From: Trond Myklebust <trond.myklebust@hammerspace.com>
Date: Mon, 21 Mar 2022 13:48:36 -0400
Subject: [PATCH] NFS: Avoid writeback threads getting stuck in mempool_alloc()
Git-commit: 0bae835b63c53f86cdc524f5962e39409585b22c
Patch-mainline: v5.18
References: git-fixes

In a low memory situation, allow the NFS writeback code to fail without
getting stuck in infinite loops in mempool_alloc().

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Acked-by: NeilBrown <neilb@suse.com>

---
 fs/nfs/pagelist.c |   10 +++++-----
 fs/nfs/write.c    |   10 ++++++++--
 2 files changed, 13 insertions(+), 7 deletions(-)

--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -90,10 +90,10 @@ void nfs_set_pgio_error(struct nfs_pgio_
 	}
 }
 
-static inline struct nfs_page *
-nfs_page_alloc(void)
+static inline struct nfs_page *nfs_page_alloc(void)
 {
-	struct nfs_page	*p = kmem_cache_zalloc(nfs_page_cachep, GFP_KERNEL);
+	struct nfs_page *p =
+		kmem_cache_zalloc(nfs_page_cachep, nfs_io_gfp_mask());
 	if (p)
 		INIT_LIST_HEAD(&p->wb_list);
 	return p;
@@ -904,7 +904,7 @@ int nfs_generic_pgio(struct nfs_pageio_d
 	struct nfs_commit_info cinfo;
 	struct nfs_page_array *pg_array = &hdr->page_array;
 	unsigned int pagecount, pageused;
-	gfp_t gfp_flags = GFP_KERNEL;
+	gfp_t gfp_flags = nfs_io_gfp_mask();
 
 	pagecount = nfs_page_array_len(mirror->pg_base, mirror->pg_count);
 	pg_array->npages = pagecount;
@@ -991,7 +991,7 @@ nfs_pageio_alloc_mirrors(struct nfs_page
 	desc->pg_mirrors_dynamic = NULL;
 	if (mirror_count == 1)
 		return desc->pg_mirrors_static;
-	ret = kmalloc_array(mirror_count, sizeof(*ret), GFP_KERNEL);
+	ret = kmalloc_array(mirror_count, sizeof(*ret), nfs_io_gfp_mask());
 	if (ret != NULL) {
 		for (i = 0; i < mirror_count; i++)
 			nfs_pageio_mirror_init(&ret[i], desc->pg_bsize);
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -94,9 +94,15 @@ EXPORT_SYMBOL_GPL(nfs_commit_free);
 
 static struct nfs_pgio_header *nfs_writehdr_alloc(void)
 {
-	struct nfs_pgio_header *p = mempool_alloc(nfs_wdata_mempool, GFP_KERNEL);
+	struct nfs_pgio_header *p;
 
-	memset(p, 0, sizeof(*p));
+	p = kmem_cache_zalloc(nfs_wdata_cachep, nfs_io_gfp_mask());
+	if (!p) {
+		p = mempool_alloc(nfs_wdata_mempool, GFP_NOWAIT);
+		if (!p)
+			return NULL;
+		memset(p, 0, sizeof(*p));
+	}
 	p->rw_mode = FMODE_WRITE;
 	return p;
 }