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[130/145] dm ioctl: set noio flag to avoid __vmalloc deadlock

Message ID 1374101277-7915-131-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa July 17, 2013, 10:47 p.m. UTC 
3.8.13.5 -stable review patch.  If anyone has any objections, please let me know.

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

From: Mikulas Patocka <mpatocka@redhat.com>

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@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
[ kamal: backport to 3.8 (memalloc_noio_save is available in linux-3.8.y.z) ]
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 drivers/md/dm-ioctl.c | 3 +++
 1 file changed, 3 insertions(+)
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Patch

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index eee353d..4c260aa 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1585,7 +1585,10 @@  static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl **param, in
 		dmi = kmalloc(tmp.data_size, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
 
 	if (!dmi) {
+		unsigned noio_flag;
+		noio_flag = memalloc_noio_save();
 		dmi = __vmalloc(tmp.data_size, GFP_NOIO | __GFP_REPEAT | __GFP_HIGH, PAGE_KERNEL);
+		memalloc_noio_restore(noio_flag);
 		*param_flags |= DM_PARAMS_VMALLOC;
 	}