637 lines
13 KiB
C
637 lines
13 KiB
C
/*
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* Copyright (C) 2011 Red Hat, Inc.
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*
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* This file is released under the GPL.
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*/
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#include "dm-block-manager.h"
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#include "dm-persistent-data-internal.h"
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#include "../dm-bufio.h"
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#include <linux/crc32c.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/rwsem.h>
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#include <linux/device-mapper.h>
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#include <linux/stacktrace.h>
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#define DM_MSG_PREFIX "block manager"
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/*----------------------------------------------------------------*/
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/*
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* This is a read/write semaphore with a couple of differences.
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*
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* i) There is a restriction on the number of concurrent read locks that
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* may be held at once. This is just an implementation detail.
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*
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* ii) Recursive locking attempts are detected and return EINVAL. A stack
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* trace is also emitted for the previous lock acquisition.
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*
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* iii) Priority is given to write locks.
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*/
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#define MAX_HOLDERS 4
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#define MAX_STACK 10
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typedef unsigned long stack_entries[MAX_STACK];
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struct block_lock {
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spinlock_t lock;
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__s32 count;
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struct list_head waiters;
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struct task_struct *holders[MAX_HOLDERS];
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#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
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struct stack_trace traces[MAX_HOLDERS];
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stack_entries entries[MAX_HOLDERS];
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#endif
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};
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struct waiter {
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struct list_head list;
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struct task_struct *task;
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int wants_write;
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};
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static unsigned __find_holder(struct block_lock *lock,
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struct task_struct *task)
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{
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unsigned i;
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for (i = 0; i < MAX_HOLDERS; i++)
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if (lock->holders[i] == task)
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break;
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BUG_ON(i == MAX_HOLDERS);
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return i;
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}
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/* call this *after* you increment lock->count */
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static void __add_holder(struct block_lock *lock, struct task_struct *task)
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{
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unsigned h = __find_holder(lock, NULL);
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#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
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struct stack_trace *t;
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#endif
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get_task_struct(task);
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lock->holders[h] = task;
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#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
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t = lock->traces + h;
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t->nr_entries = 0;
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t->max_entries = MAX_STACK;
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t->entries = lock->entries[h];
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t->skip = 2;
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save_stack_trace(t);
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#endif
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}
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/* call this *before* you decrement lock->count */
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static void __del_holder(struct block_lock *lock, struct task_struct *task)
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{
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unsigned h = __find_holder(lock, task);
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lock->holders[h] = NULL;
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put_task_struct(task);
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}
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static int __check_holder(struct block_lock *lock)
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{
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unsigned i;
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#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
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static struct stack_trace t;
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static stack_entries entries;
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#endif
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for (i = 0; i < MAX_HOLDERS; i++) {
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if (lock->holders[i] == current) {
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DMERR("recursive lock detected in metadata");
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#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
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DMERR("previously held here:");
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print_stack_trace(lock->traces + i, 4);
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DMERR("subsequent acquisition attempted here:");
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t.nr_entries = 0;
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t.max_entries = MAX_STACK;
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t.entries = entries;
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t.skip = 3;
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save_stack_trace(&t);
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print_stack_trace(&t, 4);
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#endif
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return -EINVAL;
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}
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}
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return 0;
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}
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static void __wait(struct waiter *w)
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{
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for (;;) {
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set_task_state(current, TASK_UNINTERRUPTIBLE);
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if (!w->task)
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break;
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schedule();
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}
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set_task_state(current, TASK_RUNNING);
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}
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static void __wake_waiter(struct waiter *w)
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{
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struct task_struct *task;
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list_del(&w->list);
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task = w->task;
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smp_mb();
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w->task = NULL;
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wake_up_process(task);
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}
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/*
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* We either wake a few readers or a single writer.
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*/
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static void __wake_many(struct block_lock *lock)
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{
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struct waiter *w, *tmp;
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BUG_ON(lock->count < 0);
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list_for_each_entry_safe(w, tmp, &lock->waiters, list) {
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if (lock->count >= MAX_HOLDERS)
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return;
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if (w->wants_write) {
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if (lock->count > 0)
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return; /* still read locked */
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lock->count = -1;
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__add_holder(lock, w->task);
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__wake_waiter(w);
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return;
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}
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lock->count++;
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__add_holder(lock, w->task);
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__wake_waiter(w);
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}
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}
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static void bl_init(struct block_lock *lock)
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{
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int i;
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spin_lock_init(&lock->lock);
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lock->count = 0;
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INIT_LIST_HEAD(&lock->waiters);
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for (i = 0; i < MAX_HOLDERS; i++)
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lock->holders[i] = NULL;
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}
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static int __available_for_read(struct block_lock *lock)
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{
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return lock->count >= 0 &&
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lock->count < MAX_HOLDERS &&
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list_empty(&lock->waiters);
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}
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static int bl_down_read(struct block_lock *lock)
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{
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int r;
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struct waiter w;
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spin_lock(&lock->lock);
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r = __check_holder(lock);
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if (r) {
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spin_unlock(&lock->lock);
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return r;
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}
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if (__available_for_read(lock)) {
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lock->count++;
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__add_holder(lock, current);
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spin_unlock(&lock->lock);
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return 0;
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}
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get_task_struct(current);
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w.task = current;
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w.wants_write = 0;
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list_add_tail(&w.list, &lock->waiters);
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spin_unlock(&lock->lock);
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__wait(&w);
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put_task_struct(current);
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return 0;
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}
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static int bl_down_read_nonblock(struct block_lock *lock)
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{
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int r;
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spin_lock(&lock->lock);
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r = __check_holder(lock);
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if (r)
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goto out;
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if (__available_for_read(lock)) {
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lock->count++;
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__add_holder(lock, current);
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r = 0;
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} else
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r = -EWOULDBLOCK;
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out:
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spin_unlock(&lock->lock);
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return r;
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}
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static void bl_up_read(struct block_lock *lock)
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{
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spin_lock(&lock->lock);
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BUG_ON(lock->count <= 0);
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__del_holder(lock, current);
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--lock->count;
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if (!list_empty(&lock->waiters))
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__wake_many(lock);
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spin_unlock(&lock->lock);
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}
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static int bl_down_write(struct block_lock *lock)
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{
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int r;
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struct waiter w;
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spin_lock(&lock->lock);
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r = __check_holder(lock);
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if (r) {
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spin_unlock(&lock->lock);
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return r;
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}
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if (lock->count == 0 && list_empty(&lock->waiters)) {
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lock->count = -1;
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__add_holder(lock, current);
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spin_unlock(&lock->lock);
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return 0;
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}
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get_task_struct(current);
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w.task = current;
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w.wants_write = 1;
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/*
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* Writers given priority. We know there's only one mutator in the
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* system, so ignoring the ordering reversal.
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*/
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list_add(&w.list, &lock->waiters);
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spin_unlock(&lock->lock);
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__wait(&w);
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put_task_struct(current);
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return 0;
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}
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static void bl_up_write(struct block_lock *lock)
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{
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spin_lock(&lock->lock);
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__del_holder(lock, current);
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lock->count = 0;
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if (!list_empty(&lock->waiters))
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__wake_many(lock);
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spin_unlock(&lock->lock);
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}
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static void report_recursive_bug(dm_block_t b, int r)
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{
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if (r == -EINVAL)
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DMERR("recursive acquisition of block %llu requested.",
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(unsigned long long) b);
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}
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/*----------------------------------------------------------------*/
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/*
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* Block manager is currently implemented using dm-bufio. struct
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* dm_block_manager and struct dm_block map directly onto a couple of
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* structs in the bufio interface. I want to retain the freedom to move
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* away from bufio in the future. So these structs are just cast within
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* this .c file, rather than making it through to the public interface.
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*/
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static struct dm_buffer *to_buffer(struct dm_block *b)
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{
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return (struct dm_buffer *) b;
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}
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dm_block_t dm_block_location(struct dm_block *b)
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{
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return dm_bufio_get_block_number(to_buffer(b));
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}
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EXPORT_SYMBOL_GPL(dm_block_location);
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void *dm_block_data(struct dm_block *b)
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{
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return dm_bufio_get_block_data(to_buffer(b));
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}
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EXPORT_SYMBOL_GPL(dm_block_data);
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struct buffer_aux {
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struct dm_block_validator *validator;
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struct block_lock lock;
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int write_locked;
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};
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static void dm_block_manager_alloc_callback(struct dm_buffer *buf)
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{
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struct buffer_aux *aux = dm_bufio_get_aux_data(buf);
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aux->validator = NULL;
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bl_init(&aux->lock);
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}
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static void dm_block_manager_write_callback(struct dm_buffer *buf)
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{
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struct buffer_aux *aux = dm_bufio_get_aux_data(buf);
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if (aux->validator) {
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aux->validator->prepare_for_write(aux->validator, (struct dm_block *) buf,
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dm_bufio_get_block_size(dm_bufio_get_client(buf)));
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}
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}
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/*----------------------------------------------------------------
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* Public interface
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*--------------------------------------------------------------*/
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struct dm_block_manager {
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struct dm_bufio_client *bufio;
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bool read_only:1;
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};
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struct dm_block_manager *dm_block_manager_create(struct block_device *bdev,
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unsigned block_size,
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unsigned cache_size,
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unsigned max_held_per_thread)
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{
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int r;
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struct dm_block_manager *bm;
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bm = kmalloc(sizeof(*bm), GFP_KERNEL);
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if (!bm) {
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r = -ENOMEM;
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goto bad;
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}
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bm->bufio = dm_bufio_client_create(bdev, block_size, max_held_per_thread,
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sizeof(struct buffer_aux),
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dm_block_manager_alloc_callback,
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dm_block_manager_write_callback);
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if (IS_ERR(bm->bufio)) {
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r = PTR_ERR(bm->bufio);
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kfree(bm);
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goto bad;
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}
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bm->read_only = false;
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return bm;
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bad:
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return ERR_PTR(r);
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}
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EXPORT_SYMBOL_GPL(dm_block_manager_create);
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void dm_block_manager_destroy(struct dm_block_manager *bm)
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{
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dm_bufio_client_destroy(bm->bufio);
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kfree(bm);
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}
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EXPORT_SYMBOL_GPL(dm_block_manager_destroy);
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unsigned dm_bm_block_size(struct dm_block_manager *bm)
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{
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return dm_bufio_get_block_size(bm->bufio);
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}
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EXPORT_SYMBOL_GPL(dm_bm_block_size);
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dm_block_t dm_bm_nr_blocks(struct dm_block_manager *bm)
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{
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return dm_bufio_get_device_size(bm->bufio);
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}
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static int dm_bm_validate_buffer(struct dm_block_manager *bm,
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struct dm_buffer *buf,
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struct buffer_aux *aux,
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struct dm_block_validator *v)
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{
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if (unlikely(!aux->validator)) {
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int r;
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if (!v)
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return 0;
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r = v->check(v, (struct dm_block *) buf, dm_bufio_get_block_size(bm->bufio));
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if (unlikely(r)) {
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DMERR_LIMIT("%s validator check failed for block %llu", v->name,
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(unsigned long long) dm_bufio_get_block_number(buf));
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return r;
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}
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aux->validator = v;
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} else {
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if (unlikely(aux->validator != v)) {
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DMERR_LIMIT("validator mismatch (old=%s vs new=%s) for block %llu",
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aux->validator->name, v ? v->name : "NULL",
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(unsigned long long) dm_bufio_get_block_number(buf));
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return -EINVAL;
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}
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}
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return 0;
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}
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int dm_bm_read_lock(struct dm_block_manager *bm, dm_block_t b,
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struct dm_block_validator *v,
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struct dm_block **result)
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{
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struct buffer_aux *aux;
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void *p;
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int r;
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p = dm_bufio_read(bm->bufio, b, (struct dm_buffer **) result);
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if (unlikely(IS_ERR(p)))
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return PTR_ERR(p);
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aux = dm_bufio_get_aux_data(to_buffer(*result));
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r = bl_down_read(&aux->lock);
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if (unlikely(r)) {
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dm_bufio_release(to_buffer(*result));
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report_recursive_bug(b, r);
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return r;
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}
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aux->write_locked = 0;
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r = dm_bm_validate_buffer(bm, to_buffer(*result), aux, v);
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if (unlikely(r)) {
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bl_up_read(&aux->lock);
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dm_bufio_release(to_buffer(*result));
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return r;
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}
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return 0;
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}
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EXPORT_SYMBOL_GPL(dm_bm_read_lock);
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int dm_bm_write_lock(struct dm_block_manager *bm,
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dm_block_t b, struct dm_block_validator *v,
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struct dm_block **result)
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{
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struct buffer_aux *aux;
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void *p;
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int r;
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if (bm->read_only)
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return -EPERM;
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p = dm_bufio_read(bm->bufio, b, (struct dm_buffer **) result);
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if (unlikely(IS_ERR(p)))
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return PTR_ERR(p);
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aux = dm_bufio_get_aux_data(to_buffer(*result));
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r = bl_down_write(&aux->lock);
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if (r) {
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dm_bufio_release(to_buffer(*result));
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report_recursive_bug(b, r);
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return r;
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}
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aux->write_locked = 1;
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r = dm_bm_validate_buffer(bm, to_buffer(*result), aux, v);
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if (unlikely(r)) {
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bl_up_write(&aux->lock);
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dm_bufio_release(to_buffer(*result));
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return r;
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}
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return 0;
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}
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EXPORT_SYMBOL_GPL(dm_bm_write_lock);
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int dm_bm_read_try_lock(struct dm_block_manager *bm,
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dm_block_t b, struct dm_block_validator *v,
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struct dm_block **result)
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{
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struct buffer_aux *aux;
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void *p;
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int r;
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p = dm_bufio_get(bm->bufio, b, (struct dm_buffer **) result);
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if (unlikely(IS_ERR(p)))
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return PTR_ERR(p);
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if (unlikely(!p))
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return -EWOULDBLOCK;
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aux = dm_bufio_get_aux_data(to_buffer(*result));
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r = bl_down_read_nonblock(&aux->lock);
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if (r < 0) {
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dm_bufio_release(to_buffer(*result));
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report_recursive_bug(b, r);
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return r;
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}
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aux->write_locked = 0;
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r = dm_bm_validate_buffer(bm, to_buffer(*result), aux, v);
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if (unlikely(r)) {
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bl_up_read(&aux->lock);
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dm_bufio_release(to_buffer(*result));
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return r;
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}
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return 0;
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}
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int dm_bm_write_lock_zero(struct dm_block_manager *bm,
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dm_block_t b, struct dm_block_validator *v,
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struct dm_block **result)
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{
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int r;
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struct buffer_aux *aux;
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void *p;
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if (bm->read_only)
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return -EPERM;
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p = dm_bufio_new(bm->bufio, b, (struct dm_buffer **) result);
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if (unlikely(IS_ERR(p)))
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return PTR_ERR(p);
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memset(p, 0, dm_bm_block_size(bm));
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aux = dm_bufio_get_aux_data(to_buffer(*result));
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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);
|
|
|
|
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_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);
|
|
}
|
|
|
|
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");
|
|
|
|
/*----------------------------------------------------------------*/
|