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mirror_zfs/module/zfs/vdev_raidz.c
Matthew Ahrens e8b96c6007 Illumos #4045 write throttle & i/o scheduler performance work 
4045 zfs write throttle & i/o scheduler performance work

1. The ZFS i/o scheduler (vdev_queue.c) now divides i/os into 5 classes: sync
read, sync write, async read, async write, and scrub/resilver.  The scheduler
issues a number of concurrent i/os from each class to the device.  Once a class
has been selected, an i/o is selected from this class using either an elevator
algorithem (async, scrub classes) or FIFO (sync classes).  The number of
concurrent async write i/os is tuned dynamically based on i/o load, to achieve
good sync i/o latency when there is not a high load of writes, and good write
throughput when there is.  See the block comment in vdev_queue.c (reproduced
below) for more details.

2. The write throttle (dsl_pool_tempreserve_space() and
txg_constrain_throughput()) is rewritten to produce much more consistent delays
when under constant load.  The new write throttle is based on the amount of
dirty data, rather than guesses about future performance of the system.  When
there is a lot of dirty data, each transaction (e.g. write() syscall) will be
delayed by the same small amount.  This eliminates the "brick wall of wait"
that the old write throttle could hit, causing all transactions to wait several
seconds until the next txg opens.  One of the keys to the new write throttle is
decrementing the amount of dirty data as i/o completes, rather than at the end
of spa_sync().  Note that the write throttle is only applied once the i/o
scheduler is issuing the maximum number of outstanding async writes.  See the
block comments in dsl_pool.c and above dmu_tx_delay() (reproduced below) for
more details.

This diff has several other effects, including:

 * the commonly-tuned global variable zfs_vdev_max_pending has been removed;
use per-class zfs_vdev_*_max_active values or zfs_vdev_max_active instead.

 * the size of each txg (meaning the amount of dirty data written, and thus the
time it takes to write out) is now controlled differently.  There is no longer
an explicit time goal; the primary determinant is amount of dirty data.
Systems that are under light or medium load will now often see that a txg is
always syncing, but the impact to performance (e.g. read latency) is minimal.
Tune zfs_dirty_data_max and zfs_dirty_data_sync to control this.

 * zio_taskq_batch_pct = 75 -- Only use 75% of all CPUs for compression,
checksum, etc.  This improves latency by not allowing these CPU-intensive tasks
to consume all CPU (on machines with at least 4 CPU's; the percentage is
rounded up).

--matt

APPENDIX: problems with the current i/o scheduler

The current ZFS i/o scheduler (vdev_queue.c) is deadline based.  The problem
with this is that if there are always i/os pending, then certain classes of
i/os can see very long delays.

For example, if there are always synchronous reads outstanding, then no async
writes will be serviced until they become "past due".  One symptom of this
situation is that each pass of the txg sync takes at least several seconds
(typically 3 seconds).

If many i/os become "past due" (their deadline is in the past), then we must
service all of these overdue i/os before any new i/os.  This happens when we
enqueue a batch of async writes for the txg sync, with deadlines 2.5 seconds in
the future.  If we can't complete all the i/os in 2.5 seconds (e.g. because
there were always reads pending), then these i/os will become past due.  Now we
must service all the "async" writes (which could be hundreds of megabytes)
before we service any reads, introducing considerable latency to synchronous
i/os (reads or ZIL writes).

Notes on porting to ZFS on Linux:

- zio_t gained new members io_physdone and io_phys_children.  Because
  object caches in the Linux port call the constructor only once at
  allocation time, objects may contain residual data when retrieved
  from the cache. Therefore zio_create() was updated to zero out the two
  new fields.

- vdev_mirror_pending() relied on the depth of the per-vdev pending queue
  (vq->vq_pending_tree) to select the least-busy leaf vdev to read from.
  This tree has been replaced by vq->vq_active_tree which is now used
  for the same purpose.

- vdev_queue_init() used the value of zfs_vdev_max_pending to determine
  the number of vdev I/O buffers to pre-allocate.  That global no longer
  exists, so we instead use the sum of the *_max_active values for each of
  the five I/O classes described above.

- The Illumos implementation of dmu_tx_delay() delays a transaction by
  sleeping in condition variable embedded in the thread
  (curthread->t_delay_cv).  We do not have an equivalent CV to use in
  Linux, so this change replaced the delay logic with a wrapper called
  zfs_sleep_until(). This wrapper could be adopted upstream and in other
  downstream ports to abstract away operating system-specific delay logic.

- These tunables are added as module parameters, and descriptions added
  to the zfs-module-parameters.5 man page.

  spa_asize_inflation
  zfs_deadman_synctime_ms
  zfs_vdev_max_active
  zfs_vdev_async_write_active_min_dirty_percent
  zfs_vdev_async_write_active_max_dirty_percent
  zfs_vdev_async_read_max_active
  zfs_vdev_async_read_min_active
  zfs_vdev_async_write_max_active
  zfs_vdev_async_write_min_active
  zfs_vdev_scrub_max_active
  zfs_vdev_scrub_min_active
  zfs_vdev_sync_read_max_active
  zfs_vdev_sync_read_min_active
  zfs_vdev_sync_write_max_active
  zfs_vdev_sync_write_min_active
  zfs_dirty_data_max_percent
  zfs_delay_min_dirty_percent
  zfs_dirty_data_max_max_percent
  zfs_dirty_data_max
  zfs_dirty_data_max_max
  zfs_dirty_data_sync
  zfs_delay_scale

  The latter four have type unsigned long, whereas they are uint64_t in
  Illumos.  This accommodates Linux's module_param() supported types, but
  means they may overflow on 32-bit architectures.

  The values zfs_dirty_data_max and zfs_dirty_data_max_max are the most
  likely to overflow on 32-bit systems, since they express physical RAM
  sizes in bytes.  In fact, Illumos initializes zfs_dirty_data_max_max to
  2^32 which does overflow. To resolve that, this port instead initializes
  it in arc_init() to 25% of physical RAM, and adds the tunable
  zfs_dirty_data_max_max_percent to override that percentage.  While this
  solution doesn't completely avoid the overflow issue, it should be a
  reasonable default for most systems, and the minority of affected
  systems can work around the issue by overriding the defaults.

- Fixed reversed logic in comment above zfs_delay_scale declaration.

- Clarified comments in vdev_queue.c regarding when per-queue minimums take
  effect.

- Replaced dmu_tx_write_limit in the dmu_tx kstat file
  with dmu_tx_dirty_delay and dmu_tx_dirty_over_max.  The first counts
  how many times a transaction has been delayed because the pool dirty
  data has exceeded zfs_delay_min_dirty_percent.  The latter counts how
  many times the pool dirty data has exceeded zfs_dirty_data_max (which
  we expect to never happen).

- The original patch would have regressed the bug fixed in
  zfsonlinux/zfs@c418410, which prevented users from setting the
  zfs_vdev_aggregation_limit tuning larger than SPA_MAXBLOCKSIZE.
  A similar fix is added to vdev_queue_aggregate().

- In vdev_queue_io_to_issue(), dynamically allocate 'zio_t search' on the
  heap instead of the stack.  In Linux we can't afford such large
  structures on the stack.

Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: Ned Bass <bass6@llnl.gov>
Reviewed by: Brendan Gregg <brendan.gregg@joyent.com>
Approved by: Robert Mustacchi <rm@joyent.com>

References:
  http://www.illumos.org/issues/4045
  illumos/illumos-gate@69962b5647

Ported-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1913
2013-12-06 09:32:43 -08:00

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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 (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2013 by Delphix. All rights reserved.
*/
#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 single, double, and triple parity. For single parity,
* we use a simple XOR of all the data columns. For double or triple parity,
* we use a special case of Reed-Solomon coding. This extends the
* technique described in "The mathematics of RAID-6" by H. Peter Anvin by
* drawing on the system described in "A Tutorial on Reed-Solomon Coding for
* Fault-Tolerance in RAID-like Systems" by James S. Plank on which the
* former is also based. The latter is designed to provide higher performance
* for writes.
*
* Note that the Plank paper claimed to support arbitrary N+M, but was then
* amended six years later identifying a critical flaw that invalidates its
* claims. Nevertheless, the technique can be adapted to work for up to
* triple parity. For additional parity, the amendment "Note: Correction to
* the 1997 Tutorial on Reed-Solomon Coding" by James S. Plank and Ying Ding
* is viable, but the additional complexity means that write performance will
* suffer.
*
* All of the methods above operate on a Galois field, defined over the
* integers mod 2^N. In our case we choose N=8 for GF(8) so that all elements
* can be expressed with 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)).
* As an aside, this multiplication is derived from the error correcting
* primitive polynomial x^8 + x^4 + x^3 + x^2 + 1.
*
* 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 therefore
* A ^ (255 - 1) = A^254.
*
* The up-to-three parity columns, P, Q, R 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
* R = 4^n-1 * D_0 + 4^n-2 * D_1 + ... + 4^1 * D_n-2 + 4^0 * D_n-1
* = ((...((D_0) * 4 + D_1) * 4 + ...) * 4 + D_n-2) * 4 + D_n-1
*
* We chose 1, 2, and 4 as our generators because 1 corresponds to the trival
* XOR operation, and 2 and 4 can be computed quickly and generate linearly-
* independent coefficients. (There are no additional coefficients that have
* this property which is why the uncorrected Plank method breaks down.)
*
* See the reconstruction code below for how P, Q and R 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 */
void *rc_gdata; /* used to store the "good" version */
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; /* Regular column count */
uint64_t rm_scols; /* Count including skipped columns */
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 */
uint64_t rm_nskip; /* Skipped sectors for padding */
uint64_t rm_skipstart; /* Column index of padding start */
void *rm_datacopy; /* rm_asize-buffer of copied data */
uintptr_t rm_reports; /* # of referencing checksum reports */
uint8_t rm_freed; /* map no longer has referencing ZIO */
uint8_t rm_ecksuminjected; /* checksum error was injected */
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_R 2
#define VDEV_RAIDZ_MUL_2(x) (((x) << 1) ^ (((x) & 0x80) ? 0x1d : 0))
#define VDEV_RAIDZ_MUL_4(x) (VDEV_RAIDZ_MUL_2(VDEV_RAIDZ_MUL_2(x)))
/*
* We provide a mechanism to perform the field multiplication operation on a
* 64-bit value all at once rather than a byte at a time. This works by
* creating a mask from the top bit in each byte and using that to
* conditionally apply the XOR of 0x1d.
*/
#define VDEV_RAIDZ_64MUL_2(x, mask) \
{ \
(mask) = (x) & 0x8080808080808080ULL; \
(mask) = ((mask) << 1) - ((mask) >> 7); \
(x) = (((x) << 1) & 0xfefefefefefefefeULL) ^ \
((mask) & 0x1d1d1d1d1d1d1d1dULL); \
}
#define VDEV_RAIDZ_64MUL_4(x, mask) \
{ \
VDEV_RAIDZ_64MUL_2((x), mask); \
VDEV_RAIDZ_64MUL_2((x), mask); \
}
/*
* Force reconstruction to use the general purpose method.
*/
int vdev_raidz_default_to_general;
/* Powers of 2 in the Galois field defined 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
};
/* Logs of 2 in the Galois field defined above. */
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,
};
static void vdev_raidz_generate_parity(raidz_map_t *rm);
/*
* 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(raidz_map_t *rm)
{
int c;
size_t size;
for (c = 0; c < rm->rm_firstdatacol; c++) {
zio_buf_free(rm->rm_col[c].rc_data, rm->rm_col[c].rc_size);
if (rm->rm_col[c].rc_gdata != NULL)
zio_buf_free(rm->rm_col[c].rc_gdata,
rm->rm_col[c].rc_size);
}
size = 0;
for (c = rm->rm_firstdatacol; c < rm->rm_cols; c++)
size += rm->rm_col[c].rc_size;
if (rm->rm_datacopy != NULL)
zio_buf_free(rm->rm_datacopy, size);
kmem_free(rm, offsetof(raidz_map_t, rm_col[rm->rm_scols]));
}
static void
vdev_raidz_map_free_vsd(zio_t *zio)
{
raidz_map_t *rm = zio->io_vsd;
ASSERT0(rm->rm_freed);
rm->rm_freed = 1;
if (rm->rm_reports == 0)
vdev_raidz_map_free(rm);
}
/*ARGSUSED*/
static void
vdev_raidz_cksum_free(void *arg, size_t ignored)
{
raidz_map_t *rm = arg;
ASSERT3U(rm->rm_reports, >, 0);
if (--rm->rm_reports == 0 && rm->rm_freed != 0)
vdev_raidz_map_free(rm);
}
static void
vdev_raidz_cksum_finish(zio_cksum_report_t *zcr, const void *good_data)
{
raidz_map_t *rm = zcr->zcr_cbdata;
size_t c = zcr->zcr_cbinfo;
size_t x;
const char *good = NULL;
const char *bad = rm->rm_col[c].rc_data;
if (good_data == NULL) {
zfs_ereport_finish_checksum(zcr, NULL, NULL, B_FALSE);
return;
}
if (c < rm->rm_firstdatacol) {
/*
* The first time through, calculate the parity blocks for
* the good data (this relies on the fact that the good
* data never changes for a given logical ZIO)
*/
if (rm->rm_col[0].rc_gdata == NULL) {
char *bad_parity[VDEV_RAIDZ_MAXPARITY];
char *buf;
/*
* Set up the rm_col[]s to generate the parity for
* good_data, first saving the parity bufs and
* replacing them with buffers to hold the result.
*/
for (x = 0; x < rm->rm_firstdatacol; x++) {
bad_parity[x] = rm->rm_col[x].rc_data;
rm->rm_col[x].rc_data = rm->rm_col[x].rc_gdata =
zio_buf_alloc(rm->rm_col[x].rc_size);
}
/* fill in the data columns from good_data */
buf = (char *)good_data;
for (; x < rm->rm_cols; x++) {
rm->rm_col[x].rc_data = buf;
buf += rm->rm_col[x].rc_size;
}
/*
* Construct the parity from the good data.
*/
vdev_raidz_generate_parity(rm);
/* restore everything back to its original state */
for (x = 0; x < rm->rm_firstdatacol; x++)
rm->rm_col[x].rc_data = bad_parity[x];
buf = rm->rm_datacopy;
for (x = rm->rm_firstdatacol; x < rm->rm_cols; x++) {
rm->rm_col[x].rc_data = buf;
buf += rm->rm_col[x].rc_size;
}
}
ASSERT3P(rm->rm_col[c].rc_gdata, !=, NULL);
good = rm->rm_col[c].rc_gdata;
} else {
/* adjust good_data to point at the start of our column */
good = good_data;
for (x = rm->rm_firstdatacol; x < c; x++)
good += rm->rm_col[x].rc_size;
}
/* we drop the ereport if it ends up that the data was good */
zfs_ereport_finish_checksum(zcr, good, bad, B_TRUE);
}
/*
* Invoked indirectly by zfs_ereport_start_checksum(), called
* below when our read operation fails completely. The main point
* is to keep a copy of everything we read from disk, so that at
* vdev_raidz_cksum_finish() time we can compare it with the good data.
*/
static void
vdev_raidz_cksum_report(zio_t *zio, zio_cksum_report_t *zcr, void *arg)
{
size_t c = (size_t)(uintptr_t)arg;
caddr_t buf;
raidz_map_t *rm = zio->io_vsd;
size_t size;
/* set up the report and bump the refcount */
zcr->zcr_cbdata = rm;
zcr->zcr_cbinfo = c;
zcr->zcr_finish = vdev_raidz_cksum_finish;
zcr->zcr_free = vdev_raidz_cksum_free;
rm->rm_reports++;
ASSERT3U(rm->rm_reports, >, 0);
if (rm->rm_datacopy != NULL)
return;
/*
* It's the first time we're called for this raidz_map_t, so we need
* to copy the data aside; there's no guarantee that our zio's buffer
* won't be re-used for something else.
*
* Our parity data is already in separate buffers, so there's no need
* to copy them.
*/
size = 0;
for (c = rm->rm_firstdatacol; c < rm->rm_cols; c++)
size += rm->rm_col[c].rc_size;
buf = rm->rm_datacopy = zio_buf_alloc(size);
for (c = rm->rm_firstdatacol; c < rm->rm_cols; c++) {
raidz_col_t *col = &rm->rm_col[c];
bcopy(col->rc_data, buf, col->rc_size);
col->rc_data = buf;
buf += col->rc_size;
}
ASSERT3P(buf - (caddr_t)rm->rm_datacopy, ==, size);
}
static const zio_vsd_ops_t vdev_raidz_vsd_ops = {
vdev_raidz_map_free_vsd,
vdev_raidz_cksum_report
};
/*
* Divides the IO evenly across all child vdevs; usually, dcols is
* the number of children in the target vdev.
*
* Avoid inlining the function to keep vdev_raidz_io_start(), which
* is this functions only caller, as small as possible on the stack.
*/
noinline 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;
/* The starting RAIDZ (parent) vdev sector of the block. */
uint64_t b = zio->io_offset >> unit_shift;
/* The zio's size in units of the vdev's minimum sector size. */
uint64_t s = zio->io_size >> unit_shift;
/* The first column for this stripe. */
uint64_t f = b % dcols;
/* The starting byte offset on each child vdev. */
uint64_t o = (b / dcols) << unit_shift;
uint64_t q, r, c, bc, col, acols, scols, coff, devidx, asize, tot;
/*
* "Quotient": The number of data sectors for this stripe on all but
* the "big column" child vdevs that also contain "remainder" data.
*/
q = s / (dcols - nparity);
/*
* "Remainder": The number of partial stripe data sectors in this I/O.
* This will add a sector to some, but not all, child vdevs.
*/
r = s - q * (dcols - nparity);
/* The number of "big columns" - those which contain remainder data. */
bc = (r == 0 ? 0 : r + nparity);
/*
* The total number of data and parity sectors associated with
* this I/O.
*/
tot = s + nparity * (q + (r == 0 ? 0 : 1));
/* acols: The columns that will be accessed. */
/* scols: The columns that will be accessed or skipped. */
if (q == 0) {
/* Our I/O request doesn't span all child vdevs. */
acols = bc;
scols = MIN(dcols, roundup(bc, nparity + 1));
} else {
acols = dcols;
scols = dcols;
}
ASSERT3U(acols, <=, scols);
rm = kmem_alloc(offsetof(raidz_map_t, rm_col[scols]), KM_PUSHPAGE);
rm->rm_cols = acols;
rm->rm_scols = scols;
rm->rm_bigcols = bc;
rm->rm_skipstart = bc;
rm->rm_missingdata = 0;
rm->rm_missingparity = 0;
rm->rm_firstdatacol = nparity;
rm->rm_datacopy = NULL;
rm->rm_reports = 0;
rm->rm_freed = 0;
rm->rm_ecksuminjected = 0;
asize = 0;
for (c = 0; c < scols; 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_data = NULL;
rm->rm_col[c].rc_gdata = NULL;
rm->rm_col[c].rc_error = 0;
rm->rm_col[c].rc_tried = 0;
rm->rm_col[c].rc_skipped = 0;
if (c >= acols)
rm->rm_col[c].rc_size = 0;
else if (c < bc)
rm->rm_col[c].rc_size = (q + 1) << unit_shift;
else
rm->rm_col[c].rc_size = q << unit_shift;
asize += rm->rm_col[c].rc_size;
}
ASSERT3U(asize, ==, tot << unit_shift);
rm->rm_asize = roundup(asize, (nparity + 1) << unit_shift);
rm->rm_nskip = roundup(tot, nparity + 1) - tot;
ASSERT3U(rm->rm_asize - asize, ==, rm->rm_nskip << unit_shift);
ASSERT3U(rm->rm_nskip, <=, nparity);
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.
*
* If we intend to skip a sector in the zeroth column for padding
* we must make sure to note this swap. We will never intend to
* skip the first column since at least one data and one parity
* column must appear in each row.
*/
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;
if (rm->rm_skipstart == 0)
rm->rm_skipstart = 1;
}
zio->io_vsd = rm;
zio->io_vsd_ops = &vdev_raidz_vsd_ops;
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++, src++, p++) {
*p = *src;
}
} else {
ASSERT(ccount <= pcount);
for (i = 0; i < ccount; i++, src++, p++) {
*p ^= *src;
}
}
}
}
static void
vdev_raidz_generate_parity_pq(raidz_map_t *rm)
{
uint64_t *p, *q, *src, pcnt, ccnt, mask, i;
int c;
pcnt = 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;
ccnt = rm->rm_col[c].rc_size / sizeof (src[0]);
if (c == rm->rm_firstdatacol) {
ASSERT(ccnt == pcnt || ccnt == 0);
for (i = 0; i < ccnt; i++, src++, p++, q++) {
*p = *src;
*q = *src;
}
for (; i < pcnt; i++, src++, p++, q++) {
*p = 0;
*q = 0;
}
} else {
ASSERT(ccnt <= pcnt);
/*
* Apply the algorithm described above by multiplying
* the previous result and adding in the new value.
*/
for (i = 0; i < ccnt; i++, src++, p++, q++) {
*p ^= *src;
VDEV_RAIDZ_64MUL_2(*q, mask);
*q ^= *src;
}
/*
* Treat short columns as though they are full of 0s.
* Note that there's therefore nothing needed for P.
*/
for (; i < pcnt; i++, q++) {
VDEV_RAIDZ_64MUL_2(*q, mask);
}
}
}
}
static void
vdev_raidz_generate_parity_pqr(raidz_map_t *rm)
{
uint64_t *p, *q, *r, *src, pcnt, ccnt, mask, i;
int c;
pcnt = 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);
ASSERT(rm->rm_col[VDEV_RAIDZ_P].rc_size ==
rm->rm_col[VDEV_RAIDZ_R].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;
r = rm->rm_col[VDEV_RAIDZ_R].rc_data;
ccnt = rm->rm_col[c].rc_size / sizeof (src[0]);
if (c == rm->rm_firstdatacol) {
ASSERT(ccnt == pcnt || ccnt == 0);
for (i = 0; i < ccnt; i++, src++, p++, q++, r++) {
*p = *src;
*q = *src;
*r = *src;
}
for (; i < pcnt; i++, src++, p++, q++, r++) {
*p = 0;
*q = 0;
*r = 0;
}
} else {
ASSERT(ccnt <= pcnt);
/*
* Apply the algorithm described above by multiplying
* the previous result and adding in the new value.
*/
for (i = 0; i < ccnt; i++, src++, p++, q++, r++) {
*p ^= *src;
VDEV_RAIDZ_64MUL_2(*q, mask);
*q ^= *src;
VDEV_RAIDZ_64MUL_4(*r, mask);
*r ^= *src;
}
/*
* Treat short columns as though they are full of 0s.
* Note that there's therefore nothing needed for P.
*/
for (; i < pcnt; i++, q++, r++) {
VDEV_RAIDZ_64MUL_2(*q, mask);
VDEV_RAIDZ_64MUL_4(*r, mask);
}
}
}
}
/*
* Generate RAID parity in the first virtual columns according to the number of
* parity columns available.
*/
static void
vdev_raidz_generate_parity(raidz_map_t *rm)
{
switch (rm->rm_firstdatacol) {
case 1:
vdev_raidz_generate_parity_p(rm);
break;
case 2:
vdev_raidz_generate_parity_pq(rm);
break;
case 3:
vdev_raidz_generate_parity_pqr(rm);
break;
default:
cmn_err(CE_PANIC, "invalid RAID-Z configuration");
}
}
static int
vdev_raidz_reconstruct_p(raidz_map_t *rm, int *tgts, int ntgts)
{
uint64_t *dst, *src, xcount, ccount, count, i;
int x = tgts[0];
int c;
ASSERT(ntgts == 1);
ASSERT(x >= rm->rm_firstdatacol);
ASSERT(x < rm->rm_cols);
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;
}
}
return (1 << VDEV_RAIDZ_P);
}
static int
vdev_raidz_reconstruct_q(raidz_map_t *rm, int *tgts, int ntgts)
{
uint64_t *dst, *src, xcount, ccount, count, mask, i;
uint8_t *b;
int x = tgts[0];
int c, j, exp;
ASSERT(ntgts == 1);
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 (i = 0; i < count; i++, dst++, src++) {
VDEV_RAIDZ_64MUL_2(*dst, mask);
*dst ^= *src;
}
for (; i < xcount; i++, dst++) {
VDEV_RAIDZ_64MUL_2(*dst, mask);
}
}
}
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);
}
}
return (1 << VDEV_RAIDZ_Q);
}
static int
vdev_raidz_reconstruct_pq(raidz_map_t *rm, int *tgts, int ntgts)
{
uint8_t *p, *q, *pxy, *qxy, *xd, *yd, tmp, a, b, aexp, bexp;
void *pdata, *qdata;
uint64_t xsize, ysize, i;
int x = tgts[0];
int y = tgts[1];
ASSERT(ntgts == 2);
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;
return ((1 << VDEV_RAIDZ_P) | (1 << VDEV_RAIDZ_Q));
}
/* BEGIN CSTYLED */
/*
* In the general case of reconstruction, we must solve the system of linear
* equations defined by the coeffecients used to generate parity as well as
* the contents of the data and parity disks. This can be expressed with
* vectors for the original data (D) and the actual data (d) and parity (p)
* and a matrix composed of the identity matrix (I) and a dispersal matrix (V):
*
* __ __ __ __
* | | __ __ | p_0 |
* | V | | D_0 | | p_m-1 |
* | | x | : | = | d_0 |
* | I | | D_n-1 | | : |
* | | ~~ ~~ | d_n-1 |
* ~~ ~~ ~~ ~~
*
* I is simply a square identity matrix of size n, and V is a vandermonde
* matrix defined by the coeffecients we chose for the various parity columns
* (1, 2, 4). Note that these values were chosen both for simplicity, speedy
* computation as well as linear separability.
*
* __ __ __ __
* | 1 .. 1 1 1 | | p_0 |
* | 2^n-1 .. 4 2 1 | __ __ | : |
* | 4^n-1 .. 16 4 1 | | D_0 | | p_m-1 |
* | 1 .. 0 0 0 | | D_1 | | d_0 |
* | 0 .. 0 0 0 | x | D_2 | = | d_1 |
* | : : : : | | : | | d_2 |
* | 0 .. 1 0 0 | | D_n-1 | | : |
* | 0 .. 0 1 0 | ~~ ~~ | : |
* | 0 .. 0 0 1 | | d_n-1 |
* ~~ ~~ ~~ ~~
*
* Note that I, V, d, and p are known. To compute D, we must invert the
* matrix and use the known data and parity values to reconstruct the unknown
* data values. We begin by removing the rows in V|I and d|p that correspond
* to failed or missing columns; we then make V|I square (n x n) and d|p
* sized n by removing rows corresponding to unused parity from the bottom up
* to generate (V|I)' and (d|p)'. We can then generate the inverse of (V|I)'
* using Gauss-Jordan elimination. In the example below we use m=3 parity
* columns, n=8 data columns, with errors in d_1, d_2, and p_1:
* __ __
* | 1 1 1 1 1 1 1 1 |
* | 128 64 32 16 8 4 2 1 | <-----+-+-- missing disks
* | 19 205 116 29 64 16 4 1 | / /
* | 1 0 0 0 0 0 0 0 | / /
* | 0 1 0 0 0 0 0 0 | <--' /
* (V|I) = | 0 0 1 0 0 0 0 0 | <---'
* | 0 0 0 1 0 0 0 0 |
* | 0 0 0 0 1 0 0 0 |
* | 0 0 0 0 0 1 0 0 |
* | 0 0 0 0 0 0 1 0 |
* | 0 0 0 0 0 0 0 1 |
* ~~ ~~
* __ __
* | 1 1 1 1 1 1 1 1 |
* | 128 64 32 16 8 4 2 1 |
* | 19 205 116 29 64 16 4 1 |
* | 1 0 0 0 0 0 0 0 |
* | 0 1 0 0 0 0 0 0 |
* (V|I)' = | 0 0 1 0 0 0 0 0 |
* | 0 0 0 1 0 0 0 0 |
* | 0 0 0 0 1 0 0 0 |
* | 0 0 0 0 0 1 0 0 |
* | 0 0 0 0 0 0 1 0 |
* | 0 0 0 0 0 0 0 1 |
* ~~ ~~
*
* Here we employ Gauss-Jordan elimination to find the inverse of (V|I)'. We
* have carefully chosen the seed values 1, 2, and 4 to ensure that this
* matrix is not singular.
* __ __
* | 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 |
* | 19 205 116 29 64 16 4 1 0 1 0 0 0 0 0 0 |
* | 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 |
* | 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 |
* | 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 |
* | 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 |
* | 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 |
* | 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 |
* ~~ ~~
* __ __
* | 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 |
* | 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 |
* | 19 205 116 29 64 16 4 1 0 1 0 0 0 0 0 0 |
* | 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 |
* | 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 |
* | 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 |
* | 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 |
* | 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 |
* ~~ ~~
* __ __
* | 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 |
* | 0 1 1 0 0 0 0 0 1 0 1 1 1 1 1 1 |
* | 0 205 116 0 0 0 0 0 0 1 19 29 64 16 4 1 |
* | 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 |
* | 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 |
* | 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 |
* | 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 |
* | 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 |
* ~~ ~~
* __ __
* | 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 |
* | 0 1 1 0 0 0 0 0 1 0 1 1 1 1 1 1 |
* | 0 0 185 0 0 0 0 0 205 1 222 208 141 221 201 204 |
* | 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 |
* | 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 |
* | 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 |
* | 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 |
* | 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 |
* ~~ ~~
* __ __
* | 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 |
* | 0 1 1 0 0 0 0 0 1 0 1 1 1 1 1 1 |
* | 0 0 1 0 0 0 0 0 166 100 4 40 158 168 216 209 |
* | 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 |
* | 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 |
* | 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 |
* | 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 |
* | 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 |
* ~~ ~~
* __ __
* | 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 |
* | 0 1 0 0 0 0 0 0 167 100 5 41 159 169 217 208 |
* | 0 0 1 0 0 0 0 0 166 100 4 40 158 168 216 209 |
* | 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 |
* | 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 |
* | 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 |
* | 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 |
* | 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 |
* ~~ ~~
* __ __
* | 0 0 1 0 0 0 0 0 |
* | 167 100 5 41 159 169 217 208 |
* | 166 100 4 40 158 168 216 209 |
* (V|I)'^-1 = | 0 0 0 1 0 0 0 0 |
* | 0 0 0 0 1 0 0 0 |
* | 0 0 0 0 0 1 0 0 |
* | 0 0 0 0 0 0 1 0 |
* | 0 0 0 0 0 0 0 1 |
* ~~ ~~
*
* We can then simply compute D = (V|I)'^-1 x (d|p)' to discover the values
* of the missing data.
*
* As is apparent from the example above, the only non-trivial rows in the
* inverse matrix correspond to the data disks that we're trying to
* reconstruct. Indeed, those are the only rows we need as the others would
* only be useful for reconstructing data known or assumed to be valid. For
* that reason, we only build the coefficients in the rows that correspond to
* targeted columns.
*/
/* END CSTYLED */
static void
vdev_raidz_matrix_init(raidz_map_t *rm, int n, int nmap, int *map,
uint8_t **rows)
{
int i, j;
int pow;
ASSERT(n == rm->rm_cols - rm->rm_firstdatacol);
/*
* Fill in the missing rows of interest.
*/
for (i = 0; i < nmap; i++) {
ASSERT3S(0, <=, map[i]);
ASSERT3S(map[i], <=, 2);
pow = map[i] * n;
if (pow > 255)
pow -= 255;
ASSERT(pow <= 255);
for (j = 0; j < n; j++) {
pow -= map[i];
if (pow < 0)
pow += 255;
rows[i][j] = vdev_raidz_pow2[pow];
}
}
}
static void
vdev_raidz_matrix_invert(raidz_map_t *rm, int n, int nmissing, int *missing,
uint8_t **rows, uint8_t **invrows, const uint8_t *used)
{
int i, j, ii, jj;
uint8_t log;
/*
* Assert that the first nmissing entries from the array of used
* columns correspond to parity columns and that subsequent entries
* correspond to data columns.
*/
for (i = 0; i < nmissing; i++) {
ASSERT3S(used[i], <, rm->rm_firstdatacol);
}
for (; i < n; i++) {
ASSERT3S(used[i], >=, rm->rm_firstdatacol);
}
/*
* First initialize the storage where we'll compute the inverse rows.
*/
for (i = 0; i < nmissing; i++) {
for (j = 0; j < n; j++) {
invrows[i][j] = (i == j) ? 1 : 0;
}
}
/*
* Subtract all trivial rows from the rows of consequence.
*/
for (i = 0; i < nmissing; i++) {
for (j = nmissing; j < n; j++) {
ASSERT3U(used[j], >=, rm->rm_firstdatacol);
jj = used[j] - rm->rm_firstdatacol;
ASSERT3S(jj, <, n);
invrows[i][j] = rows[i][jj];
rows[i][jj] = 0;
}
}
/*
* For each of the rows of interest, we must normalize it and subtract
* a multiple of it from the other rows.
*/
for (i = 0; i < nmissing; i++) {
for (j = 0; j < missing[i]; j++) {
ASSERT0(rows[i][j]);
}
ASSERT3U(rows[i][missing[i]], !=, 0);
/*
* Compute the inverse of the first element and multiply each
* element in the row by that value.
*/
log = 255 - vdev_raidz_log2[rows[i][missing[i]]];
for (j = 0; j < n; j++) {
rows[i][j] = vdev_raidz_exp2(rows[i][j], log);
invrows[i][j] = vdev_raidz_exp2(invrows[i][j], log);
}
for (ii = 0; ii < nmissing; ii++) {
if (i == ii)
continue;
ASSERT3U(rows[ii][missing[i]], !=, 0);
log = vdev_raidz_log2[rows[ii][missing[i]]];
for (j = 0; j < n; j++) {
rows[ii][j] ^=
vdev_raidz_exp2(rows[i][j], log);
invrows[ii][j] ^=
vdev_raidz_exp2(invrows[i][j], log);
}
}
}
/*
* Verify that the data that is left in the rows are properly part of
* an identity matrix.
*/
for (i = 0; i < nmissing; i++) {
for (j = 0; j < n; j++) {
if (j == missing[i]) {
ASSERT3U(rows[i][j], ==, 1);
} else {
ASSERT0(rows[i][j]);
}
}
}
}
static void
vdev_raidz_matrix_reconstruct(raidz_map_t *rm, int n, int nmissing,
int *missing, uint8_t **invrows, const uint8_t *used)
{
int i, j, x, cc, c;
uint8_t *src;
uint64_t ccount;
uint8_t *dst[VDEV_RAIDZ_MAXPARITY];
uint64_t dcount[VDEV_RAIDZ_MAXPARITY];
uint8_t log = 0;
uint8_t val;
int ll;
uint8_t *invlog[VDEV_RAIDZ_MAXPARITY];
uint8_t *p, *pp;
size_t psize;
psize = sizeof (invlog[0][0]) * n * nmissing;
p = kmem_alloc(psize, KM_PUSHPAGE);
for (pp = p, i = 0; i < nmissing; i++) {
invlog[i] = pp;
pp += n;
}
for (i = 0; i < nmissing; i++) {
for (j = 0; j < n; j++) {
ASSERT3U(invrows[i][j], !=, 0);
invlog[i][j] = vdev_raidz_log2[invrows[i][j]];
}
}
for (i = 0; i < n; i++) {
c = used[i];
ASSERT3U(c, <, rm->rm_cols);
src = rm->rm_col[c].rc_data;
ccount = rm->rm_col[c].rc_size;
for (j = 0; j < nmissing; j++) {
cc = missing[j] + rm->rm_firstdatacol;
ASSERT3U(cc, >=, rm->rm_firstdatacol);
ASSERT3U(cc, <, rm->rm_cols);
ASSERT3U(cc, !=, c);
dst[j] = rm->rm_col[cc].rc_data;
dcount[j] = rm->rm_col[cc].rc_size;
}
ASSERT(ccount >= rm->rm_col[missing[0]].rc_size || i > 0);
for (x = 0; x < ccount; x++, src++) {
if (*src != 0)
log = vdev_raidz_log2[*src];
for (cc = 0; cc < nmissing; cc++) {
if (x >= dcount[cc])
continue;
if (*src == 0) {
val = 0;
} else {
if ((ll = log + invlog[cc][i]) >= 255)
ll -= 255;
val = vdev_raidz_pow2[ll];
}
if (i == 0)
dst[cc][x] = val;
else
dst[cc][x] ^= val;
}
}
}
kmem_free(p, psize);
}
static int
vdev_raidz_reconstruct_general(raidz_map_t *rm, int *tgts, int ntgts)
{
int n, i, c, t, tt;
int nmissing_rows;
int missing_rows[VDEV_RAIDZ_MAXPARITY];
int parity_map[VDEV_RAIDZ_MAXPARITY];
uint8_t *p, *pp;
size_t psize;
uint8_t *rows[VDEV_RAIDZ_MAXPARITY];
uint8_t *invrows[VDEV_RAIDZ_MAXPARITY];
uint8_t *used;
int code = 0;
n = rm->rm_cols - rm->rm_firstdatacol;
/*
* Figure out which data columns are missing.
*/
nmissing_rows = 0;
for (t = 0; t < ntgts; t++) {
if (tgts[t] >= rm->rm_firstdatacol) {
missing_rows[nmissing_rows++] =
tgts[t] - rm->rm_firstdatacol;
}
}
/*
* Figure out which parity columns to use to help generate the missing
* data columns.
*/
for (tt = 0, c = 0, i = 0; i < nmissing_rows; c++) {
ASSERT(tt < ntgts);
ASSERT(c < rm->rm_firstdatacol);
/*
* Skip any targeted parity columns.
*/
if (c == tgts[tt]) {
tt++;
continue;
}
code |= 1 << c;
parity_map[i] = c;
i++;
}
ASSERT(code != 0);
ASSERT3U(code, <, 1 << VDEV_RAIDZ_MAXPARITY);
psize = (sizeof (rows[0][0]) + sizeof (invrows[0][0])) *
nmissing_rows * n + sizeof (used[0]) * n;
p = kmem_alloc(psize, KM_PUSHPAGE);
for (pp = p, i = 0; i < nmissing_rows; i++) {
rows[i] = pp;
pp += n;
invrows[i] = pp;
pp += n;
}
used = pp;
for (i = 0; i < nmissing_rows; i++) {
used[i] = parity_map[i];
}
for (tt = 0, c = rm->rm_firstdatacol; c < rm->rm_cols; c++) {
if (tt < nmissing_rows &&
c == missing_rows[tt] + rm->rm_firstdatacol) {
tt++;
continue;
}
ASSERT3S(i, <, n);
used[i] = c;
i++;
}
/*
* Initialize the interesting rows of the matrix.
*/
vdev_raidz_matrix_init(rm, n, nmissing_rows, parity_map, rows);
/*
* Invert the matrix.
*/
vdev_raidz_matrix_invert(rm, n, nmissing_rows, missing_rows, rows,
invrows, used);
/*
* Reconstruct the missing data using the generated matrix.
*/
vdev_raidz_matrix_reconstruct(rm, n, nmissing_rows, missing_rows,
invrows, used);
kmem_free(p, psize);
return (code);
}
static int
vdev_raidz_reconstruct(raidz_map_t *rm, int *t, int nt)
{
int tgts[VDEV_RAIDZ_MAXPARITY], *dt;
int ntgts;
int i, c;
int code;
int nbadparity, nbaddata;
int parity_valid[VDEV_RAIDZ_MAXPARITY];
/*
* The tgts list must already be sorted.
*/
for (i = 1; i < nt; i++) {
ASSERT(t[i] > t[i - 1]);
}
nbadparity = rm->rm_firstdatacol;
nbaddata = rm->rm_cols - nbadparity;
ntgts = 0;
for (i = 0, c = 0; c < rm->rm_cols; c++) {
if (c < rm->rm_firstdatacol)
parity_valid[c] = B_FALSE;
if (i < nt && c == t[i]) {
tgts[ntgts++] = c;
i++;
} else if (rm->rm_col[c].rc_error != 0) {
tgts[ntgts++] = c;
} else if (c >= rm->rm_firstdatacol) {
nbaddata--;
} else {
parity_valid[c] = B_TRUE;
nbadparity--;
}
}
ASSERT(ntgts >= nt);
ASSERT(nbaddata >= 0);
ASSERT(nbaddata + nbadparity == ntgts);
dt = &tgts[nbadparity];
/*
* See if we can use any of our optimized reconstruction routines.
*/
if (!vdev_raidz_default_to_general) {
switch (nbaddata) {
case 1:
if (parity_valid[VDEV_RAIDZ_P])
return (vdev_raidz_reconstruct_p(rm, dt, 1));
ASSERT(rm->rm_firstdatacol > 1);
if (parity_valid[VDEV_RAIDZ_Q])
return (vdev_raidz_reconstruct_q(rm, dt, 1));
ASSERT(rm->rm_firstdatacol > 2);
break;
case 2:
ASSERT(rm->rm_firstdatacol > 1);
if (parity_valid[VDEV_RAIDZ_P] &&
parity_valid[VDEV_RAIDZ_Q])
return (vdev_raidz_reconstruct_pq(rm, dt, 2));
ASSERT(rm->rm_firstdatacol > 2);
break;
}
}
code = vdev_raidz_reconstruct_general(rm, tgts, ntgts);
ASSERT(code < (1 << VDEV_RAIDZ_MAXPARITY));
ASSERT(code > 0);
return (code);
}
static int
vdev_raidz_open(vdev_t *vd, uint64_t *asize, uint64_t *max_asize,
uint64_t *ashift)
{
vdev_t *cvd;
uint64_t nparity = vd->vdev_nparity;
int c;
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 (SET_ERROR(EINVAL));
}
vdev_open_children(vd);
for (c = 0; c < vd->vdev_children; c++) {
cvd = vd->vdev_child[c];
if (cvd->vdev_open_error != 0) {
lasterror = cvd->vdev_open_error;
numerrors++;
continue;
}
*asize = MIN(*asize - 1, cvd->vdev_asize - 1) + 1;
*max_asize = MIN(*max_asize - 1, cvd->vdev_max_asize - 1) + 1;
*ashift = MAX(*ashift, cvd->vdev_ashift);
}
*asize *= vd->vdev_children;
*max_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;
}
/*
* Start an IO operation on a RAIDZ VDev
*
* Outline:
* - For write operations:
* 1. Generate the parity data
* 2. Create child zio write operations to each column's vdev, for both
* data and parity.
* 3. If the column skips any sectors for padding, create optional dummy
* write zio children for those areas to improve aggregation continuity.
* - For read operations:
* 1. Create child zio read operations to each data column's vdev to read
* the range of data required for zio.
* 2. If this is a scrub or resilver operation, or if any of the data
* vdevs have had errors, then create zio read operations to the parity
* columns' VDevs as well.
*/
static int
vdev_raidz_io_start(zio_t *zio)
{
vdev_t *vd = zio->io_vd;
vdev_t *tvd = vd->vdev_top;
vdev_t *cvd;
raidz_map_t *rm;
raidz_col_t *rc;
int c, i;
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) {
vdev_raidz_generate_parity(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));
}
/*
* Generate optional I/Os for any skipped sectors to improve
* aggregation contiguity.
*/
for (c = rm->rm_skipstart, i = 0; i < rm->rm_nskip; c++, i++) {
ASSERT(c <= rm->rm_scols);
if (c == rm->rm_scols)
c = 0;
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_size, NULL,
1 << tvd->vdev_ashift,
zio->io_type, zio->io_priority,
ZIO_FLAG_NODATA | ZIO_FLAG_OPTIONAL, NULL, NULL));
}
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.
*/
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 = SET_ERROR(ENXIO);
rc->rc_tried = 1; /* don't even try */
rc->rc_skipped = 1;
continue;
}
if (vdev_dtl_contains(cvd, DTL_MISSING, zio->io_txg, 1)) {
if (c >= rm->rm_firstdatacol)
rm->rm_missingdata++;
else
rm->rm_missingparity++;
rc->rc_error = SET_ERROR(ESTALE);
rc->rc_skipped = 1;
continue;
}
if (c >= rm->rm_firstdatacol || rm->rm_missingdata > 0 ||
(zio->io_flags & (ZIO_FLAG_SCRUB | ZIO_FLAG_RESILVER))) {
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, void *bad_data)
{
vdev_t *vd = zio->io_vd->vdev_child[rc->rc_devidx];
if (!(zio->io_flags & ZIO_FLAG_SPECULATIVE)) {
zio_bad_cksum_t zbc;
raidz_map_t *rm = zio->io_vsd;
mutex_enter(&vd->vdev_stat_lock);
vd->vdev_stat.vs_checksum_errors++;
mutex_exit(&vd->vdev_stat_lock);
zbc.zbc_has_cksum = 0;
zbc.zbc_injected = rm->rm_ecksuminjected;
zfs_ereport_post_checksum(zio->io_spa, vd, zio,
rc->rc_offset, rc->rc_size, rc->rc_data, bad_data,
&zbc);
}
}
/*
* We keep track of whether or not there were any injected errors, so that
* any ereports we generate can note it.
*/
static int
raidz_checksum_verify(zio_t *zio)
{
zio_bad_cksum_t zbc;
raidz_map_t *rm = zio->io_vsd;
int ret;
bzero(&zbc, sizeof (zio_bad_cksum_t));
ret = zio_checksum_error(zio, &zbc);
if (ret != 0 && zbc.zbc_injected != 0)
rm->rm_ecksuminjected = 1;
return (ret);
}
/*
* 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);
}
vdev_raidz_generate_parity(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, orig[c]);
rc->rc_error = SET_ERROR(ECKSUM);
ret++;
}
zio_buf_free(orig[c], rc->rc_size);
}
return (ret);
}
/*
* Keep statistics on all the ways that we used parity to correct data.
*/
static uint64_t raidz_corrected[1 << VDEV_RAIDZ_MAXPARITY];
static int
vdev_raidz_worst_error(raidz_map_t *rm)
{
int c, error = 0;
for (c = 0; c < rm->rm_cols; c++)
error = zio_worst_error(error, rm->rm_col[c].rc_error);
return (error);
}
/*
* Iterate over all combinations of bad data and attempt a reconstruction.
* Note that the algorithm below is non-optimal because it doesn't take into
* account how reconstruction is actually performed. For example, with
* triple-parity RAID-Z the reconstruction procedure is the same if column 4
* is targeted as invalid as if columns 1 and 4 are targeted since in both
* cases we'd only use parity information in column 0.
*/
static int
vdev_raidz_combrec(zio_t *zio, int total_errors, int data_errors)
{
raidz_map_t *rm = zio->io_vsd;
raidz_col_t *rc;
void *orig[VDEV_RAIDZ_MAXPARITY];
int tstore[VDEV_RAIDZ_MAXPARITY + 2];
int *tgts = &tstore[1];
int curr, next, i, c, n;
int code, ret = 0;
ASSERT(total_errors < rm->rm_firstdatacol);
/*
* This simplifies one edge condition.
*/
tgts[-1] = -1;
for (n = 1; n <= rm->rm_firstdatacol - total_errors; n++) {
/*
* Initialize the targets array by finding the first n columns
* that contain no error.
*
* If there were no data errors, we need to ensure that we're
* always explicitly attempting to reconstruct at least one
* data column. To do this, we simply push the highest target
* up into the data columns.
*/
for (c = 0, i = 0; i < n; i++) {
if (i == n - 1 && data_errors == 0 &&
c < rm->rm_firstdatacol) {
c = rm->rm_firstdatacol;
}
while (rm->rm_col[c].rc_error != 0) {
c++;
ASSERT3S(c, <, rm->rm_cols);
}
tgts[i] = c++;
}
/*
* Setting tgts[n] simplifies the other edge condition.
*/
tgts[n] = rm->rm_cols;
/*
* These buffers were allocated in previous iterations.
*/
for (i = 0; i < n - 1; i++) {
ASSERT(orig[i] != NULL);
}
orig[n - 1] = zio_buf_alloc(rm->rm_col[0].rc_size);
curr = 0;
next = tgts[curr];
while (curr != n) {
tgts[curr] = next;
curr = 0;
/*
* Save off the original data that we're going to
* attempt to reconstruct.
*/
for (i = 0; i < n; i++) {
ASSERT(orig[i] != NULL);
c = tgts[i];
ASSERT3S(c, >=, 0);
ASSERT3S(c, <, rm->rm_cols);
rc = &rm->rm_col[c];
bcopy(rc->rc_data, orig[i], rc->rc_size);
}
/*
* Attempt a reconstruction and exit the outer loop on
* success.
*/
code = vdev_raidz_reconstruct(rm, tgts, n);
if (raidz_checksum_verify(zio) == 0) {
atomic_inc_64(&raidz_corrected[code]);
for (i = 0; i < n; i++) {
c = tgts[i];
rc = &rm->rm_col[c];
ASSERT(rc->rc_error == 0);
if (rc->rc_tried)
raidz_checksum_error(zio, rc,
orig[i]);
rc->rc_error = SET_ERROR(ECKSUM);
}
ret = code;
goto done;
}
/*
* Restore the original data.
*/
for (i = 0; i < n; i++) {
c = tgts[i];
rc = &rm->rm_col[c];
bcopy(orig[i], rc->rc_data, rc->rc_size);
}
do {
/*
* Find the next valid column after the curr
* position..
*/
for (next = tgts[curr] + 1;
next < rm->rm_cols &&
rm->rm_col[next].rc_error != 0; next++)
continue;
ASSERT(next <= tgts[curr + 1]);
/*
* If that spot is available, we're done here.
*/
if (next != tgts[curr + 1])
break;
/*
* Otherwise, find the next valid column after
* the previous position.
*/
for (c = tgts[curr - 1] + 1;
rm->rm_col[c].rc_error != 0; c++)
continue;
tgts[curr] = c;
curr++;
} while (curr != n);
}
}
n--;
done:
for (i = 0; i < n; i++) {
zio_buf_free(orig[i], rm->rm_col[0].rc_size);
}
return (ret);
}
/*
* Complete an IO operation on a RAIDZ VDev
*
* Outline:
* - For write operations:
* 1. Check for errors on the child IOs.
* 2. Return, setting an error code if too few child VDevs were written
* to reconstruct the data later. Note that partial writes are
* considered successful if they can be reconstructed at all.
* - For read operations:
* 1. Check for errors on the child IOs.
* 2. If data errors occurred:
* a. Try to reassemble the data from the parity available.
* b. If we haven't yet read the parity drives, read them now.
* c. If all parity drives have been read but the data still doesn't
* reassemble with a correct checksum, then try combinatorial
* reconstruction.
* d. If that doesn't work, return an error.
* 3. If there were unexpected errors or this is a resilver operation,
* rewrite the vdevs that had errors.
*/
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;
int unexpected_errors = 0;
int parity_errors = 0;
int parity_untried = 0;
int data_errors = 0;
int total_errors = 0;
int n, c;
int tgts[VDEV_RAIDZ_MAXPARITY];
int code;
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) {
if (data_errors == 0) {
if (raidz_checksum_verify(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;
}
} else {
/*
* 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);
/*
* Identify the data columns that reported an error.
*/
n = 0;
for (c = rm->rm_firstdatacol; c < rm->rm_cols; c++) {
rc = &rm->rm_col[c];
if (rc->rc_error != 0) {
ASSERT(n < VDEV_RAIDZ_MAXPARITY);
tgts[n++] = c;
}
}
ASSERT(rm->rm_firstdatacol >= n);
code = vdev_raidz_reconstruct(rm, tgts, n);
if (raidz_checksum_verify(zio) == 0) {
atomic_inc_64(&raidz_corrected[code]);
/*
* If we read more parity disks than were used
* for reconstruction, confirm that the other
* parity disks produced correct data. This
* routine is suboptimal in that it regenerates
* the parity that we already used in addition
* to the parity that we're attempting to
* verify, but this should be a relatively
* uncommon case, and can be optimized if it
* becomes a problem. Note that we regenerate
* parity when resilvering so we can write it
* out to failed devices later.
*/
if (parity_errors < rm->rm_firstdatacol - n ||
(zio->io_flags & ZIO_FLAG_RESILVER)) {
n = raidz_parity_verify(zio, rm);
unexpected_errors += n;
ASSERT(parity_errors + n <=
rm->rm_firstdatacol);
}
goto done;
}
}
}
/*
* 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. We check if there is enough additional data to
* possibly reconstruct the data and then perform combinatorial
* reconstruction over all possible combinations. If that fails,
* we're cooked.
*/
if (total_errors > rm->rm_firstdatacol) {
zio->io_error = vdev_raidz_worst_error(rm);
} else if (total_errors < rm->rm_firstdatacol &&
(code = vdev_raidz_combrec(zio, total_errors, data_errors)) != 0) {
/*
* If we didn't use all the available parity for the
* combinatorial reconstruction, verify that the remaining
* parity is correct.
*/
if (code != (1 << rm->rm_firstdatacol) - 1)
(void) raidz_parity_verify(zio, rm);
} else {
/*
* We're here because either:
*
* total_errors == rm_first_datacol, or
* vdev_raidz_combrec() failed
*
* In either case, there is enough bad data to prevent
* reconstruction.
*
* Start checksum ereports for all children which haven't
* failed, and the IO wasn't speculative.
*/
zio->io_error = SET_ERROR(ECKSUM);
if (!(zio->io_flags & ZIO_FLAG_SPECULATIVE)) {
for (c = 0; c < rm->rm_cols; c++) {
rc = &rm->rm_col[c];
if (rc->rc_error == 0) {
zio_bad_cksum_t zbc;
zbc.zbc_has_cksum = 0;
zbc.zbc_injected =
rm->rm_ecksuminjected;
zfs_ereport_start_checksum(
zio->io_spa,
vd->vdev_child[rc->rc_devidx],
zio, rc->rc_offset, rc->rc_size,
(void *)(uintptr_t)c, &zbc);
}
}
}
}
done:
zio_checksum_verified(zio);
if (zio->io_error == 0 && spa_writeable(zio->io_spa) &&
(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_PRIORITY_ASYNC_WRITE,
ZIO_FLAG_IO_REPAIR | (unexpected_errors ?
ZIO_FLAG_SELF_HEAL : 0), 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,
NULL,
NULL,
VDEV_TYPE_RAIDZ, /* name of this vdev type */
B_FALSE /* not a leaf vdev */
};
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