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dm.c
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dm.c
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/*
* Copyright (C) 2001, 2002 Sistina Software (UK) Limited.
* Copyright (C) 2004-2006 Red Hat, Inc. All rights reserved.
*
* This file is released under the GPL.
*/
#include "dm.h"
#include "dm-bio-list.h"
#include <linux/init.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/moduleparam.h>
#include <linux/blkpg.h>
#include <linux/bio.h>
#include <linux/buffer_head.h>
#include <linux/mempool.h>
#include <linux/slab.h>
#include <linux/idr.h>
#include <linux/hdreg.h>
#include <linux/blktrace_api.h>
#include <linux/smp_lock.h>
#define DM_MSG_PREFIX "core"
static const char *_name = DM_NAME;
static unsigned int major = 0;
static unsigned int _major = 0;
static DEFINE_SPINLOCK(_minor_lock);
/*
* One of these is allocated per bio.
*/
struct dm_io {
struct mapped_device *md;
int error;
struct bio *bio;
atomic_t io_count;
unsigned long start_time;
};
/*
* One of these is allocated per target within a bio. Hopefully
* this will be simplified out one day.
*/
struct target_io {
struct dm_io *io;
struct dm_target *ti;
union map_info info;
};
union map_info *dm_get_mapinfo(struct bio *bio)
{
if (bio && bio->bi_private)
return &((struct target_io *)bio->bi_private)->info;
return NULL;
}
#define MINOR_ALLOCED ((void *)-1)
/*
* Bits for the md->flags field.
*/
#define DMF_BLOCK_IO 0
#define DMF_SUSPENDED 1
#define DMF_FROZEN 2
#define DMF_FREEING 3
#define DMF_DELETING 4
#define DMF_NOFLUSH_SUSPENDING 5
struct mapped_device {
struct rw_semaphore io_lock;
struct semaphore suspend_lock;
spinlock_t pushback_lock;
rwlock_t map_lock;
atomic_t holders;
atomic_t open_count;
unsigned long flags;
request_queue_t *queue;
struct gendisk *disk;
char name[16];
void *interface_ptr;
/*
* A list of ios that arrived while we were suspended.
*/
atomic_t pending;
wait_queue_head_t wait;
struct bio_list deferred;
struct bio_list pushback;
/*
* The current mapping.
*/
struct dm_table *map;
/*
* io objects are allocated from here.
*/
mempool_t *io_pool;
mempool_t *tio_pool;
struct bio_set *bs;
/*
* Event handling.
*/
atomic_t event_nr;
wait_queue_head_t eventq;
/*
* freeze/thaw support require holding onto a super block
*/
struct super_block *frozen_sb;
struct block_device *suspended_bdev;
/* forced geometry settings */
struct hd_geometry geometry;
};
#define MIN_IOS 256
static struct kmem_cache *_io_cache;
static struct kmem_cache *_tio_cache;
static int __init local_init(void)
{
int r;
/* allocate a slab for the dm_ios */
_io_cache = kmem_cache_create("dm_io",
sizeof(struct dm_io), 0, 0, NULL, NULL);
if (!_io_cache)
return -ENOMEM;
/* allocate a slab for the target ios */
_tio_cache = kmem_cache_create("dm_tio", sizeof(struct target_io),
0, 0, NULL, NULL);
if (!_tio_cache) {
kmem_cache_destroy(_io_cache);
return -ENOMEM;
}
_major = major;
r = register_blkdev(_major, _name);
if (r < 0) {
kmem_cache_destroy(_tio_cache);
kmem_cache_destroy(_io_cache);
return r;
}
if (!_major)
_major = r;
return 0;
}
static void local_exit(void)
{
kmem_cache_destroy(_tio_cache);
kmem_cache_destroy(_io_cache);
if (unregister_blkdev(_major, _name) < 0)
DMERR("unregister_blkdev failed");
_major = 0;
DMINFO("cleaned up");
}
int (*_inits[])(void) __initdata = {
local_init,
dm_target_init,
dm_linear_init,
dm_stripe_init,
dm_interface_init,
};
void (*_exits[])(void) = {
local_exit,
dm_target_exit,
dm_linear_exit,
dm_stripe_exit,
dm_interface_exit,
};
static int __init dm_init(void)
{
const int count = ARRAY_SIZE(_inits);
int r, i;
for (i = 0; i < count; i++) {
r = _inits[i]();
if (r)
goto bad;
}
return 0;
bad:
while (i--)
_exits[i]();
return r;
}
static void __exit dm_exit(void)
{
int i = ARRAY_SIZE(_exits);
while (i--)
_exits[i]();
}
/*
* Block device functions
*/
static int dm_blk_open(struct inode *inode, struct file *file)
{
struct mapped_device *md;
spin_lock(&_minor_lock);
md = inode->i_bdev->bd_disk->private_data;
if (!md)
goto out;
if (test_bit(DMF_FREEING, &md->flags) ||
test_bit(DMF_DELETING, &md->flags)) {
md = NULL;
goto out;
}
dm_get(md);
atomic_inc(&md->open_count);
out:
spin_unlock(&_minor_lock);
return md ? 0 : -ENXIO;
}
static int dm_blk_close(struct inode *inode, struct file *file)
{
struct mapped_device *md;
md = inode->i_bdev->bd_disk->private_data;
atomic_dec(&md->open_count);
dm_put(md);
return 0;
}
int dm_open_count(struct mapped_device *md)
{
return atomic_read(&md->open_count);
}
/*
* Guarantees nothing is using the device before it's deleted.
*/
int dm_lock_for_deletion(struct mapped_device *md)
{
int r = 0;
spin_lock(&_minor_lock);
if (dm_open_count(md))
r = -EBUSY;
else
set_bit(DMF_DELETING, &md->flags);
spin_unlock(&_minor_lock);
return r;
}
static int dm_blk_getgeo(struct block_device *bdev, struct hd_geometry *geo)
{
struct mapped_device *md = bdev->bd_disk->private_data;
return dm_get_geometry(md, geo);
}
static int dm_blk_ioctl(struct inode *inode, struct file *file,
unsigned int cmd, unsigned long arg)
{
struct mapped_device *md;
struct dm_table *map;
struct dm_target *tgt;
int r = -ENOTTY;
/* We don't really need this lock, but we do need 'inode'. */
unlock_kernel();
md = inode->i_bdev->bd_disk->private_data;
map = dm_get_table(md);
if (!map || !dm_table_get_size(map))
goto out;
/* We only support devices that have a single target */
if (dm_table_get_num_targets(map) != 1)
goto out;
tgt = dm_table_get_target(map, 0);
if (dm_suspended(md)) {
r = -EAGAIN;
goto out;
}
if (tgt->type->ioctl)
r = tgt->type->ioctl(tgt, inode, file, cmd, arg);
out:
dm_table_put(map);
lock_kernel();
return r;
}
static inline struct dm_io *alloc_io(struct mapped_device *md)
{
return mempool_alloc(md->io_pool, GFP_NOIO);
}
static inline void free_io(struct mapped_device *md, struct dm_io *io)
{
mempool_free(io, md->io_pool);
}
static inline struct target_io *alloc_tio(struct mapped_device *md)
{
return mempool_alloc(md->tio_pool, GFP_NOIO);
}
static inline void free_tio(struct mapped_device *md, struct target_io *tio)
{
mempool_free(tio, md->tio_pool);
}
static void start_io_acct(struct dm_io *io)
{
struct mapped_device *md = io->md;
io->start_time = jiffies;
preempt_disable();
disk_round_stats(dm_disk(md));
preempt_enable();
dm_disk(md)->in_flight = atomic_inc_return(&md->pending);
}
static int end_io_acct(struct dm_io *io)
{
struct mapped_device *md = io->md;
struct bio *bio = io->bio;
unsigned long duration = jiffies - io->start_time;
int pending;
int rw = bio_data_dir(bio);
preempt_disable();
disk_round_stats(dm_disk(md));
preempt_enable();
dm_disk(md)->in_flight = pending = atomic_dec_return(&md->pending);
disk_stat_add(dm_disk(md), ticks[rw], duration);
return !pending;
}
/*
* Add the bio to the list of deferred io.
*/
static int queue_io(struct mapped_device *md, struct bio *bio)
{
down_write(&md->io_lock);
if (!test_bit(DMF_BLOCK_IO, &md->flags)) {
up_write(&md->io_lock);
return 1;
}
bio_list_add(&md->deferred, bio);
up_write(&md->io_lock);
return 0; /* deferred successfully */
}
/*
* Everyone (including functions in this file), should use this
* function to access the md->map field, and make sure they call
* dm_table_put() when finished.
*/
struct dm_table *dm_get_table(struct mapped_device *md)
{
struct dm_table *t;
read_lock(&md->map_lock);
t = md->map;
if (t)
dm_table_get(t);
read_unlock(&md->map_lock);
return t;
}
/*
* Get the geometry associated with a dm device
*/
int dm_get_geometry(struct mapped_device *md, struct hd_geometry *geo)
{
*geo = md->geometry;
return 0;
}
/*
* Set the geometry of a device.
*/
int dm_set_geometry(struct mapped_device *md, struct hd_geometry *geo)
{
sector_t sz = (sector_t)geo->cylinders * geo->heads * geo->sectors;
if (geo->start > sz) {
DMWARN("Start sector is beyond the geometry limits.");
return -EINVAL;
}
md->geometry = *geo;
return 0;
}
/*-----------------------------------------------------------------
* CRUD START:
* A more elegant soln is in the works that uses the queue
* merge fn, unfortunately there are a couple of changes to
* the block layer that I want to make for this. So in the
* interests of getting something for people to use I give
* you this clearly demarcated crap.
*---------------------------------------------------------------*/
static int __noflush_suspending(struct mapped_device *md)
{
return test_bit(DMF_NOFLUSH_SUSPENDING, &md->flags);
}
/*
* Decrements the number of outstanding ios that a bio has been
* cloned into, completing the original io if necc.
*/
static void dec_pending(struct dm_io *io, int error)
{
unsigned long flags;
/* Push-back supersedes any I/O errors */
if (error && !(io->error > 0 && __noflush_suspending(io->md)))
io->error = error;
if (atomic_dec_and_test(&io->io_count)) {
if (io->error == DM_ENDIO_REQUEUE) {
/*
* Target requested pushing back the I/O.
* This must be handled before the sleeper on
* suspend queue merges the pushback list.
*/
spin_lock_irqsave(&io->md->pushback_lock, flags);
if (__noflush_suspending(io->md))
bio_list_add(&io->md->pushback, io->bio);
else
/* noflush suspend was interrupted. */
io->error = -EIO;
spin_unlock_irqrestore(&io->md->pushback_lock, flags);
}
if (end_io_acct(io))
/* nudge anyone waiting on suspend queue */
wake_up(&io->md->wait);
if (io->error != DM_ENDIO_REQUEUE) {
blk_add_trace_bio(io->md->queue, io->bio,
BLK_TA_COMPLETE);
bio_endio(io->bio, io->bio->bi_size, io->error);
}
free_io(io->md, io);
}
}
static int clone_endio(struct bio *bio, unsigned int done, int error)
{
int r = 0;
struct target_io *tio = bio->bi_private;
struct mapped_device *md = tio->io->md;
dm_endio_fn endio = tio->ti->type->end_io;
if (bio->bi_size)
return 1;
if (!bio_flagged(bio, BIO_UPTODATE) && !error)
error = -EIO;
if (endio) {
r = endio(tio->ti, bio, error, &tio->info);
if (r < 0 || r == DM_ENDIO_REQUEUE)
/*
* error and requeue request are handled
* in dec_pending().
*/
error = r;
else if (r == DM_ENDIO_INCOMPLETE)
/* The target will handle the io */
return 1;
else if (r) {
DMWARN("unimplemented target endio return value: %d", r);
BUG();
}
}
dec_pending(tio->io, error);
/*
* Store md for cleanup instead of tio which is about to get freed.
*/
bio->bi_private = md->bs;
bio_put(bio);
free_tio(md, tio);
return r;
}
static sector_t max_io_len(struct mapped_device *md,
sector_t sector, struct dm_target *ti)
{
sector_t offset = sector - ti->begin;
sector_t len = ti->len - offset;
/*
* Does the target need to split even further ?
*/
if (ti->split_io) {
sector_t boundary;
boundary = ((offset + ti->split_io) & ~(ti->split_io - 1))
- offset;
if (len > boundary)
len = boundary;
}
return len;
}
static void __map_bio(struct dm_target *ti, struct bio *clone,
struct target_io *tio)
{
int r;
sector_t sector;
struct mapped_device *md;
/*
* Sanity checks.
*/
BUG_ON(!clone->bi_size);
clone->bi_end_io = clone_endio;
clone->bi_private = tio;
/*
* Map the clone. If r == 0 we don't need to do
* anything, the target has assumed ownership of
* this io.
*/
atomic_inc(&tio->io->io_count);
sector = clone->bi_sector;
r = ti->type->map(ti, clone, &tio->info);
if (r == DM_MAPIO_REMAPPED) {
/* the bio has been remapped so dispatch it */
blk_add_trace_remap(bdev_get_queue(clone->bi_bdev), clone,
tio->io->bio->bi_bdev->bd_dev, sector,
clone->bi_sector);
generic_make_request(clone);
} else if (r < 0 || r == DM_MAPIO_REQUEUE) {
/* error the io and bail out, or requeue it if needed */
md = tio->io->md;
dec_pending(tio->io, r);
/*
* Store bio_set for cleanup.
*/
clone->bi_private = md->bs;
bio_put(clone);
free_tio(md, tio);
} else if (r) {
DMWARN("unimplemented target map return value: %d", r);
BUG();
}
}
struct clone_info {
struct mapped_device *md;
struct dm_table *map;
struct bio *bio;
struct dm_io *io;
sector_t sector;
sector_t sector_count;
unsigned short idx;
};
static void dm_bio_destructor(struct bio *bio)
{
struct bio_set *bs = bio->bi_private;
bio_free(bio, bs);
}
/*
* Creates a little bio that is just does part of a bvec.
*/
static struct bio *split_bvec(struct bio *bio, sector_t sector,
unsigned short idx, unsigned int offset,
unsigned int len, struct bio_set *bs)
{
struct bio *clone;
struct bio_vec *bv = bio->bi_io_vec + idx;
clone = bio_alloc_bioset(GFP_NOIO, 1, bs);
clone->bi_destructor = dm_bio_destructor;
*clone->bi_io_vec = *bv;
clone->bi_sector = sector;
clone->bi_bdev = bio->bi_bdev;
clone->bi_rw = bio->bi_rw;
clone->bi_vcnt = 1;
clone->bi_size = to_bytes(len);
clone->bi_io_vec->bv_offset = offset;
clone->bi_io_vec->bv_len = clone->bi_size;
return clone;
}
/*
* Creates a bio that consists of range of complete bvecs.
*/
static struct bio *clone_bio(struct bio *bio, sector_t sector,
unsigned short idx, unsigned short bv_count,
unsigned int len, struct bio_set *bs)
{
struct bio *clone;
clone = bio_alloc_bioset(GFP_NOIO, bio->bi_max_vecs, bs);
__bio_clone(clone, bio);
clone->bi_destructor = dm_bio_destructor;
clone->bi_sector = sector;
clone->bi_idx = idx;
clone->bi_vcnt = idx + bv_count;
clone->bi_size = to_bytes(len);
clone->bi_flags &= ~(1 << BIO_SEG_VALID);
return clone;
}
static void __clone_and_map(struct clone_info *ci)
{
struct bio *clone, *bio = ci->bio;
struct dm_target *ti = dm_table_find_target(ci->map, ci->sector);
sector_t len = 0, max = max_io_len(ci->md, ci->sector, ti);
struct target_io *tio;
/*
* Allocate a target io object.
*/
tio = alloc_tio(ci->md);
tio->io = ci->io;
tio->ti = ti;
memset(&tio->info, 0, sizeof(tio->info));
if (ci->sector_count <= max) {
/*
* Optimise for the simple case where we can do all of
* the remaining io with a single clone.
*/
clone = clone_bio(bio, ci->sector, ci->idx,
bio->bi_vcnt - ci->idx, ci->sector_count,
ci->md->bs);
__map_bio(ti, clone, tio);
ci->sector_count = 0;
} else if (to_sector(bio->bi_io_vec[ci->idx].bv_len) <= max) {
/*
* There are some bvecs that don't span targets.
* Do as many of these as possible.
*/
int i;
sector_t remaining = max;
sector_t bv_len;
for (i = ci->idx; remaining && (i < bio->bi_vcnt); i++) {
bv_len = to_sector(bio->bi_io_vec[i].bv_len);
if (bv_len > remaining)
break;
remaining -= bv_len;
len += bv_len;
}
clone = clone_bio(bio, ci->sector, ci->idx, i - ci->idx, len,
ci->md->bs);
__map_bio(ti, clone, tio);
ci->sector += len;
ci->sector_count -= len;
ci->idx = i;
} else {
/*
* Handle a bvec that must be split between two or more targets.
*/
struct bio_vec *bv = bio->bi_io_vec + ci->idx;
sector_t remaining = to_sector(bv->bv_len);
unsigned int offset = 0;
do {
if (offset) {
ti = dm_table_find_target(ci->map, ci->sector);
max = max_io_len(ci->md, ci->sector, ti);
tio = alloc_tio(ci->md);
tio->io = ci->io;
tio->ti = ti;
memset(&tio->info, 0, sizeof(tio->info));
}
len = min(remaining, max);
clone = split_bvec(bio, ci->sector, ci->idx,
bv->bv_offset + offset, len,
ci->md->bs);
__map_bio(ti, clone, tio);
ci->sector += len;
ci->sector_count -= len;
offset += to_bytes(len);
} while (remaining -= len);
ci->idx++;
}
}
/*
* Split the bio into several clones.
*/
static void __split_bio(struct mapped_device *md, struct bio *bio)
{
struct clone_info ci;
ci.map = dm_get_table(md);
if (!ci.map) {
bio_io_error(bio, bio->bi_size);
return;
}
ci.md = md;
ci.bio = bio;
ci.io = alloc_io(md);
ci.io->error = 0;
atomic_set(&ci.io->io_count, 1);
ci.io->bio = bio;
ci.io->md = md;
ci.sector = bio->bi_sector;
ci.sector_count = bio_sectors(bio);
ci.idx = bio->bi_idx;
start_io_acct(ci.io);
while (ci.sector_count)
__clone_and_map(&ci);
/* drop the extra reference count */
dec_pending(ci.io, 0);
dm_table_put(ci.map);
}
/*-----------------------------------------------------------------
* CRUD END
*---------------------------------------------------------------*/
/*
* The request function that just remaps the bio built up by
* dm_merge_bvec.
*/
static int dm_request(request_queue_t *q, struct bio *bio)
{
int r;
int rw = bio_data_dir(bio);
struct mapped_device *md = q->queuedata;
down_read(&md->io_lock);
disk_stat_inc(dm_disk(md), ios[rw]);
disk_stat_add(dm_disk(md), sectors[rw], bio_sectors(bio));
/*
* If we're suspended we have to queue
* this io for later.
*/
while (test_bit(DMF_BLOCK_IO, &md->flags)) {
up_read(&md->io_lock);
if (bio_rw(bio) == READA) {
bio_io_error(bio, bio->bi_size);
return 0;
}
r = queue_io(md, bio);
if (r < 0) {
bio_io_error(bio, bio->bi_size);
return 0;
} else if (r == 0)
return 0; /* deferred successfully */
/*
* We're in a while loop, because someone could suspend
* before we get to the following read lock.
*/
down_read(&md->io_lock);
}
__split_bio(md, bio);
up_read(&md->io_lock);
return 0;
}
static int dm_flush_all(request_queue_t *q, struct gendisk *disk,
sector_t *error_sector)
{
struct mapped_device *md = q->queuedata;
struct dm_table *map = dm_get_table(md);
int ret = -ENXIO;
if (map) {
ret = dm_table_flush_all(map);
dm_table_put(map);
}
return ret;
}
static void dm_unplug_all(request_queue_t *q)
{
struct mapped_device *md = q->queuedata;
struct dm_table *map = dm_get_table(md);
if (map) {
dm_table_unplug_all(map);
dm_table_put(map);
}
}
static int dm_any_congested(void *congested_data, int bdi_bits)
{
int r;
struct mapped_device *md = (struct mapped_device *) congested_data;
struct dm_table *map = dm_get_table(md);
if (!map || test_bit(DMF_BLOCK_IO, &md->flags))
r = bdi_bits;
else
r = dm_table_any_congested(map, bdi_bits);
dm_table_put(map);
return r;
}
/*-----------------------------------------------------------------
* An IDR is used to keep track of allocated minor numbers.
*---------------------------------------------------------------*/
static DEFINE_IDR(_minor_idr);
static void free_minor(int minor)
{
spin_lock(&_minor_lock);
idr_remove(&_minor_idr, minor);
spin_unlock(&_minor_lock);
}
/*
* See if the device with a specific minor # is free.
*/
static int specific_minor(struct mapped_device *md, int minor)
{
int r, m;
if (minor >= (1 << MINORBITS))
return -EINVAL;
r = idr_pre_get(&_minor_idr, GFP_KERNEL);
if (!r)
return -ENOMEM;
spin_lock(&_minor_lock);
if (idr_find(&_minor_idr, minor)) {
r = -EBUSY;
goto out;
}
r = idr_get_new_above(&_minor_idr, MINOR_ALLOCED, minor, &m);
if (r)
goto out;
if (m != minor) {
idr_remove(&_minor_idr, m);
r = -EBUSY;
goto out;
}
out:
spin_unlock(&_minor_lock);
return r;
}
static int next_free_minor(struct mapped_device *md, int *minor)
{
int r, m;
r = idr_pre_get(&_minor_idr, GFP_KERNEL);
if (!r)
return -ENOMEM;
spin_lock(&_minor_lock);
r = idr_get_new(&_minor_idr, MINOR_ALLOCED, &m);
if (r) {
goto out;
}
if (m >= (1 << MINORBITS)) {
idr_remove(&_minor_idr, m);
r = -ENOSPC;
goto out;
}
*minor = m;
out:
spin_unlock(&_minor_lock);
return r;
}
static struct block_device_operations dm_blk_dops;
/*
* Allocate and initialise a blank device with a given minor.
*/
static struct mapped_device *alloc_dev(int minor)
{
int r;
struct mapped_device *md = kmalloc(sizeof(*md), GFP_KERNEL);
void *old_md;
if (!md) {
DMWARN("unable to allocate device, out of memory.");
return NULL;
}
if (!try_module_get(THIS_MODULE))
goto bad0;
/* get a minor number for the dev */
if (minor == DM_ANY_MINOR)
r = next_free_minor(md, &minor);
else
r = specific_minor(md, minor);
if (r < 0)
goto bad1;
memset(md, 0, sizeof(*md));
init_rwsem(&md->io_lock);
init_MUTEX(&md->suspend_lock);
spin_lock_init(&md->pushback_lock);
rwlock_init(&md->map_lock);
atomic_set(&md->holders, 1);
atomic_set(&md->open_count, 0);
atomic_set(&md->event_nr, 0);
md->queue = blk_alloc_queue(GFP_KERNEL);
if (!md->queue)
goto bad1_free_minor;
md->queue->queuedata = md;
md->queue->backing_dev_info.congested_fn = dm_any_congested;