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Hugh Dickins 9b15b817f3 swap: fix shmem swapping when more than 8 areas 
Minchan Kim reports that when a system has many swap areas, and tmpfs
swaps out to the ninth or more, shmem_getpage_gfp()'s attempts to read
back the page cannot locate it, and the read fails with -ENOMEM.

Whoops.  Yes, I blindly followed read_swap_header()'s pte_to_swp_entry(
swp_entry_to_pte()) technique for determining maximum usable swap
offset, without stopping to realize that that actually depends upon the
pte swap encoding shifting swap offset to the higher bits and truncating
it there.  Whereas our radix_tree swap encoding leaves offset in the
lower bits: it's swap "type" (that is, index of swap area) that was
truncated.

Fix it by reducing the SWP_TYPE_SHIFT() in swapops.h, and removing the
broken radix_to_swp_entry(swp_to_radix_entry()) from read_swap_header().

This does not reduce the usable size of a swap area any further, it
leaves it as claimed when making the original commit: no change from 3.0
on x86_64, nor on i386 without PAE; but 3.0's 512GB is reduced to 128GB
per swapfile on i386 with PAE.  It's not a change I would have risked
five years ago, but with x86_64 supported for ten years, I believe it's
appropriate now.

Hmm, and what if some architecture implements its swap pte with offset
encoded below type? That would equally break the maximum usable swap
offset check.  Happily, they all follow the same tradition of encoding
offset above type, but I'll prepare a check on that for next.

Reported-and-Reviewed-and-Tested-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: stable@vger.kernel.org [3.1, 3.2, 3.3, 3.4]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-06-15 21:48:14 -07:00
..
backing-dev.c backing-dev: fix wakeup timer races with bdi_unregister() 2012-02-01 16:52:49 +08:00
bootmem.c mm/bootmem.c: cleanup on addition to bootmem data list 2012-05-29 16:22:24 -07:00
bounce.c mm: remove the second argument of k[un]map_atomic() 2012-03-20 21:48:27 +08:00
cleancache.c ->encode_fh() API change 2012-05-29 23:28:33 -04:00
compaction.c Revert "mm: compaction: handle incorrect MIGRATE_UNMOVABLE type pageblocks" 2012-06-03 20:05:57 -07:00
debug-pagealloc.c mm, x86: Remove debug_pagealloc_enabled 2011-12-06 09:24:07 +01:00
dmapool.c mm: fix implicit stat.h usage in dmapool.c 2011-10-31 09:20:12 -04:00
fadvise.c fadvise: only initiate writeback for specified range with FADV_DONTNEED 2012-01-10 16:30:43 -08:00
failslab.c switch debugfs to umode_t 2012-01-03 22:54:56 -05:00
filemap.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-06-01 10:34:35 -07:00
filemap_xip.c fs: introduce inode operation ->update_time 2012-06-01 12:07:25 -04:00
fremap.c mm: delete various needless include <linux/module.h> 2011-10-31 09:20:11 -04:00
frontswap.c frontswap: s/put_page/store/g s/get_page/load 2012-05-15 11:34:08 -04:00
highmem.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
huge_memory.c mm/memcg: apply add/del_page to lruvec 2012-05-29 16:22:28 -07:00
hugetlb.c mm: fix vma_resv_map() NULL pointer 2012-05-30 08:48:13 -07:00
hwpoison-inject.c HWPOISON: Clean up memory_failure() vs. __memory_failure() 2012-01-03 12:06:32 -08:00
init-mm.c atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
internal.h Revert "mm: compaction: handle incorrect MIGRATE_UNMOVABLE type pageblocks" 2012-06-03 20:05:57 -07:00
Kconfig Frontswap provides a "transcendent memory" interface for swap pages. 2012-06-04 12:28:45 -07:00
Kconfig.debug mm: more intensive memory corruption debugging 2012-01-10 16:30:42 -08:00
kmemcheck.c
kmemleak-test.c
kmemleak.c kmemleak: Disable early logging when kmemleak is off by default 2012-01-20 16:57:05 +00:00
ksm.c ksm: cleanup: introduce find_mergeable_vma() 2012-03-21 17:54:59 -07:00
maccess.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
madvise.c mm/fs: route MADV_REMOVE to FALLOC_FL_PUNCH_HOLE 2012-05-29 16:22:22 -07:00
Makefile Frontswap provides a "transcendent memory" interface for swap pages. 2012-06-04 12:28:45 -07:00
memblock.c memblock: Document memblock_is_region_{memory,reserved}() 2012-06-08 11:59:46 +02:00
memcontrol.c memcg: decrement static keys at real destroy time 2012-05-29 16:22:28 -07:00
memory-failure.c mm/memory_failure: let the compiler add the function name 2012-05-29 16:22:18 -07:00
memory.c thp, memcg: split hugepage for memcg oom on cow 2012-05-29 16:22:19 -07:00
memory_hotplug.c mm: print physical addresses consistently with other parts of kernel 2012-05-29 16:22:21 -07:00
mempolicy.c mm: do_migrate_pages(): rename arguments 2012-05-29 16:22:20 -07:00
mempool.c mempool: fix first round failure behavior 2012-01-10 16:30:45 -08:00
migrate.c mm: fix warning in __set_page_dirty_nobuffers 2012-06-03 20:05:47 -07:00
mincore.c mm: thp: fix pmd_bad() triggering in code paths holding mmap_sem read mode 2012-03-21 17:54:54 -07:00
mlock.c vm: avoid using find_vma_prev() unnecessarily 2012-03-06 18:23:36 -08:00
mm_init.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
mmap.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2012-06-01 10:34:35 -07:00
mmu_context.c mm, counters: remove task argument to sync_mm_rss() and __sync_task_rss_stat() 2012-03-21 17:54:59 -07:00
mmu_notifier.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
mmzone.c mm: add link from struct lruvec to struct zone 2012-05-29 16:22:26 -07:00
mprotect.c Merge branch 'akpm' (Andrew's patch-bomb) 2012-03-22 09:04:48 -07:00
mremap.c move security_mmap_addr() to saner place 2012-06-01 10:37:16 -04:00
msync.c
nobootmem.c mm: remove sparsemem allocation details from the bootmem allocator 2012-05-29 16:22:22 -07:00
nommu.c nommu: fix compilation of nommu.c 2012-06-04 17:17:31 -04:00
oom_kill.c mm, oom: fix badness score underflow 2012-06-08 15:07:35 -07:00
page-writeback.c writeback: initialize global_dirty_limit 2012-05-06 13:41:58 +08:00
page_alloc.c Revert "mm: compaction: handle incorrect MIGRATE_UNMOVABLE type pageblocks" 2012-06-03 20:05:57 -07:00
page_cgroup.c page_cgroup: fix horrid swap accounting regression 2012-03-06 08:18:23 -08:00
page_io.c frontswap: s/put_page/store/g s/get_page/load 2012-05-15 11:34:08 -04:00
page_isolation.c mm: page_isolation: MIGRATE_CMA isolation functions added 2012-05-21 15:09:33 +02:00
pagewalk.c mm: thp: fix pmd_bad() triggering in code paths holding mmap_sem read mode 2012-03-21 17:54:54 -07:00
percpu-km.c
percpu-vm.c percpu: use bitmap_clear 2012-01-20 09:23:16 -08:00
percpu.c kmemleak: Fix the kmemleak tracking of the percpu areas with !SMP 2012-05-09 10:13:29 -07:00
pgtable-generic.c arch/tile: allow building Linux with transparent huge pages enabled 2012-05-25 12:48:21 -04:00
prio_tree.c sanitize <linux/prefetch.h> usage 2011-05-20 12:50:29 -07:00
process_vm_access.c aio/vfs: cleanup of rw_copy_check_uvector() and compat_rw_copy_check_uvector() 2012-05-31 17:49:32 -07:00
quicklist.c mm: delete various needless include <linux/module.h> 2011-10-31 09:20:11 -04:00
readahead.c mm: move readahead syscall to mm/readahead.c 2012-05-29 16:22:23 -07:00
rmap.c mm: remove swap token code 2012-05-29 16:22:19 -07:00
shmem.c shmem: replace_page must flush_dcache and others 2012-06-07 14:43:54 -07:00
slab.c Merge branch 'slab/for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/linux 2012-03-28 15:04:26 -07:00
slob.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
slub.c Merge branch 'slab/for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/linux 2012-06-01 16:50:23 -07:00
sparse-vmemmap.c mm: delete various needless include <linux/module.h> 2011-10-31 09:20:11 -04:00
sparse.c mm: remove sparsemem allocation details from the bootmem allocator 2012-05-29 16:22:22 -07:00
swap.c mm/memcg: apply add/del_page to lruvec 2012-05-29 16:22:28 -07:00
swap_state.c mm: fix s390 BUG by __set_page_dirty_no_writeback on swap 2012-04-23 18:19:22 -07:00
swapfile.c swap: fix shmem swapping when more than 8 areas 2012-06-15 21:48:14 -07:00
truncate.c mm/fs: remove truncate_range 2012-05-29 16:22:23 -07:00
util.c new helper: vm_mmap_pgoff() 2012-06-01 10:37:18 -04:00
vmalloc.c mm: fix faulty initialization in vmalloc_init() 2012-05-29 16:22:24 -07:00
vmscan.c mm/memcg: apply add/del_page to lruvec 2012-05-29 16:22:28 -07:00
vmstat.c mm/vmstat.c: remove debug fs entries on failure of file creation and made extfrag_debug_root dentry local 2012-05-29 16:22:19 -07:00