fix msync error on unmapped area
Fix the 2.6.18 sys_msync to report -ENOMEM correctly when an unmapped area
falls within its range, and not to overshoot: to satisfy LSB 3.1 tests and
to fix Debian Bug#394392. Took the 2.6.19 sys_msync as starting point
(including its cleanup of repeated "current->mm"s), reintroducing the
msync_interval and balance_dirty_pages_ratelimited_nr needed in 2.6.18.
The misbehaviour fixed here may not seem very serious; but it was enough
to mislead Debian into backporting 2.6.19's dirty page tracking patches,
with attendant mayhem when those resulted in unsuspected file corruption.
Signed-off-by: Hugh Dickins <firstname.lastname@example.org>
Signed-off-by: Chris Wright <email@example.com>
Signed-off-by: Greg Kroah-Hartman <firstname.lastname@example.org>