Messages in this thread Patch in this message | | | From | KOSAKI Motohiro <> | Subject | [RFC][PATCH v3 4/6] aio: Don't inherit aio ring memory at fork | Date | Tue, 14 Apr 2009 15:20:20 +0900 (JST) |
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AIO folks, Am I missing anything?
=============== Subject: [RFC][PATCH] aio: Don't inherit aio ring memory at fork
Currently, mm_struct::ioctx_list member isn't copyed at fork. IOW aio context don't inherit at fork. but only ring memory inherited. that's strange.
This patch mark DONTFORK to ring-memory too. In addition, This patch has good side effect. it also fix "get_user_pages() vs fork" problem.
I think "man fork" also sould be changed. it only say
* The child does not inherit outstanding asynchronous I/O operations from its parent (aio_read(3), aio_write(3)).
but aio_context_t (return value of io_setup(2)) also don't inherit in current implementaion.
Cc: Jeff Moyer <jmoyer@redhat.com> Cc: Zach Brown <zach.brown@oracle.com> Cc: Jens Axboe <jens.axboe@oracle.com> Cc: linux-fsdevel@vger.kernel.org Cc: linux-api@vger.kernel.org, Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> --- fs/aio.c | 8 ++++++++ 1 file changed, 8 insertions(+)
Index: b/fs/aio.c =================================================================== --- a/fs/aio.c 2009-04-12 23:33:59.000000000 +0900 +++ b/fs/aio.c 2009-04-13 02:56:05.000000000 +0900 @@ -106,6 +106,7 @@ static int aio_setup_ring(struct kioctx unsigned nr_events = ctx->max_reqs; unsigned long size; int nr_pages; + int ret; /* Compensate for the ring buffer's head/tail overlap entry */ nr_events += 2; /* 1 is required, 2 for good luck */ @@ -140,6 +141,13 @@ static int aio_setup_ring(struct kioctx return -EAGAIN; } + /* + * aio context doesn't inherit while fork. (see mm_init()) + * Then, aio ring also mark DONTFORK. + */ + ret = sys_madvise(info->mmap_base, info->mmap_size, MADV_DONTFORK); + BUG_ON(ret); + dprintk("mmap address: 0x%08lx\n", info->mmap_base); info->nr_pages = get_user_pages(current, ctx->mm, info->mmap_base, nr_pages,
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