NFS: Use GFP_NOIO for two allocations in writeback

Prevent a deadlock that can occur if we wait on allocations
that try to write back our pages.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Fixes: 00bfa30abe869 ("NFS: Create a common pgio_alloc and pgio_release...")
Cc: stable@vger.kernel.org # 3.16+
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 3917268..7d83f3a 100644 (file)
--- 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;
        }
@@ -681,6 +682,7 @@ 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;
@@ -700,8 +702,10 @@ 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;
 
@@ -755,9 +759,12 @@ 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)) {
                nfs_pgio_error(hdr);
                desc->pg_error = -ENOMEM;
                return desc->pg_error;