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swap_info: note SWAP_MAP_SHMEM

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While we're fiddling with the swap_map values, let's assign a particular
value to shmem/tmpfs swap pages: their swap counts are never incremented,
and it helps swapoff's try_to_unuse() a little if it can immediately
distinguish those pages from process pages.

Since we've no use for SWAP_MAP_BAD | COUNT_CONTINUED,
we might as well use that 0xbf value for SWAP_MAP_SHMEM.

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Hugh Dickins
2009-12-14 17:58:47 -08:00
committed by Linus Torvalds
parent 570a335b8e
commit aaa468653b
3 changed files with 42 additions and 22 deletions
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11
mm/shmem.c
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@@ -1017,7 +1017,14 @@ int shmem_unuse(swp_entry_t entry, struct page *page)
goto out;
}
mutex_unlock(&shmem_swaplist_mutex);
out: return found; /* 0 or 1 or -ENOMEM */
/*
* Can some race bring us here? We've been holding page lock,
* so I think not; but would rather try again later than BUG()
*/
unlock_page(page);
page_cache_release(page);
out:
return (found < 0) ? found : 0;
}
/*
@@ -1080,7 +1087,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
else
inode = NULL;
spin_unlock(&info->lock);
swap_duplicate(swap);
swap_shmem_alloc(swap);
BUG_ON(page_mapped(page));
page_cache_release(page); /* pagecache ref */
swap_writepage(page, wbc);