diff options
Diffstat (limited to 'fs/aio.c')
| -rw-r--r-- | fs/aio.c | 136 |
1 files changed, 107 insertions, 29 deletions
@@ -440,8 +440,6 @@ void exit_aio(struct mm_struct *mm) static struct kiocb *__aio_get_req(struct kioctx *ctx) { struct kiocb *req = NULL; - struct aio_ring *ring; - int okay = 0; req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL); if (unlikely(!req)) @@ -459,39 +457,114 @@ static struct kiocb *__aio_get_req(struct kioctx *ctx) INIT_LIST_HEAD(&req->ki_run_list); req->ki_eventfd = NULL; - /* Check if the completion queue has enough free space to - * accept an event from this io. - */ + return req; +} + +/* + * struct kiocb's are allocated in batches to reduce the number of + * times the ctx lock is acquired and released. + */ +#define KIOCB_BATCH_SIZE 32L +struct kiocb_batch { + struct list_head head; + long count; /* number of requests left to allocate */ +}; + +static void kiocb_batch_init(struct kiocb_batch *batch, long total) +{ + INIT_LIST_HEAD(&batch->head); + batch->count = total; +} + +static void kiocb_batch_free(struct kiocb_batch *batch) +{ + struct kiocb *req, *n; + + list_for_each_entry_safe(req, n, &batch->head, ki_batch) { + list_del(&req->ki_batch); + kmem_cache_free(kiocb_cachep, req); + } +} + +/* + * Allocate a batch of kiocbs. This avoids taking and dropping the + * context lock a lot during setup. + */ +static int kiocb_batch_refill(struct kioctx *ctx, struct kiocb_batch *batch) +{ + unsigned short allocated, to_alloc; + long avail; + bool called_fput = false; + struct kiocb *req, *n; + struct aio_ring *ring; + + to_alloc = min(batch->count, KIOCB_BATCH_SIZE); + for (allocated = 0; allocated < to_alloc; allocated++) { + req = __aio_get_req(ctx); + if (!req) + /* allocation failed, go with what we've got */ + break; + list_add(&req->ki_batch, &batch->head); + } + + if (allocated == 0) + goto out; + +retry: spin_lock_irq(&ctx->ctx_lock); - ring = kmap_atomic(ctx->ring_info.ring_pages[0], KM_USER0); - if (ctx->reqs_active < aio_ring_avail(&ctx->ring_info, ring)) { + ring = kmap_atomic(ctx->ring_info.ring_pages[0]); + + avail = aio_ring_avail(&ctx->ring_info, ring) - ctx->reqs_active; + BUG_ON(avail < 0); + if (avail == 0 && !called_fput) { + /* + * Handle a potential starvation case. It is possible that + * we hold the last reference on a struct file, causing us + * to delay the final fput to non-irq context. In this case, + * ctx->reqs_active is artificially high. Calling the fput + * routine here may free up a slot in the event completion + * ring, allowing this allocation to succeed. + */ + kunmap_atomic(ring); + spin_unlock_irq(&ctx->ctx_lock); + aio_fput_routine(NULL); + called_fput = true; + goto retry; + } + + if (avail < allocated) { + /* Trim back the number of requests. */ + list_for_each_entry_safe(req, n, &batch->head, ki_batch) { + list_del(&req->ki_batch); + kmem_cache_free(kiocb_cachep, req); + if (--allocated <= avail) + break; + } + } + + batch->count -= allocated; + list_for_each_entry(req, &batch->head, ki_batch) { list_add(&req->ki_list, &ctx->active_reqs); ctx->reqs_active++; - okay = 1; } - kunmap_atomic(ring, KM_USER0); - spin_unlock_irq(&ctx->ctx_lock); - if (!okay) { - kmem_cache_free(kiocb_cachep, req); - req = NULL; - } + kunmap_atomic(ring); + spin_unlock_irq(&ctx->ctx_lock); - return req; +out: + return allocated; } -static inline struct kiocb *aio_get_req(struct kioctx *ctx) +static inline struct kiocb *aio_get_req(struct kioctx *ctx, + struct kiocb_batch *batch) { struct kiocb *req; - /* Handle a potential starvation case -- should be exceedingly rare as - * requests will be stuck on fput_head only if the aio_fput_routine is - * delayed and the requests were the last user of the struct file. - */ - req = __aio_get_req(ctx); - if (unlikely(NULL == req)) { - aio_fput_routine(NULL); - req = __aio_get_req(ctx); - } + + if (list_empty(&batch->head)) + if (kiocb_batch_refill(ctx, batch) == 0) + return NULL; + req = list_first_entry(&batch->head, struct kiocb, ki_batch); + list_del(&req->ki_batch); return req; } @@ -1515,7 +1588,8 @@ static ssize_t aio_setup_iocb(struct kiocb *kiocb, bool compat) } static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb, - struct iocb *iocb, bool compat) + struct iocb *iocb, struct kiocb_batch *batch, + bool compat) { struct kiocb *req; struct file *file; @@ -1541,7 +1615,7 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb, if (unlikely(!file)) return -EBADF; - req = aio_get_req(ctx); /* returns with 2 references to req */ + req = aio_get_req(ctx, batch); /* returns with 2 references to req */ if (unlikely(!req)) { fput(file); return -EAGAIN; @@ -1621,8 +1695,9 @@ long do_io_submit(aio_context_t ctx_id, long nr, { struct kioctx *ctx; long ret = 0; - int i; + int i = 0; struct blk_plug plug; + struct kiocb_batch batch; if (unlikely(nr < 0)) return -EINVAL; @@ -1639,6 +1714,8 @@ long do_io_submit(aio_context_t ctx_id, long nr, return -EINVAL; } + kiocb_batch_init(&batch, nr); + blk_start_plug(&plug); /* @@ -1659,12 +1736,13 @@ long do_io_submit(aio_context_t ctx_id, long nr, break; } - ret = io_submit_one(ctx, user_iocb, &tmp, compat); + ret = io_submit_one(ctx, user_iocb, &tmp, &batch, compat); if (ret) break; } blk_finish_plug(&plug); + kiocb_batch_free(&batch); put_ioctx(ctx); return i ? i : ret; } |