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From: "Sébastien Dugué" <sebastien.dugue@bull.net> To: linux-kernel <linux-kernel@vger.kernel.org> Cc: Christoph Hellwig <hch@infradead.org>, linux-aio <linux-aio@kvack.org>, Andrew Morton <akpm@osdl.org>, Suparna Bhattacharya <suparna@in.ibm.com>, Zach Brown <zach.brown@oracle.com>, Badari Pulavarty <pbadari@us.ibm.com>, Ulrich Drepper <drepper@redhat.com>, Jean Pierre Dion <jean-pierre.dion@bull.net>, Bharata B Rao <bharata@in.ibm.com> Subject: Re: [PATCH -mm 4/5][AIO] - AIO completion signal notification Date: Thu, 30 Nov 2006 16:50:28 +0100 [thread overview] Message-ID: <20061130165028.3cc53376@frecb000686> (raw) In-Reply-To: <20061130163839.38689215@frecb000686> AIO completion signal notification The current 2.6 kernel does not support notification of user space via an RT signal upon an asynchronous IO completion. The POSIX specification states that when an AIO request completes, a signal can be delivered to the application as notification. This patch adds a struct sigevent *aio_sigeventp to the iocb. The relevant fields (pid, signal number and value) are stored in the kiocb for use when the request completes. That sigevent structure is filled by the application as part of the AIO request preparation. Upon request completion, the kernel notifies the application using those sigevent parameters. If SIGEV_NONE has been specified, then the old behaviour is retained and the application must rely on polling the completion queue using io_getevents(). A struct sigevent *aio_sigeventp field is added to struct iocb in include/linux/aio_abi.h A struct aio_notify containing the sigevent parameters is defined in aio.h: struct aio_notify { struct task_struct *target; __u16 signo; __u16 notify; sigval_t value; }; A struct aio_notify ki_notify is added to struct kiocb in include/linux/aio.h In io_submit_one(), if the application provided a sigevent then setup_sigevent() is called which does the following: - check access to the user sigevent and make a local copy - if the requested notification is SIGEV_NONE, then nothing to do - fill in the kiocb->ki_notify fields (notify, signo, value) - check sigevent consistency, get the signal target task and save it in kiocb->ki_notify.target - preallocate a sigqueue for this event using sigqueue_alloc() Upon request completion, in aio_complete(), if notification is needed for this request (iocb->ki_notify.notify != SIGEV_NONE), then aio_send_signal() is called to signal the target task as follows: - fill in the siginfo struct to be sent to the task - if notify is SIGEV_THREAD_ID then send signal to specific task using send_sigqueue() - else send signal to task group using send_5group_sigqueue() Notes concerning sigqueue preallocation: To ensure reliable delivery of completion notification, the sigqueue is preallocated in the submission path so that there is no chance it can fail in the completion path. Unlike the posix-timers case (currently the single other user of sigqueue preallocation), where the sigqueue is allocated for the lifetime of the timer and freed at timer destruction time, the aio case is a bit more tricky due to the async nature of the whole thing. In the aio case, the sigqueue exists for the lifetime of the request, therefore it must be freed only once the signal for the request completion has been delivered. This involves changing __sigqueue_free() to free the sigqueue when the signal is collected if si_code is SI_ASYNCIO even if it was preallocated as well as explicitly calling sigqueue_free() in submission and completion error paths. fs/aio.c | 115 ++++++++++++++++++++++++++++++++++++++++++++++-- fs/compat.c | 18 +++++++ include/linux/aio.h | 12 +++++ include/linux/aio_abi.h | 3 - kernel/signal.c | 2 5 files changed, 144 insertions(+), 6 deletions(-) Signed-off-by: Sébastien Dugué <sebastien.dugue@bull.net> Signed-off-by: Laurent Vivier <laurent.vivier@bull.net> Index: linux-2.6.19-rc6-mm2/fs/aio.c =================================================================== --- linux-2.6.19-rc6-mm2.orig/fs/aio.c 2006-11-30 10:54:16.000000000 +0100 +++ linux-2.6.19-rc6-mm2/fs/aio.c 2006-11-30 15:18:52.000000000 +0100 @@ -416,6 +416,7 @@ static struct kiocb fastcall *__aio_get_ req->ki_dtor = NULL; req->private = NULL; req->ki_iovec = NULL; + req->ki_notify.sigq = NULL; INIT_LIST_HEAD(&req->ki_run_list); /* Check if the completion queue has enough free space to @@ -463,6 +464,12 @@ static inline void really_put_req(struct req->ki_dtor(req); if (req->ki_iovec != &req->ki_inline_vec) kfree(req->ki_iovec); + + /* Release task ref */ + if (req->ki_notify.notify == SIGEV_THREAD_ID || + req->ki_notify.notify == SIGEV_SIGNAL) + put_task_struct(req->ki_notify.target); + kmem_cache_free(kiocb_cachep, req); ctx->reqs_active--; @@ -929,6 +936,79 @@ void fastcall kick_iocb(struct kiocb *io } EXPORT_SYMBOL(kick_iocb); +static int aio_send_signal(struct aio_notify *notify) +{ + struct sigqueue *sigq = notify->sigq; + struct siginfo *info = &sigq->info; + int ret; + + memset(info, 0, sizeof(struct siginfo)); + + info->si_signo = notify->signo; + info->si_errno = 0; + info->si_code = SI_ASYNCIO; + info->si_pid = 0; + info->si_uid = 0; + info->si_value = notify->value; + + if (notify->notify & SIGEV_THREAD_ID) + ret = send_sigqueue(notify->signo, sigq, notify->target); + else + ret = send_group_sigqueue(notify->signo, sigq, notify->target); + + return ret; +} + +static long aio_setup_sigevent(struct aio_notify *notify, + struct sigevent __user *user_event) +{ + sigevent_t event; + struct task_struct *target; + + if (copy_from_user(&event, user_event, sizeof (event))) + return -EFAULT; + + if (event.sigev_notify == SIGEV_NONE) + return 0; + + notify->notify = event.sigev_notify; + notify->signo = event.sigev_signo; + notify->value = event.sigev_value; + + read_lock(&tasklist_lock); + target = good_sigevent(&event); + + if (unlikely(!target || (target->flags & PF_EXITING))) + goto out_unlock; + + /* + * At this point, we know that notify is either SIGEV_SIGNAL or + * SIGEV_THREAD_ID and the target task is valid. So get a reference + * on the task, it will be dropped in really_put_req() when + * we're done with the request. + */ + get_task_struct(target); + notify->target = target; + read_unlock(&tasklist_lock); + + /* + * NOTE: we cannot free the sigqueue in the completion path as + * the signal may not have been delivered to the target task. + * Therefore it has to be freed in __sigqueue_free() when the + * signal is collected if si_code is SI_ASYNCIO. + */ + notify->sigq = sigqueue_alloc(); + + if (unlikely(!notify->sigq)) + return -EAGAIN; + + return 0; + +out_unlock: + read_unlock(&tasklist_lock); + return -EINVAL; +} + /* aio_complete * Called when the io request on the given iocb is complete. * Returns true if this is the last user of the request. The @@ -976,8 +1056,11 @@ int fastcall aio_complete(struct kiocb * * cancelled requests don't get events, userland was given one * when the event got cancelled. */ - if (kiocbIsCancelled(iocb)) + if (kiocbIsCancelled(iocb)) { + if (iocb->ki_notify.sigq) + sigqueue_free(iocb->ki_notify.sigq); goto put_rq; + } ring = kmap_atomic(info->ring_pages[0], KM_IRQ1); @@ -1008,6 +1091,14 @@ int fastcall aio_complete(struct kiocb * pr_debug("added to ring %p at [%lu]\n", iocb, tail); + if (iocb->ki_notify.notify != SIGEV_NONE) { + ret = aio_send_signal(&iocb->ki_notify); + + /* If signal generation failed, release the sigqueue */ + if (ret) + sigqueue_free(iocb->ki_notify.sigq); + } + pr_debug("%ld retries: %zd of %zd\n", iocb->ki_retried, iocb->ki_nbytes - iocb->ki_left, iocb->ki_nbytes); put_rq: @@ -1549,8 +1640,7 @@ int fastcall io_submit_one(struct kioctx ssize_t ret; /* enforce forwards compatibility on users */ - if (unlikely(iocb->aio_reserved1 || iocb->aio_reserved2 || - iocb->aio_reserved3)) { + if (unlikely(iocb->aio_reserved1 || iocb->aio_reserved3)) { pr_debug("EINVAL: io_submit: reserve field set\n"); return -EINVAL; } @@ -1559,6 +1649,7 @@ int fastcall io_submit_one(struct kioctx if (unlikely( (iocb->aio_buf != (unsigned long)iocb->aio_buf) || (iocb->aio_nbytes != (size_t)iocb->aio_nbytes) || + (iocb->aio_sigeventp != (unsigned long)iocb->aio_sigeventp) || ((ssize_t)iocb->aio_nbytes < 0) )) { pr_debug("EINVAL: io_submit: overflow check\n"); @@ -1593,10 +1684,21 @@ int fastcall io_submit_one(struct kioctx INIT_LIST_HEAD(&req->ki_wait.task_list); req->ki_retried = 0; + /* handle setting up the sigevent for POSIX AIO signals */ + req->ki_notify.notify = SIGEV_NONE; + + if (iocb->aio_sigeventp) { + ret = aio_setup_sigevent(&req->ki_notify, + (struct sigevent __user *)(unsigned long) + iocb->aio_sigeventp); + if (ret) + goto out_put_req; + } + ret = aio_setup_iocb(req); if (ret) - goto out_put_req; + goto out_sigqfree; spin_lock_irq(&ctx->ctx_lock); aio_run_iocb(req); @@ -1609,6 +1711,11 @@ int fastcall io_submit_one(struct kioctx aio_put_req(req); /* drop extra ref to req */ return 0; +out_sigqfree: + /* Undo the sigqueue alloc if someting went bad */ + if (req->ki_notify.sigq) + sigqueue_free(req->ki_notify.sigq); + out_put_req: aio_put_req(req); /* drop extra ref to req */ aio_put_req(req); /* drop i/o ref to req */ Index: linux-2.6.19-rc6-mm2/include/linux/aio_abi.h =================================================================== --- linux-2.6.19-rc6-mm2.orig/include/linux/aio_abi.h 2006-11-30 10:54:16.000000000 +0100 +++ linux-2.6.19-rc6-mm2/include/linux/aio_abi.h 2006-11-30 15:06:05.000000000 +0100 @@ -82,8 +82,9 @@ struct iocb { __u64 aio_nbytes; __s64 aio_offset; + __u64 aio_sigeventp; /* pointer to struct sigevent */ + /* extra parameters */ - __u64 aio_reserved2; /* TODO: use this for a (struct sigevent *) */ __u64 aio_reserved3; }; /* 64 bytes */ Index: linux-2.6.19-rc6-mm2/include/linux/aio.h =================================================================== --- linux-2.6.19-rc6-mm2.orig/include/linux/aio.h 2006-11-30 13:18:15.000000000 +0100 +++ linux-2.6.19-rc6-mm2/include/linux/aio.h 2006-11-30 15:06:05.000000000 +0100 @@ -7,6 +7,7 @@ #include <linux/uio.h> #include <asm/atomic.h> +#include <asm/siginfo.h> #define AIO_MAXSEGS 4 #define AIO_KIOGRP_NR_ATOMIC 8 @@ -49,6 +50,14 @@ struct kioctx; #define kiocbIsKicked(iocb) test_bit(KIF_KICKED, &(iocb)->ki_flags) #define kiocbIsCancelled(iocb) test_bit(KIF_CANCELLED, &(iocb)->ki_flags) +struct aio_notify { + struct task_struct *target; + __u16 signo; + __u16 notify; + sigval_t value; + struct sigqueue *sigq; +}; + /* is there a better place to document function pointer methods? */ /** * ki_retry - iocb forward progress callback @@ -118,6 +127,9 @@ struct kiocb { struct list_head ki_list; /* the aio core uses this * for cancellation */ + + /* to notify a process on I/O event */ + struct aio_notify ki_notify; }; #define is_sync_kiocb(iocb) ((iocb)->ki_key == KIOCB_SYNC_KEY) Index: linux-2.6.19-rc6-mm2/kernel/signal.c =================================================================== --- linux-2.6.19-rc6-mm2.orig/kernel/signal.c 2006-11-30 13:33:10.000000000 +0100 +++ linux-2.6.19-rc6-mm2/kernel/signal.c 2006-11-30 15:06:05.000000000 +0100 @@ -297,7 +297,7 @@ static struct sigqueue *__sigqueue_alloc static void __sigqueue_free(struct sigqueue *q) { - if (q->flags & SIGQUEUE_PREALLOC) + if (q->flags & SIGQUEUE_PREALLOC && q->info.si_code != SI_ASYNCIO) return; atomic_dec(&q->user->sigpending); free_uid(q->user); Index: linux-2.6.19-rc6-mm2/fs/compat.c =================================================================== --- linux-2.6.19-rc6-mm2.orig/fs/compat.c 2006-11-30 13:12:32.000000000 +0100 +++ linux-2.6.19-rc6-mm2/fs/compat.c 2006-11-30 15:06:05.000000000 +0100 @@ -663,6 +663,7 @@ compat_sys_io_submit(aio_context_t ctx_i compat_uptr_t uptr; struct iocb __user *user_iocb; struct iocb tmp; + struct compat_sigevent __user *uevent; if (unlikely(get_user(uptr, iocb + i))) { ret = -EFAULT; @@ -676,6 +677,23 @@ compat_sys_io_submit(aio_context_t ctx_i break; } + uevent = (struct compat_sigevent __user *)tmp.aio_sigeventp; + + if (uevent) { + struct sigevent __user *event = NULL; + struct sigevent kevent; + + event = compat_alloc_user_space(sizeof(*event)); + + if (get_compat_sigevent(&kevent, uevent) || + copy_to_user(event, &kevent, sizeof(*event))) { + ret = -EFAULT; + break; + } + + tmp.aio_sigeventp = (__u64)event; + } + ret = io_submit_one(ctx, user_iocb, &tmp); if (ret) break;
next prev parent reply other threads:[~2006-11-30 15:51 UTC|newest] Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top 2006-11-30 15:38 [PATCH -mm 0/5][AIO] - AIO completion signal notification v4 Sébastien Dugué 2006-11-30 15:49 ` [PATCH -mm 1/5][AIO] - Rework compat_sys_io_submit Sébastien Dugué 2006-11-30 15:49 ` [PATCH -mm 2/5][AIO] - fix aio.h includes Sébastien Dugué 2006-11-30 15:50 ` [PATCH -mm 3/5][AIO] - Make good_sigevent non-static Sébastien Dugué 2006-11-30 15:50 ` Sébastien Dugué [this message] 2006-11-30 15:50 ` [PATCH -mm 5/5][AIO] - Add listio support Sébastien Dugué [not found] <20070117104601.36b2ab18@frecb000686> 2007-01-17 9:50 ` [PATCH -mm 4/5][AIO] - AIO completion signal notification Sébastien Dugué 2007-01-24 5:35 ` Andrew Morton 2007-01-24 11:11 ` Sébastien Dugué 2007-01-25 5:42 ` Christoph Hellwig 2007-01-25 8:46 ` Sébastien Dugué -- strict thread matches above, loose matches on Subject: below -- 2006-11-29 10:24 [PATCH -mm 0/5][AIO] - AIO completion signal notification v3 Sébastien Dugué 2006-11-29 10:33 ` [PATCH -mm 4/5][AIO] - AIO completion signal notification Sébastien Dugué 2006-11-29 10:51 ` Christoph Hellwig 2006-11-29 13:08 ` Sébastien Dugué 2006-11-29 13:50 ` Christoph Hellwig 2006-11-29 14:18 ` Sébastien Dugué 2006-11-29 11:33 ` Jakub Jelinek 2006-11-29 13:25 ` Sébastien Dugué
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