swapin: fix valid_swaphandles defect
authorHugh Dickins <hugh@veritas.com>
Tue, 5 Feb 2008 06:28:45 +0000 (22:28 -0800)
committerLinus Torvalds <torvalds@woody.linux-foundation.org>
Tue, 5 Feb 2008 17:44:15 +0000 (09:44 -0800)
commit8952898b0d25223f38daf46b86156fd1c4d17ad0
tree10912460cd9d42195d4aba8250ed1c3bd3577bb4
parent5402b976ae0be96b3a32f3508ab7308c380d6477
swapin: fix valid_swaphandles defect

valid_swaphandles is supposed to do a quick pass over the swap map entries
neigbouring the entry which swapin_readahead is targetting, to determine for
it a range worth reading all together.  But since it always starts its search
from the beginning of the swap "cluster", a reject (free entry) there
immediately curtails the readaround, and every swapin_readahead from that
cluster is for just a single page.  Instead scan forwards and backwards around
the target entry.

Use better names for some variables: a swap_info pointer is usually called
"si" not "swapdev".  And at the end, if only the target page should be read,
return count of 0 to disable readaround, to avoid the unnecessarily repeated
call to read_swap_cache_async.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Acked-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/swapfile.c