From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758033AbdACKXN (ORCPT ); Tue, 3 Jan 2017 05:23:13 -0500 Received: from mx2.suse.de ([195.135.220.15]:44040 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757812AbdACKXK (ORCPT ); Tue, 3 Jan 2017 05:23:10 -0500 Subject: Re: [PATCH] mm: introduce kv[mz]alloc helpers To: Michal Hocko , Andrew Morton References: <20170102133700.1734-1-mhocko@kernel.org> Cc: David Rientjes , Mel Gorman , Johannes Weiner , Al Viro , linux-mm@kvack.org, LKML , kvm@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-security-module@vger.kernel.org, linux-ext4@vger.kernel.org, Joe Perches , Michal Hocko , Anatoly Stepanov , Paolo Bonzini , Mike Snitzer , "Michael S. Tsirkin" , "Theodore Ts'o" , Andreas Dilger From: Vlastimil Babka Message-ID: <74a00631-ab1f-b818-6608-1554bcd7cbc1@suse.cz> Date: Tue, 3 Jan 2017 11:23:04 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: <20170102133700.1734-1-mhocko@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/02/2017 02:37 PM, Michal Hocko wrote: > From: Michal Hocko > > Using kmalloc with the vmalloc fallback for larger allocations is a > common pattern in the kernel code. Yet we do not have any common helper > for that and so users have invented their own helpers. Some of them are > really creative when doing so. Let's just add kv[mz]alloc and make sure > it is implemented properly. This implementation makes sure to not make > a large memory pressure for > PAGE_SZE requests (__GFP_NORETRY) and also > to not warn about allocation failures. This also rules out the OOM > killer as the vmalloc is a more approapriate fallback than a disruptive > user visible action. > > This patch also changes some existing users and removes helpers which > are specific for them. In some cases this is not possible (e.g. > ext4_kvmalloc, libcfs_kvzalloc, __aa_kvmalloc) because those seems to be > broken and require GFP_NO{FS,IO} context which is not vmalloc compatible > in general (note that the page table allocation is GFP_KERNEL). Those > need to be fixed separately. > > apparmor has already claimed kv[mz]alloc so remove those and use > __aa_kvmalloc instead to prevent from the naming clashes. > > Changes since v1 > - define __vmalloc_node_flags for CONFIG_MMU=n > > Cc: Anatoly Stepanov > Cc: Paolo Bonzini > Cc: Mike Snitzer > Cc: "Michael S. Tsirkin" > Cc: "Theodore Ts'o" > Reviewed-by: Andreas Dilger # ext4 part > Signed-off-by: Michal Hocko Acked-by: Vlastimil Babka (but with a small fix and suggestion below) > --- a/mm/util.c > +++ b/mm/util.c > @@ -346,6 +346,46 @@ unsigned long vm_mmap(struct file *file, unsigned long addr, > } > EXPORT_SYMBOL(vm_mmap); > > +/** > + * kvmalloc_node - allocate contiguous memory from SLAB with vmalloc fallback > + * @size: size of the request. > + * @flags: gfp mask for the allocation - must be compatible with GFP_KERNEL. > + * @node: numa node to allocate from > + * > + * Uses kmalloc to get the memory but if the allocation fails then falls back > + * to the vmalloc allocator. Use kvfree for freeing the memory. > + */ > +void *kvmalloc_node(size_t size, gfp_t flags, int node) > +{ > + gfp_t kmalloc_flags = flags; > + void *ret; > + > + /* > + * vmalloc uses GFP_KERNEL for some internal allocations (e.g page tables) > + * so the given set of flags has to be compatible. > + */ > + WARN_ON((flags & GFP_KERNEL) != GFP_KERNEL); Wouldn't a _ONCE be sufficient? It's unlikely that multiple wrong call sites appear out of the blue, but we don't want to flood the log from a single frequently called site. No strong feelings though. > + > + /* > + * Make sure that larger requests are not too disruptive - no OOM > + * killer and no allocation failure warnings as we have a fallback > + */ > + if (size > PAGE_SIZE) > + kmalloc_flags |= __GFP_NORETRY | __GFP_NOWARN; > + > + ret = kmalloc_node(size, kmalloc_flags, node); > + > + /* > + * It doesn't really make sense to fallback to vmalloc for sub page > + * requests > + */ > + if (ret || size < PAGE_SIZE) This should be size <= PAGE_SIZE. > + return ret; > + > + return __vmalloc_node_flags(size, node, flags); > +} > +EXPORT_SYMBOL(kvmalloc_node); > + > void kvfree(const void *addr) > { > if (is_vmalloc_addr(addr))