NFS: Use GFP_NOIO for two allocations in writeback

commit ae97aa524ef495b6276fd26f5d5449fb22975d7c upstream.

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...")
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 11 insertions, 4 deletions

diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 965db474f4b0..142a74f3c59b 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;
         }
@@ -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;