Core retry infrastructure fs/aio.c | 525 +++++++++++++++++++++++++++++++++++++++------- include/linux/aio.h | 22 + include/linux/errno.h | 1 include/linux/init_task.h | 1 include/linux/sched.h | 7 include/linux/wait.h | 9 kernel/fork.c | 15 + 7 files changed, 501 insertions(+), 79 deletions(-) diff -puN fs/aio.c~aio-01-retry fs/aio.c --- 25/fs/aio.c~aio-01-retry 2003-08-16 13:54:21.000000000 -0700 +++ 25-akpm/fs/aio.c 2003-08-16 13:54:21.000000000 -0700 @@ -39,6 +39,9 @@ #define dprintk(x...) do { ; } while (0) #endif +long aio_run = 0; /* for testing only */ +long aio_wakeups = 0; /* for testing only */ + /*------ sysctl variables----*/ atomic_t aio_nr = ATOMIC_INIT(0); /* current system wide number of aio requests */ unsigned aio_max_nr = 0x10000; /* system wide maximum number of aio requests */ @@ -282,6 +285,7 @@ static void aio_cancel_all(struct kioctx struct kiocb *iocb = list_kiocb(pos); list_del_init(&iocb->ki_list); cancel = iocb->ki_cancel; + kiocbSetCancelled(iocb); if (cancel) { iocb->ki_users++; spin_unlock_irq(&ctx->ctx_lock); @@ -396,6 +400,7 @@ static struct kiocb *__aio_get_req(struc req->ki_cancel = NULL; req->ki_retry = NULL; req->ki_user_obj = NULL; + INIT_LIST_HEAD(&req->ki_run_list); /* Check if the completion queue has enough free space to * accept an event from this io. @@ -537,65 +542,277 @@ struct kioctx *lookup_ioctx(unsigned lon return ioctx; } +/* + * use_mm + * Makes the calling kernel thread take on the specified + * mm context. + * Called by the retry thread execute retries within the + * iocb issuer's mm context, so that copy_from/to_user + * operations work seamlessly for aio. + * (Note: this routine is intended to be called only + * from a kernel thread context) + */ static void use_mm(struct mm_struct *mm) { struct mm_struct *active_mm = current->active_mm; atomic_inc(&mm->mm_count); current->mm = mm; - if (mm != active_mm) { - current->active_mm = mm; - activate_mm(active_mm, mm); - } + + current->active_mm = mm; + activate_mm(active_mm, mm); + mmdrop(active_mm); } -static void unuse_mm(struct mm_struct *mm) +/* + * unuse_mm + * Reverses the effect of use_mm, i.e. releases the + * specified mm context which was earlier taken on + * by the calling kernel thread + * (Note: this routine is intended to be called only + * from a kernel thread context) + */ +void unuse_mm(struct mm_struct *mm) { current->mm = NULL; /* active_mm is still 'mm' */ enter_lazy_tlb(mm, current); } -/* Run on kevent's context. FIXME: needs to be per-cpu and warn if an - * operation blocks. +/* + * Queue up a kiocb to be retried. Assumes that the kiocb + * has already been marked as kicked, and places it on + * the retry run list for the corresponding ioctx, if it + * isn't already queued. Returns 1 if it actually queued + * the kiocb (to tell the caller to activate the work + * queue to process it), or 0, if it found that it was + * already queued. + * + * Should be called with the spin lock iocb->ki_ctx->ctx_lock + * held */ -static void aio_kick_handler(void *data) +static inline int __queue_kicked_iocb(struct kiocb *iocb) { - struct kioctx *ctx = data; + struct kioctx *ctx = iocb->ki_ctx; - use_mm(ctx->mm); + if (list_empty(&iocb->ki_run_list)) { + list_add_tail(&iocb->ki_run_list, + &ctx->run_list); + iocb->ki_queued++; + return 1; + } + return 0; +} - spin_lock_irq(&ctx->ctx_lock); - while (!list_empty(&ctx->run_list)) { - struct kiocb *iocb; - long ret; +/* aio_run_iocb + * This is the core aio execution routine. It is + * invoked both for initial i/o submission and + * subsequent retries via the aio_kick_handler. + * Expects to be invoked with iocb->ki_ctx->lock + * already held. The lock is released and reaquired + * as needed during processing. + * + * Calls the iocb retry method (already setup for the + * iocb on initial submission) for operation specific + * handling, but takes care of most of common retry + * execution details for a given iocb. The retry method + * needs to be non-blocking as far as possible, to avoid + * holding up other iocbs waiting to be serviced by the + * retry kernel thread. + * + * The trickier parts in this code have to do with + * ensuring that only one retry instance is in progress + * for a given iocb at any time. Providing that guarantee + * simplifies the coding of individual aio operations as + * it avoids various potential races. + */ +static ssize_t aio_run_iocb(struct kiocb *iocb) +{ + struct kioctx *ctx = iocb->ki_ctx; + ssize_t (*retry)(struct kiocb *); + ssize_t ret; - iocb = list_entry(ctx->run_list.next, struct kiocb, - ki_run_list); - list_del(&iocb->ki_run_list); - iocb->ki_users ++; - spin_unlock_irq(&ctx->ctx_lock); + if (iocb->ki_retried++ > 1024*1024) { + printk("Maximal retry count. Bytes done %Zd\n", + iocb->ki_nbytes - iocb->ki_left); + return -EAGAIN; + } + + if (!(iocb->ki_retried & 0xff)) { + pr_debug("%ld retry: %d of %d (kick %ld, Q %ld run %ld, wake %ld)\n", + iocb->ki_retried, + iocb->ki_nbytes - iocb->ki_left, iocb->ki_nbytes, + iocb->ki_kicked, iocb->ki_queued, aio_run, aio_wakeups); + } + + if (!(retry = iocb->ki_retry)) { + printk("aio_run_iocb: iocb->ki_retry = NULL\n"); + return 0; + } + + /* + * We don't want the next retry iteration for this + * operation to start until this one has returned and + * updated the iocb state. However, wait_queue functions + * can trigger a kick_iocb from interrupt context in the + * meantime, indicating that data is available for the next + * iteration. We want to remember that and enable the + * next retry iteration _after_ we are through with + * this one. + * + * So, in order to be able to register a "kick", but + * prevent it from being queued now, we clear the kick + * flag, but make the kick code *think* that the iocb is + * still on the run list until we are actually done. + * When we are done with this iteration, we check if + * the iocb was kicked in the meantime and if so, queue + * it up afresh. + */ - kiocbClearKicked(iocb); - ret = iocb->ki_retry(iocb); + kiocbClearKicked(iocb); + + /* + * This is so that aio_complete knows it doesn't need to + * pull the iocb off the run list (We can't just call + * INIT_LIST_HEAD because we don't want a kick_iocb to + * queue this on the run list yet) + */ + iocb->ki_run_list.next = iocb->ki_run_list.prev = NULL; + iocb->ki_retry = NULL; + spin_unlock_irq(&ctx->ctx_lock); + + /* Quit retrying if the i/o has been cancelled */ + if (kiocbIsCancelled(iocb)) { + ret = -EINTR; + aio_complete(iocb, ret, 0); + /* must not access the iocb after this */ + goto out; + } + + /* + * Now we are all set to call the retry method in async + * context. By setting this thread's io_wait context + * to point to the wait queue entry inside the currently + * running iocb for the duration of the retry, we ensure + * that async notification wakeups are queued by the + * operation instead of blocking waits, and when notified, + * cause the iocb to be kicked for continuation (through + * the aio_wake_function callback). + */ + BUG_ON(current->io_wait != NULL); + current->io_wait = &iocb->ki_wait; + ret = retry(iocb); + current->io_wait = NULL; + + if (-EIOCBRETRY != ret) { if (-EIOCBQUEUED != ret) { + BUG_ON(!list_empty(&iocb->ki_wait.task_list)); aio_complete(iocb, ret, 0); - iocb = NULL; + /* must not access the iocb after this */ } + } else { + /* + * Issue an additional retry to avoid waiting forever if + * no waits were queued (e.g. in case of a short read). + */ + if (list_empty(&iocb->ki_wait.task_list)) + kiocbSetKicked(iocb); + } +out: + spin_lock_irq(&ctx->ctx_lock); - spin_lock_irq(&ctx->ctx_lock); - if (NULL != iocb) - __aio_put_req(ctx, iocb); + if (-EIOCBRETRY == ret) { + /* + * OK, now that we are done with this iteration + * and know that there is more left to go, + * this is where we let go so that a subsequent + * "kick" can start the next iteration + */ + iocb->ki_retry = retry; + /* will make __queue_kicked_iocb succeed from here on */ + INIT_LIST_HEAD(&iocb->ki_run_list); + /* we must queue the next iteration ourselves, if it + * has already been kicked */ + if (kiocbIsKicked(iocb)) { + __queue_kicked_iocb(iocb); + } + } + return ret; +} + +/* + * aio_run_iocbs: + * Process all pending retries queued on the ioctx + * run list. + * Assumes it is operating within the aio issuer's mm + * context. + */ +static void aio_run_iocbs(struct kioctx *ctx) +{ + struct kiocb *iocb; + ssize_t ret; + int count = 0; + + spin_lock_irq(&ctx->ctx_lock); + while (!list_empty(&ctx->run_list)) { + iocb = list_entry(ctx->run_list.next, struct kiocb, + ki_run_list); + list_del(&iocb->ki_run_list); + ret = aio_run_iocb(iocb); + count++; } spin_unlock_irq(&ctx->ctx_lock); + aio_run++; +} +/* + * aio_kick_handler: + * Work queue handler triggered to process pending + * retries on an ioctx. Takes on the aio issuer's + * mm context before running the iocbs. + * Run on aiod's context. + */ +static void aio_kick_handler(void *data) +{ + struct kioctx *ctx = data; + + use_mm(ctx->mm); + aio_run_iocbs(ctx); unuse_mm(ctx->mm); } -void kick_iocb(struct kiocb *iocb) + +/* + * Called by kick_iocb to queue the kiocb for retry + * and if required activate the aio work queue to process + * it + */ +void queue_kicked_iocb(struct kiocb *iocb) { struct kioctx *ctx = iocb->ki_ctx; + unsigned long flags; + int run = 0; + + WARN_ON((!list_empty(&iocb->ki_wait.task_list))); + spin_lock_irqsave(&ctx->ctx_lock, flags); + run = __queue_kicked_iocb(iocb); + spin_unlock_irqrestore(&ctx->ctx_lock, flags); + if (run) { + queue_work(aio_wq, &ctx->wq); + aio_wakeups++; + } +} + +/* + * kick_iocb: + * Called typically from a wait queue callback context + * (aio_wake_function) to trigger a retry of the iocb. + * The retry is usually executed by aio workqueue + * threads (See aio_kick_handler). + */ +void kick_iocb(struct kiocb *iocb) +{ /* sync iocbs are easy: they can only ever be executing from a * single context. */ if (is_sync_kiocb(iocb)) { @@ -604,12 +821,10 @@ void kick_iocb(struct kiocb *iocb) return; } + iocb->ki_kicked++; + /* If its already kicked we shouldn't queue it again */ if (!kiocbTryKick(iocb)) { - unsigned long flags; - spin_lock_irqsave(&ctx->ctx_lock, flags); - list_add_tail(&iocb->ki_run_list, &ctx->run_list); - spin_unlock_irqrestore(&ctx->ctx_lock, flags); - schedule_work(&ctx->wq); + queue_kicked_iocb(iocb); } } @@ -662,6 +877,9 @@ int aio_complete(struct kiocb *iocb, lon */ spin_lock_irqsave(&ctx->ctx_lock, flags); + if (iocb->ki_run_list.prev && !list_empty(&iocb->ki_run_list)) + list_del_init(&iocb->ki_run_list); + ring = kmap_atomic(info->ring_pages[0], KM_IRQ1); tail = info->tail; @@ -690,6 +908,11 @@ int aio_complete(struct kiocb *iocb, lon pr_debug("added to ring %p at [%lu]\n", iocb, tail); + pr_debug("%ld retries: %d of %d (kicked %ld, Q %ld run %ld wake %ld)\n", + iocb->ki_retried, + iocb->ki_nbytes - iocb->ki_left, iocb->ki_nbytes, + iocb->ki_kicked, iocb->ki_queued, aio_run, aio_wakeups); + /* everything turned out well, dispose of the aiocb. */ ret = __aio_put_req(ctx, iocb); @@ -804,6 +1027,7 @@ static int read_events(struct kioctx *ct int i = 0; struct io_event ent; struct timeout to; + int event_loop = 0; /* testing only */ /* needed to zero any padding within an entry (there shouldn't be * any, but C is fun! @@ -853,7 +1077,6 @@ static int read_events(struct kioctx *ct add_wait_queue_exclusive(&ctx->wait, &wait); do { set_task_state(tsk, TASK_INTERRUPTIBLE); - ret = aio_read_evt(ctx, &ent); if (ret) break; @@ -863,6 +1086,7 @@ static int read_events(struct kioctx *ct if (to.timed_out) /* Only check after read evt */ break; schedule(); + event_loop++; if (signal_pending(tsk)) { ret = -EINTR; break; @@ -890,6 +1114,9 @@ static int read_events(struct kioctx *ct if (timeout) clear_timeout(&to); out: + pr_debug("event loop executed %d times\n", event_loop); + pr_debug("aio_run %ld\n", aio_run); + pr_debug("aio_wakeups %ld\n", aio_wakeups); return i ? i : ret; } @@ -981,13 +1208,179 @@ asmlinkage long sys_io_destroy(aio_conte return -EINVAL; } +/* + * Retry method for aio_read (also used for first time submit) + * Responsible for updating iocb state as retries progress + */ +static ssize_t aio_pread(struct kiocb *iocb) +{ + struct file *file = iocb->ki_filp; + ssize_t ret = 0; + + ret = file->f_op->aio_read(iocb, iocb->ki_buf, + iocb->ki_left, iocb->ki_pos); + + /* + * Can't just depend on iocb->ki_left to determine + * whether we are done. This may have been a short read. + */ + if (ret > 0) { + iocb->ki_buf += ret; + iocb->ki_left -= ret; + + ret = -EIOCBRETRY; + } + + /* This means we must have transferred all that we could */ + /* No need to retry anymore */ + if ((ret == 0) || (iocb->ki_left == 0)) + ret = iocb->ki_nbytes - iocb->ki_left; + + return ret; +} + +/* + * Retry method for aio_write (also used for first time submit) + * Responsible for updating iocb state as retries progress + */ +static ssize_t aio_pwrite(struct kiocb *iocb) +{ + struct file *file = iocb->ki_filp; + ssize_t ret = 0; + + ret = file->f_op->aio_write(iocb, iocb->ki_buf, + iocb->ki_left, iocb->ki_pos); + + /* + * TBD: Even if iocb->ki_left = 0, could we need to + * wait for data to be sync'd ? Or can we assume + * that aio_fdsync/aio_fsync would be called explicitly + * as required. + */ + if (ret > 0) { + iocb->ki_buf += ret; + iocb->ki_left -= ret; + + ret = -EIOCBRETRY; + } + + /* This means we must have transferred all that we could */ + /* No need to retry anymore */ + if (ret == 0) + ret = iocb->ki_nbytes - iocb->ki_left; + + return ret; +} + +static ssize_t aio_fdsync(struct kiocb *iocb) +{ + struct file *file = iocb->ki_filp; + ssize_t ret = -EINVAL; + + if (file->f_op->aio_fsync) + ret = file->f_op->aio_fsync(iocb, 1); + return ret; +} + +static ssize_t aio_fsync(struct kiocb *iocb) +{ + struct file *file = iocb->ki_filp; + ssize_t ret = -EINVAL; + + if (file->f_op->aio_fsync) + ret = file->f_op->aio_fsync(iocb, 0); + return ret; +} + +/* + * aio_setup_iocb: + * Performs the initial checks and aio retry method + * setup for the kiocb at the time of io submission. + */ +ssize_t aio_setup_iocb(struct kiocb *kiocb) +{ + struct file *file = kiocb->ki_filp; + ssize_t ret = 0; + + switch (kiocb->ki_opcode) { + case IOCB_CMD_PREAD: + ret = -EBADF; + if (unlikely(!(file->f_mode & FMODE_READ))) + break; + ret = -EFAULT; + if (unlikely(!access_ok(VERIFY_WRITE, kiocb->ki_buf, + kiocb->ki_left))) + break; + ret = -EINVAL; + if (file->f_op->aio_read) + kiocb->ki_retry = aio_pread; + break; + case IOCB_CMD_PWRITE: + ret = -EBADF; + if (unlikely(!(file->f_mode & FMODE_WRITE))) + break; + ret = -EFAULT; + if (unlikely(!access_ok(VERIFY_READ, kiocb->ki_buf, + kiocb->ki_left))) + break; + ret = -EINVAL; + if (file->f_op->aio_write) + kiocb->ki_retry = aio_pwrite; + break; + case IOCB_CMD_FDSYNC: + ret = -EINVAL; + if (file->f_op->aio_fsync) + kiocb->ki_retry = aio_fdsync; + break; + case IOCB_CMD_FSYNC: + ret = -EINVAL; + if (file->f_op->aio_fsync) + kiocb->ki_retry = aio_fsync; + break; + default: + dprintk("EINVAL: io_submit: no operation provided\n"); + ret = -EINVAL; + } + + if (!kiocb->ki_retry) + return ret; + + return 0; +} + +/* + * aio_wake_function: + * wait queue callback function for aio notification, + * Simply triggers a retry of the operation via kick_iocb. + * + * This callback is specified in the wait queue entry in + * a kiocb (current->io_wait points to this wait queue + * entry when an aio operation executes; it is used + * instead of a synchronous wait when an i/o blocking + * condition is encountered during aio). + * + * Note: + * This routine is executed with the wait queue lock held. + * Since kick_iocb acquires iocb->ctx->ctx_lock, it nests + * the ioctx lock inside the wait queue lock. This is safe + * because this callback isn't used for wait queues which + * are nested inside ioctx lock (i.e. ctx->wait) + */ +int aio_wake_function(wait_queue_t *wait, unsigned mode, int sync) +{ + struct kiocb *iocb = container_of(wait, struct kiocb, ki_wait); + + list_del_init(&wait->task_list); + kick_iocb(iocb); + return 1; +} + int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb, struct iocb *iocb) { struct kiocb *req; struct file *file; ssize_t ret; - char *buf; /* enforce forwards compatibility on users */ if (unlikely(iocb->aio_reserved1 || iocb->aio_reserved2 || @@ -1028,51 +1421,31 @@ int io_submit_one(struct kioctx *ctx, st req->ki_user_data = iocb->aio_data; req->ki_pos = iocb->aio_offset; - buf = (char *)(unsigned long)iocb->aio_buf; + req->ki_buf = (char *)(unsigned long)iocb->aio_buf; + req->ki_left = req->ki_nbytes = iocb->aio_nbytes; + req->ki_opcode = iocb->aio_lio_opcode; + init_waitqueue_func_entry(&req->ki_wait, aio_wake_function); + INIT_LIST_HEAD(&req->ki_wait.task_list); + req->ki_run_list.next = req->ki_run_list.prev = NULL; + req->ki_retry = NULL; + req->ki_retried = 0; + req->ki_kicked = 0; + req->ki_queued = 0; + aio_run = 0; + aio_wakeups = 0; - switch (iocb->aio_lio_opcode) { - case IOCB_CMD_PREAD: - ret = -EBADF; - if (unlikely(!(file->f_mode & FMODE_READ))) - goto out_put_req; - ret = -EFAULT; - if (unlikely(!access_ok(VERIFY_WRITE, buf, iocb->aio_nbytes))) - goto out_put_req; - ret = -EINVAL; - if (file->f_op->aio_read) - ret = file->f_op->aio_read(req, buf, - iocb->aio_nbytes, req->ki_pos); - break; - case IOCB_CMD_PWRITE: - ret = -EBADF; - if (unlikely(!(file->f_mode & FMODE_WRITE))) - goto out_put_req; - ret = -EFAULT; - if (unlikely(!access_ok(VERIFY_READ, buf, iocb->aio_nbytes))) - goto out_put_req; - ret = -EINVAL; - if (file->f_op->aio_write) - ret = file->f_op->aio_write(req, buf, - iocb->aio_nbytes, req->ki_pos); - break; - case IOCB_CMD_FDSYNC: - ret = -EINVAL; - if (file->f_op->aio_fsync) - ret = file->f_op->aio_fsync(req, 1); - break; - case IOCB_CMD_FSYNC: - ret = -EINVAL; - if (file->f_op->aio_fsync) - ret = file->f_op->aio_fsync(req, 0); - break; - default: - dprintk("EINVAL: io_submit: no operation provided\n"); - ret = -EINVAL; - } + ret = aio_setup_iocb(req); + + if ((-EBADF == ret) || (-EFAULT == ret)) + goto out_put_req; + + spin_lock_irq(&ctx->ctx_lock); + ret = aio_run_iocb(req); + spin_unlock_irq(&ctx->ctx_lock); + + if (-EIOCBRETRY == ret) + queue_work(aio_wq, &ctx->wq); - if (likely(-EIOCBQUEUED == ret)) - return 0; - aio_complete(req, ret, 0); return 0; out_put_req: diff -puN include/linux/aio.h~aio-01-retry include/linux/aio.h --- 25/include/linux/aio.h~aio-01-retry 2003-08-16 13:54:21.000000000 -0700 +++ 25-akpm/include/linux/aio.h 2003-08-16 13:54:21.000000000 -0700 @@ -54,7 +54,7 @@ struct kiocb { struct file *ki_filp; struct kioctx *ki_ctx; /* may be NULL for sync ops */ int (*ki_cancel)(struct kiocb *, struct io_event *); - long (*ki_retry)(struct kiocb *); + ssize_t (*ki_retry)(struct kiocb *); struct list_head ki_list; /* the aio core uses this * for cancellation */ @@ -63,6 +63,16 @@ struct kiocb { __u64 ki_user_data; /* user's data for completion */ loff_t ki_pos; + /* State that we remember to be able to restart/retry */ + unsigned short ki_opcode; + size_t ki_nbytes; /* copy of iocb->aio_nbytes */ + char *ki_buf; /* remaining iocb->aio_buf */ + size_t ki_left; /* remaining bytes */ + wait_queue_t ki_wait; + long ki_retried; /* just for testing */ + long ki_kicked; /* just for testing */ + long ki_queued; /* just for testing */ + char private[KIOCB_PRIVATE_SIZE]; }; @@ -77,6 +87,8 @@ struct kiocb { (x)->ki_ctx = &tsk->active_mm->default_kioctx; \ (x)->ki_cancel = NULL; \ (x)->ki_user_obj = tsk; \ + (x)->ki_user_data = 0; \ + init_wait((&(x)->ki_wait)); \ } while (0) #define AIO_RING_MAGIC 0xa10a10a1 @@ -159,6 +171,14 @@ int FASTCALL(io_submit_one(struct kioctx #define get_ioctx(kioctx) do { if (unlikely(atomic_read(&(kioctx)->users) <= 0)) BUG(); atomic_inc(&(kioctx)->users); } while (0) #define put_ioctx(kioctx) do { if (unlikely(atomic_dec_and_test(&(kioctx)->users))) __put_ioctx(kioctx); else if (unlikely(atomic_read(&(kioctx)->users) < 0)) BUG(); } while (0) +#define in_aio() !is_sync_wait(current->io_wait) +/* may be used for debugging */ +#define warn_if_async() if (in_aio()) {\ + printk(KERN_ERR "%s(%s:%d) called in async context!\n", \ + __FUNCTION__, __FILE__, __LINE__); \ + dump_stack(); \ + } + #include static inline struct kiocb *list_kiocb(struct list_head *h) diff -puN include/linux/errno.h~aio-01-retry include/linux/errno.h --- 25/include/linux/errno.h~aio-01-retry 2003-08-16 13:54:21.000000000 -0700 +++ 25-akpm/include/linux/errno.h 2003-08-16 13:54:21.000000000 -0700 @@ -22,6 +22,7 @@ #define EBADTYPE 527 /* Type not supported by server */ #define EJUKEBOX 528 /* Request initiated, but will not complete before timeout */ #define EIOCBQUEUED 529 /* iocb queued, will get completion event */ +#define EIOCBRETRY 530 /* iocb queued, will trigger a retry */ #endif diff -puN include/linux/init_task.h~aio-01-retry include/linux/init_task.h --- 25/include/linux/init_task.h~aio-01-retry 2003-08-16 13:54:21.000000000 -0700 +++ 25-akpm/include/linux/init_task.h 2003-08-16 13:54:21.000000000 -0700 @@ -108,6 +108,7 @@ .proc_lock = SPIN_LOCK_UNLOCKED, \ .switch_lock = SPIN_LOCK_UNLOCKED, \ .journal_info = NULL, \ + .io_wait = NULL, \ } diff -puN include/linux/sched.h~aio-01-retry include/linux/sched.h --- 25/include/linux/sched.h~aio-01-retry 2003-08-16 13:54:21.000000000 -0700 +++ 25-akpm/include/linux/sched.h 2003-08-16 13:54:21.000000000 -0700 @@ -464,6 +464,13 @@ struct task_struct { unsigned long ptrace_message; siginfo_t *last_siginfo; /* For ptrace use. */ long debug; +/* + * current io wait handle: wait queue entry to use for io waits + * If this thread is processing aio, this points at the waitqueue + * inside the currently handled kiocb. It may be NULL (i.e. default + * to a stack based synchronous wait) if its doing sync IO. + */ + wait_queue_t *io_wait; }; extern void __put_task_struct(struct task_struct *tsk); diff -puN include/linux/wait.h~aio-01-retry include/linux/wait.h --- 25/include/linux/wait.h~aio-01-retry 2003-08-16 13:54:21.000000000 -0700 +++ 25-akpm/include/linux/wait.h 2003-08-16 13:54:21.000000000 -0700 @@ -80,6 +80,15 @@ static inline int waitqueue_active(wait_ return !list_empty(&q->task_list); } +/* + * Used to distinguish between sync and async io wait context: + * sync i/o typically specifies a NULL wait queue entry or a wait + * queue entry bound to a task (current task) to wake up. + * aio specifies a wait queue entry with an async notification + * callback routine, not associated with any task. + */ +#define is_sync_wait(wait) (!(wait) || ((wait)->task)) + extern void FASTCALL(add_wait_queue(wait_queue_head_t *q, wait_queue_t * wait)); extern void FASTCALL(add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t * wait)); extern void FASTCALL(remove_wait_queue(wait_queue_head_t *q, wait_queue_t * wait)); diff -puN kernel/fork.c~aio-01-retry kernel/fork.c --- 25/kernel/fork.c~aio-01-retry 2003-08-16 13:54:21.000000000 -0700 +++ 25-akpm/kernel/fork.c 2003-08-16 13:54:21.000000000 -0700 @@ -121,7 +121,12 @@ void prepare_to_wait(wait_queue_head_t * { unsigned long flags; - __set_current_state(state); + /* + * don't alter the task state if this is just going to + * queue an async wait queue callback + */ + if (is_sync_wait(wait)) + __set_current_state(state); wait->flags &= ~WQ_FLAG_EXCLUSIVE; spin_lock_irqsave(&q->lock, flags); if (list_empty(&wait->task_list)) @@ -134,7 +139,12 @@ prepare_to_wait_exclusive(wait_queue_hea { unsigned long flags; - __set_current_state(state); + /* + * don't alter the task state if this is just going to + * queue an async wait queue callback + */ + if (is_sync_wait(wait)) + __set_current_state(state); wait->flags |= WQ_FLAG_EXCLUSIVE; spin_lock_irqsave(&q->lock, flags); if (list_empty(&wait->task_list)) @@ -867,6 +877,7 @@ struct task_struct *copy_process(unsigne p->start_time = get_jiffies_64(); p->security = NULL; p->io_context = NULL; + p->io_wait = NULL; retval = -ENOMEM; if ((retval = security_task_alloc(p))) _