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;
20 * get_io_context - increment reference count to io_context
21 * @ioc: io_context to get
23 * Increment reference count to @ioc.
25 void get_io_context(struct io_context *ioc)
27 BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
28 atomic_long_inc(&ioc->refcount);
30 EXPORT_SYMBOL(get_io_context);
32 static void cfq_dtor(struct io_context *ioc)
34 if (!hlist_empty(&ioc->cic_list)) {
35 struct cfq_io_context *cic;
37 cic = hlist_entry(ioc->cic_list.first, struct cfq_io_context,
44 * put_io_context - put a reference of io_context
45 * @ioc: io_context to put
47 * Decrement reference count of @ioc and release it if the count reaches
50 void put_io_context(struct io_context *ioc)
55 BUG_ON(atomic_long_read(&ioc->refcount) <= 0);
57 if (!atomic_long_dec_and_test(&ioc->refcount))
64 kmem_cache_free(iocontext_cachep, ioc);
66 EXPORT_SYMBOL(put_io_context);
68 static void cfq_exit(struct io_context *ioc)
72 if (!hlist_empty(&ioc->cic_list)) {
73 struct cfq_io_context *cic;
75 cic = hlist_entry(ioc->cic_list.first, struct cfq_io_context,
82 /* Called by the exiting task */
83 void exit_io_context(struct task_struct *task)
85 struct io_context *ioc;
87 /* PF_EXITING prevents new io_context from being attached to @task */
88 WARN_ON_ONCE(!(current->flags & PF_EXITING));
91 ioc = task->io_context;
92 task->io_context = NULL;
95 if (atomic_dec_and_test(&ioc->nr_tasks))
101 static struct io_context *create_task_io_context(struct task_struct *task,
102 gfp_t gfp_flags, int node,
105 struct io_context *ioc;
107 ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags | __GFP_ZERO,
113 atomic_long_set(&ioc->refcount, 1);
114 atomic_set(&ioc->nr_tasks, 1);
115 spin_lock_init(&ioc->lock);
116 INIT_RADIX_TREE(&ioc->radix_root, GFP_ATOMIC | __GFP_HIGH);
117 INIT_HLIST_HEAD(&ioc->cic_list);
119 /* try to install, somebody might already have beaten us to it */
122 if (!task->io_context && !(task->flags & PF_EXITING)) {
123 task->io_context = ioc;
125 kmem_cache_free(iocontext_cachep, ioc);
126 ioc = task->io_context;
137 * current_io_context - get io_context of %current
138 * @gfp_flags: allocation flags, used if allocation is necessary
139 * @node: allocation node, used if allocation is necessary
141 * Return io_context of %current. If it doesn't exist, it is created with
142 * @gfp_flags and @node. The returned io_context does NOT have its
143 * reference count incremented. Because io_context is exited only on task
144 * exit, %current can be sure that the returned io_context is valid and
145 * alive as long as it is executing.
147 struct io_context *current_io_context(gfp_t gfp_flags, int node)
149 might_sleep_if(gfp_flags & __GFP_WAIT);
151 if (current->io_context)
152 return current->io_context;
154 return create_task_io_context(current, gfp_flags, node, false);
156 EXPORT_SYMBOL(current_io_context);
159 * get_task_io_context - get io_context of a task
160 * @task: task of interest
161 * @gfp_flags: allocation flags, used if allocation is necessary
162 * @node: allocation node, used if allocation is necessary
164 * Return io_context of @task. If it doesn't exist, it is created with
165 * @gfp_flags and @node. The returned io_context has its reference count
168 * This function always goes through task_lock() and it's better to use
169 * current_io_context() + get_io_context() for %current.
171 struct io_context *get_task_io_context(struct task_struct *task,
172 gfp_t gfp_flags, int node)
174 struct io_context *ioc;
176 might_sleep_if(gfp_flags & __GFP_WAIT);
179 ioc = task->io_context;
187 return create_task_io_context(task, gfp_flags, node, true);
189 EXPORT_SYMBOL(get_task_io_context);
191 static int __init blk_ioc_init(void)
193 iocontext_cachep = kmem_cache_create("blkdev_ioc",
194 sizeof(struct io_context), 0, SLAB_PANIC, NULL);
197 subsys_initcall(blk_ioc_init);