c]));
			mc->mc_offset = DVA_GET_OFFSET(&dva[c]);
		}
	} else {
		c = vd->vdev_children;

		mm = kmem_zalloc(offsetof(mirror_map_t, mm_child[c]), KM_SLEEP);
		mm->mm_children = c;
		mm->mm_replacing = (vd->vdev_ops == &vdev_replacing_ops ||
		    vd->vdev_ops == &vdev_spare_ops);
		mm->mm_preferred = mm->mm_replacing ? 0 :
		    (zio->io_offset >> vdev_mirror_shift) % c;
		mm->mm_root = B_FALSE;

		for (c = 0; c < mm->mm_children; c++) {
			mc = &mm->mm_child[c];
			mc->mc_vd = vd->vdev_child[c];
			mc->mc_offset = zio->io_offset;
		}
	}

	zio->io_vsd = mm;
	zio->io_vsd_ops = &vdev_mirror_vsd_ops;
	return (mm);
}

static int
vdev_mirror_open(vdev_t *vd, uint64_t *asize, uint64_t *ashift)
{
	int numerrors = 0;
	int lasterror = 0;

	if (vd->vdev_children == 0) {
		vd->vdev_stat.vs_aux = VDEV_AUX_BAD_LABEL;
		return (EINVAL);
	}

	vdev_open_children(vd);

	for (int c = 0; c < vd->vdev_children; c++) {
		vdev_t *cvd = vd->vdev_child[c];

		if (cvd->vdev_open_error) {
			lasterror = cvd->vdev_open_error;
			numerrors++;
			continue;
		}

		*asize = MIN(*asize - 1, cvd->vdev_asize - 1) + 1;
		*ashift = MAX(*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)
{
	for (int c = 0; c < vd->vdev_children; c++)
		vdev_close(vd->vdev_child[c]);
}

static void
vdev_mirror_child_done(zio_t *zio)
{
	mirror_child_t *mc = zio->io_private;

	mc->mc_error = zio->io_error;
	mc->mc_tried = 1;
	mc->mc_skipped = 0;
}

static void
vdev_mirror_scrub_done(zio_t *zio)
{
	mirror_child_t *mc = zio->io_private;

	if (zio->io_error == 0) {
		zio_t *pio;

		mutex_enter(&zio->io_lock);
		while ((pio = zio_walk_parents(zio)) != NULL) {
			mutex_enter(&pio->io_lock);
			ASSERT3U(zio->io_size, >=, pio->io_size);
			bcopy(zio->io_data, pio->io_data, pio->io_size);
			mutex_exit(&pio->io_lock);
		}
		mutex_exit(&zio->io_lock);
	}

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

	mc->mc_error = zio->io_error;
	mc->mc_tried = 1;
	mc->mc_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;
	mirror_child_t *mc;
	uint64_t txg = zio->io_txg;
	int i, c;

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

	/*
	 * 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_readable() returning B_FALSE), don't even try.
	 */
	for (i = 0, c = mm->mm_preferred; i < mm->mm_children; i++, c++) {
		if (c >= mm->mm_children)
			c = 0;
		mc = &mm->mm_child[c];
		if (mc->mc_tried || mc->mc_skipped)
			continue;
		if (!vdev_readable(mc->mc_vd)) {
			mc->mc_error = ENXIO;
			mc->mc_tried = 1;	/* don't even try */
			mc->mc_skipped = 1;
			continue;
		}
		if (!vdev_dtl_contains(mc->mc_vd, DTL_MISSING, txg, 1))
			return (c);
		mc->mc_error = ESTALE;
		mc->mc_skipped = 1;
		mc->mc_speculative = 1;
	}

	/*
	 * Every device is either missing or has this txg in its DTL.
	 * Look for any child we haven't already tried before giving up.
	 */
	for (c = 0; c < mm->mm_children; c++)
		if (!mm->mm_child[c].mc_tried)
			return (c);

	/*
	 * Every child failed.  There's no place left to look.
	 */
	return (-1);
}

static int
vdev_mirror_io_start(zio_t *zio)
{
	mirror_map_t *mm;
	mirror_child_t *mc;
	int c, children;

	mm = vdev_mirror_map_alloc(zio);

	if (zio->io_type == ZIO_TYPE_READ) {
		if ((zio->io_flags & ZIO_FLAG_SCRUB) && !mm->mm_replacing) {
			/*
			 * 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 < mm->mm_children; c++) {
				mc = &mm->mm_child[c];
				zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
				    mc->mc_vd, mc->mc_offset,
				    zio_buf_alloc(zio->io_size), zio->io_size,
				    zio->io_type, zio->io_priority, 0,
				    vdev_mirror_scrub_done, mc));
			}
			return (ZIO_PIPELINE_CONTINUE);
		}
		/*
		 * For normal reads just pick one child.
		 */
		c = vdev_mirror_child_select(zio);
		children = (c >= 0);
	} else {
		ASSERT(zio->io_type == ZIO_TYPE_WRITE);

		/*
		 * Writes go to all children.
		 */
		c = 0;
		children = mm->mm_children;
	}

	while (children--) {
		mc = &mm->mm_child[c];
		zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
		    mc->mc_vd, mc->mc_offset, zio->io_data, zio->io_size,
		    zio->io_type, zio->io_priority, 0,
		    vdev_mirror_child_done, mc));
		c++;
	}

	return (ZIO_PIPELINE_CONTINUE);
}

static int
vdev_mirror_worst_error(mirror_map_t *mm)
{
	int error[2] = { 0, 0 };

	for (int c = 0; c < mm->mm_children; c++) {
		mirror_child_t *mc = &mm->mm_child[c];
		int s = mc->mc_speculative;
		error[s] = zio_worst_error(error[s], mc->mc_error);
	}

	return (error[0] ? error[0] : error[1]);
}

static void
vdev_mirror_io_done(zio_t *zio)
{
	mirror_map_t *mm = zio->io_vsd;
	mirror_child_t *mc;
	int c;
	int good_copies = 0;
	int unexpected_errors = 0;

	for (c = 0; c < mm->mm_children; c++) {
		mc = &mm->mm_child[c];

		if (mc->mc_error) {
			if (!mc->mc_skipped)
				unexpected_errors++;
		} else if (mc->mc_tried) {
			good_copies++;
		}
	}

	if (zio->io_type == ZIO_TYPE_WRITE) {
		/*
		 * XXX -- for now, treat partial writes as success.
		 *
		 * Now that we support write reallocation, it would be better
		 * to treat partial failure as real failure unless there are
		 * no non-degraded top-level vdevs left, and not update DTLs
		 * if we intend to reallocate.
		 */
		/* XXPOLICY */
		if (good_copies != mm->mm_children) {
			/*
			 * Always require at least one good copy.
			 *
			 * For ditto blocks (io_vd == NULL), require
			 * all copies to be good.
			 *
			 * XXX -- for replacing vdevs, there's no great answer.
			 * If the old device is really dead, we may not even
			 * be able to access it -- so we only want to
			 * require good writes to the new device.  But if
			 * the new device turns out to be flaky, we want
			 * to be able to detach it -- which requires all
			 * writes to the old device to have succeeded.
			 */
			if (good_copies == 0 || zio->io_vd == NULL)
				zio->io_error = vdev_mirror_worst_error(mm);
		}
		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 < mm->mm_children);
		mc = &mm->mm_child[c];
		zio_vdev_io_redone(zio);
		zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
		    mc->mc_vd, mc->mc_offset, zio->io_data, zio->io_size,
		    ZIO_TYPE_READ, zio->io_priority, 0,
		    vdev_mirror_child_done, mc));
		return;
	}

	/* XXPOLICY */
	if (good_copies == 0) {
		zio->io_error = vdev_mirror_worst_error(mm);
		ASSERT(zio->io_error != 0);
	}

	if (good_copies && spa_writeable(zio->io_spa) &&
	    (unexpected_errors ||
	    (zio->io_flags & ZIO_FLAG_RESILVER) ||
	    ((zio->io_flags & ZIO_FLAG_SCRUB) && mm->mm_replacing))) {
		/*
		 * Use the good data we have in hand to repair damaged children.
		 */
		for (c = 0; c < mm->mm_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!
			 */
			mc = &mm->mm_child[c];

			if (mc->mc_error == 0) {
				if (mc->mc_tried)
					continue;
				if (!(zio->io_flags & ZIO_FLAG_SCRUB) &&
				    !vdev_dtl_contains(mc->mc_vd, DTL_PARTIAL,
				    zio->io_txg, 1))
					continue;
				mc->mc_error = ESTALE;
			}

			zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
			    mc->mc_vd, mc->mc_offset,
			    zio->io_data, zio->io_size,
			    ZIO_TYPE_WRITE, zio->io_priority,
			    ZIO_FLAG_IO_REPAIR | (unexpected_errors ?
			    ZIO_FLAG_SELF_HEAL : 0), NULL, NULL));
		}
	}
}

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,
	NULL,
	NULL,
	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,
	NULL,
	NULL,
	VDEV_TYPE_REPLACING,	/* name of this vdev type */
	B_FALSE			/* not a leaf vdev */
};

vdev_ops_t vdev_spare_ops = {
	vdev_mirror_open,
	vdev_mirror_close,
	vdev_default_asize,
	vdev_mirror_io_start,
	vdev_mirror_io_done,
	vdev_mirror_state_change,
	NULL,
	NULL,
	VDEV_TYPE_SPARE,	/* name of this vdev type */
	B_FALSE			/* not a leaf vdev */
};
Commit	Line	Data
34dc7c2f BB	1	/*
	2	* CDDL HEADER START
	3	*
	4	* The contents of this file are subject to the terms of the
	5	* Common Development and Distribution License (the "License").
	6	* You may not use this file except in compliance with the License.
	7	*
	8	* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
	9	* or http://www.opensolaris.org/os/licensing.
	10	* See the License for the specific language governing permissions
	11	* and limitations under the License.
	12	*
	13	* When distributing Covered Code, include this CDDL HEADER in each
	14	* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
	15	* If applicable, add the following below this CDDL HEADER, with the
	16	* fields enclosed by brackets "[]" replaced with your own identifying
	17	* information: Portions Copyright [yyyy] [name of copyright owner]
	18	*
	19	* CDDL HEADER END
	20	*/
	21	/*
428870ff	22	* Copyright 2010 Sun Microsystems, Inc. All rights reserved.
34dc7c2f BB	23	* Use is subject to license terms.
	24	*/
	25
34dc7c2f BB	26	#include <sys/zfs_context.h>
	27	#include <sys/spa.h>
	28	#include <sys/vdev_impl.h>
	29	#include <sys/zio.h>
	30	#include <sys/fs/zfs.h>
	31
	32	/*
	33	* Virtual device vector for mirroring.
	34	*/
	35
	36	typedef struct mirror_child {
	37	vdev_t *mc_vd;
	38	uint64_t mc_offset;
	39	int mc_error;
b128c09f BB	40	uint8_t mc_tried;
	41	uint8_t mc_skipped;
	42	uint8_t mc_speculative;
34dc7c2f BB	43	} mirror_child_t;
	44
	45	typedef struct mirror_map {
	46	int mm_children;
	47	int mm_replacing;
	48	int mm_preferred;
	49	int mm_root;
	50	mirror_child_t mm_child[1];
	51	} mirror_map_t;
	52
	53	int vdev_mirror_shift = 21;
	54
b128c09f BB	55	static void
	56	vdev_mirror_map_free(zio_t *zio)
	57	{
	58	mirror_map_t *mm = zio->io_vsd;
	59
	60	kmem_free(mm, offsetof(mirror_map_t, mm_child[mm->mm_children]));
	61	}
	62
428870ff BB	63	static const zio_vsd_ops_t vdev_mirror_vsd_ops = {
	64	vdev_mirror_map_free,
	65	zio_vsd_default_cksum_report
	66	};
	67
34dc7c2f BB	68	static mirror_map_t *
	69	vdev_mirror_map_alloc(zio_t *zio)
	70	{
	71	mirror_map_t *mm = NULL;
	72	mirror_child_t *mc;
	73	vdev_t *vd = zio->io_vd;
	74	int c, d;
	75
	76	if (vd == NULL) {
	77	dva_t *dva = zio->io_bp->blk_dva;
	78	spa_t *spa = zio->io_spa;
	79
	80	c = BP_GET_NDVAS(zio->io_bp);
	81
	82	mm = kmem_zalloc(offsetof(mirror_map_t, mm_child[c]), KM_SLEEP);
	83	mm->mm_children = c;
	84	mm->mm_replacing = B_FALSE;
	85	mm->mm_preferred = spa_get_random(c);
	86	mm->mm_root = B_TRUE;
	87
	88	/*
	89	* Check the other, lower-index DVAs to see if they're on
	90	* the same vdev as the child we picked. If they are, use
	91	* them since they are likely to have been allocated from
	92	* the primary metaslab in use at the time, and hence are
	93	* more likely to have locality with single-copy data.
	94	*/
	95	for (c = mm->mm_preferred, d = c - 1; d >= 0; d--) {
	96	if (DVA_GET_VDEV(&dva[d]) == DVA_GET_VDEV(&dva[c]))
	97	mm->mm_preferred = d;
	98	}
	99
	100	for (c = 0; c < mm->mm_children; c++) {
	101	mc = &mm->mm_child[c];
	102
	103	mc->mc_vd = vdev_lookup_top(spa, DVA_GET_VDEV(&dva[c]));
	104	mc->mc_offset = DVA_GET_OFFSET(&dva[c]);
	105	}
	106	} else {
	107	c = vd->vdev_children;
	108
	109	mm = kmem_zalloc(offsetof(mirror_map_t, mm_child[c]), KM_SLEEP);
	110	mm->mm_children = c;
	111	mm->mm_replacing = (vd->vdev_ops == &vdev_replacing_ops \|\|
	112	vd->vdev_ops == &vdev_spare_ops);
	113	mm->mm_preferred = mm->mm_replacing ? 0 :
	114	(zio->io_offset >> vdev_mirror_shift) % c;
	115	mm->mm_root = B_FALSE;
	116
	117	for (c = 0; c < mm->mm_children; c++) {
	118	mc = &mm->mm_child[c];
	119	mc->mc_vd = vd->vdev_child[c];
	120	mc->mc_offset = zio->io_offset;
	121	}
	122	}
	123
	124	zio->io_vsd = mm;
428870ff	125	zio->io_vsd_ops = &vdev_mirror_vsd_ops;
34dc7c2f BB	126	return (mm);
	127	}
	128
34dc7c2f BB	129	static int
	130	vdev_mirror_open(vdev_t vd, uint64_t asize, uint64_t *ashift)
	131	{
34dc7c2f	132	int numerrors = 0;
45d1cae3	133	int lasterror = 0;
34dc7c2f BB	134
	135	if (vd->vdev_children == 0) {
	136	vd->vdev_stat.vs_aux = VDEV_AUX_BAD_LABEL;
	137	return (EINVAL);
	138	}
	139
45d1cae3	140	vdev_open_children(vd);
34dc7c2f	141
45d1cae3 BB	142	for (int c = 0; c < vd->vdev_children; c++) {
	143	vdev_t *cvd = vd->vdev_child[c];
	144
	145	if (cvd->vdev_open_error) {
	146	lasterror = cvd->vdev_open_error;
34dc7c2f BB	147	numerrors++;
	148	continue;
	149	}
	150
	151	asize = MIN(asize - 1, cvd->vdev_asize - 1) + 1;
	152	ashift = MAX(ashift, cvd->vdev_ashift);
	153	}
	154
	155	if (numerrors == vd->vdev_children) {
	156	vd->vdev_stat.vs_aux = VDEV_AUX_NO_REPLICAS;
	157	return (lasterror);
	158	}
	159
	160	return (0);
	161	}
	162
	163	static void
	164	vdev_mirror_close(vdev_t *vd)
	165	{
45d1cae3	166	for (int c = 0; c < vd->vdev_children; c++)
34dc7c2f BB	167	vdev_close(vd->vdev_child[c]);
	168	}
	169
	170	static void
	171	vdev_mirror_child_done(zio_t *zio)
	172	{
	173	mirror_child_t *mc = zio->io_private;
	174
	175	mc->mc_error = zio->io_error;
	176	mc->mc_tried = 1;
	177	mc->mc_skipped = 0;
	178	}
	179
	180	static void
	181	vdev_mirror_scrub_done(zio_t *zio)
	182	{
	183	mirror_child_t *mc = zio->io_private;
	184
	185	if (zio->io_error == 0) {
d164b209 BB	186	zio_t *pio;
	187
	188	mutex_enter(&zio->io_lock);
	189	while ((pio = zio_walk_parents(zio)) != NULL) {
	190	mutex_enter(&pio->io_lock);
	191	ASSERT3U(zio->io_size, >=, pio->io_size);
	192	bcopy(zio->io_data, pio->io_data, pio->io_size);
	193	mutex_exit(&pio->io_lock);
	194	}
	195	mutex_exit(&zio->io_lock);
34dc7c2f BB	196	}
	197
	198	zio_buf_free(zio->io_data, zio->io_size);
	199
	200	mc->mc_error = zio->io_error;
	201	mc->mc_tried = 1;
	202	mc->mc_skipped = 0;
	203	}
	204
34dc7c2f BB	205	/*
	206	* Try to find a child whose DTL doesn't contain the block we want to read.
	207	* If we can't, try the read on any vdev we haven't already tried.
	208	*/
	209	static int
	210	vdev_mirror_child_select(zio_t *zio)
	211	{
	212	mirror_map_t *mm = zio->io_vsd;
	213	mirror_child_t *mc;
	214	uint64_t txg = zio->io_txg;
	215	int i, c;
	216
428870ff	217	ASSERT(zio->io_bp == NULL \|\| BP_PHYSICAL_BIRTH(zio->io_bp) == txg);
34dc7c2f BB	218
	219	/*
	220	* Try to find a child whose DTL doesn't contain the block to read.
	221	* If a child is known to be completely inaccessible (indicated by
	222	* vdev_readable() returning B_FALSE), don't even try.
	223	*/
	224	for (i = 0, c = mm->mm_preferred; i < mm->mm_children; i++, c++) {
	225	if (c >= mm->mm_children)
	226	c = 0;
	227	mc = &mm->mm_child[c];
	228	if (mc->mc_tried \|\| mc->mc_skipped)
	229	continue;
b128c09f	230	if (!vdev_readable(mc->mc_vd)) {
34dc7c2f BB	231	mc->mc_error = ENXIO;
	232	mc->mc_tried = 1; /* don't even try */
	233	mc->mc_skipped = 1;
	234	continue;
	235	}
fb5f0bc8	236	if (!vdev_dtl_contains(mc->mc_vd, DTL_MISSING, txg, 1))
34dc7c2f BB	237	return (c);
	238	mc->mc_error = ESTALE;
	239	mc->mc_skipped = 1;
b128c09f	240	mc->mc_speculative = 1;
34dc7c2f BB	241	}
	242
	243	/*
	244	* Every device is either missing or has this txg in its DTL.
	245	* Look for any child we haven't already tried before giving up.
	246	*/
	247	for (c = 0; c < mm->mm_children; c++)
	248	if (!mm->mm_child[c].mc_tried)
	249	return (c);
	250
	251	/*
	252	* Every child failed. There's no place left to look.
	253	*/
	254	return (-1);
	255	}
	256
	257	static int
	258	vdev_mirror_io_start(zio_t *zio)
	259	{
	260	mirror_map_t *mm;
	261	mirror_child_t *mc;
	262	int c, children;
	263
	264	mm = vdev_mirror_map_alloc(zio);
	265
	266	if (zio->io_type == ZIO_TYPE_READ) {
	267	if ((zio->io_flags & ZIO_FLAG_SCRUB) && !mm->mm_replacing) {
	268	/*
	269	* For scrubbing reads we need to allocate a read
	270	* buffer for each child and issue reads to all
	271	* children. If any child succeeds, it will copy its
	272	* data into zio->io_data in vdev_mirror_scrub_done.
	273	*/
	274	for (c = 0; c < mm->mm_children; c++) {
	275	mc = &mm->mm_child[c];
	276	zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
	277	mc->mc_vd, mc->mc_offset,
	278	zio_buf_alloc(zio->io_size), zio->io_size,
b128c09f	279	zio->io_type, zio->io_priority, 0,
34dc7c2f BB	280	vdev_mirror_scrub_done, mc));
34dc7c2f BB	281	}
b128c09f	282	return (ZIO_PIPELINE_CONTINUE);
34dc7c2f BB	283	}
	284	/*
	285	* For normal reads just pick one child.
	286	*/
	287	c = vdev_mirror_child_select(zio);
	288	children = (c >= 0);
	289	} else {
	290	ASSERT(zio->io_type == ZIO_TYPE_WRITE);
	291
	292	/*
fb5f0bc8	293	* Writes go to all children.
34dc7c2f	294	*/
fb5f0bc8 BB	295	c = 0;
fb5f0bc8 BB	296	children = mm->mm_children;
34dc7c2f BB	297	}
	298
	299	while (children--) {
	300	mc = &mm->mm_child[c];
	301	zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
b128c09f BB	302	mc->mc_vd, mc->mc_offset, zio->io_data, zio->io_size,
	303	zio->io_type, zio->io_priority, 0,
	304	vdev_mirror_child_done, mc));
34dc7c2f BB	305	c++;
	306	}
	307
b128c09f	308	return (ZIO_PIPELINE_CONTINUE);
34dc7c2f BB	309	}
	310
	311	static int
b128c09f BB	312	vdev_mirror_worst_error(mirror_map_t *mm)
	313	{
	314	int error[2] = { 0, 0 };
	315
	316	for (int c = 0; c < mm->mm_children; c++) {
	317	mirror_child_t *mc = &mm->mm_child[c];
	318	int s = mc->mc_speculative;
	319	error[s] = zio_worst_error(error[s], mc->mc_error);
	320	}
	321
	322	return (error[0] ? error[0] : error[1]);
	323	}
	324
	325	static void
34dc7c2f BB	326	vdev_mirror_io_done(zio_t *zio)
	327	{
	328	mirror_map_t *mm = zio->io_vsd;
	329	mirror_child_t *mc;
	330	int c;
	331	int good_copies = 0;
	332	int unexpected_errors = 0;
	333
34dc7c2f BB	334	for (c = 0; c < mm->mm_children; c++) {
	335	mc = &mm->mm_child[c];
	336
34dc7c2f	337	if (mc->mc_error) {
34dc7c2f BB	338	if (!mc->mc_skipped)
34dc7c2f BB	339	unexpected_errors++;
b128c09f BB	340	} else if (mc->mc_tried) {
b128c09f BB	341	good_copies++;
34dc7c2f BB	342	}
	343	}
	344
	345	if (zio->io_type == ZIO_TYPE_WRITE) {
	346	/*
	347	* XXX -- for now, treat partial writes as success.
b128c09f BB	348	*
	349	* Now that we support write reallocation, it would be better
	350	* to treat partial failure as real failure unless there are
	351	* no non-degraded top-level vdevs left, and not update DTLs
	352	* if we intend to reallocate.
34dc7c2f BB	353	*/
34dc7c2f BB	354	/* XXPOLICY */
b128c09f BB	355	if (good_copies != mm->mm_children) {
	356	/*
	357	* Always require at least one good copy.
	358	*
	359	* For ditto blocks (io_vd == NULL), require
	360	* all copies to be good.
	361	*
	362	* XXX -- for replacing vdevs, there's no great answer.
	363	* If the old device is really dead, we may not even
	364	* be able to access it -- so we only want to
	365	* require good writes to the new device. But if
	366	* the new device turns out to be flaky, we want
	367	* to be able to detach it -- which requires all
	368	* writes to the old device to have succeeded.
	369	*/
	370	if (good_copies == 0 \|\| zio->io_vd == NULL)
	371	zio->io_error = vdev_mirror_worst_error(mm);
	372	}
	373	return;
34dc7c2f BB	374	}
	375
	376	ASSERT(zio->io_type == ZIO_TYPE_READ);
	377
	378	/*
	379	* If we don't have a good copy yet, keep trying other children.
	380	*/
	381	/* XXPOLICY */
	382	if (good_copies == 0 && (c = vdev_mirror_child_select(zio)) != -1) {
	383	ASSERT(c >= 0 && c < mm->mm_children);
	384	mc = &mm->mm_child[c];
34dc7c2f BB	385	zio_vdev_io_redone(zio);
	386	zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
	387	mc->mc_vd, mc->mc_offset, zio->io_data, zio->io_size,
b128c09f	388	ZIO_TYPE_READ, zio->io_priority, 0,
34dc7c2f	389	vdev_mirror_child_done, mc));
b128c09f	390	return;
34dc7c2f BB	391	}
	392
	393	/* XXPOLICY */
b128c09f BB	394	if (good_copies == 0) {
b128c09f BB	395	zio->io_error = vdev_mirror_worst_error(mm);
34dc7c2f	396	ASSERT(zio->io_error != 0);
b128c09f	397	}
34dc7c2f	398
fb5f0bc8	399	if (good_copies && spa_writeable(zio->io_spa) &&
34dc7c2f BB	400	(unexpected_errors \|\|
	401	(zio->io_flags & ZIO_FLAG_RESILVER) \|\|
	402	((zio->io_flags & ZIO_FLAG_SCRUB) && mm->mm_replacing))) {
34dc7c2f BB	403	/*
34dc7c2f BB	404	* Use the good data we have in hand to repair damaged children.
34dc7c2f	405	*/
34dc7c2f BB	406	for (c = 0; c < mm->mm_children; c++) {
	407	/*
	408	* Don't rewrite known good children.
	409	* Not only is it unnecessary, it could
	410	* actually be harmful: if the system lost
	411	* power while rewriting the only good copy,
	412	* there would be no good copies left!
	413	*/
	414	mc = &mm->mm_child[c];
	415
	416	if (mc->mc_error == 0) {
	417	if (mc->mc_tried)
	418	continue;
	419	if (!(zio->io_flags & ZIO_FLAG_SCRUB) &&
fb5f0bc8	420	!vdev_dtl_contains(mc->mc_vd, DTL_PARTIAL,
34dc7c2f BB	421	zio->io_txg, 1))
	422	continue;
	423	mc->mc_error = ESTALE;
	424	}
	425
b128c09f BB	426	zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
	427	mc->mc_vd, mc->mc_offset,
	428	zio->io_data, zio->io_size,
34dc7c2f	429	ZIO_TYPE_WRITE, zio->io_priority,
fb5f0bc8 BB	430	ZIO_FLAG_IO_REPAIR \| (unexpected_errors ?
fb5f0bc8 BB	431	ZIO_FLAG_SELF_HEAL : 0), NULL, NULL));
34dc7c2f	432	}
34dc7c2f	433	}
34dc7c2f BB	434	}
	435
	436	static void
	437	vdev_mirror_state_change(vdev_t *vd, int faulted, int degraded)
	438	{
	439	if (faulted == vd->vdev_children)
	440	vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
	441	VDEV_AUX_NO_REPLICAS);
	442	else if (degraded + faulted != 0)
	443	vdev_set_state(vd, B_FALSE, VDEV_STATE_DEGRADED, VDEV_AUX_NONE);
	444	else
	445	vdev_set_state(vd, B_FALSE, VDEV_STATE_HEALTHY, VDEV_AUX_NONE);
	446	}
	447
	448	vdev_ops_t vdev_mirror_ops = {
	449	vdev_mirror_open,
	450	vdev_mirror_close,
34dc7c2f BB	451	vdev_default_asize,
	452	vdev_mirror_io_start,
	453	vdev_mirror_io_done,
	454	vdev_mirror_state_change,
428870ff BB	455	NULL,
428870ff BB	456	NULL,
34dc7c2f BB	457	VDEV_TYPE_MIRROR, /* name of this vdev type */
	458	B_FALSE /* not a leaf vdev */
	459	};
	460
	461	vdev_ops_t vdev_replacing_ops = {
	462	vdev_mirror_open,
	463	vdev_mirror_close,
34dc7c2f BB	464	vdev_default_asize,
	465	vdev_mirror_io_start,
	466	vdev_mirror_io_done,
	467	vdev_mirror_state_change,
428870ff BB	468	NULL,
428870ff BB	469	NULL,
34dc7c2f BB	470	VDEV_TYPE_REPLACING, /* name of this vdev type */
	471	B_FALSE /* not a leaf vdev */
	472	};
	473
	474	vdev_ops_t vdev_spare_ops = {
	475	vdev_mirror_open,
	476	vdev_mirror_close,
34dc7c2f BB	477	vdev_default_asize,
	478	vdev_mirror_io_start,
	479	vdev_mirror_io_done,
	480	vdev_mirror_state_change,
428870ff BB	481	NULL,
428870ff BB	482	NULL,
34dc7c2f BB	483	VDEV_TYPE_SPARE, /* name of this vdev type */
	484	B_FALSE /* not a leaf vdev */
	485	};