Re: [PATCH 04/16] page-flags: define PG_locked behavior on compound pages

[Christoph Lameter]

On Thu, 24 Sep 2015, Kirill A. Shutemov wrote:

> SLUB uses PG_locked as a bit spin locked.  IIUC, tail pages should never
> appear there.  VM_BUG_ON() is added to make sure that this assumption is
> correct.

Correct. However, VM_BUG_ON is superfluous. If there is a tail page there
then the information in the page will be not as expected (free list
parameter f.e.) and things will fall apart rapidly with segfaults.

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