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Diffstat (limited to 'Documentation/mm/transhuge.rst')
| -rw-r--r-- | Documentation/mm/transhuge.rst | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/Documentation/mm/transhuge.rst b/Documentation/mm/transhuge.rst index af4c9d70321d..ec3dc5b04226 100644 --- a/Documentation/mm/transhuge.rst +++ b/Documentation/mm/transhuge.rst @@ -118,15 +118,14 @@ pages: succeeds on tail pages. - map/unmap of PMD entry for the whole compound page increment/decrement - ->compound_mapcount, stored in the first tail page of the compound page. + ->compound_mapcount, stored in the first tail page of the compound page; + and also increment/decrement ->subpages_mapcount (also in the first tail) + by COMPOUND_MAPPED when compound_mapcount goes from -1 to 0 or 0 to -1. - map/unmap of sub-pages with PTE entry increment/decrement ->_mapcount on relevant sub-page of the compound page, and also increment/decrement ->subpages_mapcount, stored in first tail page of the compound page, when _mapcount goes from -1 to 0 or 0 to -1: counting sub-pages mapped by PTE. - In order to have race-free accounting of sub-pages mapped, changes to - sub-page ->_mapcount, ->subpages_mapcount and ->compound_mapcount are - are all locked by bit_spin_lock of PG_locked in the first tail ->flags. split_huge_page internally has to distribute the refcounts in the head page to the tail pages before clearing all PG_head/tail bits from the page |