diff options
| -rw-r--r-- | block/ll_rw_blk.c | 46 | ||||
| -rw-r--r-- | fs/ioprio.c | 1 | ||||
| -rw-r--r-- | include/linux/blkdev.h | 2 | ||||
| -rw-r--r-- | include/linux/iocontext.h | 22 | ||||
| -rw-r--r-- | kernel/fork.c | 1 |
5 files changed, 49 insertions, 23 deletions
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c index b9bb02e..d4550ec 100644 --- a/block/ll_rw_blk.c +++ b/block/ll_rw_blk.c @@ -3854,12 +3854,13 @@ int __init blk_dev_init(void) } /* - * IO Context helper functions + * IO Context helper functions. put_io_context() returns 1 if there are no + * more users of this io context, 0 otherwise. */ -void put_io_context(struct io_context *ioc) +int put_io_context(struct io_context *ioc) { if (ioc == NULL) - return; + return 1; BUG_ON(atomic_read(&ioc->refcount) == 0); @@ -3878,7 +3879,9 @@ void put_io_context(struct io_context *ioc) rcu_read_unlock(); kmem_cache_free(iocontext_cachep, ioc); + return 1; } + return 0; } EXPORT_SYMBOL(put_io_context); @@ -3893,15 +3896,17 @@ void exit_io_context(void) current->io_context = NULL; task_unlock(current); - ioc->task = NULL; - if (ioc->aic && ioc->aic->exit) - ioc->aic->exit(ioc->aic); - if (ioc->cic_root.rb_node != NULL) { - cic = rb_entry(rb_first(&ioc->cic_root), struct cfq_io_context, rb_node); - cic->exit(ioc); - } + if (atomic_dec_and_test(&ioc->nr_tasks)) { + if (ioc->aic && ioc->aic->exit) + ioc->aic->exit(ioc->aic); + if (ioc->cic_root.rb_node != NULL) { + cic = rb_entry(rb_first(&ioc->cic_root), + struct cfq_io_context, rb_node); + cic->exit(ioc); + } - put_io_context(ioc); + put_io_context(ioc); + } } struct io_context *alloc_io_context(gfp_t gfp_flags, int node) @@ -3911,7 +3916,8 @@ struct io_context *alloc_io_context(gfp_t gfp_flags, int node) ret = kmem_cache_alloc_node(iocontext_cachep, gfp_flags, node); if (ret) { atomic_set(&ret->refcount, 1); - ret->task = current; + 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... */ @@ -3959,10 +3965,18 @@ static struct io_context *current_io_context(gfp_t gfp_flags, int node) */ struct io_context *get_io_context(gfp_t gfp_flags, int node) { - struct io_context *ret; - ret = current_io_context(gfp_flags, node); - if (likely(ret)) - atomic_inc(&ret->refcount); + 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_inc_not_zero(&ret->refcount)); + return ret; } EXPORT_SYMBOL(get_io_context); diff --git a/fs/ioprio.c b/fs/ioprio.c index a760040..06b5d97 100644 --- a/fs/ioprio.c +++ b/fs/ioprio.c @@ -54,7 +54,6 @@ static int set_task_ioprio(struct task_struct *task, int ioprio) break; } task->io_context = ioc; - ioc->task = task; } while (1); if (!err) { diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 510a18b..2483a05 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -34,7 +34,7 @@ struct sg_io_hdr; #define BLKDEV_MIN_RQ 4 #define BLKDEV_MAX_RQ 128 /* Default maximum */ -void put_io_context(struct io_context *ioc); +int put_io_context(struct io_context *ioc); void exit_io_context(void); struct io_context *get_io_context(gfp_t gfp_flags, int node); struct io_context *alloc_io_context(gfp_t gfp_flags, int node); diff --git a/include/linux/iocontext.h b/include/linux/iocontext.h index 186807e..cd44d45 100644 --- a/include/linux/iocontext.h +++ b/include/linux/iocontext.h @@ -54,13 +54,15 @@ struct cfq_io_context { }; /* - * This is the per-process I/O subsystem state. It is refcounted and - * kmalloc'ed. Currently all fields are modified in process io context - * (apart from the atomic refcount), so require no locking. + * I/O subsystem state of the associated processes. It is refcounted + * and kmalloc'ed. These could be shared between processes. */ struct io_context { atomic_t refcount; - struct task_struct *task; + atomic_t nr_tasks; + + /* all the fields below are protected by this lock */ + spinlock_t lock; unsigned short ioprio; unsigned short ioprio_changed; @@ -76,4 +78,16 @@ struct io_context { void *ioc_data; }; +static inline struct io_context *ioc_task_link(struct io_context *ioc) +{ + /* + * if ref count is zero, don't allow sharing (ioc is going away, it's + * a race). + */ + if (ioc && atomic_inc_not_zero(&ioc->refcount)) + return ioc; + + return NULL; +} + #endif diff --git a/kernel/fork.c b/kernel/fork.c index 2a86c9d..1987c57 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -805,7 +805,6 @@ static int copy_io(struct task_struct *tsk) if (unlikely(!tsk->io_context)) return -ENOMEM; - tsk->io_context->task = tsk; tsk->io_context->ioprio = ioc->ioprio; } #endif |
