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Vlastimil Babka 8ea1d2a198 mm, frontswap: convert frontswap_enabled to static key 
I have noticed that frontswap.h first declares "frontswap_enabled" as
extern bool variable, and then overrides it with "#define
frontswap_enabled (1)" for CONFIG_FRONTSWAP=Y or (0) when disabled.  The
bool variable isn't actually instantiated anywhere.

This all looks like an unfinished attempt to make frontswap_enabled
reflect whether a backend is instantiated.  But in the current state,
all frontswap hooks call unconditionally into frontswap.c just to check
if frontswap_ops is non-NULL.  This should at least be checked inline,
but we can further eliminate the overhead when CONFIG_FRONTSWAP is
enabled and no backend registered, using a static key that is initially
disabled, and gets enabled only upon first backend registration.

Thus, checks for "frontswap_enabled" are replaced with
"frontswap_enabled()" wrapping the static key check.  There are two
exceptions:

- xen's selfballoon_process() was testing frontswap_enabled in code guarded
  by #ifdef CONFIG_FRONTSWAP, which was effectively always true when reachable.
  The patch just removes this check. Using frontswap_enabled() does not sound
  correct here, as this can be true even without xen's own backend being
  registered.

- in SYSCALL_DEFINE2(swapon), change the check to IS_ENABLED(CONFIG_FRONTSWAP)
  as it seems the bitmap allocation cannot currently be postponed until a
  backend is registered. This means that frontswap will still have some
  memory overhead by being configured, but without a backend.

After the patch, we can expect that some functions in frontswap.c are
called only when frontswap_ops is non-NULL.  Change the checks there to
VM_BUG_ONs.  While at it, convert other BUG_ONs to VM_BUG_ONs as
frontswap has been stable for some time.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/1463152235-9717-1-git-send-email-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2016-07-26 16:19:19 -07:00
..
kasan kasan/quarantine: fix bugs on qlist_move_cache() 2016-07-15 14:54:27 +09:00
Kconfig mm: disable DEFERRED_STRUCT_PAGE_INIT on !NO_BOOTMEM 2016-05-27 14:49:37 -07:00
Kconfig.debug mm/page_ref: add tracepoint to track down page reference manipulation 2016-03-17 15:09:34 -07:00
Makefile z3fold: the 3-fold allocator for compressed pages 2016-05-20 17:58:30 -07:00
backing-dev.c mm: throttle on IO only when there are too many dirty and writeback pages 2016-05-20 17:58:30 -07:00
balloon_compaction.c mm: balloon: use general non-lru movable page feature 2016-07-26 16:19:19 -07:00
bootmem.c mm: convert printk(KERN_<LEVEL> to pr_<level> 2016-03-17 15:09:34 -07:00
cleancache.c cleancache: constify cleancache_ops structure 2016-01-27 09:09:57 -05:00
cma.c mm/cma: silence warnings due to max() usage 2016-05-27 14:49:37 -07:00
cma.h mm: cma: mark cma_bitmap_maxno() inline in header 2015-08-14 15:56:32 -07:00
cma_debug.c mm/cma_debug: correct size input to bitmap function 2015-07-17 16:39:54 -07:00
compaction.c mm/page_alloc: introduce post allocation processing on page allocator 2016-07-26 16:19:19 -07:00
debug.c mm: introduce page reference manipulation functions 2016-03-17 15:09:34 -07:00
debug_page_ref.c mm/page_ref: add tracepoint to track down page reference manipulation 2016-03-17 15:09:34 -07:00
dmapool.c mm: convert printk(KERN_<LEVEL> to pr_<level> 2016-03-17 15:09:34 -07:00
early_ioremap.c mm/early_ioremap: use offset_in_page macro 2015-11-05 19:34:48 -08:00
fadvise.c mm/fadvise.c: do not discard partial pages with POSIX_FADV_DONTNEED 2016-06-09 14:23:11 -07:00
failslab.c mm: fault-inject take over bootstrap kmem_cache check 2016-03-15 16:55:16 -07:00
filemap.c Revert "mm: make faultaround produce old ptes" 2016-06-24 17:23:52 -07:00
frame_vector.c mm/gup: Switch all callers of get_user_pages() to not pass tsk/mm 2016-02-16 10:11:12 +01:00
frontswap.c mm, frontswap: convert frontswap_enabled to static key 2016-07-26 16:19:19 -07:00
gup.c mm: thp: check pmd_trans_unstable() after split_huge_pmd() 2016-07-26 16:19:19 -07:00
highmem.c mm/highmem: make nr_free_highpages() handles all highmem zones by itself 2016-05-19 19:12:14 -07:00
huge_memory.c mm/mmu_gather: track page size with mmu gather and force flush if page size change 2016-07-26 16:19:19 -07:00
hugetlb.c mm/mmu_gather: track page size with mmu gather and force flush if page size change 2016-07-26 16:19:19 -07:00
hugetlb_cgroup.c mm, hugetlb_cgroup: round limit_in_bytes down to hugepage size 2016-05-20 17:58:30 -07:00
hwpoison-inject.c hwpoison: use page_cgroup_ino for filtering by memcg 2015-09-10 13:29:01 -07:00
init-mm.c
…
internal.h mm/page_alloc: introduce post allocation processing on page allocator 2016-07-26 16:19:19 -07:00
interval_tree.c mm: replace vma->sharead.linear with vma->shared 2015-02-10 14:30:31 -08:00
kmemcheck.c mm: convert printk(KERN_<LEVEL> to pr_<level> 2016-03-17 15:09:34 -07:00
kmemleak-test.c mm: convert printk(KERN_<LEVEL> to pr_<level> 2016-03-17 15:09:34 -07:00
kmemleak.c mm: prevent KASAN false positives in kmemleak 2016-06-24 17:23:52 -07:00
ksm.c mm: migrate: support non-lru movable page migration 2016-07-26 16:19:19 -07:00
list_lru.c mm: memcontrol: move kmem accounting code to CONFIG_MEMCG 2016-01-20 17:09:18 -08:00
maccess.c x86: remove more uaccess_32.h complexity 2016-05-22 17:21:27 -07:00
madvise.c mm: make mmap_sem for write waits killable for mm syscalls 2016-05-23 17:04:14 -07:00
memblock.c mm/memblock.c: remove unnecessary always-true comparison 2016-05-20 17:58:30 -07:00
memcontrol.c mm,oom: remove unused argument from oom_scan_process_thread(). 2016-07-26 16:19:19 -07:00
memory-failure.c mm/memory-failure.c: replace "MCE" with "Memory failure" 2016-05-20 17:58:30 -07:00
memory.c mm/mmu_gather: track page size with mmu gather and force flush if page size change 2016-07-26 16:19:19 -07:00
memory_hotplug.c memory-hotplug: more general validation of zone during online 2016-07-26 16:19:19 -07:00
mempolicy.c mm: thp: check pmd_trans_unstable() after split_huge_pmd() 2016-07-26 16:19:19 -07:00
mempool.c mm: mempool: kasan: don't poot mempool objects in quarantine 2016-06-24 17:23:52 -07:00
memtest.c memtest: remove unused header files 2015-09-08 15:35:28 -07:00
migrate.c mm: balloon: use general non-lru movable page feature 2016-07-26 16:19:19 -07:00
mincore.c mm, fs: remove remaining PAGE_CACHE_* and page_cache_{get,release} usage 2016-04-04 10:41:08 -07:00
mlock.c mm: make mmap_sem for write waits killable for mm syscalls 2016-05-23 17:04:14 -07:00
mm_init.c mm: convert printk(KERN_<LEVEL> to pr_<level> 2016-03-17 15:09:34 -07:00
mmap.c x86/vdso: Add mremap hook to vm_special_mapping 2016-07-08 14:17:51 +02:00
mmu_context.c mm/mmu_context, sched/core: Fix mmu_context.h assumption 2016-04-28 11:44:19 +02:00
mmu_notifier.c fix Christoph's email addresses 2016-03-17 15:09:34 -07:00
mmzone.c mm, page_alloc: inline the fast path of the zonelist iterator 2016-05-19 19:12:14 -07:00
mprotect.c mm: thp: check pmd_trans_unstable() after split_huge_pmd() 2016-07-26 16:19:19 -07:00
mremap.c mm: thp: check pmd_trans_unstable() after split_huge_pmd() 2016-07-26 16:19:19 -07:00
msync.c mm/msync: use offset_in_page macro 2015-11-05 19:34:48 -08:00
nobootmem.c mm: convert printk(KERN_<LEVEL> to pr_<level> 2016-03-17 15:09:34 -07:00
nommu.c mm: remove more IS_ERR_VALUE abuses 2016-05-27 15:57:31 -07:00
oom_kill.c mm,oom: remove unused argument from oom_scan_process_thread(). 2016-07-26 16:19:19 -07:00
page-writeback.c fs/fs-writeback.c: add a new writeback list for sync 2016-07-26 16:19:19 -07:00
page_alloc.c mm: charge/uncharge kmemcg from generic page allocator paths 2016-07-26 16:19:19 -07:00
page_counter.c mm: page_counter: let page_counter_try_charge() return bool 2015-11-05 19:34:48 -08:00
page_ext.c mm: use early_pfn_to_nid in page_ext_init 2016-05-27 14:49:37 -07:00
page_idle.c mm: add page_check_address_transhuge() helper 2016-01-15 17:56:32 -08:00
page_io.c Merge branch 'work.preadv2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-05-17 15:05:23 -07:00
page_isolation.c mm/page_isolation: clean up confused code 2016-07-26 16:19:19 -07:00
page_owner.c mm/page_owner: use stackdepot to store stacktrace 2016-07-26 16:19:19 -07:00
page_poison.c mm: check the return value of lookup_page_ext for all call sites 2016-06-03 15:06:22 -07:00
pagewalk.c thp: rename split_huge_page_pmd() to split_huge_pmd() 2016-01-15 17:56:32 -08:00
percpu-km.c mm: percpu: use pr_fmt to prefix output 2016-03-17 15:09:34 -07:00
percpu-vm.c percpu: move region iterations out of pcpu_[de]populate_chunk() 2014-09-02 14:46:02 -04:00
percpu.c percpu: fix synchronization between synchronous map extension and chunk destruction 2016-05-25 11:48:25 -04:00
pgtable-generic.c mm/thp/migration: switch from flush_tlb_range to flush_pmd_tlb_range 2016-03-17 15:09:34 -07:00
process_vm_access.c mm/gup: Introduce get_user_pages_remote() 2016-02-16 10:04:09 +01:00
quicklist.c fix Christoph's email addresses 2016-03-17 15:09:34 -07:00
readahead.c mm, fs: get rid of PAGE_CACHE_* and page_cache_{get,release} macros 2016-04-04 10:41:08 -07:00
rmap.c mm: thp: refix false positive BUG in page_move_anon_rmap() 2016-07-15 14:54:27 +09:00
shmem.c tmpfs: fix regression hang in fallocate undo 2016-07-10 20:08:44 -07:00
slab.c mm/slab: use list_move instead of list_del/list_add 2016-07-26 16:19:19 -07:00
slab.h mm: memcontrol: cleanup kmem charge functions 2016-07-26 16:19:19 -07:00
slab_common.c mm: charge/uncharge kmemcg from generic page allocator paths 2016-07-26 16:19:19 -07:00
slob.c mm: slab: free kmem_cache_node after destroy sysfs file 2016-02-18 16:23:24 -08:00
slub.c mm: charge/uncharge kmemcg from generic page allocator paths 2016-07-26 16:19:19 -07:00
sparse-vmemmap.c mm: convert printk(KERN_<LEVEL> to pr_<level> 2016-03-17 15:09:34 -07:00
sparse.c mm: convert printk(KERN_<LEVEL> to pr_<level> 2016-03-17 15:09:34 -07:00
swap.c mm/swap.c: flush lru pvecs on compound page arrival 2016-06-24 17:23:52 -07:00
swap_cgroup.c mm: convert printk(KERN_<LEVEL> to pr_<level> 2016-03-17 15:09:34 -07:00
swap_state.c mm: thp: broken page count after commit aa88b68c3b 2016-06-09 14:23:11 -07:00
swapfile.c mm, frontswap: convert frontswap_enabled to static key 2016-07-26 16:19:19 -07:00
truncate.c dax: New fault locking 2016-05-19 15:20:54 -06:00
userfaultfd.c mm, fs: get rid of PAGE_CACHE_* and page_cache_{get,release} macros 2016-04-04 10:41:08 -07:00
util.c mm: migrate: support non-lru movable page migration 2016-07-26 16:19:19 -07:00
vmacache.c mm/vmacache: inline vmacache_valid_mm() 2015-11-05 19:34:48 -08:00
vmalloc.c mm: charge/uncharge kmemcg from generic page allocator paths 2016-07-26 16:19:19 -07:00
vmpressure.c mm/vmpressure.c: fix subtree pressure detection 2016-02-03 08:28:43 -08:00
vmscan.c mm: balloon: use general non-lru movable page feature 2016-07-26 16:19:19 -07:00
vmstat.c mm: check the return value of lookup_page_ext for all call sites 2016-06-03 15:06:22 -07:00
workingset.c mm: workingset: printk missing log level, use pr_info() 2016-07-15 14:54:27 +09:00
z3fold.c mm/z3fold.c: avoid modifying HEADLESS page and minor cleanup 2016-06-03 16:02:55 -07:00
zbud.c mm/zbud.c: use list_last_entry() instead of list_tail_entry() 2016-01-15 11:40:52 -08:00
zpool.c mm: zsmalloc: constify struct zs_pool name 2015-11-06 17:50:42 -08:00
zsmalloc.c zsmalloc: use OBJ_TAG_BIT for bit shifter 2016-07-26 16:19:19 -07:00
zswap.c mm/zswap: use workqueue to destroy pool 2016-05-20 17:58:30 -07:00