alistair23-linux/drivers/md/dm-stripe.c
Christoph Hellwig 7b6d91daee block: unify flags for struct bio and struct request
Remove the current bio flags and reuse the request flags for the bio, too.
This allows to more easily trace the type of I/O from the filesystem
down to the block driver.  There were two flags in the bio that were
missing in the requests:  BIO_RW_UNPLUG and BIO_RW_AHEAD.  Also I've
renamed two request flags that had a superflous RW in them.

Note that the flags are in bio.h despite having the REQ_ name - as
blkdev.h includes bio.h that is the only way to go for now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2010-08-07 18:20:39 +02:00

381 lines
8.1 KiB
C

/*
* Copyright (C) 2001-2003 Sistina Software (UK) Limited.
*
* This file is released under the GPL.
*/
#include <linux/device-mapper.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/blkdev.h>
#include <linux/bio.h>
#include <linux/slab.h>
#include <linux/log2.h>
#define DM_MSG_PREFIX "striped"
#define DM_IO_ERROR_THRESHOLD 15
struct stripe {
struct dm_dev *dev;
sector_t physical_start;
atomic_t error_count;
};
struct stripe_c {
uint32_t stripes;
/* The size of this target / num. stripes */
sector_t stripe_width;
/* stripe chunk size */
uint32_t chunk_shift;
sector_t chunk_mask;
/* Needed for handling events */
struct dm_target *ti;
/* Work struct used for triggering events*/
struct work_struct kstriped_ws;
struct stripe stripe[0];
};
static struct workqueue_struct *kstriped;
/*
* An event is triggered whenever a drive
* drops out of a stripe volume.
*/
static void trigger_event(struct work_struct *work)
{
struct stripe_c *sc = container_of(work, struct stripe_c, kstriped_ws);
dm_table_event(sc->ti->table);
}
static inline struct stripe_c *alloc_context(unsigned int stripes)
{
size_t len;
if (dm_array_too_big(sizeof(struct stripe_c), sizeof(struct stripe),
stripes))
return NULL;
len = sizeof(struct stripe_c) + (sizeof(struct stripe) * stripes);
return kmalloc(len, GFP_KERNEL);
}
/*
* Parse a single <dev> <sector> pair
*/
static int get_stripe(struct dm_target *ti, struct stripe_c *sc,
unsigned int stripe, char **argv)
{
unsigned long long start;
if (sscanf(argv[1], "%llu", &start) != 1)
return -EINVAL;
if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
&sc->stripe[stripe].dev))
return -ENXIO;
sc->stripe[stripe].physical_start = start;
return 0;
}
/*
* Construct a striped mapping.
* <number of stripes> <chunk size (2^^n)> [<dev_path> <offset>]+
*/
static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
struct stripe_c *sc;
sector_t width;
uint32_t stripes;
uint32_t chunk_size;
char *end;
int r;
unsigned int i;
if (argc < 2) {
ti->error = "Not enough arguments";
return -EINVAL;
}
stripes = simple_strtoul(argv[0], &end, 10);
if (!stripes || *end) {
ti->error = "Invalid stripe count";
return -EINVAL;
}
chunk_size = simple_strtoul(argv[1], &end, 10);
if (*end) {
ti->error = "Invalid chunk_size";
return -EINVAL;
}
/*
* chunk_size is a power of two
*/
if (!is_power_of_2(chunk_size) ||
(chunk_size < (PAGE_SIZE >> SECTOR_SHIFT))) {
ti->error = "Invalid chunk size";
return -EINVAL;
}
if (ti->len & (chunk_size - 1)) {
ti->error = "Target length not divisible by "
"chunk size";
return -EINVAL;
}
width = ti->len;
if (sector_div(width, stripes)) {
ti->error = "Target length not divisible by "
"number of stripes";
return -EINVAL;
}
/*
* Do we have enough arguments for that many stripes ?
*/
if (argc != (2 + 2 * stripes)) {
ti->error = "Not enough destinations "
"specified";
return -EINVAL;
}
sc = alloc_context(stripes);
if (!sc) {
ti->error = "Memory allocation for striped context "
"failed";
return -ENOMEM;
}
INIT_WORK(&sc->kstriped_ws, trigger_event);
/* Set pointer to dm target; used in trigger_event */
sc->ti = ti;
sc->stripes = stripes;
sc->stripe_width = width;
ti->split_io = chunk_size;
ti->num_flush_requests = stripes;
sc->chunk_mask = ((sector_t) chunk_size) - 1;
for (sc->chunk_shift = 0; chunk_size; sc->chunk_shift++)
chunk_size >>= 1;
sc->chunk_shift--;
/*
* Get the stripe destinations.
*/
for (i = 0; i < stripes; i++) {
argv += 2;
r = get_stripe(ti, sc, i, argv);
if (r < 0) {
ti->error = "Couldn't parse stripe destination";
while (i--)
dm_put_device(ti, sc->stripe[i].dev);
kfree(sc);
return r;
}
atomic_set(&(sc->stripe[i].error_count), 0);
}
ti->private = sc;
return 0;
}
static void stripe_dtr(struct dm_target *ti)
{
unsigned int i;
struct stripe_c *sc = (struct stripe_c *) ti->private;
for (i = 0; i < sc->stripes; i++)
dm_put_device(ti, sc->stripe[i].dev);
flush_workqueue(kstriped);
kfree(sc);
}
static int stripe_map(struct dm_target *ti, struct bio *bio,
union map_info *map_context)
{
struct stripe_c *sc = (struct stripe_c *) ti->private;
sector_t offset, chunk;
uint32_t stripe;
if (unlikely(bio_empty_barrier(bio))) {
BUG_ON(map_context->flush_request >= sc->stripes);
bio->bi_bdev = sc->stripe[map_context->flush_request].dev->bdev;
return DM_MAPIO_REMAPPED;
}
offset = bio->bi_sector - ti->begin;
chunk = offset >> sc->chunk_shift;
stripe = sector_div(chunk, sc->stripes);
bio->bi_bdev = sc->stripe[stripe].dev->bdev;
bio->bi_sector = sc->stripe[stripe].physical_start +
(chunk << sc->chunk_shift) + (offset & sc->chunk_mask);
return DM_MAPIO_REMAPPED;
}
/*
* Stripe status:
*
* INFO
* #stripes [stripe_name <stripe_name>] [group word count]
* [error count 'A|D' <error count 'A|D'>]
*
* TABLE
* #stripes [stripe chunk size]
* [stripe_name physical_start <stripe_name physical_start>]
*
*/
static int stripe_status(struct dm_target *ti,
status_type_t type, char *result, unsigned int maxlen)
{
struct stripe_c *sc = (struct stripe_c *) ti->private;
char buffer[sc->stripes + 1];
unsigned int sz = 0;
unsigned int i;
switch (type) {
case STATUSTYPE_INFO:
DMEMIT("%d ", sc->stripes);
for (i = 0; i < sc->stripes; i++) {
DMEMIT("%s ", sc->stripe[i].dev->name);
buffer[i] = atomic_read(&(sc->stripe[i].error_count)) ?
'D' : 'A';
}
buffer[i] = '\0';
DMEMIT("1 %s", buffer);
break;
case STATUSTYPE_TABLE:
DMEMIT("%d %llu", sc->stripes,
(unsigned long long)sc->chunk_mask + 1);
for (i = 0; i < sc->stripes; i++)
DMEMIT(" %s %llu", sc->stripe[i].dev->name,
(unsigned long long)sc->stripe[i].physical_start);
break;
}
return 0;
}
static int stripe_end_io(struct dm_target *ti, struct bio *bio,
int error, union map_info *map_context)
{
unsigned i;
char major_minor[16];
struct stripe_c *sc = ti->private;
if (!error)
return 0; /* I/O complete */
if ((error == -EWOULDBLOCK) && (bio->bi_rw & REQ_RAHEAD))
return error;
if (error == -EOPNOTSUPP)
return error;
memset(major_minor, 0, sizeof(major_minor));
sprintf(major_minor, "%d:%d",
MAJOR(disk_devt(bio->bi_bdev->bd_disk)),
MINOR(disk_devt(bio->bi_bdev->bd_disk)));
/*
* Test to see which stripe drive triggered the event
* and increment error count for all stripes on that device.
* If the error count for a given device exceeds the threshold
* value we will no longer trigger any further events.
*/
for (i = 0; i < sc->stripes; i++)
if (!strcmp(sc->stripe[i].dev->name, major_minor)) {
atomic_inc(&(sc->stripe[i].error_count));
if (atomic_read(&(sc->stripe[i].error_count)) <
DM_IO_ERROR_THRESHOLD)
queue_work(kstriped, &sc->kstriped_ws);
}
return error;
}
static int stripe_iterate_devices(struct dm_target *ti,
iterate_devices_callout_fn fn, void *data)
{
struct stripe_c *sc = ti->private;
int ret = 0;
unsigned i = 0;
do {
ret = fn(ti, sc->stripe[i].dev,
sc->stripe[i].physical_start,
sc->stripe_width, data);
} while (!ret && ++i < sc->stripes);
return ret;
}
static void stripe_io_hints(struct dm_target *ti,
struct queue_limits *limits)
{
struct stripe_c *sc = ti->private;
unsigned chunk_size = (sc->chunk_mask + 1) << 9;
blk_limits_io_min(limits, chunk_size);
blk_limits_io_opt(limits, chunk_size * sc->stripes);
}
static struct target_type stripe_target = {
.name = "striped",
.version = {1, 3, 0},
.module = THIS_MODULE,
.ctr = stripe_ctr,
.dtr = stripe_dtr,
.map = stripe_map,
.end_io = stripe_end_io,
.status = stripe_status,
.iterate_devices = stripe_iterate_devices,
.io_hints = stripe_io_hints,
};
int __init dm_stripe_init(void)
{
int r;
r = dm_register_target(&stripe_target);
if (r < 0) {
DMWARN("target registration failed");
return r;
}
kstriped = create_singlethread_workqueue("kstriped");
if (!kstriped) {
DMERR("failed to create workqueue kstriped");
dm_unregister_target(&stripe_target);
return -ENOMEM;
}
return r;
}
void dm_stripe_exit(void)
{
dm_unregister_target(&stripe_target);
destroy_workqueue(kstriped);
return;
}