Re: [Xen-devel] [GIT PULL] (xen) stable/for-jens-3.10 xenwatch: page allocation failure: order:7, mode:0x10c0d0

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 25/04/13 16:52, Roger Pau Monné wrote:
> 
> [PATCH] xen-blkback: allocate list of pending reqs in small chunks
> 
> Allocate pending requests in smaller chunks instead of allocating them
> all at the same time.
> 
> Also remove the global array of pending_reqs, it is no longer
> necessary.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
>  drivers/block/xen-blkback/common.h |    2 -
>  drivers/block/xen-blkback/xenbus.c |   41 ++++++++++++++++++++++-------------
>  2 files changed, 26 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/block/xen-blkback/common.h 
> b/drivers/block/xen-blkback/common.h
> index 1ac53da..2bbda8637 100644
> --- a/drivers/block/xen-blkback/common.h
> +++ b/drivers/block/xen-blkback/common.h
> @@ -297,8 +297,6 @@ struct xen_blkif {
>       int                     free_pages_num;
>       struct list_head        free_pages;
>  
> -     /* Allocation of pending_reqs */
> -     struct pending_req      *pending_reqs;
>       /* List of all 'pending_req' available */
>       struct list_head        pending_free;
>       /* And its spinlock. */
> diff --git a/drivers/block/xen-blkback/xenbus.c 
> b/drivers/block/xen-blkback/xenbus.c
> index afab208..ceefbe4 100644
> --- a/drivers/block/xen-blkback/xenbus.c
> +++ b/drivers/block/xen-blkback/xenbus.c
> @@ -105,6 +105,7 @@ static void xen_update_blkif_status(struct xen_blkif 
> *blkif)
>  static struct xen_blkif *xen_blkif_alloc(domid_t domid)
>  {
>       struct xen_blkif *blkif;
> +     struct pending_req *req, *n;
>       int i;
>  
>       BUILD_BUG_ON(MAX_INDIRECT_PAGES > BLKIF_MAX_INDIRECT_PAGES_PER_REQUEST);
> @@ -127,22 +128,29 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid)
>       blkif->free_pages_num = 0;
>       atomic_set(&blkif->persistent_gnt_in_use, 0);
>  
> -     blkif->pending_reqs = kcalloc(XEN_BLKIF_REQS,
> -                                   sizeof(blkif->pending_reqs[0]),
> -                                   GFP_KERNEL);
> -     if (!blkif->pending_reqs) {
> -             kmem_cache_free(xen_blkif_cachep, blkif);
> -             return ERR_PTR(-ENOMEM);
> -     }
>       INIT_LIST_HEAD(&blkif->pending_free);
> +
> +     for (i = 0; i < XEN_BLKIF_REQS; i++) {
> +             req = kzalloc(sizeof(*req), GFP_KERNEL);

This still requires an order 2 allocation, right?  Can you make further
changes to make all allocations order 0?

> +             if (!req)
> +                     goto fail;
> +             list_add_tail(&req->free_list,
> +                           &blkif->pending_free);
> +     }

David

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