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zfs/module/zfs/vdev_raidz.c

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/*
* 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 2008 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/zio_checksum.h>
#include <sys/fs/zfs.h>
#include <sys/fm/fs/zfs.h>
/*
* Virtual device vector for RAID-Z.
*
* This vdev supports both single and double parity. For single parity, we
* use a simple XOR of all the data columns. For double parity, we use both
* the simple XOR as well as a technique described in "The mathematics of
* RAID-6" by H. Peter Anvin. This technique defines a Galois field, GF(2^8),
* over the integers expressable in a single byte. Briefly, the operations on
* the field are defined as follows:
*
* o addition (+) is represented by a bitwise XOR
* o subtraction (-) is therefore identical to addition: A + B = A - B
* o multiplication of A by 2 is defined by the following bitwise expression:
* (A * 2)_7 = A_6
* (A * 2)_6 = A_5
* (A * 2)_5 = A_4
* (A * 2)_4 = A_3 + A_7
* (A * 2)_3 = A_2 + A_7
* (A * 2)_2 = A_1 + A_7
* (A * 2)_1 = A_0
* (A * 2)_0 = A_7
*
* In C, multiplying by 2 is therefore ((a << 1) ^ ((a & 0x80) ? 0x1d : 0)).
*
* Observe that any number in the field (except for 0) can be expressed as a
* power of 2 -- a generator for the field. We store a table of the powers of
* 2 and logs base 2 for quick look ups, and exploit the fact that A * B can
* be rewritten as 2^(log_2(A) + log_2(B)) (where '+' is normal addition rather
* than field addition). The inverse of a field element A (A^-1) is A^254.
*
* The two parity columns, P and Q, over several data columns, D_0, ... D_n-1,
* can be expressed by field operations:
*
* P = D_0 + D_1 + ... + D_n-2 + D_n-1
* Q = 2^n-1 * D_0 + 2^n-2 * D_1 + ... + 2^1 * D_n-2 + 2^0 * D_n-1
* = ((...((D_0) * 2 + D_1) * 2 + ...) * 2 + D_n-2) * 2 + D_n-1
*
* See the reconstruction code below for how P and Q can used individually or
* in concert to recover missing data columns.
*/
typedef struct raidz_col {
uint64_t rc_devidx; /* child device index for I/O */
uint64_t rc_offset; /* device offset */
uint64_t rc_size; /* I/O size */
void *rc_data; /* I/O data */
int rc_error; /* I/O error for this device */
uint8_t rc_tried; /* Did we attempt this I/O column? */
uint8_t rc_skipped; /* Did we skip this I/O column? */
} raidz_col_t;
typedef struct raidz_map {
uint64_t rm_cols; /* Column count */
uint64_t rm_bigcols; /* Number of oversized columns */
uint64_t rm_asize; /* Actual total I/O size */
uint64_t rm_missingdata; /* Count of missing data devices */
uint64_t rm_missingparity; /* Count of missing parity devices */
uint64_t rm_firstdatacol; /* First data column/parity count */
raidz_col_t rm_col[1]; /* Flexible array of I/O columns */
} raidz_map_t;
#define VDEV_RAIDZ_P 0
#define VDEV_RAIDZ_Q 1
#define VDEV_RAIDZ_MAXPARITY 2
#define VDEV_RAIDZ_MUL_2(a) (((a) << 1) ^ (((a) & 0x80) ? 0x1d : 0))
/*
* These two tables represent powers and logs of 2 in the Galois field defined
* above. These values were computed by repeatedly multiplying by 2 as above.
*/
static const uint8_t vdev_raidz_pow2[256] = {
0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80,
0x1d, 0x3a, 0x74, 0xe8, 0xcd, 0x87, 0x13, 0x26,
0x4c, 0x98, 0x2d, 0x5a, 0xb4, 0x75, 0xea, 0xc9,
0x8f, 0x03, 0x06, 0x0c, 0x18, 0x30, 0x60, 0xc0,
0x9d, 0x27, 0x4e, 0x9c, 0x25, 0x4a, 0x94, 0x35,
0x6a, 0xd4, 0xb5, 0x77, 0xee, 0xc1, 0x9f, 0x23,
0x46, 0x8c, 0x05, 0x0a, 0x14, 0x28, 0x50, 0xa0,
0x5d, 0xba, 0x69, 0xd2, 0xb9, 0x6f, 0xde, 0xa1,
0x5f, 0xbe, 0x61, 0xc2, 0x99, 0x2f, 0x5e, 0xbc,
0x65, 0xca, 0x89, 0x0f, 0x1e, 0x3c, 0x78, 0xf0,
0xfd, 0xe7, 0xd3, 0xbb, 0x6b, 0xd6, 0xb1, 0x7f,
0xfe, 0xe1, 0xdf, 0xa3, 0x5b, 0xb6, 0x71, 0xe2,
0xd9, 0xaf, 0x43, 0x86, 0x11, 0x22, 0x44, 0x88,
0x0d, 0x1a, 0x34, 0x68, 0xd0, 0xbd, 0x67, 0xce,
0x81, 0x1f, 0x3e, 0x7c, 0xf8, 0xed, 0xc7, 0x93,
0x3b, 0x76, 0xec, 0xc5, 0x97, 0x33, 0x66, 0xcc,
0x85, 0x17, 0x2e, 0x5c, 0xb8, 0x6d, 0xda, 0xa9,
0x4f, 0x9e, 0x21, 0x42, 0x84, 0x15, 0x2a, 0x54,
0xa8, 0x4d, 0x9a, 0x29, 0x52, 0xa4, 0x55, 0xaa,
0x49, 0x92, 0x39, 0x72, 0xe4, 0xd5, 0xb7, 0x73,
0xe6, 0xd1, 0xbf, 0x63, 0xc6, 0x91, 0x3f, 0x7e,
0xfc, 0xe5, 0xd7, 0xb3, 0x7b, 0xf6, 0xf1, 0xff,
0xe3, 0xdb, 0xab, 0x4b, 0x96, 0x31, 0x62, 0xc4,
0x95, 0x37, 0x6e, 0xdc, 0xa5, 0x57, 0xae, 0x41,
0x82, 0x19, 0x32, 0x64, 0xc8, 0x8d, 0x07, 0x0e,
0x1c, 0x38, 0x70, 0xe0, 0xdd, 0xa7, 0x53, 0xa6,
0x51, 0xa2, 0x59, 0xb2, 0x79, 0xf2, 0xf9, 0xef,
0xc3, 0x9b, 0x2b, 0x56, 0xac, 0x45, 0x8a, 0x09,
0x12, 0x24, 0x48, 0x90, 0x3d, 0x7a, 0xf4, 0xf5,
0xf7, 0xf3, 0xfb, 0xeb, 0xcb, 0x8b, 0x0b, 0x16,
0x2c, 0x58, 0xb0, 0x7d, 0xfa, 0xe9, 0xcf, 0x83,
0x1b, 0x36, 0x6c, 0xd8, 0xad, 0x47, 0x8e, 0x01
};
static const uint8_t vdev_raidz_log2[256] = {
0x00, 0x00, 0x01, 0x19, 0x02, 0x32, 0x1a, 0xc6,
0x03, 0xdf, 0x33, 0xee, 0x1b, 0x68, 0xc7, 0x4b,
0x04, 0x64, 0xe0, 0x0e, 0x34, 0x8d, 0xef, 0x81,
0x1c, 0xc1, 0x69, 0xf8, 0xc8, 0x08, 0x4c, 0x71,
0x05, 0x8a, 0x65, 0x2f, 0xe1, 0x24, 0x0f, 0x21,
0x35, 0x93, 0x8e, 0xda, 0xf0, 0x12, 0x82, 0x45,
0x1d, 0xb5, 0xc2, 0x7d, 0x6a, 0x27, 0xf9, 0xb9,
0xc9, 0x9a, 0x09, 0x78, 0x4d, 0xe4, 0x72, 0xa6,
0x06, 0xbf, 0x8b, 0x62, 0x66, 0xdd, 0x30, 0xfd,
0xe2, 0x98, 0x25, 0xb3, 0x10, 0x91, 0x22, 0x88,
0x36, 0xd0, 0x94, 0xce, 0x8f, 0x96, 0xdb, 0xbd,
0xf1, 0xd2, 0x13, 0x5c, 0x83, 0x38, 0x46, 0x40,
0x1e, 0x42, 0xb6, 0xa3, 0xc3, 0x48, 0x7e, 0x6e,
0x6b, 0x3a, 0x28, 0x54, 0xfa, 0x85, 0xba, 0x3d,
0xca, 0x5e, 0x9b, 0x9f, 0x0a, 0x15, 0x79, 0x2b,
0x4e, 0xd4, 0xe5, 0xac, 0x73, 0xf3, 0xa7, 0x57,
0x07, 0x70, 0xc0, 0xf7, 0x8c, 0x80, 0x63, 0x0d,
0x67, 0x4a, 0xde, 0xed, 0x31, 0xc5, 0xfe, 0x18,
0xe3, 0xa5, 0x99, 0x77, 0x26, 0xb8, 0xb4, 0x7c,
0x11, 0x44, 0x92, 0xd9, 0x23, 0x20, 0x89, 0x2e,
0x37, 0x3f, 0xd1, 0x5b, 0x95, 0xbc, 0xcf, 0xcd,
0x90, 0x87, 0x97, 0xb2, 0xdc, 0xfc, 0xbe, 0x61,
0xf2, 0x56, 0xd3, 0xab, 0x14, 0x2a, 0x5d, 0x9e,
0x84, 0x3c, 0x39, 0x53, 0x47, 0x6d, 0x41, 0xa2,
0x1f, 0x2d, 0x43, 0xd8, 0xb7, 0x7b, 0xa4, 0x76,
0xc4, 0x17, 0x49, 0xec, 0x7f, 0x0c, 0x6f, 0xf6,
0x6c, 0xa1, 0x3b, 0x52, 0x29, 0x9d, 0x55, 0xaa,
0xfb, 0x60, 0x86, 0xb1, 0xbb, 0xcc, 0x3e, 0x5a,
0xcb, 0x59, 0x5f, 0xb0, 0x9c, 0xa9, 0xa0, 0x51,
0x0b, 0xf5, 0x16, 0xeb, 0x7a, 0x75, 0x2c, 0xd7,
0x4f, 0xae, 0xd5, 0xe9, 0xe6, 0xe7, 0xad, 0xe8,
0x74, 0xd6, 0xf4, 0xea, 0xa8, 0x50, 0x58, 0xaf,
};
/*
* Multiply a given number by 2 raised to the given power.
*/
static uint8_t
vdev_raidz_exp2(uint_t a, int exp)
{
if (a == 0)
return (0);
ASSERT(exp >= 0);
ASSERT(vdev_raidz_log2[a] > 0 || a == 1);
exp += vdev_raidz_log2[a];
if (exp > 255)
exp -= 255;
return (vdev_raidz_pow2[exp]);
}
static void
vdev_raidz_map_free(zio_t *zio)
{
raidz_map_t *rm = zio->io_vsd;
int c;
for (c = 0; c < rm->rm_firstdatacol; c++)
zio_buf_free(rm->rm_col[c].rc_data, rm->rm_col[c].rc_size);
kmem_free(rm, offsetof(raidz_map_t, rm_col[rm->rm_cols]));
}
static raidz_map_t *
vdev_raidz_map_alloc(zio_t *zio, uint64_t unit_shift, uint64_t dcols,
uint64_t nparity)
{
raidz_map_t *rm;
uint64_t b = zio->io_offset >> unit_shift;
uint64_t s = zio->io_size >> unit_shift;
uint64_t f = b % dcols;
uint64_t o = (b / dcols) << unit_shift;
uint64_t q, r, c, bc, col, acols, coff, devidx;
q = s / (dcols - nparity);
r = s - q * (dcols - nparity);
bc = (r == 0 ? 0 : r + nparity);
acols = (q == 0 ? bc : dcols);
rm = kmem_alloc(offsetof(raidz_map_t, rm_col[acols]), KM_SLEEP);
rm->rm_cols = acols;
rm->rm_bigcols = bc;
rm->rm_asize = 0;
rm->rm_missingdata = 0;
rm->rm_missingparity = 0;
rm->rm_firstdatacol = nparity;
for (c = 0; c < acols; c++) {
col = f + c;
coff = o;
if (col >= dcols) {
col -= dcols;
coff += 1ULL << unit_shift;
}
rm->rm_col[c].rc_devidx = col;
rm->rm_col[c].rc_offset = coff;
rm->rm_col[c].rc_size = (q + (c < bc)) << unit_shift;
rm->rm_col[c].rc_data = NULL;
rm->rm_col[c].rc_error = 0;
rm->rm_col[c].rc_tried = 0;
rm->rm_col[c].rc_skipped = 0;
rm->rm_asize += rm->rm_col[c].rc_size;
}
rm->rm_asize = roundup(rm->rm_asize, (nparity + 1) << unit_shift);
for (c = 0; c < rm->rm_firstdatacol; c++)
rm->rm_col[c].rc_data = zio_buf_alloc(rm->rm_col[c].rc_size);
rm->rm_col[c].rc_data = zio->io_data;
for (c = c + 1; c < acols; c++)
rm->rm_col[c].rc_data = (char *)rm->rm_col[c - 1].rc_data +
rm->rm_col[c - 1].rc_size;
/*
* If all data stored spans all columns, there's a danger that parity
* will always be on the same device and, since parity isn't read
* during normal operation, that that device's I/O bandwidth won't be
* used effectively. We therefore switch the parity every 1MB.
*
* ... at least that was, ostensibly, the theory. As a practical
* matter unless we juggle the parity between all devices evenly, we
* won't see any benefit. Further, occasional writes that aren't a
* multiple of the LCM of the number of children and the minimum
* stripe width are sufficient to avoid pessimal behavior.
* Unfortunately, this decision created an implicit on-disk format
* requirement that we need to support for all eternity, but only
* for single-parity RAID-Z.
*/
ASSERT(rm->rm_cols >= 2);
ASSERT(rm->rm_col[0].rc_size == rm->rm_col[1].rc_size);
if (rm->rm_firstdatacol == 1 && (zio->io_offset & (1ULL << 20))) {
devidx = rm->rm_col[0].rc_devidx;
o = rm->rm_col[0].rc_offset;
rm->rm_col[0].rc_devidx = rm->rm_col[1].rc_devidx;
rm->rm_col[0].rc_offset = rm->rm_col[1].rc_offset;
rm->rm_col[1].rc_devidx = devidx;
rm->rm_col[1].rc_offset = o;
}
zio->io_vsd = rm;
zio->io_vsd_free = vdev_raidz_map_free;
return (rm);
}
static void
vdev_raidz_generate_parity_p(raidz_map_t *rm)
{
uint64_t *p, *src, pcount, ccount, i;
int c;
pcount = rm->rm_col[VDEV_RAIDZ_P].rc_size / sizeof (src[0]);
for (c = rm->rm_firstdatacol; c < rm->rm_cols; c++) {
src = rm->rm_col[c].rc_data;
p = rm->rm_col[VDEV_RAIDZ_P].rc_data;
ccount = rm->rm_col[c].rc_size / sizeof (src[0]);
if (c == rm->rm_firstdatacol) {
ASSERT(ccount == pcount);
for (i = 0; i < ccount; i++, p++, src++) {
*p = *src;
}
} else {
ASSERT(ccount <= pcount);
for (i = 0; i < ccount; i++, p++, src++) {
*p ^= *src;
}
}
}
}
static void
vdev_raidz_generate_parity_pq(raidz_map_t *rm)
{
uint64_t *q, *p, *src, pcount, ccount, mask, i;
int c;
pcount = rm->rm_col[VDEV_RAIDZ_P].rc_size / sizeof (src[0]);
ASSERT(rm->rm_col[VDEV_RAIDZ_P].rc_size ==
rm->rm_col[VDEV_RAIDZ_Q].rc_size);
for (c = rm->rm_firstdatacol; c < rm->rm_cols; c++) {
src = rm->rm_col[c].rc_data;
p = rm->rm_col[VDEV_RAIDZ_P].rc_data;
q = rm->rm_col[VDEV_RAIDZ_Q].rc_data;
ccount = rm->rm_col[c].rc_size / sizeof (src[0]);
if (c == rm->rm_firstdatacol) {
ASSERT(ccount == pcount || ccount == 0);
for (i = 0; i < ccount; i++, p++, q++, src++) {
*q = *src;
*p = *src;
}
for (; i < pcount; i++, p++, q++, src++) {
*q = 0;
*p = 0;
}
} else {
ASSERT(ccount <= pcount);
/*
* Rather than multiplying each byte individually (as
* described above), we are able to handle 8 at once
* by generating a mask based on the high bit in each
* byte and using that to conditionally XOR in 0x1d.
*/
for (i = 0; i < ccount; i++, p++, q++, src++) {
mask = *q & 0x8080808080808080ULL;
mask = (mask << 1) - (mask >> 7);
*q = ((*q << 1) & 0xfefefefefefefefeULL) ^
(mask & 0x1d1d1d1d1d1d1d1dULL);
*q ^= *src;
*p ^= *src;
}
/*
* Treat short columns as though they are full of 0s.
*/
for (; i < pcount; i++, q++) {
mask = *q & 0x8080808080808080ULL;
mask = (mask << 1) - (mask >> 7);
*q = ((*q << 1) & 0xfefefefefefefefeULL) ^
(mask & 0x1d1d1d1d1d1d1d1dULL);
}
}
}
}
static void
vdev_raidz_reconstruct_p(raidz_map_t *rm, int x)
{
uint64_t *dst, *src, xcount, ccount, count, i;
int c;
xcount = rm->rm_col[x].rc_size / sizeof (src[0]);
ASSERT(xcount <= rm->rm_col[VDEV_RAIDZ_P].rc_size / sizeof (src[0]));
ASSERT(xcount > 0);
src = rm->rm_col[VDEV_RAIDZ_P].rc_data;
dst = rm->rm_col[x].rc_data;
for (i = 0; i < xcount; i++, dst++, src++) {
*dst = *src;
}
for (c = rm->rm_firstdatacol; c < rm->rm_cols; c++) {
src = rm->rm_col[c].rc_data;
dst = rm->rm_col[x].rc_data;
if (c == x)
continue;
ccount = rm->rm_col[c].rc_size / sizeof (src[0]);
count = MIN(ccount, xcount);
for (i = 0; i < count; i++, dst++, src++) {
*dst ^= *src;
}
}
}
static void
vdev_raidz_reconstruct_q(raidz_map_t *rm, int x)
{
uint64_t *dst, *src, xcount, ccount, count, mask, i;
uint8_t *b;
int c, j, exp;
xcount = rm->rm_col[x].rc_size / sizeof (src[0]);
ASSERT(xcount <= rm->rm_col[VDEV_RAIDZ_Q].rc_size / sizeof (src[0]));
for (c = rm->rm_firstdatacol; c < rm->rm_cols; c++) {
src = rm->rm_col[c].rc_data;
dst = rm->rm_col[x].rc_data;
if (c == x)
ccount = 0;
else
ccount = rm->rm_col[c].rc_size / sizeof (src[0]);
count = MIN(ccount, xcount);
if (c == rm->rm_firstdatacol) {
for (i = 0; i < count; i++, dst++, src++) {
*dst = *src;
}
for (; i < xcount; i++, dst++) {
*dst = 0;
}
} else {
/*
* For an explanation of this, see the comment in
* vdev_raidz_generate_parity_pq() above.
*/
for (i = 0; i < count; i++, dst++, src++) {
mask = *dst & 0x8080808080808080ULL;
mask = (mask << 1) - (mask >> 7);
*dst = ((*dst << 1) & 0xfefefefefefefefeULL) ^
(mask & 0x1d1d1d1d1d1d1d1dULL);
*dst ^= *src;
}
for (; i < xcount; i++, dst++) {
mask = *dst & 0x8080808080808080ULL;
mask = (mask << 1) - (mask >> 7);
*dst = ((*dst << 1) & 0xfefefefefefefefeULL) ^
(mask & 0x1d1d1d1d1d1d1d1dULL);
}
}
}
src = rm->rm_col[VDEV_RAIDZ_Q].rc_data;
dst = rm->rm_col[x].rc_data;
exp = 255 - (rm->rm_cols - 1 - x);
for (i = 0; i < xcount; i++, dst++, src++) {
*dst ^= *src;
for (j = 0, b = (uint8_t *)dst; j < 8; j++, b++) {
*b = vdev_raidz_exp2(*b, exp);
}
}
}
static void
vdev_raidz_reconstruct_pq(raidz_map_t *rm, int x, int y)
{
uint8_t *p, *q, *pxy, *qxy, *xd, *yd, tmp, a, b, aexp, bexp;
void *pdata, *qdata;
uint64_t xsize, ysize, i;
ASSERT(x < y);
ASSERT(x >= rm->rm_firstdatacol);
ASSERT(y < rm->rm_cols);
ASSERT(rm->rm_col[x].rc_size >= rm->rm_col[y].rc_size);
/*
* Move the parity data aside -- we're going to compute parity as
* though columns x and y were full of zeros -- Pxy and Qxy. We want to
* reuse the parity generation mechanism without trashing the actual
* parity so we make those columns appear to be full of zeros by
* setting their lengths to zero.
*/
pdata = rm->rm_col[VDEV_RAIDZ_P].rc_data;
qdata = rm->rm_col[VDEV_RAIDZ_Q].rc_data;
xsize = rm->rm_col[x].rc_size;
ysize = rm->rm_col[y].rc_size;
rm->rm_col[VDEV_RAIDZ_P].rc_data =
zio_buf_alloc(rm->rm_col[VDEV_RAIDZ_P].rc_size);
rm->rm_col[VDEV_RAIDZ_Q].rc_data =
zio_buf_alloc(rm->rm_col[VDEV_RAIDZ_Q].rc_size);
rm->rm_col[x].rc_size = 0;
rm->rm_col[y].rc_size = 0;
vdev_raidz_generate_parity_pq(rm);
rm->rm_col[x].rc_size = xsize;
rm->rm_col[y].rc_size = ysize;
p = pdata;
q = qdata;
pxy = rm->rm_col[VDEV_RAIDZ_P].rc_data;
qxy = rm->rm_col[VDEV_RAIDZ_Q].rc_data;
xd = rm->rm_col[x].rc_data;
yd = rm->rm_col[y].rc_data;
/*
* We now have:
* Pxy = P + D_x + D_y
* Qxy = Q + 2^(ndevs - 1 - x) * D_x + 2^(ndevs - 1 - y) * D_y
*
* We can then solve for D_x:
* D_x = A * (P + Pxy) + B * (Q + Qxy)
* where
* A = 2^(x - y) * (2^(x - y) + 1)^-1
* B = 2^(ndevs - 1 - x) * (2^(x - y) + 1)^-1
*
* With D_x in hand, we can easily solve for D_y:
* D_y = P + Pxy + D_x
*/
a = vdev_raidz_pow2[255 + x - y];
b = vdev_raidz_pow2[255 - (rm->rm_cols - 1 - x)];
tmp = 255 - vdev_raidz_log2[a ^ 1];
aexp = vdev_raidz_log2[vdev_raidz_exp2(a, tmp)];
bexp = vdev_raidz_log2[vdev_raidz_exp2(b, tmp)];
for (i = 0; i < xsize; i++, p++, q++, pxy++, qxy++, xd++, yd++) {
*xd = vdev_raidz_exp2(*p ^ *pxy, aexp) ^
vdev_raidz_exp2(*q ^ *qxy, bexp);
if (i < ysize)
*yd = *p ^ *pxy ^ *xd;
}
zio_buf_free(rm->rm_col[VDEV_RAIDZ_P].rc_data,
rm->rm_col[VDEV_RAIDZ_P].rc_size);
zio_buf_free(rm->rm_col[VDEV_RAIDZ_Q].rc_data,
rm->rm_col[VDEV_RAIDZ_Q].rc_size);
/*
* Restore the saved parity data.
*/
rm->rm_col[VDEV_RAIDZ_P].rc_data = pdata;
rm->rm_col[VDEV_RAIDZ_Q].rc_data = qdata;
}
static int
vdev_raidz_open(vdev_t *vd, uint64_t *asize, uint64_t *ashift)
{
vdev_t *cvd;
uint64_t nparity = vd->vdev_nparity;
int c, error;
int lasterror = 0;
int numerrors = 0;
ASSERT(nparity > 0);
if (nparity > VDEV_RAIDZ_MAXPARITY ||
vd->vdev_children < nparity + 1) {
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 ((error = vdev_open(cvd)) != 0) {
lasterror = error;
numerrors++;
continue;
}
*asize = MIN(*asize - 1, cvd->vdev_asize - 1) + 1;
*ashift = MAX(*ashift, cvd->vdev_ashift);
}
*asize *= vd->vdev_children;
if (numerrors > nparity) {
vd->vdev_stat.vs_aux = VDEV_AUX_NO_REPLICAS;
return (lasterror);
}
return (0);
}
static void
vdev_raidz_close(vdev_t *vd)
{
int c;
for (c = 0; c < vd->vdev_children; c++)
vdev_close(vd->vdev_child[c]);
}
static uint64_t
vdev_raidz_asize(vdev_t *vd, uint64_t psize)
{
uint64_t asize;
uint64_t ashift = vd->vdev_top->vdev_ashift;
uint64_t cols = vd->vdev_children;
uint64_t nparity = vd->vdev_nparity;
asize = ((psize - 1) >> ashift) + 1;
asize += nparity * ((asize + cols - nparity - 1) / (cols - nparity));
asize = roundup(asize, nparity + 1) << ashift;
return (asize);
}
static void
vdev_raidz_child_done(zio_t *zio)
{
raidz_col_t *rc = zio->io_private;
rc->rc_error = zio->io_error;
rc->rc_tried = 1;
rc->rc_skipped = 0;
}
static int
vdev_raidz_io_start(zio_t *zio)
{
vdev_t *vd = zio->io_vd;
vdev_t *tvd = vd->vdev_top;
vdev_t *cvd;
blkptr_t *bp = zio->io_bp;
raidz_map_t *rm;
raidz_col_t *rc;
int c;
rm = vdev_raidz_map_alloc(zio, tvd->vdev_ashift, vd->vdev_children,
vd->vdev_nparity);
ASSERT3U(rm->rm_asize, ==, vdev_psize_to_asize(vd, zio->io_size));
if (zio->io_type == ZIO_TYPE_WRITE) {
/*
* Generate RAID parity in the first virtual columns.
*/
if (rm->rm_firstdatacol == 1)
vdev_raidz_generate_parity_p(rm);
else
vdev_raidz_generate_parity_pq(rm);
for (c = 0; c < rm->rm_cols; c++) {
rc = &rm->rm_col[c];
cvd = vd->vdev_child[rc->rc_devidx];
zio_nowait(zio_vdev_child_io(zio, NULL, cvd,
rc->rc_offset, rc->rc_data, rc->rc_size,
zio->io_type, zio->io_priority, 0,
vdev_raidz_child_done, rc));
}
return (ZIO_PIPELINE_CONTINUE);
}
ASSERT(zio->io_type == ZIO_TYPE_READ);
/*
* Iterate over the columns in reverse order so that we hit the parity
* last -- any errors along the way will force us to read the parity
* data.
*/
for (c = rm->rm_cols - 1; c >= 0; c--) {
rc = &rm->rm_col[c];
cvd = vd->vdev_child[rc->rc_devidx];
if (!vdev_readable(cvd)) {
if (c >= rm->rm_firstdatacol)
rm->rm_missingdata++;
else
rm->rm_missingparity++;
rc->rc_error = ENXIO;
rc->rc_tried = 1; /* don't even try */
rc->rc_skipped = 1;
continue;
}
if (vdev_dtl_contains(&cvd->vdev_dtl_map, bp->blk_birth, 1)) {
if (c >= rm->rm_firstdatacol)
rm->rm_missingdata++;
else
rm->rm_missingparity++;
rc->rc_error = ESTALE;
rc->rc_skipped = 1;
continue;
}
if (c >= rm->rm_firstdatacol || rm->rm_missingdata > 0 ||
(zio->io_flags & ZIO_FLAG_SCRUB)) {
zio_nowait(zio_vdev_child_io(zio, NULL, cvd,
rc->rc_offset, rc->rc_data, rc->rc_size,
zio->io_type, zio->io_priority, 0,
vdev_raidz_child_done, rc));
}
}
return (ZIO_PIPELINE_CONTINUE);
}
/*
* Report a checksum error for a child of a RAID-Z device.
*/
static void
raidz_checksum_error(zio_t *zio, raidz_col_t *rc)
{
vdev_t *vd = zio->io_vd->vdev_child[rc->rc_devidx];
if (!(zio->io_flags & ZIO_FLAG_SPECULATIVE)) {
mutex_enter(&vd->vdev_stat_lock);
vd->vdev_stat.vs_checksum_errors++;
mutex_exit(&vd->vdev_stat_lock);
}
if (!(zio->io_flags & ZIO_FLAG_SPECULATIVE))
zfs_ereport_post(FM_EREPORT_ZFS_CHECKSUM,
zio->io_spa, vd, zio, rc->rc_offset, rc->rc_size);
}
/*
* Generate the parity from the data columns. If we tried and were able to
* read the parity without error, verify that the generated parity matches the
* data we read. If it doesn't, we fire off a checksum error. Return the
* number such failures.
*/
static int
raidz_parity_verify(zio_t *zio, raidz_map_t *rm)
{
void *orig[VDEV_RAIDZ_MAXPARITY];
int c, ret = 0;
raidz_col_t *rc;
for (c = 0; c < rm->rm_firstdatacol; c++) {
rc = &rm->rm_col[c];
if (!rc->rc_tried || rc->rc_error != 0)
continue;
orig[c] = zio_buf_alloc(rc->rc_size);
bcopy(rc->rc_data, orig[c], rc->rc_size);
}
if (rm->rm_firstdatacol == 1)
vdev_raidz_generate_parity_p(rm);
else
vdev_raidz_generate_parity_pq(rm);
for (c = 0; c < rm->rm_firstdatacol; c++) {
rc = &rm->rm_col[c];
if (!rc->rc_tried || rc->rc_error != 0)
continue;
if (bcmp(orig[c], rc->rc_data, rc->rc_size) != 0) {
raidz_checksum_error(zio, rc);
rc->rc_error = ECKSUM;
ret++;
}
zio_buf_free(orig[c], rc->rc_size);
}
return (ret);
}
static uint64_t raidz_corrected_p;
static uint64_t raidz_corrected_q;
static uint64_t raidz_corrected_pq;
static int
vdev_raidz_worst_error(raidz_map_t *rm)
{
int error = 0;
for (int c = 0; c < rm->rm_cols; c++)
error = zio_worst_error(error, rm->rm_col[c].rc_error);
return (error);
}
static void
vdev_raidz_io_done(zio_t *zio)
{
vdev_t *vd = zio->io_vd;
vdev_t *cvd;
raidz_map_t *rm = zio->io_vsd;
raidz_col_t *rc = NULL, *rc1;
int unexpected_errors = 0;
int parity_errors = 0;
int parity_untried = 0;
int data_errors = 0;
int total_errors = 0;
int n, c, c1;
ASSERT(zio->io_bp != NULL); /* XXX need to add code to enforce this */
ASSERT(rm->rm_missingparity <= rm->rm_firstdatacol);
ASSERT(rm->rm_missingdata <= rm->rm_cols - rm->rm_firstdatacol);
for (c = 0; c < rm->rm_cols; c++) {
rc = &rm->rm_col[c];
if (rc->rc_error) {
ASSERT(rc->rc_error != ECKSUM); /* child has no bp */
if (c < rm->rm_firstdatacol)
parity_errors++;
else
data_errors++;
if (!rc->rc_skipped)
unexpected_errors++;
total_errors++;
} else if (c < rm->rm_firstdatacol && !rc->rc_tried) {
parity_untried++;
}
}
if (zio->io_type == ZIO_TYPE_WRITE) {
/*
* XXX -- for now, treat partial writes as a success.
* (If we couldn't write enough columns to reconstruct
* the data, the I/O failed. Otherwise, good enough.)
*
* 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 (total_errors > rm->rm_firstdatacol)
zio->io_error = vdev_raidz_worst_error(rm);
return;
}
ASSERT(zio->io_type == ZIO_TYPE_READ);
/*
* There are three potential phases for a read:
* 1. produce valid data from the columns read
* 2. read all disks and try again
* 3. perform combinatorial reconstruction
*
* Each phase is progressively both more expensive and less likely to
* occur. If we encounter more errors than we can repair or all phases
* fail, we have no choice but to return an error.
*/
/*
* If the number of errors we saw was correctable -- less than or equal
* to the number of parity disks read -- attempt to produce data that
* has a valid checksum. Naturally, this case applies in the absence of
* any errors.
*/
if (total_errors <= rm->rm_firstdatacol - parity_untried) {
switch (data_errors) {
case 0:
if (zio_checksum_error(zio) == 0) {
/*
* If we read parity information (unnecessarily
* as it happens since no reconstruction was
* needed) regenerate and verify the parity.
* We also regenerate parity when resilvering
* so we can write it out to the failed device
* later.
*/
if (parity_errors + parity_untried <
rm->rm_firstdatacol ||
(zio->io_flags & ZIO_FLAG_RESILVER)) {
n = raidz_parity_verify(zio, rm);
unexpected_errors += n;
ASSERT(parity_errors + n <=
rm->rm_firstdatacol);
}
goto done;
}
break;
case 1:
/*
* We either attempt to read all the parity columns or
* none of them. If we didn't try to read parity, we
* wouldn't be here in the correctable case. There must
* also have been fewer parity errors than parity
* columns or, again, we wouldn't be in this code path.
*/
ASSERT(parity_untried == 0);
ASSERT(parity_errors < rm->rm_firstdatacol);
/*
* Find the column that reported the error.
*/
for (c = rm->rm_firstdatacol; c < rm->rm_cols; c++) {
rc = &rm->rm_col[c];
if (rc->rc_error != 0)
break;
}
ASSERT(c != rm->rm_cols);
ASSERT(!rc->rc_skipped || rc->rc_error == ENXIO ||
rc->rc_error == ESTALE);
if (rm->rm_col[VDEV_RAIDZ_P].rc_error == 0) {
vdev_raidz_reconstruct_p(rm, c);
} else {
ASSERT(rm->rm_firstdatacol > 1);
vdev_raidz_reconstruct_q(rm, c);
}
if (zio_checksum_error(zio) == 0) {
if (rm->rm_col[VDEV_RAIDZ_P].rc_error == 0)
atomic_inc_64(&raidz_corrected_p);
else
atomic_inc_64(&raidz_corrected_q);
/*
* If there's more than one parity disk that
* was successfully read, confirm that the
* other parity disk produced the correct data.
* This routine is suboptimal in that it
* regenerates both the parity we wish to test
* as well as the parity we just used to
* perform the reconstruction, but this should
* be a relatively uncommon case, and can be
* optimized if it becomes a problem.
* We also regenerate parity when resilvering
* so we can write it out to the failed device
* later.
*/
if (parity_errors < rm->rm_firstdatacol - 1 ||
(zio->io_flags & ZIO_FLAG_RESILVER)) {
n = raidz_parity_verify(zio, rm);
unexpected_errors += n;
ASSERT(parity_errors + n <=
rm->rm_firstdatacol);
}
goto done;
}
break;
case 2:
/*
* Two data column errors require double parity.
*/
ASSERT(rm->rm_firstdatacol == 2);
/*
* Find the two columns that reported errors.
*/
for (c = rm->rm_firstdatacol; c < rm->rm_cols; c++) {
rc = &rm->rm_col[c];
if (rc->rc_error != 0)
break;
}
ASSERT(c != rm->rm_cols);
ASSERT(!rc->rc_skipped || rc->rc_error == ENXIO ||
rc->rc_error == ESTALE);
for (c1 = c++; c < rm->rm_cols; c++) {
rc = &rm->rm_col[c];
if (rc->rc_error != 0)
break;
}
ASSERT(c != rm->rm_cols);
ASSERT(!rc->rc_skipped || rc->rc_error == ENXIO ||
rc->rc_error == ESTALE);
vdev_raidz_reconstruct_pq(rm, c1, c);
if (zio_checksum_error(zio) == 0) {
atomic_inc_64(&raidz_corrected_pq);
goto done;
}
break;
default:
ASSERT(rm->rm_firstdatacol <= 2);
ASSERT(0);
}
}
/*
* This isn't a typical situation -- either we got a read error or
* a child silently returned bad data. Read every block so we can
* try again with as much data and parity as we can track down. If
* we've already been through once before, all children will be marked
* as tried so we'll proceed to combinatorial reconstruction.
*/
unexpected_errors = 1;
rm->rm_missingdata = 0;
rm->rm_missingparity = 0;
for (c = 0; c < rm->rm_cols; c++) {
if (rm->rm_col[c].rc_tried)
continue;
zio_vdev_io_redone(zio);
do {
rc = &rm->rm_col[c];
if (rc->rc_tried)
continue;
zio_nowait(zio_vdev_child_io(zio, NULL,
vd->vdev_child[rc->rc_devidx],
rc->rc_offset, rc->rc_data, rc->rc_size,
zio->io_type, zio->io_priority, 0,
vdev_raidz_child_done, rc));
} while (++c < rm->rm_cols);
return;
}
/*
* At this point we've attempted to reconstruct the data given the
* errors we detected, and we've attempted to read all columns. There
* must, therefore, be one or more additional problems -- silent errors
* resulting in invalid data rather than explicit I/O errors resulting
* in absent data. Before we attempt combinatorial reconstruction make
* sure we have a chance of coming up with the right answer.
*/
if (total_errors >= rm->rm_firstdatacol) {
zio->io_error = vdev_raidz_worst_error(rm);
/*
* If there were exactly as many device errors as parity
* columns, yet we couldn't reconstruct the data, then at
* least one device must have returned bad data silently.
*/
if (total_errors == rm->rm_firstdatacol)
zio->io_error = zio_worst_error(zio->io_error, ECKSUM);
goto done;
}
if (rm->rm_col[VDEV_RAIDZ_P].rc_error == 0) {
/*
* Attempt to reconstruct the data from parity P.
*/
for (c = rm->rm_firstdatacol; c < rm->rm_cols; c++) {
void *orig;
rc = &rm->rm_col[c];
orig = zio_buf_alloc(rc->rc_size);
bcopy(rc->rc_data, orig, rc->rc_size);
vdev_raidz_reconstruct_p(rm, c);
if (zio_checksum_error(zio) == 0) {
zio_buf_free(orig, rc->rc_size);
atomic_inc_64(&raidz_corrected_p);
/*
* If this child didn't know that it returned
* bad data, inform it.
*/
if (rc->rc_tried && rc->rc_error == 0)
raidz_checksum_error(zio, rc);
rc->rc_error = ECKSUM;
goto done;
}
bcopy(orig, rc->rc_data, rc->rc_size);
zio_buf_free(orig, rc->rc_size);
}
}
if (rm->rm_firstdatacol > 1 && rm->rm_col[VDEV_RAIDZ_Q].rc_error == 0) {
/*
* Attempt to reconstruct the data from parity Q.
*/
for (c = rm->rm_firstdatacol; c < rm->rm_cols; c++) {
void *orig;
rc = &rm->rm_col[c];
orig = zio_buf_alloc(rc->rc_size);
bcopy(rc->rc_data, orig, rc->rc_size);
vdev_raidz_reconstruct_q(rm, c);
if (zio_checksum_error(zio) == 0) {
zio_buf_free(orig, rc->rc_size);
atomic_inc_64(&raidz_corrected_q);
/*
* If this child didn't know that it returned
* bad data, inform it.
*/
if (rc->rc_tried && rc->rc_error == 0)
raidz_checksum_error(zio, rc);
rc->rc_error = ECKSUM;
goto done;
}
bcopy(orig, rc->rc_data, rc->rc_size);
zio_buf_free(orig, rc->rc_size);
}
}
if (rm->rm_firstdatacol > 1 &&
rm->rm_col[VDEV_RAIDZ_P].rc_error == 0 &&
rm->rm_col[VDEV_RAIDZ_Q].rc_error == 0) {
/*
* Attempt to reconstruct the data from both P and Q.
*/
for (c = rm->rm_firstdatacol; c < rm->rm_cols - 1; c++) {
void *orig, *orig1;
rc = &rm->rm_col[c];
orig = zio_buf_alloc(rc->rc_size);
bcopy(rc->rc_data, orig, rc->rc_size);
for (c1 = c + 1; c1 < rm->rm_cols; c1++) {
rc1 = &rm->rm_col[c1];
orig1 = zio_buf_alloc(rc1->rc_size);
bcopy(rc1->rc_data, orig1, rc1->rc_size);
vdev_raidz_reconstruct_pq(rm, c, c1);
if (zio_checksum_error(zio) == 0) {
zio_buf_free(orig, rc->rc_size);
zio_buf_free(orig1, rc1->rc_size);
atomic_inc_64(&raidz_corrected_pq);
/*
* If these children didn't know they
* returned bad data, inform them.
*/
if (rc->rc_tried && rc->rc_error == 0)
raidz_checksum_error(zio, rc);
if (rc1->rc_tried && rc1->rc_error == 0)
raidz_checksum_error(zio, rc1);
rc->rc_error = ECKSUM;
rc1->rc_error = ECKSUM;
goto done;
}
bcopy(orig1, rc1->rc_data, rc1->rc_size);
zio_buf_free(orig1, rc1->rc_size);
}
bcopy(orig, rc->rc_data, rc->rc_size);
zio_buf_free(orig, rc->rc_size);
}
}
/*
* All combinations failed to checksum. Generate checksum ereports for
* all children.
*/
zio->io_error = ECKSUM;
if (!(zio->io_flags & ZIO_FLAG_SPECULATIVE)) {
for (c = 0; c < rm->rm_cols; c++) {
rc = &rm->rm_col[c];
zfs_ereport_post(FM_EREPORT_ZFS_CHECKSUM,
zio->io_spa, vd->vdev_child[rc->rc_devidx], zio,
rc->rc_offset, rc->rc_size);
}
}
done:
zio_checksum_verified(zio);
if (zio->io_error == 0 && (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 < rm->rm_cols; c++) {
rc = &rm->rm_col[c];
cvd = vd->vdev_child[rc->rc_devidx];
if (rc->rc_error == 0)
continue;
zio_nowait(zio_vdev_child_io(zio, NULL, cvd,
rc->rc_offset, rc->rc_data, rc->rc_size,
ZIO_TYPE_WRITE, zio->io_priority,
ZIO_FLAG_IO_REPAIR, NULL, NULL));
}
}
}
static void
vdev_raidz_state_change(vdev_t *vd, int faulted, int degraded)
{
if (faulted > vd->vdev_nparity)
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_raidz_ops = {
vdev_raidz_open,
vdev_raidz_close,
vdev_raidz_asize,
vdev_raidz_io_start,
vdev_raidz_io_done,
vdev_raidz_state_change,
VDEV_TYPE_RAIDZ, /* name of this vdev type */
B_FALSE /* not a leaf vdev */
};
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