165 lines
3.7 KiB
C
165 lines
3.7 KiB
C
/*
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* Functions related to io context handling
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/bio.h>
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#include <linux/blkdev.h>
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#include <linux/bootmem.h> /* for max_pfn/max_low_pfn */
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#include <linux/slab.h>
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#include "blk.h"
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/*
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* For io context allocations
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*/
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static struct kmem_cache *iocontext_cachep;
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static void cfq_dtor(struct io_context *ioc)
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{
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if (!hlist_empty(&ioc->cic_list)) {
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struct cfq_io_context *cic;
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cic = hlist_entry(ioc->cic_list.first, struct cfq_io_context,
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cic_list);
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cic->dtor(ioc);
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}
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}
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/*
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* IO Context helper functions. put_io_context() returns 1 if there are no
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* more users of this io context, 0 otherwise.
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*/
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int put_io_context(struct io_context *ioc)
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{
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if (ioc == NULL)
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return 1;
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BUG_ON(atomic_long_read(&ioc->refcount) == 0);
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if (atomic_long_dec_and_test(&ioc->refcount)) {
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rcu_read_lock();
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cfq_dtor(ioc);
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rcu_read_unlock();
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kmem_cache_free(iocontext_cachep, ioc);
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return 1;
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}
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return 0;
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}
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EXPORT_SYMBOL(put_io_context);
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static void cfq_exit(struct io_context *ioc)
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{
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rcu_read_lock();
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if (!hlist_empty(&ioc->cic_list)) {
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struct cfq_io_context *cic;
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cic = hlist_entry(ioc->cic_list.first, struct cfq_io_context,
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cic_list);
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cic->exit(ioc);
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}
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rcu_read_unlock();
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}
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/* Called by the exiting task */
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void exit_io_context(struct task_struct *task)
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{
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struct io_context *ioc;
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task_lock(task);
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ioc = task->io_context;
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task->io_context = NULL;
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task_unlock(task);
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if (atomic_dec_and_test(&ioc->nr_tasks))
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cfq_exit(ioc);
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put_io_context(ioc);
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}
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struct io_context *alloc_io_context(gfp_t gfp_flags, int node)
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{
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struct io_context *ioc;
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ioc = kmem_cache_alloc_node(iocontext_cachep, gfp_flags, node);
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if (ioc) {
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atomic_long_set(&ioc->refcount, 1);
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atomic_set(&ioc->nr_tasks, 1);
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spin_lock_init(&ioc->lock);
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ioc->ioprio_changed = 0;
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ioc->ioprio = 0;
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ioc->last_waited = 0; /* doesn't matter... */
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ioc->nr_batch_requests = 0; /* because this is 0 */
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INIT_RADIX_TREE(&ioc->radix_root, GFP_ATOMIC | __GFP_HIGH);
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INIT_HLIST_HEAD(&ioc->cic_list);
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ioc->ioc_data = NULL;
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#if defined(CONFIG_BLK_CGROUP) || defined(CONFIG_BLK_CGROUP_MODULE)
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ioc->cgroup_changed = 0;
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#endif
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}
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return ioc;
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}
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/*
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* If the current task has no IO context then create one and initialise it.
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* Otherwise, return its existing IO context.
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*
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* This returned IO context doesn't have a specifically elevated refcount,
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* but since the current task itself holds a reference, the context can be
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* used in general code, so long as it stays within `current` context.
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*/
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struct io_context *current_io_context(gfp_t gfp_flags, int node)
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{
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struct task_struct *tsk = current;
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struct io_context *ret;
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ret = tsk->io_context;
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if (likely(ret))
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return ret;
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ret = alloc_io_context(gfp_flags, node);
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if (ret) {
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/* make sure set_task_ioprio() sees the settings above */
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smp_wmb();
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tsk->io_context = ret;
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}
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return ret;
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}
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/*
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* If the current task has no IO context then create one and initialise it.
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* If it does have a context, take a ref on it.
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*
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* This is always called in the context of the task which submitted the I/O.
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*/
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struct io_context *get_io_context(gfp_t gfp_flags, int node)
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{
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struct io_context *ioc = NULL;
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/*
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* Check for unlikely race with exiting task. ioc ref count is
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* zero when ioc is being detached.
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*/
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do {
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ioc = current_io_context(gfp_flags, node);
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if (unlikely(!ioc))
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break;
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} while (!atomic_long_inc_not_zero(&ioc->refcount));
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return ioc;
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}
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EXPORT_SYMBOL(get_io_context);
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static int __init blk_ioc_init(void)
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{
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iocontext_cachep = kmem_cache_create("blkdev_ioc",
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sizeof(struct io_context), 0, SLAB_PANIC, NULL);
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return 0;
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}
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subsys_initcall(blk_ioc_init);
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