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author | Benjamin LaHaise <bcrl@kvack.org> | 2014-07-14 12:49:26 -0400 |
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committer | Benjamin LaHaise <bcrl@kvack.org> | 2014-07-14 13:05:26 -0400 |
commit | 263782c1c95bbddbb022dc092fd89a36bb8d5577 (patch) | |
tree | 93044b03084bf998eec530621486791e987717ed | |
parent | 1795cd9b3a91d4b5473c97f491d63892442212ab (diff) | |
download | linux-stable-263782c1c95bbddbb022dc092fd89a36bb8d5577.tar.gz linux-stable-263782c1c95bbddbb022dc092fd89a36bb8d5577.tar.bz2 linux-stable-263782c1c95bbddbb022dc092fd89a36bb8d5577.zip |
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 <Elliott@hp.com>
Tested-by: Robert Elliot <Elliott@hp.com>
Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
Cc: Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@infradead.org>
Cc: stable@vger.kenel.org
-rw-r--r-- | fs/aio.c | 7 |
1 files changed, 7 insertions, 0 deletions
@@ -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; } |