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author | Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> | 2009-09-22 00:02:50 (GMT) |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-09-22 14:17:35 (GMT) |
commit | 31a5639623a487d6db996c8138c9e53fef2e2d91 (patch) | |
tree | 4fff22b4a0333df084a6cd89e8ecbc332dbfa299 /mm/shmem.c | |
parent | 8fbb398f5c78832ee61e0d5ed0793fa8857bd853 (diff) | |
download | linux-fsl-qoriq-31a5639623a487d6db996c8138c9e53fef2e2d91.tar.xz |
mm: add_to_swap_cache() must not sleep
After commit 355cfa73 ("mm: modify swap_map and add SWAP_HAS_CACHE flag"),
read_swap_cache_async() will busy-wait while a entry doesn't exist in swap
cache but it has SWAP_HAS_CACHE flag.
Such entries can exist on add/delete path of swap cache. On add path,
add_to_swap_cache() is called soon after SWAP_HAS_CACHE flag is set, and
on delete path, swapcache_free() will be called (SWAP_HAS_CACHE flag is
cleared) soon after __delete_from_swap_cache() is called. So, the
busy-wait works well in most cases.
But this mechanism can cause soft lockup if add_to_swap_cache() sleeps and
read_swap_cache_async() tries to swap-in the same entry on the same cpu.
This patch calls radix_tree_preload() before swapcache_prepare() and
divides add_to_swap_cache() into two part: radix_tree_preload() part and
radix_tree_insert() part(define it as __add_to_swap_cache()).
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/shmem.c')
0 files changed, 0 insertions, 0 deletions