From patchwork Tue Jul 28 17:54:46 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Michael S. Tsirkin" X-Patchwork-Id: 37872 Received: from vger.kernel.org (vger.kernel.org [209.132.176.167]) by demeter.kernel.org (8.14.2/8.14.2) with ESMTP id n6SHvKsk017783 for ; Tue, 28 Jul 2009 17:57:20 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755286AbZG1Rzt (ORCPT ); Tue, 28 Jul 2009 13:55:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755261AbZG1Rzt (ORCPT ); Tue, 28 Jul 2009 13:55:49 -0400 Received: from mx2.redhat.com ([66.187.237.31]:35624 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755266AbZG1Rzr (ORCPT ); Tue, 28 Jul 2009 13:55:47 -0400 Received: from int-mx2.corp.redhat.com (int-mx2.corp.redhat.com [172.16.27.26]) by mx2.redhat.com (8.13.8/8.13.8) with ESMTP id n6SHtl5s015144; Tue, 28 Jul 2009 13:55:47 -0400 Received: from ns3.rdu.redhat.com (ns3.rdu.redhat.com [10.11.255.199]) by int-mx2.corp.redhat.com (8.13.1/8.13.1) with ESMTP id n6SHtk6t010699; Tue, 28 Jul 2009 13:55:47 -0400 Received: from redhat.com (dhcp-0-94.tlv.redhat.com [10.35.0.94]) by ns3.rdu.redhat.com (8.13.8/8.13.8) with ESMTP id n6SHtioH019319; Tue, 28 Jul 2009 13:55:45 -0400 Date: Tue, 28 Jul 2009 20:54:46 +0300 From: "Michael S. Tsirkin" To: davidel@xmailserver.org, avi@redhat.com, gleb@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH-RFC 1/2] eventfd: reorganize the code to simplify new flags Message-ID: <20090728175446.GB21549@redhat.com> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.19 (2009-01-05) X-Scanned-By: MIMEDefang 2.58 on 172.16.27.26 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org This slightly reorganizes the code in eventfd, encapsulating counter math in inline functions, so that it will be easier to add a new flag. No functional changes. Signed-off-by: Michael S. Tsirkin --- fs/eventfd.c | 56 ++++++++++++++++++++++++++++++++++++++++++-------------- 1 files changed, 42 insertions(+), 14 deletions(-) diff --git a/fs/eventfd.c b/fs/eventfd.c index 31d12de..347a0e0 100644 --- a/fs/eventfd.c +++ b/fs/eventfd.c @@ -34,6 +34,37 @@ struct eventfd_ctx { unsigned int flags; }; + +static inline int eventfd_readable(struct eventfd_ctx *ctx) +{ + return ctx->count > 0; +} + +static inline int eventfd_writeable(struct eventfd_ctx *ctx, u64 n) +{ + return ULLONG_MAX - n > ctx->count; +} + +static inline int eventfd_overflow(struct eventfd_ctx *ctx, u64 cnt) +{ + return cnt == ULLONG_MAX; +} + +static inline void eventfd_dowrite(struct eventfd_ctx *ctx, u64 ucnt) +{ + if (eventfd_writeable(ctx, ucnt)) + ucnt = ULLONG_MAX - ctx->count; + + ctx->count += ucnt; +} + +static inline u64 eventfd_doread(struct eventfd_ctx *ctx) +{ + u64 ucnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count; + ctx->count -= ucnt; + return ucnt; +} + /** * eventfd_signal - Adds @n to the eventfd counter. * @ctx: [in] Pointer to the eventfd context. @@ -57,9 +88,7 @@ int eventfd_signal(struct eventfd_ctx *ctx, int n) if (n < 0) return -EINVAL; spin_lock_irqsave(&ctx->wqh.lock, flags); - if (ULLONG_MAX - ctx->count < n) - n = (int) (ULLONG_MAX - ctx->count); - ctx->count += n; + eventfd_dowrite(ctx, n); if (waitqueue_active(&ctx->wqh)) wake_up_locked_poll(&ctx->wqh, POLLIN); spin_unlock_irqrestore(&ctx->wqh.lock, flags); @@ -119,11 +148,11 @@ static unsigned int eventfd_poll(struct file *file, poll_table *wait) poll_wait(file, &ctx->wqh, wait); spin_lock_irqsave(&ctx->wqh.lock, flags); - if (ctx->count > 0) + if (eventfd_readable(ctx)) events |= POLLIN; - if (ctx->count == ULLONG_MAX) + if (eventfd_overflow(ctx, ctx->count)) events |= POLLERR; - if (ULLONG_MAX - 1 > ctx->count) + if (eventfd_writeable(ctx, 1)) events |= POLLOUT; spin_unlock_irqrestore(&ctx->wqh.lock, flags); @@ -142,13 +171,13 @@ static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count, return -EINVAL; spin_lock_irq(&ctx->wqh.lock); res = -EAGAIN; - if (ctx->count > 0) + if (eventfd_readable(ctx)) res = sizeof(ucnt); else if (!(file->f_flags & O_NONBLOCK)) { __add_wait_queue(&ctx->wqh, &wait); for (res = 0;;) { set_current_state(TASK_INTERRUPTIBLE); - if (ctx->count > 0) { + if (eventfd_readable(ctx)) { res = sizeof(ucnt); break; } @@ -164,8 +193,7 @@ static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count, __set_current_state(TASK_RUNNING); } if (likely(res > 0)) { - ucnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count; - ctx->count -= ucnt; + ucnt = eventfd_doread(ctx); if (waitqueue_active(&ctx->wqh)) wake_up_locked_poll(&ctx->wqh, POLLOUT); } @@ -188,17 +216,17 @@ static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t c return -EINVAL; if (copy_from_user(&ucnt, buf, sizeof(ucnt))) return -EFAULT; - if (ucnt == ULLONG_MAX) + if (eventfd_overflow(ctx, ucnt)) return -EINVAL; spin_lock_irq(&ctx->wqh.lock); res = -EAGAIN; - if (ULLONG_MAX - ctx->count > ucnt) + if (eventfd_writeable(ctx, ucnt)) res = sizeof(ucnt); else if (!(file->f_flags & O_NONBLOCK)) { __add_wait_queue(&ctx->wqh, &wait); for (res = 0;;) { set_current_state(TASK_INTERRUPTIBLE); - if (ULLONG_MAX - ctx->count > ucnt) { + if (eventfd_writeable(ctx, ucnt)) { res = sizeof(ucnt); break; } @@ -214,7 +242,7 @@ static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t c __set_current_state(TASK_RUNNING); } if (likely(res > 0)) { - ctx->count += ucnt; + eventfd_dowrite(ctx, ucnt); if (waitqueue_active(&ctx->wqh)) wake_up_locked_poll(&ctx->wqh, POLLIN); }