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Subject[PATCH v4] aio: Don't inherit aio ring memory at fork
Date
ChangeLog
since V3
- remvoe BUG_ON
- change comment properly (thanks Jeff!)

V1, V2: not posted

--------------------------------
Subject: [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.


Reviewed-by: 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
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
---
fs/aio.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

Index: b/fs/aio.c
===================================================================
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -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 +141,18 @@ static int aio_setup_ring(struct kioctx
return -EAGAIN;
}

+ /*
+ * The io_context is not inherited by the child after fork()
+ * (see mm_init). Therefore, it makes little sense for the
+ * completion ring to be inherited.
+ */
+ ret = sys_madvise(info->mmap_base, info->mmap_size, MADV_DONTFORK);
+ if (ret < 0) {
+ up_write(&ctx->mm->mmap_sem);
+ aio_free_ring(ctx);
+ return -EAGAIN;
+ }
+
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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