Patch "aio: protect reqs_available updates from changes in interrupt handlers" has been added to the 3.15-stable tree

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This is a note to let you know that I've just added the patch titled

    aio: protect reqs_available updates from changes in interrupt handlers

to the 3.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     aio-protect-reqs_available-updates-from-changes-in-interrupt-handlers.patch
and it can be found in the queue-3.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 263782c1c95bbddbb022dc092fd89a36bb8d5577 Mon Sep 17 00:00:00 2001
From: Benjamin LaHaise <bcrl@xxxxxxxxx>
Date: Mon, 14 Jul 2014 12:49:26 -0400
Subject: aio: protect reqs_available updates from changes in interrupt handlers

From: Benjamin LaHaise <bcrl@xxxxxxxxx>

commit 263782c1c95bbddbb022dc092fd89a36bb8d5577 upstream.

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 <Elliott@xxxxxx>
Tested-by: Robert Elliot <Elliott@xxxxxx>
Signed-off-by: Benjamin LaHaise <bcrl@xxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/aio.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- 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 ki
 {
 	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 ki
 	ret = true;
 	kcpu->reqs_available--;
 out:
+	local_irq_restore(flags);
 	preempt_enable();
 	return ret;
 }


Patches currently in stable-queue which might be from bcrl@xxxxxxxxx are

queue-3.15/aio-protect-reqs_available-updates-from-changes-in-interrupt-handlers.patch
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