649 lines
14 KiB
C
649 lines
14 KiB
C
/*
|
|
* Copyright (C) 2011 Red Hat, Inc.
|
|
*
|
|
* This file is released under the GPL.
|
|
*/
|
|
#include "dm-block-manager.h"
|
|
#include "dm-persistent-data-internal.h"
|
|
#include "../dm-bufio.h"
|
|
|
|
#include <linux/crc32c.h>
|
|
#include <linux/module.h>
|
|
#include <linux/slab.h>
|
|
#include <linux/rwsem.h>
|
|
#include <linux/device-mapper.h>
|
|
#include <linux/stacktrace.h>
|
|
|
|
#define DM_MSG_PREFIX "block manager"
|
|
|
|
/*----------------------------------------------------------------*/
|
|
|
|
#ifdef CONFIG_DM_DEBUG_BLOCK_MANAGER_LOCKING
|
|
|
|
/*
|
|
* This is a read/write semaphore with a couple of differences.
|
|
*
|
|
* i) There is a restriction on the number of concurrent read locks that
|
|
* may be held at once. This is just an implementation detail.
|
|
*
|
|
* ii) Recursive locking attempts are detected and return EINVAL. A stack
|
|
* trace is also emitted for the previous lock acquisition.
|
|
*
|
|
* iii) Priority is given to write locks.
|
|
*/
|
|
#define MAX_HOLDERS 4
|
|
#define MAX_STACK 10
|
|
|
|
typedef unsigned long stack_entries[MAX_STACK];
|
|
|
|
struct block_lock {
|
|
spinlock_t lock;
|
|
__s32 count;
|
|
struct list_head waiters;
|
|
struct task_struct *holders[MAX_HOLDERS];
|
|
|
|
#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
|
|
struct stack_trace traces[MAX_HOLDERS];
|
|
stack_entries entries[MAX_HOLDERS];
|
|
#endif
|
|
};
|
|
|
|
struct waiter {
|
|
struct list_head list;
|
|
struct task_struct *task;
|
|
int wants_write;
|
|
};
|
|
|
|
static unsigned __find_holder(struct block_lock *lock,
|
|
struct task_struct *task)
|
|
{
|
|
unsigned i;
|
|
|
|
for (i = 0; i < MAX_HOLDERS; i++)
|
|
if (lock->holders[i] == task)
|
|
break;
|
|
|
|
BUG_ON(i == MAX_HOLDERS);
|
|
return i;
|
|
}
|
|
|
|
/* call this *after* you increment lock->count */
|
|
static void __add_holder(struct block_lock *lock, struct task_struct *task)
|
|
{
|
|
unsigned h = __find_holder(lock, NULL);
|
|
#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
|
|
struct stack_trace *t;
|
|
#endif
|
|
|
|
get_task_struct(task);
|
|
lock->holders[h] = task;
|
|
|
|
#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
|
|
t = lock->traces + h;
|
|
t->nr_entries = 0;
|
|
t->max_entries = MAX_STACK;
|
|
t->entries = lock->entries[h];
|
|
t->skip = 2;
|
|
save_stack_trace(t);
|
|
#endif
|
|
}
|
|
|
|
/* call this *before* you decrement lock->count */
|
|
static void __del_holder(struct block_lock *lock, struct task_struct *task)
|
|
{
|
|
unsigned h = __find_holder(lock, task);
|
|
lock->holders[h] = NULL;
|
|
put_task_struct(task);
|
|
}
|
|
|
|
static int __check_holder(struct block_lock *lock)
|
|
{
|
|
unsigned i;
|
|
|
|
for (i = 0; i < MAX_HOLDERS; i++) {
|
|
if (lock->holders[i] == current) {
|
|
DMERR("recursive lock detected in metadata");
|
|
#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
|
|
DMERR("previously held here:");
|
|
print_stack_trace(lock->traces + i, 4);
|
|
|
|
DMERR("subsequent acquisition attempted here:");
|
|
dump_stack();
|
|
#endif
|
|
return -EINVAL;
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void __wait(struct waiter *w)
|
|
{
|
|
for (;;) {
|
|
set_task_state(current, TASK_UNINTERRUPTIBLE);
|
|
|
|
if (!w->task)
|
|
break;
|
|
|
|
schedule();
|
|
}
|
|
|
|
set_task_state(current, TASK_RUNNING);
|
|
}
|
|
|
|
static void __wake_waiter(struct waiter *w)
|
|
{
|
|
struct task_struct *task;
|
|
|
|
list_del(&w->list);
|
|
task = w->task;
|
|
smp_mb();
|
|
w->task = NULL;
|
|
wake_up_process(task);
|
|
}
|
|
|
|
/*
|
|
* We either wake a few readers or a single writer.
|
|
*/
|
|
static void __wake_many(struct block_lock *lock)
|
|
{
|
|
struct waiter *w, *tmp;
|
|
|
|
BUG_ON(lock->count < 0);
|
|
list_for_each_entry_safe(w, tmp, &lock->waiters, list) {
|
|
if (lock->count >= MAX_HOLDERS)
|
|
return;
|
|
|
|
if (w->wants_write) {
|
|
if (lock->count > 0)
|
|
return; /* still read locked */
|
|
|
|
lock->count = -1;
|
|
__add_holder(lock, w->task);
|
|
__wake_waiter(w);
|
|
return;
|
|
}
|
|
|
|
lock->count++;
|
|
__add_holder(lock, w->task);
|
|
__wake_waiter(w);
|
|
}
|
|
}
|
|
|
|
static void bl_init(struct block_lock *lock)
|
|
{
|
|
int i;
|
|
|
|
spin_lock_init(&lock->lock);
|
|
lock->count = 0;
|
|
INIT_LIST_HEAD(&lock->waiters);
|
|
for (i = 0; i < MAX_HOLDERS; i++)
|
|
lock->holders[i] = NULL;
|
|
}
|
|
|
|
static int __available_for_read(struct block_lock *lock)
|
|
{
|
|
return lock->count >= 0 &&
|
|
lock->count < MAX_HOLDERS &&
|
|
list_empty(&lock->waiters);
|
|
}
|
|
|
|
static int bl_down_read(struct block_lock *lock)
|
|
{
|
|
int r;
|
|
struct waiter w;
|
|
|
|
spin_lock(&lock->lock);
|
|
r = __check_holder(lock);
|
|
if (r) {
|
|
spin_unlock(&lock->lock);
|
|
return r;
|
|
}
|
|
|
|
if (__available_for_read(lock)) {
|
|
lock->count++;
|
|
__add_holder(lock, current);
|
|
spin_unlock(&lock->lock);
|
|
return 0;
|
|
}
|
|
|
|
get_task_struct(current);
|
|
|
|
w.task = current;
|
|
w.wants_write = 0;
|
|
list_add_tail(&w.list, &lock->waiters);
|
|
spin_unlock(&lock->lock);
|
|
|
|
__wait(&w);
|
|
put_task_struct(current);
|
|
return 0;
|
|
}
|
|
|
|
static int bl_down_read_nonblock(struct block_lock *lock)
|
|
{
|
|
int r;
|
|
|
|
spin_lock(&lock->lock);
|
|
r = __check_holder(lock);
|
|
if (r)
|
|
goto out;
|
|
|
|
if (__available_for_read(lock)) {
|
|
lock->count++;
|
|
__add_holder(lock, current);
|
|
r = 0;
|
|
} else
|
|
r = -EWOULDBLOCK;
|
|
|
|
out:
|
|
spin_unlock(&lock->lock);
|
|
return r;
|
|
}
|
|
|
|
static void bl_up_read(struct block_lock *lock)
|
|
{
|
|
spin_lock(&lock->lock);
|
|
BUG_ON(lock->count <= 0);
|
|
__del_holder(lock, current);
|
|
--lock->count;
|
|
if (!list_empty(&lock->waiters))
|
|
__wake_many(lock);
|
|
spin_unlock(&lock->lock);
|
|
}
|
|
|
|
static int bl_down_write(struct block_lock *lock)
|
|
{
|
|
int r;
|
|
struct waiter w;
|
|
|
|
spin_lock(&lock->lock);
|
|
r = __check_holder(lock);
|
|
if (r) {
|
|
spin_unlock(&lock->lock);
|
|
return r;
|
|
}
|
|
|
|
if (lock->count == 0 && list_empty(&lock->waiters)) {
|
|
lock->count = -1;
|
|
__add_holder(lock, current);
|
|
spin_unlock(&lock->lock);
|
|
return 0;
|
|
}
|
|
|
|
get_task_struct(current);
|
|
w.task = current;
|
|
w.wants_write = 1;
|
|
|
|
/*
|
|
* Writers given priority. We know there's only one mutator in the
|
|
* system, so ignoring the ordering reversal.
|
|
*/
|
|
list_add(&w.list, &lock->waiters);
|
|
spin_unlock(&lock->lock);
|
|
|
|
__wait(&w);
|
|
put_task_struct(current);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void bl_up_write(struct block_lock *lock)
|
|
{
|
|
spin_lock(&lock->lock);
|
|
__del_holder(lock, current);
|
|
lock->count = 0;
|
|
if (!list_empty(&lock->waiters))
|
|
__wake_many(lock);
|
|
spin_unlock(&lock->lock);
|
|
}
|
|
|
|
static void report_recursive_bug(dm_block_t b, int r)
|
|
{
|
|
if (r == -EINVAL)
|
|
DMERR("recursive acquisition of block %llu requested.",
|
|
(unsigned long long) b);
|
|
}
|
|
|
|
#else /* !CONFIG_DM_DEBUG_BLOCK_MANAGER_LOCKING */
|
|
|
|
#define bl_init(x) do { } while (0)
|
|
#define bl_down_read(x) 0
|
|
#define bl_down_read_nonblock(x) 0
|
|
#define bl_up_read(x) do { } while (0)
|
|
#define bl_down_write(x) 0
|
|
#define bl_up_write(x) do { } while (0)
|
|
#define report_recursive_bug(x, y) do { } while (0)
|
|
|
|
#endif /* CONFIG_DM_DEBUG_BLOCK_MANAGER_LOCKING */
|
|
|
|
/*----------------------------------------------------------------*/
|
|
|
|
/*
|
|
* Block manager is currently implemented using dm-bufio. struct
|
|
* dm_block_manager and struct dm_block map directly onto a couple of
|
|
* structs in the bufio interface. I want to retain the freedom to move
|
|
* away from bufio in the future. So these structs are just cast within
|
|
* this .c file, rather than making it through to the public interface.
|
|
*/
|
|
static struct dm_buffer *to_buffer(struct dm_block *b)
|
|
{
|
|
return (struct dm_buffer *) b;
|
|
}
|
|
|
|
dm_block_t dm_block_location(struct dm_block *b)
|
|
{
|
|
return dm_bufio_get_block_number(to_buffer(b));
|
|
}
|
|
EXPORT_SYMBOL_GPL(dm_block_location);
|
|
|
|
void *dm_block_data(struct dm_block *b)
|
|
{
|
|
return dm_bufio_get_block_data(to_buffer(b));
|
|
}
|
|
EXPORT_SYMBOL_GPL(dm_block_data);
|
|
|
|
struct buffer_aux {
|
|
struct dm_block_validator *validator;
|
|
int write_locked;
|
|
|
|
#ifdef CONFIG_DM_DEBUG_BLOCK_MANAGER_LOCKING
|
|
struct block_lock lock;
|
|
#endif
|
|
};
|
|
|
|
static void dm_block_manager_alloc_callback(struct dm_buffer *buf)
|
|
{
|
|
struct buffer_aux *aux = dm_bufio_get_aux_data(buf);
|
|
aux->validator = NULL;
|
|
bl_init(&aux->lock);
|
|
}
|
|
|
|
static void dm_block_manager_write_callback(struct dm_buffer *buf)
|
|
{
|
|
struct buffer_aux *aux = dm_bufio_get_aux_data(buf);
|
|
if (aux->validator) {
|
|
aux->validator->prepare_for_write(aux->validator, (struct dm_block *) buf,
|
|
dm_bufio_get_block_size(dm_bufio_get_client(buf)));
|
|
}
|
|
}
|
|
|
|
/*----------------------------------------------------------------
|
|
* Public interface
|
|
*--------------------------------------------------------------*/
|
|
struct dm_block_manager {
|
|
struct dm_bufio_client *bufio;
|
|
bool read_only:1;
|
|
};
|
|
|
|
struct dm_block_manager *dm_block_manager_create(struct block_device *bdev,
|
|
unsigned block_size,
|
|
unsigned cache_size,
|
|
unsigned max_held_per_thread)
|
|
{
|
|
int r;
|
|
struct dm_block_manager *bm;
|
|
|
|
bm = kmalloc(sizeof(*bm), GFP_KERNEL);
|
|
if (!bm) {
|
|
r = -ENOMEM;
|
|
goto bad;
|
|
}
|
|
|
|
bm->bufio = dm_bufio_client_create(bdev, block_size, max_held_per_thread,
|
|
sizeof(struct buffer_aux),
|
|
dm_block_manager_alloc_callback,
|
|
dm_block_manager_write_callback);
|
|
if (IS_ERR(bm->bufio)) {
|
|
r = PTR_ERR(bm->bufio);
|
|
kfree(bm);
|
|
goto bad;
|
|
}
|
|
|
|
bm->read_only = false;
|
|
|
|
return bm;
|
|
|
|
bad:
|
|
return ERR_PTR(r);
|
|
}
|
|
EXPORT_SYMBOL_GPL(dm_block_manager_create);
|
|
|
|
void dm_block_manager_destroy(struct dm_block_manager *bm)
|
|
{
|
|
dm_bufio_client_destroy(bm->bufio);
|
|
kfree(bm);
|
|
}
|
|
EXPORT_SYMBOL_GPL(dm_block_manager_destroy);
|
|
|
|
unsigned dm_bm_block_size(struct dm_block_manager *bm)
|
|
{
|
|
return dm_bufio_get_block_size(bm->bufio);
|
|
}
|
|
EXPORT_SYMBOL_GPL(dm_bm_block_size);
|
|
|
|
dm_block_t dm_bm_nr_blocks(struct dm_block_manager *bm)
|
|
{
|
|
return dm_bufio_get_device_size(bm->bufio);
|
|
}
|
|
|
|
static int dm_bm_validate_buffer(struct dm_block_manager *bm,
|
|
struct dm_buffer *buf,
|
|
struct buffer_aux *aux,
|
|
struct dm_block_validator *v)
|
|
{
|
|
if (unlikely(!aux->validator)) {
|
|
int r;
|
|
if (!v)
|
|
return 0;
|
|
r = v->check(v, (struct dm_block *) buf, dm_bufio_get_block_size(bm->bufio));
|
|
if (unlikely(r)) {
|
|
DMERR_LIMIT("%s validator check failed for block %llu", v->name,
|
|
(unsigned long long) dm_bufio_get_block_number(buf));
|
|
return r;
|
|
}
|
|
aux->validator = v;
|
|
} else {
|
|
if (unlikely(aux->validator != v)) {
|
|
DMERR_LIMIT("validator mismatch (old=%s vs new=%s) for block %llu",
|
|
aux->validator->name, v ? v->name : "NULL",
|
|
(unsigned long long) dm_bufio_get_block_number(buf));
|
|
return -EINVAL;
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
int dm_bm_read_lock(struct dm_block_manager *bm, dm_block_t b,
|
|
struct dm_block_validator *v,
|
|
struct dm_block **result)
|
|
{
|
|
struct buffer_aux *aux;
|
|
void *p;
|
|
int r;
|
|
|
|
p = dm_bufio_read(bm->bufio, b, (struct dm_buffer **) result);
|
|
if (IS_ERR(p))
|
|
return PTR_ERR(p);
|
|
|
|
aux = dm_bufio_get_aux_data(to_buffer(*result));
|
|
r = bl_down_read(&aux->lock);
|
|
if (unlikely(r)) {
|
|
dm_bufio_release(to_buffer(*result));
|
|
report_recursive_bug(b, r);
|
|
return r;
|
|
}
|
|
|
|
aux->write_locked = 0;
|
|
|
|
r = dm_bm_validate_buffer(bm, to_buffer(*result), aux, v);
|
|
if (unlikely(r)) {
|
|
bl_up_read(&aux->lock);
|
|
dm_bufio_release(to_buffer(*result));
|
|
return r;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(dm_bm_read_lock);
|
|
|
|
int dm_bm_write_lock(struct dm_block_manager *bm,
|
|
dm_block_t b, struct dm_block_validator *v,
|
|
struct dm_block **result)
|
|
{
|
|
struct buffer_aux *aux;
|
|
void *p;
|
|
int r;
|
|
|
|
if (bm->read_only)
|
|
return -EPERM;
|
|
|
|
p = dm_bufio_read(bm->bufio, b, (struct dm_buffer **) result);
|
|
if (IS_ERR(p))
|
|
return PTR_ERR(p);
|
|
|
|
aux = dm_bufio_get_aux_data(to_buffer(*result));
|
|
r = bl_down_write(&aux->lock);
|
|
if (r) {
|
|
dm_bufio_release(to_buffer(*result));
|
|
report_recursive_bug(b, r);
|
|
return r;
|
|
}
|
|
|
|
aux->write_locked = 1;
|
|
|
|
r = dm_bm_validate_buffer(bm, to_buffer(*result), aux, v);
|
|
if (unlikely(r)) {
|
|
bl_up_write(&aux->lock);
|
|
dm_bufio_release(to_buffer(*result));
|
|
return r;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(dm_bm_write_lock);
|
|
|
|
int dm_bm_read_try_lock(struct dm_block_manager *bm,
|
|
dm_block_t b, struct dm_block_validator *v,
|
|
struct dm_block **result)
|
|
{
|
|
struct buffer_aux *aux;
|
|
void *p;
|
|
int r;
|
|
|
|
p = dm_bufio_get(bm->bufio, b, (struct dm_buffer **) result);
|
|
if (IS_ERR(p))
|
|
return PTR_ERR(p);
|
|
if (unlikely(!p))
|
|
return -EWOULDBLOCK;
|
|
|
|
aux = dm_bufio_get_aux_data(to_buffer(*result));
|
|
r = bl_down_read_nonblock(&aux->lock);
|
|
if (r < 0) {
|
|
dm_bufio_release(to_buffer(*result));
|
|
report_recursive_bug(b, r);
|
|
return r;
|
|
}
|
|
aux->write_locked = 0;
|
|
|
|
r = dm_bm_validate_buffer(bm, to_buffer(*result), aux, v);
|
|
if (unlikely(r)) {
|
|
bl_up_read(&aux->lock);
|
|
dm_bufio_release(to_buffer(*result));
|
|
return r;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
int dm_bm_write_lock_zero(struct dm_block_manager *bm,
|
|
dm_block_t b, struct dm_block_validator *v,
|
|
struct dm_block **result)
|
|
{
|
|
int r;
|
|
struct buffer_aux *aux;
|
|
void *p;
|
|
|
|
if (bm->read_only)
|
|
return -EPERM;
|
|
|
|
p = dm_bufio_new(bm->bufio, b, (struct dm_buffer **) result);
|
|
if (IS_ERR(p))
|
|
return PTR_ERR(p);
|
|
|
|
memset(p, 0, dm_bm_block_size(bm));
|
|
|
|
aux = dm_bufio_get_aux_data(to_buffer(*result));
|
|
r = bl_down_write(&aux->lock);
|
|
if (r) {
|
|
dm_bufio_release(to_buffer(*result));
|
|
return r;
|
|
}
|
|
|
|
aux->write_locked = 1;
|
|
aux->validator = v;
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(dm_bm_write_lock_zero);
|
|
|
|
void dm_bm_unlock(struct dm_block *b)
|
|
{
|
|
struct buffer_aux *aux;
|
|
aux = dm_bufio_get_aux_data(to_buffer(b));
|
|
|
|
if (aux->write_locked) {
|
|
dm_bufio_mark_buffer_dirty(to_buffer(b));
|
|
bl_up_write(&aux->lock);
|
|
} else
|
|
bl_up_read(&aux->lock);
|
|
|
|
dm_bufio_release(to_buffer(b));
|
|
}
|
|
EXPORT_SYMBOL_GPL(dm_bm_unlock);
|
|
|
|
int dm_bm_flush(struct dm_block_manager *bm)
|
|
{
|
|
if (bm->read_only)
|
|
return -EPERM;
|
|
|
|
return dm_bufio_write_dirty_buffers(bm->bufio);
|
|
}
|
|
EXPORT_SYMBOL_GPL(dm_bm_flush);
|
|
|
|
void dm_bm_prefetch(struct dm_block_manager *bm, dm_block_t b)
|
|
{
|
|
dm_bufio_prefetch(bm->bufio, b, 1);
|
|
}
|
|
|
|
bool dm_bm_is_read_only(struct dm_block_manager *bm)
|
|
{
|
|
return bm->read_only;
|
|
}
|
|
EXPORT_SYMBOL_GPL(dm_bm_is_read_only);
|
|
|
|
void dm_bm_set_read_only(struct dm_block_manager *bm)
|
|
{
|
|
bm->read_only = true;
|
|
}
|
|
EXPORT_SYMBOL_GPL(dm_bm_set_read_only);
|
|
|
|
void dm_bm_set_read_write(struct dm_block_manager *bm)
|
|
{
|
|
bm->read_only = false;
|
|
}
|
|
EXPORT_SYMBOL_GPL(dm_bm_set_read_write);
|
|
|
|
u32 dm_bm_checksum(const void *data, size_t len, u32 init_xor)
|
|
{
|
|
return crc32c(~(u32) 0, data, len) ^ init_xor;
|
|
}
|
|
EXPORT_SYMBOL_GPL(dm_bm_checksum);
|
|
|
|
/*----------------------------------------------------------------*/
|
|
|
|
MODULE_LICENSE("GPL");
|
|
MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
|
|
MODULE_DESCRIPTION("Immutable metadata library for dm");
|
|
|
|
/*----------------------------------------------------------------*/
|