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author | root <root@artemis.panaceas.org> | 2015-12-25 04:40:36 +0000 |
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committer | root <root@artemis.panaceas.org> | 2015-12-25 04:40:36 +0000 |
commit | 849369d6c66d3054688672f97d31fceb8e8230fb (patch) | |
tree | 6135abc790ca67dedbe07c39806591e70eda81ce /block/blk-ioc.c | |
download | linux-3.0.35-kobo-849369d6c66d3054688672f97d31fceb8e8230fb.tar.gz linux-3.0.35-kobo-849369d6c66d3054688672f97d31fceb8e8230fb.tar.bz2 linux-3.0.35-kobo-849369d6c66d3054688672f97d31fceb8e8230fb.zip |
initial_commit
Diffstat (limited to 'block/blk-ioc.c')
-rw-r--r-- | block/blk-ioc.c | 164 |
1 files changed, 164 insertions, 0 deletions
diff --git a/block/blk-ioc.c b/block/blk-ioc.c new file mode 100644 index 00000000..342eae9b --- /dev/null +++ b/block/blk-ioc.c @@ -0,0 +1,164 @@ +/* + * 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 <linux/slab.h> + +#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 = hlist_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 = hlist_entry(ioc->cic_list.first, struct cfq_io_context, + cic_list); + cic->exit(ioc); + } + rcu_read_unlock(); +} + +/* Called by the exiting 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 = 0; /* 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; +#if defined(CONFIG_BLK_CGROUP) || defined(CONFIG_BLK_CGROUP_MODULE) + ret->cgroup_changed = 0; +#endif + } + + 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); + +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); |