Return-Path: Received: from mail-pd0-f172.google.com ([209.85.192.172]:32853 "EHLO mail-pd0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751123AbbFZBqG (ORCPT ); Thu, 25 Jun 2015 21:46:06 -0400 Received: by pdjn11 with SMTP id n11so64615759pdj.0 for ; Thu, 25 Jun 2015 18:46:05 -0700 (PDT) From: Peng Tao To: linux-nfs@vger.kernel.org Cc: Trond Myklebust , Peng Tao Subject: [PATCH] pnfs/flexfiles: protect ktime manipulation with mirror lock Date: Fri, 26 Jun 2015 09:45:49 +0800 Message-Id: <1435283149-14223-1-git-send-email-tao.peng@primarydata.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: It looks as if xchg() and cmpxchg() are not available for 64-bit integers on sparc32: > New breakage seen in linux-next today: > > ERROR: "__xchg_called_with_bad_pointer" [fs/nfs/flexfilelayout/nfs_layout_flexfiles.ko] undefined! > ERROR: "__cmpxchg_called_with_bad_pointer" [fs/nfs/flexfilelayout/nfs_layout_flexfiles.ko] undefined! > make[2]: *** [__modpost] Error 1 > make[1]: *** [modules] Error 2 Given that mirror ktime manipulation is already under mirror->lock, let's make use of the fact. Reported-by: Paul Gortmaker Signed-off-by: Peng Tao --- fs/nfs/flexfilelayout/flexfilelayout.c | 31 ++++++++++++------------------- 1 file changed, 12 insertions(+), 19 deletions(-) diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c index d3b3b62..85b4234 100644 --- a/fs/nfs/flexfilelayout/flexfilelayout.c +++ b/fs/nfs/flexfilelayout/flexfilelayout.c @@ -417,21 +417,9 @@ ff_layout_get_lseg_count(struct nfs4_ff_layout_segment *fls) static void nfs4_ff_start_busy_timer(struct nfs4_ff_busy_timer *timer) { - ktime_t old, new; - - /* - * Note: careful here! - * If the counter is zero, then we must not increment it until after - * we've set the start_time. - * If we were instead to use atomic_inc_return(), then another - * request might come in, bump, and then call end_busy_timer() - * before we've set the timer->start_time. - */ - old = timer->start_time; - if (atomic_inc_not_zero(&timer->n_ops) == 0) { - new = ktime_get(); - cmpxchg(&timer->start_time.tv64, old.tv64, new.tv64); - atomic_inc(&timer->n_ops); + /* first IO request? */ + if (atomic_inc_return(&timer->n_ops) == 1) { + timer->start_time = ktime_get(); } } @@ -440,9 +428,12 @@ nfs4_ff_end_busy_timer(struct nfs4_ff_busy_timer *timer) { ktime_t start, now; + if (atomic_dec_return(&timer->n_ops) < 0) + WARN_ON_ONCE(1); + now = ktime_get(); - start.tv64 = xchg(&timer->start_time.tv64, now.tv64); - atomic_dec(&timer->n_ops); + start = timer->start_time; + timer->start_time = now; return ktime_sub(now, start); } @@ -460,8 +451,10 @@ nfs4_ff_layoutstat_start_io(struct nfs4_ff_layout_mirror *mirror, ktime_t now = ktime_get(); nfs4_ff_start_busy_timer(&layoutstat->busy_timer); - cmpxchg(&mirror->start_time.tv64, notime.tv64, now.tv64); - cmpxchg(&mirror->last_report_time.tv64, notime.tv64, now.tv64); + if (ktime_equal(mirror->start_time, notime)) + mirror->start_time = now; + if (ktime_equal(mirror->last_report_time, notime)) + mirror->last_report_time = now; if (ktime_to_ms(ktime_sub(now, mirror->last_report_time)) >= FF_LAYOUTSTATS_REPORT_INTERVAL) { mirror->last_report_time = now; -- 1.8.3.1