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