diff options
Diffstat (limited to 'drivers/md/persistent-data/dm-block-manager.c')
| -rw-r--r-- | drivers/md/persistent-data/dm-block-manager.c | 620 |
1 files changed, 620 insertions, 0 deletions
diff --git a/drivers/md/persistent-data/dm-block-manager.c b/drivers/md/persistent-data/dm-block-manager.c new file mode 100644 index 000000000000..0317ecdc6e53 --- /dev/null +++ b/drivers/md/persistent-data/dm-block-manager.c @@ -0,0 +1,620 @@ +/* + * 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" + +/*----------------------------------------------------------------*/ + +/* + * 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 aquisition. + * + * 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; +#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING + static struct stack_trace t; + static stack_entries entries; +#endif + + for (i = 0; i < MAX_HOLDERS; i++) { + if (lock->holders[i] == current) { + DMERR("recursive lock detected in pool metadata"); +#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING + DMERR("previously held here:"); + print_stack_trace(lock->traces + i, 4); + + DMERR("subsequent aquisition attempted here:"); + t.nr_entries = 0; + t.max_entries = MAX_STACK; + t.entries = entries; + t.skip = 3; + save_stack_trace(&t); + print_stack_trace(&t, 4); +#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); +} + +/*----------------------------------------------------------------*/ + +/* + * 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; +} + +static struct dm_bufio_client *to_bufio(struct dm_block_manager *bm) +{ + return (struct dm_bufio_client *) bm; +} + +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; + struct block_lock lock; + int write_locked; +}; + +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 *dm_block_manager_create(struct block_device *bdev, + unsigned block_size, + unsigned cache_size, + unsigned max_held_per_thread) +{ + return (struct dm_block_manager *) + 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); +} +EXPORT_SYMBOL_GPL(dm_block_manager_create); + +void dm_block_manager_destroy(struct dm_block_manager *bm) +{ + return dm_bufio_client_destroy(to_bufio(bm)); +} +EXPORT_SYMBOL_GPL(dm_block_manager_destroy); + +unsigned dm_bm_block_size(struct dm_block_manager *bm) +{ + return dm_bufio_get_block_size(to_bufio(bm)); +} +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(to_bufio(bm)); +} + +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(to_bufio(bm))); + if (unlikely(r)) + return r; + aux->validator = v; + } else { + if (unlikely(aux->validator != v)) { + DMERR("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(to_bufio(bm), b, (struct dm_buffer **) result); + if (unlikely(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; + + p = dm_bufio_read(to_bufio(bm), b, (struct dm_buffer **) result); + if (unlikely(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(to_bufio(bm), b, (struct dm_buffer **) result); + if (unlikely(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; + + p = dm_bufio_new(to_bufio(bm), b, (struct dm_buffer **) result); + if (unlikely(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; +} + +int 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)); + + return 0; +} +EXPORT_SYMBOL_GPL(dm_bm_unlock); + +int dm_bm_unlock_move(struct dm_block *b, dm_block_t n) +{ + 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_move(to_buffer(b), n); + return 0; +} + +int dm_bm_flush_and_unlock(struct dm_block_manager *bm, + struct dm_block *superblock) +{ + int r; + + r = dm_bufio_write_dirty_buffers(to_bufio(bm)); + if (unlikely(r)) + return r; + r = dm_bufio_issue_flush(to_bufio(bm)); + if (unlikely(r)) + return r; + + dm_bm_unlock(superblock); + + r = dm_bufio_write_dirty_buffers(to_bufio(bm)); + if (unlikely(r)) + return r; + r = dm_bufio_issue_flush(to_bufio(bm)); + if (unlikely(r)) + return r; + + return 0; +} + +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"); + +/*----------------------------------------------------------------*/ |