From 263782c1c95bbddbb022dc092fd89a36bb8d5577 Mon Sep 17 00:00:00 2001 From: Benjamin LaHaise Date: Mon, 14 Jul 2014 12:49:26 -0400 Subject: [PATCH] aio: protect reqs_available updates from changes in interrupt handlers As of commit f8567a3845ac05bb28f3c1b478ef752762bd39ef it is now possible to have put_reqs_available() called from irq context. While put_reqs_available() is per cpu, it did not protect itself from interrupts on the same CPU. This lead to aio_complete() corrupting the available io requests count when run under a heavy O_DIRECT workloads as reported by Robert Elliott. Fix this by disabling irq updates around the per cpu batch updates of reqs_available. Many thanks to Robert and folks for testing and tracking this down. Reported-by: Robert Elliot Tested-by: Robert Elliot Signed-off-by: Benjamin LaHaise Cc: Jens Axboe , Christoph Hellwig Cc: stable@vger.kenel.org --- fs/aio.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/fs/aio.c b/fs/aio.c index 955947ef3e02..1c9c5f0a9e2b 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -830,16 +830,20 @@ void exit_aio(struct mm_struct *mm) static void put_reqs_available(struct kioctx *ctx, unsigned nr) { struct kioctx_cpu *kcpu; + unsigned long flags; preempt_disable(); kcpu = this_cpu_ptr(ctx->cpu); + local_irq_save(flags); kcpu->reqs_available += nr; + while (kcpu->reqs_available >= ctx->req_batch * 2) { kcpu->reqs_available -= ctx->req_batch; atomic_add(ctx->req_batch, &ctx->reqs_available); } + local_irq_restore(flags); preempt_enable(); } @@ -847,10 +851,12 @@ static bool get_reqs_available(struct kioctx *ctx) { struct kioctx_cpu *kcpu; bool ret = false; + unsigned long flags; preempt_disable(); kcpu = this_cpu_ptr(ctx->cpu); + local_irq_save(flags); if (!kcpu->reqs_available) { int old, avail = atomic_read(&ctx->reqs_available); @@ -869,6 +875,7 @@ static bool get_reqs_available(struct kioctx *ctx) ret = true; kcpu->reqs_available--; out: + local_irq_restore(flags); preempt_enable(); return ret; } -- 2.30.2