ACK: [SRU][X][PATCH 1/1] NFS: Use GFP_NOIO for two allocations in writeback

[Juerg Haefliger]

On 05/08/2018 08:34 AM, Daniel Axtens wrote:
> From: Benjamin Coddington <bcodding at redhat.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1750038
> 
> Prevent a deadlock that can occur if we wait on allocations
> that try to write back our pages.
> 
> Signed-off-by: Benjamin Coddington <bcodding at redhat.com>
> Fixes: 00bfa30abe869 ("NFS: Create a common pgio_alloc and pgio_release...")
> Cc: stable at vger.kernel.org # 3.16+
> Signed-off-by: Trond Myklebust <trond.myklebust at primarydata.com>
> (backported from commit ae97aa524ef495b6276fd26f5d5449fb22975d7c)
> Signed-off-by: Daniel Axtens <daniel.axtens at canonical.com>

Looks reasonable.

Acked-by: Juerg Haefliger <juergh at canonical.com>


> ---
>  fs/nfs/pagelist.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
> index 8ebfdd00044b..1dc47d1aa7ce 100644
> --- a/fs/nfs/pagelist.c
> +++ b/fs/nfs/pagelist.c
> @@ -29,13 +29,14 @@
>  static struct kmem_cache *nfs_page_cachep;
>  static const struct rpc_call_ops nfs_pgio_common_ops;
>  
> -static bool nfs_pgarray_set(struct nfs_page_array *p, unsigned int pagecount)
> +static bool nfs_pgarray_set(struct nfs_page_array *p, unsigned int pagecount,
> +					gfp_t gfp_flags)
>  {
>  	p->npages = pagecount;
>  	if (pagecount <= ARRAY_SIZE(p->page_array))
>  		p->pagevec = p->page_array;
>  	else {
> -		p->pagevec = kcalloc(pagecount, sizeof(struct page *), GFP_KERNEL);
> +		p->pagevec = kcalloc(pagecount, sizeof(struct page *), gfp_flags);
>  		if (!p->pagevec)
>  			p->npages = 0;
>  	}
> @@ -722,6 +723,7 @@ void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
>  {
>  	struct nfs_pgio_mirror *new;
>  	int i;
> +	gfp_t gfp_flags = GFP_KERNEL;
>  
>  	desc->pg_moreio = 0;
>  	desc->pg_inode = inode;
> @@ -741,8 +743,10 @@ void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
>  	if (pg_ops->pg_get_mirror_count) {
>  		/* until we have a request, we don't have an lseg and no
>  		 * idea how many mirrors there will be */
> +		if (desc->pg_rw_ops->rw_mode == FMODE_WRITE)
> +			gfp_flags = GFP_NOIO;
>  		new = kcalloc(NFS_PAGEIO_DESCRIPTOR_MIRROR_MAX,
> -			      sizeof(struct nfs_pgio_mirror), GFP_KERNEL);
> +			      sizeof(struct nfs_pgio_mirror), gfp_flags);
>  		desc->pg_mirrors_dynamic = new;
>  		desc->pg_mirrors = new;
>  
> @@ -796,10 +800,14 @@ int nfs_generic_pgio(struct nfs_pageio_descriptor *desc,
>  	struct list_head *head = &mirror->pg_list;
>  	struct nfs_commit_info cinfo;
>  	unsigned int pagecount, pageused;
> +	gfp_t gfp_flags = GFP_KERNEL;
>  
>  	pagecount = nfs_page_array_len(mirror->pg_base, mirror->pg_count);
> -	if (!nfs_pgarray_set(&hdr->page_array, pagecount))
> +	if (desc->pg_rw_ops->rw_mode == FMODE_WRITE)
> +		gfp_flags = GFP_NOIO;
> +	if (!nfs_pgarray_set(&hdr->page_array, pagecount, gfp_flags)) {
>  		return nfs_pgio_error(desc, hdr);
> +	}
>  
>  	nfs_init_cinfo(&cinfo, desc->pg_inode, desc->pg_dreq);
>  	pages = hdr->page_array.pagevec;
> 


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