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
= list_entry(ioc
->cic_list
.first
, struct cfq_io_context
,
31 * IO Context helper functions. put_io_context() returns 1 if there are no
32 * more users of this io context, 0 otherwise.
34 int put_io_context(struct io_context
*ioc
)
39 BUG_ON(atomic_long_read(&ioc
->refcount
) == 0);
41 if (atomic_long_dec_and_test(&ioc
->refcount
)) {
46 kmem_cache_free(iocontext_cachep
, ioc
);
51 EXPORT_SYMBOL(put_io_context
);
53 static void cfq_exit(struct io_context
*ioc
)
57 if (!hlist_empty(&ioc
->cic_list
)) {
58 struct cfq_io_context
*cic
;
60 cic
= list_entry(ioc
->cic_list
.first
, struct cfq_io_context
,
67 /* Called by the exitting task */
68 void exit_io_context(struct task_struct
*task
)
70 struct io_context
*ioc
;
73 ioc
= task
->io_context
;
74 task
->io_context
= NULL
;
77 if (atomic_dec_and_test(&ioc
->nr_tasks
)) {
84 struct io_context
*alloc_io_context(gfp_t gfp_flags
, int node
)
86 struct io_context
*ret
;
88 ret
= kmem_cache_alloc_node(iocontext_cachep
, gfp_flags
, node
);
90 atomic_long_set(&ret
->refcount
, 1);
91 atomic_set(&ret
->nr_tasks
, 1);
92 spin_lock_init(&ret
->lock
);
93 ret
->ioprio_changed
= 0;
95 ret
->last_waited
= 0; /* doesn't matter... */
96 ret
->nr_batch_requests
= 0; /* because this is 0 */
97 INIT_RADIX_TREE(&ret
->radix_root
, GFP_ATOMIC
| __GFP_HIGH
);
98 INIT_HLIST_HEAD(&ret
->cic_list
);
106 * If the current task has no IO context then create one and initialise it.
107 * Otherwise, return its existing IO context.
109 * This returned IO context doesn't have a specifically elevated refcount,
110 * but since the current task itself holds a reference, the context can be
111 * used in general code, so long as it stays within `current` context.
113 struct io_context
*current_io_context(gfp_t gfp_flags
, int node
)
115 struct task_struct
*tsk
= current
;
116 struct io_context
*ret
;
118 ret
= tsk
->io_context
;
122 ret
= alloc_io_context(gfp_flags
, node
);
124 /* make sure set_task_ioprio() sees the settings above */
126 tsk
->io_context
= ret
;
133 * If the current task has no IO context then create one and initialise it.
134 * If it does have a context, take a ref on it.
136 * This is always called in the context of the task which submitted the I/O.
138 struct io_context
*get_io_context(gfp_t gfp_flags
, int node
)
140 struct io_context
*ret
= NULL
;
143 * Check for unlikely race with exiting task. ioc ref count is
144 * zero when ioc is being detached.
147 ret
= current_io_context(gfp_flags
, node
);
150 } while (!atomic_long_inc_not_zero(&ret
->refcount
));
154 EXPORT_SYMBOL(get_io_context
);
156 void copy_io_context(struct io_context
**pdst
, struct io_context
**psrc
)
158 struct io_context
*src
= *psrc
;
159 struct io_context
*dst
= *pdst
;
162 BUG_ON(atomic_long_read(&src
->refcount
) == 0);
163 atomic_long_inc(&src
->refcount
);
168 EXPORT_SYMBOL(copy_io_context
);
170 static int __init
blk_ioc_init(void)
172 iocontext_cachep
= kmem_cache_create("blkdev_ioc",
173 sizeof(struct io_context
), 0, SLAB_PANIC
, NULL
);
176 subsys_initcall(blk_ioc_init
);
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