2 * Functions related to io context handling
4 #include <linux/kernel.h>
5 #include <linux/module.h>
6 #include <linux/init.h>
8 #include <linux/blkdev.h>
9 #include <linux/bootmem.h> /* for max_pfn/max_low_pfn */
14 * For io context allocations
16 static struct kmem_cache *iocontext_cachep;
18 static void cfq_dtor(struct io_context *ioc)
20 if (!hlist_empty(&ioc->cic_list)) {
21 struct cfq_io_context *cic;
23 cic = list_entry(ioc->cic_list.first, struct cfq_io_context,
30 * IO Context helper functions. put_io_context() returns 1 if there are no
31 * more users of this io context, 0 otherwise.
33 int put_io_context(struct io_context *ioc)
38 BUG_ON(atomic_read(&ioc->refcount) == 0);
40 if (atomic_dec_and_test(&ioc->refcount)) {
42 if (ioc->aic && ioc->aic->dtor)
43 ioc->aic->dtor(ioc->aic);
47 kmem_cache_free(iocontext_cachep, ioc);
52 EXPORT_SYMBOL(put_io_context);
54 static void cfq_exit(struct io_context *ioc)
58 if (!hlist_empty(&ioc->cic_list)) {
59 struct cfq_io_context *cic;
61 cic = list_entry(ioc->cic_list.first, struct cfq_io_context,
68 /* Called by the exitting task */
69 void exit_io_context(void)
71 struct io_context *ioc;
74 ioc = current->io_context;
75 current->io_context = NULL;
78 if (atomic_dec_and_test(&ioc->nr_tasks)) {
79 if (ioc->aic && ioc->aic->exit)
80 ioc->aic->exit(ioc->aic);
87 struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
89 struct io_context *ret;
91 ret = kmem_cache_alloc_node(iocontext_cachep, gfp_flags, node);
93 atomic_set(&ret->refcount, 1);
94 atomic_set(&ret->nr_tasks, 1);
95 spin_lock_init(&ret->lock);
96 ret->ioprio_changed = 0;
98 ret->last_waited = jiffies; /* doesn't matter... */
99 ret->nr_batch_requests = 0; /* because this is 0 */
101 INIT_RADIX_TREE(&ret->radix_root, GFP_ATOMIC | __GFP_HIGH);
102 INIT_HLIST_HEAD(&ret->cic_list);
103 ret->ioc_data = NULL;
110 * If the current task has no IO context then create one and initialise it.
111 * Otherwise, return its existing IO context.
113 * This returned IO context doesn't have a specifically elevated refcount,
114 * but since the current task itself holds a reference, the context can be
115 * used in general code, so long as it stays within `current` context.
117 struct io_context *current_io_context(gfp_t gfp_flags, int node)
119 struct task_struct *tsk = current;
120 struct io_context *ret;
122 ret = tsk->io_context;
126 ret = alloc_io_context(gfp_flags, node);
128 /* make sure set_task_ioprio() sees the settings above */
130 tsk->io_context = ret;
137 * If the current task has no IO context then create one and initialise it.
138 * If it does have a context, take a ref on it.
140 * This is always called in the context of the task which submitted the I/O.
142 struct io_context *get_io_context(gfp_t gfp_flags, int node)
144 struct io_context *ret = NULL;
147 * Check for unlikely race with exiting task. ioc ref count is
148 * zero when ioc is being detached.
151 ret = current_io_context(gfp_flags, node);
154 } while (!atomic_inc_not_zero(&ret->refcount));
158 EXPORT_SYMBOL(get_io_context);
160 void copy_io_context(struct io_context **pdst, struct io_context **psrc)
162 struct io_context *src = *psrc;
163 struct io_context *dst = *pdst;
166 BUG_ON(atomic_read(&src->refcount) == 0);
167 atomic_inc(&src->refcount);
172 EXPORT_SYMBOL(copy_io_context);
174 static int __init blk_ioc_init(void)
176 iocontext_cachep = kmem_cache_create("blkdev_ioc",
177 sizeof(struct io_context), 0, SLAB_PANIC, NULL);
180 subsys_initcall(blk_ioc_init);