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
);
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