linux-kernel - [ 64/99] dm ioctl: set noio flag to avoid _

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Message-Id: <20130802100234.946549211@linuxfoundation.org>
Date:	Fri,  2 Aug 2013 18:08:17 +0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Mikulas Patocka <mpatocka@...hat.com>,
	Alasdair G Kergon <agk@...hat.com>
Subject: [ 64/99] dm ioctl: set noio flag to avoid __vmalloc deadlock

3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mikulas Patocka <mpatocka@...hat.com>

commit 1c0e883e86ece31880fac2f84b260545d66a39e0 upstream.

Set noio flag while calling __vmalloc() because it doesn't fully respect
gfp flags to avoid a possible deadlock (see commit
502624bdad3dba45dfaacaf36b7d83e39e74b2d2).

This should be backported to stable kernels 3.8 and newer. The kernel 3.8
doesn't have memalloc_noio_save(), so we should set and restore process
flag PF_MEMALLOC instead.

Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>
Signed-off-by: Alasdair G Kergon <agk@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/md/dm-ioctl.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1644,7 +1644,10 @@ static int copy_params(struct dm_ioctl _
 	}
 
 	if (!dmi) {
+		unsigned noio_flag;
+		noio_flag = memalloc_noio_save();
 		dmi = __vmalloc(param_kernel->data_size, GFP_NOIO | __GFP_REPEAT | __GFP_HIGH, PAGE_KERNEL);
+		memalloc_noio_restore(noio_flag);
 		if (dmi)
 			*param_flags |= DM_PARAMS_VMALLOC;
 	}


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