vmscan: merge duplicate code in shrink_active_list()
The "move pages to active list" and "move pages to inactive list" code blocks are mostly identical and can be served by a function. Thanks to Andrew Morton for pointing this out. Note that buffer_heads_over_limit check will also be carried out for re-activated pages, which is slightly different from pre-2.6.28 kernels. Also, Rik's "vmscan: evict use-once pages first" patch could totally stop scans of active file list when memory pressure is low. So the net effect could be, the number of buffer heads is now more likely to grow large. However that's fine according to Johannes' comments: I don't think that this could be harmful. We just preserve the buffer mappings of what we consider the working set and with low memory pressure, as you say, this set is not big. As to stripping of reactivated pages: the only pages we re-activate for now are those VM_EXEC mapped ones. Since we don't expect IO from or to these pages, removing the buffer mappings in case they grow too large should be okay, I guess. Cc: Pekka Enberg <penberg@cs.helsinki.fi> Acked-by: Peter Zijlstra <peterz@infradead.org> Reviewed-by: Rik van Riel <riel@redhat.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Reviewed-by: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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