2020-04-03 09:01:14

by Jürgen Groß

Subject: [PATCH] xen/blkfront: fix memory allocation flags in blkfront_setup_indirect()

Commit 1d5c76e664333 ("xen-blkfront: switch kcalloc to kvcalloc for
large array allocation") didn't fix the issue it was meant to, as the
flags for allocating the memory are GFP_NOIO, which will lead the
memory allocation falling back to kmalloc().

So instead of GFP_NOIO use GFP_KERNEL and do all the memory allocation
in blkfront_setup_indirect() in a memalloc_noio_{save,restore} section.

Fixes: 1d5c76e664333 ("xen-blkfront: switch kcalloc to kvcalloc for large array allocation")
Cc: [email protected]
Signed-off-by: Juergen Gross <[email protected]>
---
drivers/block/xen-blkfront.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 915cf5b6388c..3b889ea950c2 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -47,6 +47,7 @@
#include <linux/bitmap.h>
#include <linux/list.h>
#include <linux/workqueue.h>
+#include <linux/sched/mm.h>

#include <xen/xen.h>
#include <xen/xenbus.h>
@@ -2189,10 +2190,12 @@ static void blkfront_setup_discard(struct blkfront_info *info)

static int blkfront_setup_indirect(struct blkfront_ring_info *rinfo)
{
- unsigned int psegs, grants;
+ unsigned int psegs, grants, memflags;
int err, i;
struct blkfront_info *info = rinfo->dev_info;

+ memflags = memalloc_noio_save();
+
if (info->max_indirect_segments == 0) {
if (!HAS_EXTRA_REQ)
grants = BLKIF_MAX_SEGMENTS_PER_REQUEST;
@@ -2224,7 +2227,7 @@ static int blkfront_setup_indirect(struct blkfront_ring_info *rinfo)

BUG_ON(!list_empty(&rinfo->indirect_pages));
for (i = 0; i < num; i++) {
- struct page *indirect_page = alloc_page(GFP_NOIO);
+ struct page *indirect_page = alloc_page(GFP_KERNEL);
if (!indirect_page)
goto out_of_memory;
list_add(&indirect_page->lru, &rinfo->indirect_pages);
@@ -2235,15 +2238,15 @@ static int blkfront_setup_indirect(struct blkfront_ring_info *rinfo)
rinfo->shadow[i].grants_used =
kvcalloc(grants,
sizeof(rinfo->shadow[i].grants_used[0]),
- GFP_NOIO);
+ GFP_KERNEL);
rinfo->shadow[i].sg = kvcalloc(psegs,
sizeof(rinfo->shadow[i].sg[0]),
- GFP_NOIO);
+ GFP_KERNEL);
if (info->max_indirect_segments)
rinfo->shadow[i].indirect_grants =
kvcalloc(INDIRECT_GREFS(grants),
sizeof(rinfo->shadow[i].indirect_grants[0]),
- GFP_NOIO);
+ GFP_KERNEL);
if ((rinfo->shadow[i].grants_used == NULL) ||
(rinfo->shadow[i].sg == NULL) ||
(info->max_indirect_segments &&
@@ -2252,6 +2255,7 @@ static int blkfront_setup_indirect(struct blkfront_ring_info *rinfo)
sg_init_table(rinfo->shadow[i].sg, psegs);
}

+ memalloc_noio_restore(memflags);

return 0;

@@ -2271,6 +2275,9 @@ static int blkfront_setup_indirect(struct blkfront_ring_info *rinfo)
__free_page(indirect_page);
}
}
+
+ memalloc_noio_restore(memflags);
+
return -ENOMEM;
}

--
2.16.4

2020-04-03 21:54:31

by Boris Ostrovsky

Subject: Re: [PATCH] xen/blkfront: fix memory allocation flags in blkfront_setup_indirect()

On 4/3/20 5:00 AM, Juergen Gross wrote:
> Commit 1d5c76e664333 ("xen-blkfront: switch kcalloc to kvcalloc for
> large array allocation") didn't fix the issue it was meant to, as the
> flags for allocating the memory are GFP_NOIO, which will lead the
> memory allocation falling back to kmalloc().
>
> So instead of GFP_NOIO use GFP_KERNEL and do all the memory allocation
> in blkfront_setup_indirect() in a memalloc_noio_{save,restore} section.
>
> Fixes: 1d5c76e664333 ("xen-blkfront: switch kcalloc to kvcalloc for large array allocation")
> Cc: [email protected]
> Signed-off-by: Juergen Gross <[email protected]>

Reviewed-by: Boris Ostrovsky <[email protected]>

2020-04-06 09:03:48

by Roger Pau Monne

Subject: Re: [PATCH] xen/blkfront: fix memory allocation flags in blkfront_setup_indirect()

On Fri, Apr 03, 2020 at 11:00:34AM +0200, Juergen Gross wrote:
> Commit 1d5c76e664333 ("xen-blkfront: switch kcalloc to kvcalloc for
> large array allocation") didn't fix the issue it was meant to, as the
> flags for allocating the memory are GFP_NOIO, which will lead the
> memory allocation falling back to kmalloc().
>
> So instead of GFP_NOIO use GFP_KERNEL and do all the memory allocation
> in blkfront_setup_indirect() in a memalloc_noio_{save,restore} section.
>
> Fixes: 1d5c76e664333 ("xen-blkfront: switch kcalloc to kvcalloc for large array allocation")
> Cc: [email protected]
> Signed-off-by: Juergen Gross <[email protected]>

Acked-by: Roger Pau Monné <[email protected]>

Thanks!