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Subject[PATCH 4.9 160/164] NFS: Use GFP_NOIO for two allocations in writeback
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Benjamin Coddington <bcodding@redhat.com>

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>

---
fs/nfs/pagelist.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)

--- 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_d
{
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_d
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_d
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;

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