NFS: nfsiod should not block forever in mempool_alloc()

The concern is that since nfsiod is sometimes required to kick off a
commit, it can get locked up waiting forever in mempool_alloc() instead
of failing gracefully and leaving the commit until later.

Try to allocate from the slab first, with GFP_KERNEL | __GFP_NORETRY,
then fall back to a non-blocking attempt to allocate from the memory
pool.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

1 files changed, 9 insertions, 15 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 599a82406d38..ef47e3700e4b 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -70,27 +70,17 @@ static mempool_t *nfs_wdata_mempool;
 static struct kmem_cache *nfs_cdata_cachep;
 static mempool_t *nfs_commit_mempool;
 
-struct nfs_commit_data *nfs_commitdata_alloc(bool never_fail)
+struct nfs_commit_data *nfs_commitdata_alloc(void)
 {
 	struct nfs_commit_data *p;
 
-	if (never_fail)
-		p = mempool_alloc(nfs_commit_mempool, GFP_NOIO);
-	else {
-		/* It is OK to do some reclaim, not no safe to wait
-		 * for anything to be returned to the pool.
-		 * mempool_alloc() cannot handle that particular combination,
-		 * so we need two separate attempts.
-		 */
+	p = kmem_cache_zalloc(nfs_cdata_cachep, nfs_io_gfp_mask());
+	if (!p) {
 		p = mempool_alloc(nfs_commit_mempool, GFP_NOWAIT);
 		if (!p)
-			p = kmem_cache_alloc(nfs_cdata_cachep, GFP_NOIO |
-					     __GFP_NOWARN | __GFP_NORETRY);
-		if (!p)
 			return NULL;
+		memset(p, 0, sizeof(*p));
 	}
-
-	memset(p, 0, sizeof(*p));
 	INIT_LIST_HEAD(&p->pages);
 	return p;
 }
@@ -1826,7 +1816,11 @@ nfs_commit_list(struct inode *inode, struct list_head *head, int how,
 	if (list_empty(head))
 		return 0;
 
-	data = nfs_commitdata_alloc(true);
+	data = nfs_commitdata_alloc();
+	if (!data) {
+		nfs_retry_commit(head, NULL, cinfo, -1);
+		return -ENOMEM;
+	}
 
 	/* Set up the argument struct */
 	nfs_init_commit(data, head, NULL, cinfo);