On Wed, Jul 30, 2014 at 12:11:43PM +0200, Jan Kara wrote: > > sb_bread allocates page from movable area but it is not movable until the > > reference counter of the buffer-head becomes zero. > > There is no lock for the buffer but the reference counter acts like lock. > OK, but why do you care about a single page (of at most handful if you > have more filesystems) which isn't movable? That shouldn't make a big > difference to compaction... The thing is, CMA _must_ be able to clear all the pages in its range, otherwise its broken. So placing nonmovable pages in a movable block utterly wrecks that. Now, Ted said that there's more effectively pinned stuff from filesystems (and I imagine those would be things like the root inode etc.) and those would equally wreck this.. But Gioh didn't mention any of that.. he should I suppose.
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