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 */
10 #include <linux/slab.h>
15 * For io context allocations
17 static struct kmem_cache *iocontext_cachep;
19 static void cfq_dtor(struct io_context *ioc)
21 if (!hlist_empty(&ioc->cic_list)) {
22 struct cfq_io_context *cic;
24 cic = hlist_entry(ioc->cic_list.first, struct cfq_io_context,
31 * put_io_context - put a reference of io_context
32 * @ioc: io_context to put
34 * Decrement reference count of @ioc and release it if the count reaches
37 void put_io_context(struct io_context *ioc)
42 BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
44 if (!atomic_long_dec_and_test(&ioc->refcount))
51 kmem_cache_free(iocontext_cachep, ioc);
53 EXPORT_SYMBOL(put_io_context);
55 static void cfq_exit(struct io_context *ioc)
59 if (!hlist_empty(&ioc->cic_list)) {
60 struct cfq_io_context *cic;
62 cic = hlist_entry(ioc->cic_list.first, struct cfq_io_context,
69 /* Called by the exiting task */
70 void exit_io_context(struct task_struct *task)
72 struct io_context *ioc;
75 ioc = task->io_context;
76 task->io_context = NULL;
79 if (atomic_dec_and_test(&ioc->nr_tasks))
85 struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
87 struct io_context *ioc;
89 ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
95 atomic_long_set(&ioc->refcount, 1);
96 atomic_set(&ioc->nr_tasks, 1);
97 spin_lock_init(&ioc->lock);
98 INIT_RADIX_TREE(&ioc->radix_root, GFP_ATOMIC | __GFP_HIGH);
99 INIT_HLIST_HEAD(&ioc->cic_list);
105 * current_io_context - get io_context of %current
106 * @gfp_flags: allocation flags, used if allocation is necessary
107 * @node: allocation node, used if allocation is necessary
109 * Return io_context of %current. If it doesn't exist, it is created with
110 * @gfp_flags and @node. The returned io_context does NOT have its
111 * reference count incremented. Because io_context is exited only on task
112 * exit, %current can be sure that the returned io_context is valid and
113 * alive as long as it is executing.
115 struct io_context *current_io_context(gfp_t gfp_flags, int node)
117 struct task_struct *tsk = current;
118 struct io_context *ret;
120 ret = tsk->io_context;
124 ret = alloc_io_context(gfp_flags, node);
126 /* make sure set_task_ioprio() sees the settings above */
128 tsk->io_context = ret;
135 * If the current task has no IO context then create one and initialise it.
136 * If it does have a context, take a ref on it.
138 * This is always called in the context of the task which submitted the I/O.
140 struct io_context *get_io_context(gfp_t gfp_flags, int node)
142 struct io_context *ioc = NULL;
145 * Check for unlikely race with exiting task. ioc ref count is
146 * zero when ioc is being detached.
149 ioc = current_io_context(gfp_flags, node);
152 } while (!atomic_long_inc_not_zero(&ioc->refcount));
156 EXPORT_SYMBOL(get_io_context);
158 static int __init blk_ioc_init(void)
160 iocontext_cachep = kmem_cache_create("blkdev_ioc",
161 sizeof(struct io_context), 0, SLAB_PANIC, NULL);
164 subsys_initcall(blk_ioc_init);