Re: [PATCH mmotm] mm: __isolate_lru_page_prepare() in isolate_migratepages_block()

[David Rientjes <rientjes@google.com>]

On Fri, 4 Mar 2022, Hugh Dickins wrote:

> __isolate_lru_page_prepare() conflates two unrelated functions, with
> the flags to one disjoint from the flags to the other; and hides some
> of the important checks outside of isolate_migratepages_block(), where
> the sequence is better to be visible.  It comes from the days of lumpy
> reclaim, before compaction, when the combination made more sense.
> 
> Move what's needed by mm/compaction.c isolate_migratepages_block() inline
> there, and what's needed by mm/vmscan.c isolate_lru_pages() inline there.
> 
> Shorten "isolate_mode" to "mode", so the sequence of conditions is easier
> to read.  Declare a "mapping" variable, to save one call to page_mapping()
> (but not another: calling again after page is locked is necessary).
> Simplify isolate_lru_pages() with a "move_to" list pointer.
> 
> Signed-off-by: Hugh Dickins <hughd@google.com>

Acked-by: David Rientjes <rientjes@google.com>