[ 64/99] dm ioctl: set noio flag to avoid __vmalloc deadlock

From: Greg Kroah-Hartman
Date: Fri Aug 02 2013 - 06:11:24 EST


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

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

From: Mikulas Patocka <mpatocka@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Alasdair G Kergon <agk@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
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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