Messages in this thread | | | Date | Fri, 9 Dec 2016 12:44:17 +1100 | From | Dave Chinner <> | Subject | Re: [RFC PATCH] mm: introduce kv[mz]alloc helpers |
| |
On Thu, Dec 08, 2016 at 11:33:00AM +0100, Michal Hocko wrote: > From: Michal Hocko <mhocko@suse.com> > > 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
| |