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mm: move PageDoubleMap bit 

Patch series "Fix PageDoubleMap".

This is a purely theoretical problem for now as none of the filesystems
which use PG_private_2 (ie PG_fscache) are being converted at this time,
but it's confusing to leave it like this.

This patch (of 2):

PG_private_2 is defined as being PF_ANY (applicable to tail pages as well
as regular & head pages).  That means that the first tail page of a
double-map page will appear to have Private2 set.  Use the Workingset bit
instead which is defined as PF_HEAD so any attempt to access the
Workingset bit on a tail page will redirect to the head page's Workingset
bit.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Link: https://lkml.kernel.org/r/20200629151933.15671-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20200629151933.15671-2-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2020-10-13 16:53:50 -07:00 committed by Linus Torvalds
parent ff9f47f6f0
commit e18c45ffcf
1 changed files with 1 additions and 1 deletions
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2
include/linux/page-flags.h
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@ -167,7 +167,7 @@ enum pageflags {
PG_slob_free = PG_private, PG_slob_free = PG_private,
/* Compound pages. Stored in first tail page's flags */ /* Compound pages. Stored in first tail page's flags */
PG_double_map = PG_private_2, PG_double_map = PG_workingset,
/* non-lru isolated movable page */ /* non-lru isolated movable page */
PG_isolated = PG_reclaim, PG_isolated = PG_reclaim,