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Shaohua Li edfe23dac3 swap: fix races exposed by swap discard 
The previous patch can expose races, according to Hugh:

swapoff was sometimes failing with "Cannot allocate memory", coming from
try_to_unuse()'s -ENOMEM: it needs to allow for swap_duplicate() failing
on a free entry temporarily SWAP_MAP_BAD while being discarded.

We should use ACCESS_ONCE() there, and whenever accessing swap_map
locklessly; but rather than peppering it throughout try_to_unuse(), just
declare *swap_map with volatile.

try_to_unuse() is accustomed to *swap_map going down racily, but not
necessarily to it jumping up from 0 to SWAP_MAP_BAD: we'll be safer to
prevent that transition once SWP_WRITEOK is switched off, when it's a
waste of time to issue discards anyway (swapon can do a whole discard).

Another issue is:

In swapin_readahead(), read_swap_cache_async() can read a bad swap entry,
because we don't check if readahead swap entry is bad.  This doesn't break
anything but such swapin page is wasteful and can only be freed at page
reclaim.  We should avoid read such swap entry.  And in discard, we mark
swap entry SWAP_MAP_BAD and then switch it to normal when discard is
finished.  If readahead reads such swap entry, we have the same issue, so
we much check if swap entry is bad too.

Thanks Hugh to inspire swapin_readahead could use bad swap entry.

[include Hugh's patch 'swap: fix swapoff ENOMEMs from discard']
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Kyungmin Park <kmpark@infradead.org>
Cc: Rafael Aquini <aquini@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2013-09-11 15:57:16 -07:00
..
Kconfig Merge remote-tracking branch 'origin/next' into kvm-ppc-next 2013-08-29 00:41:59 +02:00
Kconfig.debug
…
Makefile zswap: add to mm/ 2013-07-10 18:11:34 -07:00
backing-dev.c backing-dev: convert class code to use dev_groups 2013-08-19 21:22:34 -07:00
balloon_compaction.c mm: introduce a common interface for balloon pages mobility 2012-12-11 17:22:26 -08:00
bootmem.c mm: kill free_all_bootmem_node() 2013-07-03 16:07:39 -07:00
bounce.c Merge branch 'for-3.10/core' of git://git.kernel.dk/linux-block 2013-05-08 10:13:35 -07:00
cleancache.c mm: cleancache: clean up cleancache_enabled 2013-04-30 17:04:01 -07:00
compaction.c mm: add & use zone_end_pfn() and zone_spans_pfn() 2013-02-23 17:50:20 -08:00
debug-pagealloc.c
…
dmapool.c dmapool: make DMAPOOL_DEBUG detect corruption of free marker 2012-12-11 17:22:24 -08:00
fadvise.c teach SYSCALL_DEFINE<n> how to deal with long long/unsigned long long 2013-03-03 22:46:22 -05:00
failslab.c
…
filemap.c direct-io: Handle O_(D)SYNC AIO 2013-09-04 09:23:46 -04:00
filemap_xip.c lift sb_start_write() out of ->write() 2013-04-09 14:12:56 -04:00
fremap.c mm: save soft-dirty bits on file pages 2013-08-13 17:57:48 -07:00
frontswap.c frontswap: fix incorrect zeroing and allocation size for frontswap_map 2013-06-12 16:29:46 -07:00
highmem.c Some nice cleanups, and even a patch my wife did as a "live" demo for 2012-12-20 08:37:05 -08:00
huge_memory.c mm: replace strict_strtoul() with kstrtoul() 2013-09-11 15:57:11 -07:00
hugetlb.c mm: replace strict_strtoul() with kstrtoul() 2013-09-11 15:57:11 -07:00
hugetlb_cgroup.c cgroup: pass around cgroup_subsys_state instead of cgroup in file methods 2013-08-08 20:11:24 -04:00
hwpoison-inject.c
…
init-mm.c
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internal.h mm: remove unused __put_page() 2013-07-09 10:33:22 -07:00
interval_tree.c
…
kmemcheck.c
…
kmemleak-test.c
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kmemleak.c mm: replace strict_strtoul() with kstrtoul() 2013-09-11 15:57:11 -07:00
ksm.c mm: replace strict_strtoul() with kstrtoul() 2013-09-11 15:57:11 -07:00
maccess.c
…
madvise.c mm/madvise.c: fix coding-style errors 2013-09-11 15:57:00 -07:00
memblock.c mm/memblock.c: fix wrong comment in __next_free_mem_range() 2013-07-09 10:33:23 -07:00
memcontrol.c Merge branch 'for-3.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2013-09-03 18:25:03 -07:00
memory-failure.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2013-09-06 09:36:28 -07:00
memory.c Merge 3.11-rc6 into char-misc-next 2013-08-18 20:40:33 -07:00
memory_hotplug.c mm/memory_hotplug.c: fix return value of online_pages() 2013-07-09 10:33:25 -07:00
mempolicy.c mm: mempolicy: turn vma_set_policy() into vma_dup_policy() 2013-09-11 15:57:00 -07:00
mempool.c
…
migrate.c mm: migration: add migrate_entry_wait_huge() 2013-06-12 16:29:46 -07:00
mincore.c swap: make each swap partition have one address_space 2013-02-23 17:50:17 -08:00
mlock.c Revert "mm: introduce VM_POPULATE flag to better deal with racy userspace programs" 2013-03-28 17:45:51 -07:00
mm_init.c mm: tune vm_committed_as percpu_counter batching size 2013-07-03 16:07:32 -07:00
mmap.c mm: mmap_region: kill correct_wcount/inode, use allow_write_access() 2013-09-11 15:57:07 -07:00
mmu_context.c mm: remove old aio use_mm() comment 2013-05-07 18:38:27 -07:00
mmu_notifier.c treewide: relase -> release 2013-06-28 14:34:33 +02:00
mmzone.c mm: rename page struct field helpers 2013-02-23 17:50:18 -08:00
mprotect.c mm/mprotect.c: coding-style cleanups 2012-12-18 15:02:15 -08:00
mremap.c mm: move_ptes -- Set soft dirty bit depending on pte type 2013-08-27 09:36:17 -07:00
msync.c
…
nobootmem.c mm: concentrate modification of totalram_pages into the mm core 2013-07-03 16:07:33 -07:00
nommu.c mm: remove free_area_cache 2013-07-10 18:11:34 -07:00
oom_kill.c mm/oom_kill: remove weird use of ERR_PTR()/PTR_ERR(). 2013-07-15 11:25:05 +09:30
page-writeback.c kernel: delete __cpuinit usage from all core kernel files 2013-07-14 19:36:59 -04:00
page_alloc.c mm/page_alloc.c: use '__paginginit' instead of '__init' 2013-09-11 15:57:13 -07:00
page_cgroup.c memcontrol: use N_MEMORY instead N_HIGH_MEMORY 2012-12-12 17:38:32 -08:00
page_io.c mm: remove compressed copy from zram in-memory 2013-07-03 16:07:26 -07:00
page_isolation.c page_isolation: Fix a comment typo in test_pages_isolated() 2013-08-20 13:03:41 +02:00
pagewalk.c mm/pagewalk.c: walk_page_range should avoid VM_PFNMAP areas 2013-05-24 16:22:53 -07:00
percpu-km.c
…
percpu-vm.c
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percpu.c mm, percpu: Make sure percpu_alloc early parameter has an argument 2012-12-02 06:23:04 -08:00
pgtable-generic.c mm/THP: add pmd args to pgtable deposit and withdraw APIs 2013-06-20 16:55:07 +10:00
process_vm_access.c Fix: compat_rw_copy_check_uvector() misuse in aio, readv, writev, and security keys 2013-03-12 11:05:45 -07:00
quicklist.c
…
readahead.c mm: change invalidatepage prototype to accept length 2013-05-21 23:17:23 -04:00
rmap.c s390/mm: implement software referenced bits 2013-08-29 13:20:11 +02:00
shmem.c shm_mnt is as longterm as it gets, TYVM... 2013-09-03 22:50:27 -04:00
slab.c kernel: delete __cpuinit usage from all core kernel files 2013-07-14 19:36:59 -04:00
slab.h memcg: check that kmem_cache has memcg_params before accessing it 2013-08-28 19:26:38 -07:00
slab_common.c Merge branch 'slab/for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/linux 2013-07-14 15:14:29 -07:00
slob.c Merge branch 'slab/for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/linux 2013-07-14 15:14:29 -07:00
slub.c mm: replace strict_strtoul() with kstrtoul() 2013-09-11 15:57:11 -07:00
sparse-vmemmap.c sparse-vmemmap: specify vmemmap population range in bytes 2013-04-29 15:54:35 -07:00
sparse.c mm/sparse.c: put clear_hwpoisoned_pages within CONFIG_MEMORY_HOTREMOVE 2013-07-09 10:33:22 -07:00
swap.c thp, mm: avoid PageUnevictable on active/inactive lru lists 2013-07-31 14:41:03 -07:00
swap_state.c swap: avoid read_swap_cache_async() race to deadlock while waiting on discard I/O completion 2013-06-12 16:29:45 -07:00
swapfile.c swap: fix races exposed by swap discard 2013-09-11 15:57:16 -07:00
truncate.c mm: teach truncate_inode_pages_range() to handle non page aligned ranges 2013-05-27 23:32:35 -04:00
util.c mm: remove free_area_cache 2013-07-10 18:11:34 -07:00
vmalloc.c mm/vmalloc.c: fix an overflow bug in alloc_vmap_area() 2013-07-09 10:33:23 -07:00
vmpressure.c Merge branch 'for-3.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2013-09-03 18:25:03 -07:00
vmscan.c mm: vmscan: do not scale writeback pages when deciding whether to set ZONE_WRITEBACK 2013-07-09 10:33:23 -07:00
vmstat.c mm: vmstats: track TLB flush stats on UP too 2013-09-11 15:57:09 -07:00
zbud.c mm: zbud: fix condition check on allocation size 2013-07-31 14:41:03 -07:00
zswap.c mm/zswap.c: get swapper address_space by using macro 2013-09-11 15:57:08 -07:00