swapin: fix valid_swaphandles defect

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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>

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Hugh Dickins 2008-02-04 22:28:45 -08:00 • committed by Linus Torvalds

parent 5402b976ae

commit 8952898b0d

1 changed files with 33 additions and 16 deletions

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mm/swapfile.c

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