From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Chinner Subject: Re: [RFC PATCH] mm: introduce kv[mz]alloc helpers Date: Fri, 9 Dec 2016 12:44:17 +1100 Message-ID: <20161209014417.GN4326@dastard> References: <20161208103300.23217-1-mhocko@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-mm@kvack.org, Andrew Morton , Vlastimil Babka , David Rientjes , Mel Gorman , Johannes Weiner , Anatoly Stepanov , LKML , Michal Hocko , Paolo Bonzini , Mike Snitzer , dm-devel@redhat.com, "Michael S. Tsirkin" , Theodore Ts'o , kvm@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-security-module@vger.kernel.org To: Michal Hocko Return-path: Content-Disposition: inline In-Reply-To: <20161208103300.23217-1-mhocko@kernel.org> Sender: owner-linux-mm@kvack.org List-Id: linux-ext4.vger.kernel.org On Thu, Dec 08, 2016 at 11:33:00AM +0100, 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. See fs/xfs/kmem.c::kmem_zalloc_large(), which is XFS's version of kvmalloc() that is GFP_NOFS/GFP_NOIO safe. Any generic API for this functionality will have to play these memalloc_noio_save/ memalloc_noio_restore games to ensure they are GFP_NOFS safe.... Cheers, Dave. -- Dave Chinner david@fromorbit.com -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org