The kiocb refcount is only needed for cancellation - to ensure a kiocb isn't freed while a ki_cancel callback is running. But if we restrict ki_cancel callbacks to not block (which they currently don't), we can simply drop the refcount.
Signed-off-by: Kent Overstreet <koverstr...@google.com> Cc: Zach Brown <z...@redhat.com> Cc: Felipe Balbi <ba...@ti.com> Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org> Cc: Mark Fasheh <mfas...@suse.com> Cc: Joel Becker <jl...@evilplan.org> Cc: Rusty Russell <ru...@rustcorp.com.au> Cc: Jens Axboe <ax...@kernel.dk> Cc: Asai Thambi S P <asamymuth...@micron.com> Cc: Selvan Mani <sm...@micron.com> Cc: Sam Bradshaw <sbrads...@micron.com> Cc: Jeff Moyer <jmo...@redhat.com> Cc: Al Viro <v...@zeniv.linux.org.uk> Cc: Benjamin LaHaise <b...@kvack.org> Cc: Theodore Ts'o <ty...@mit.edu> --- fs/aio.c | 47 ++++++++++++----------------------------------- include/linux/aio.h | 5 ----- 2 files changed, 12 insertions(+), 40 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index 280b014..40781ff 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -262,7 +262,6 @@ EXPORT_SYMBOL(kiocb_set_cancel_fn); static int kiocb_cancel(struct kioctx *ctx, struct kiocb *kiocb) { kiocb_cancel_fn *old, *cancel; - int ret = -EINVAL; /* * Don't want to set kiocb->ki_cancel = KIOCB_CANCELLED unless it @@ -272,21 +271,13 @@ static int kiocb_cancel(struct kioctx *ctx, struct kiocb *kiocb) cancel = ACCESS_ONCE(kiocb->ki_cancel); do { if (!cancel || cancel == KIOCB_CANCELLED) - return ret; + return -EINVAL; old = cancel; cancel = cmpxchg(&kiocb->ki_cancel, old, KIOCB_CANCELLED); } while (cancel != old); - atomic_inc(&kiocb->ki_users); - spin_unlock_irq(&ctx->ctx_lock); - - ret = cancel(kiocb); - - spin_lock_irq(&ctx->ctx_lock); - aio_put_req(kiocb); - - return ret; + return cancel(kiocb); } static void free_ioctx_rcu(struct rcu_head *head) @@ -510,16 +501,16 @@ static void kill_ioctx(struct kioctx *ctx) /* wait_on_sync_kiocb: * Waits on the given sync kiocb to complete. */ -ssize_t wait_on_sync_kiocb(struct kiocb *iocb) +ssize_t wait_on_sync_kiocb(struct kiocb *req) { - while (atomic_read(&iocb->ki_users)) { + while (!req->ki_ctx) { set_current_state(TASK_UNINTERRUPTIBLE); - if (!atomic_read(&iocb->ki_users)) + if (req->ki_ctx) break; io_schedule(); } __set_current_state(TASK_RUNNING); - return iocb->ki_user_data; + return req->ki_user_data; } EXPORT_SYMBOL(wait_on_sync_kiocb); @@ -601,14 +592,8 @@ out: } /* aio_get_req - * Allocate a slot for an aio request. Increments the ki_users count - * of the kioctx so that the kioctx stays around until all requests are - * complete. Returns NULL if no requests are free. - * - * Returns with kiocb->ki_users set to 2. The io submit code path holds - * an extra reference while submitting the i/o. - * This prevents races between the aio code path referencing the - * req (after submitting it) and aio_complete() freeing the req. + * Allocate a slot for an aio request. + * Returns NULL if no requests are free. */ static inline struct kiocb *aio_get_req(struct kioctx *ctx) { @@ -621,7 +606,6 @@ static inline struct kiocb *aio_get_req(struct kioctx *ctx) if (unlikely(!req)) goto out_put; - atomic_set(&req->ki_users, 1); req->ki_ctx = ctx; return req; out_put: @@ -640,13 +624,6 @@ static void kiocb_free(struct kiocb *req) kmem_cache_free(kiocb_cachep, req); } -void aio_put_req(struct kiocb *req) -{ - if (atomic_dec_and_test(&req->ki_users)) - kiocb_free(req); -} -EXPORT_SYMBOL(aio_put_req); - static struct kioctx *lookup_ioctx(unsigned long ctx_id) { struct mm_struct *mm = current->mm; @@ -685,9 +662,9 @@ void aio_complete(struct kiocb *iocb, long res, long res2) * - the sync task helpfully left a reference to itself in the iocb */ if (is_sync_kiocb(iocb)) { - BUG_ON(atomic_read(&iocb->ki_users) != 1); iocb->ki_user_data = res; - atomic_set(&iocb->ki_users, 0); + smp_wmb(); + iocb->ki_ctx = ERR_PTR(-EXDEV); wake_up_process(iocb->ki_obj.tsk); return; } @@ -759,7 +736,7 @@ void aio_complete(struct kiocb *iocb, long res, long res2) eventfd_signal(iocb->ki_eventfd, 1); /* everything turned out well, dispose of the aiocb. */ - aio_put_req(iocb); + kiocb_free(iocb); /* * We have to order our ring_info tail store above and test @@ -1183,7 +1160,7 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb, return 0; out_put_req: put_reqs_available(ctx, 1); - aio_put_req(req); + kiocb_free(req); return ret; } diff --git a/include/linux/aio.h b/include/linux/aio.h index b570472..c4f07ff 100644 --- a/include/linux/aio.h +++ b/include/linux/aio.h @@ -30,8 +30,6 @@ struct kiocb; typedef int (kiocb_cancel_fn)(struct kiocb *); struct kiocb { - atomic_t ki_users; - struct file *ki_filp; struct kioctx *ki_ctx; /* NULL for sync ops */ kiocb_cancel_fn *ki_cancel; @@ -65,7 +63,6 @@ static inline bool is_sync_kiocb(struct kiocb *kiocb) static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp) { *kiocb = (struct kiocb) { - .ki_users = ATOMIC_INIT(1), .ki_ctx = NULL, .ki_filp = filp, .ki_obj.tsk = current, @@ -75,7 +72,6 @@ static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp) /* prototypes */ #ifdef CONFIG_AIO extern ssize_t wait_on_sync_kiocb(struct kiocb *iocb); -extern void aio_put_req(struct kiocb *iocb); extern void aio_complete(struct kiocb *iocb, long res, long res2); struct mm_struct; extern void exit_aio(struct mm_struct *mm); @@ -84,7 +80,6 @@ extern long do_io_submit(aio_context_t ctx_id, long nr, void kiocb_set_cancel_fn(struct kiocb *req, kiocb_cancel_fn *cancel); #else static inline ssize_t wait_on_sync_kiocb(struct kiocb *iocb) { return 0; } -static inline void aio_put_req(struct kiocb *iocb) { } static inline void aio_complete(struct kiocb *iocb, long res, long res2) { } struct mm_struct; static inline void exit_aio(struct mm_struct *mm) { } -- 1.8.2.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/