Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:53392 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758156AbcH3Ls0 (ORCPT ); Tue, 30 Aug 2016 07:48:26 -0400 From: Jeff Layton To: bfields@fieldses.org Cc: linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, Olaf Hering , Linus Torvalds Subject: [PATCH] nfsd: more robust allocation failure handling in nfsd_reply_cache_init Date: Tue, 30 Aug 2016 07:48:23 -0400 Message-Id: <1472557703-5985-1-git-send-email-jlayton@redhat.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: Currently, we try to allocate the cache as a single, large chunk, which can fail if no big chunks of memory are available. We _do_ try to size it according to the amount of memory in the box, but if the server is started well after boot time, then the allocation can fail due to memory fragmentation. Try to handle this more gracefully by cutting the max_drc_entries in half and then retrying if the allocation fails. Only give up if the failed allocation is smaller than a page. Reported-by: Olaf Hering Cc: Linus Torvalds Signed-off-by: Jeff Layton --- fs/nfsd/nfscache.c | 27 +++++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-) While this would be good to get in, I don't see any particular urgency here. This seems like it'd be reasonable for v4.9. diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c index 54cde9a5864e..b8aaa7a71412 100644 --- a/fs/nfsd/nfscache.c +++ b/fs/nfsd/nfscache.c @@ -155,14 +155,12 @@ nfsd_reply_cache_free(struct nfsd_drc_bucket *b, struct svc_cacherep *rp) int nfsd_reply_cache_init(void) { - unsigned int hashsize; + unsigned int hashsize, target_hashsize; unsigned int i; int status = 0; max_drc_entries = nfsd_cache_size_limit(); atomic_set(&num_drc_entries, 0); - hashsize = nfsd_hashsize(max_drc_entries); - maskbits = ilog2(hashsize); status = register_shrinker(&nfsd_reply_cache_shrinker); if (status) @@ -173,9 +171,30 @@ int nfsd_reply_cache_init(void) if (!drc_slab) goto out_nomem; - drc_hashtbl = kcalloc(hashsize, sizeof(*drc_hashtbl), GFP_KERNEL); + /* + * Attempt to allocate the hashtable, and progressively shrink the + * size as the allocations fail. If the allocation size ends up being + * smaller than a page however, then just give up. + */ + target_hashsize = nfsd_hashsize(max_drc_entries); + hashsize = target_hashsize; + do { + maskbits = ilog2(hashsize); + drc_hashtbl = kcalloc(hashsize, sizeof(*drc_hashtbl), + GFP_KERNEL|__GFP_NOWARN); + if (drc_hashtbl) + break; + max_drc_entries /= 2; + hashsize = nfsd_hashsize(max_drc_entries); + } while ((hashsize * sizeof(*drc_hashtbl)) >= PAGE_SIZE); + if (!drc_hashtbl) goto out_nomem; + + if (hashsize != target_hashsize) + pr_warn("NFSD: had to shrink reply cache hashtable (wanted %u, got %u)\n", + target_hashsize, hashsize); + for (i = 0; i < hashsize; i++) { INIT_LIST_HEAD(&drc_hashtbl[i].lru_head); spin_lock_init(&drc_hashtbl[i].cache_lock); -- 2.7.4