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Diffstat (limited to 'Documentation/mm/transhuge.rst')
| -rw-r--r-- | Documentation/mm/transhuge.rst | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/Documentation/mm/transhuge.rst b/Documentation/mm/transhuge.rst index 1e2a637cc607..af4c9d70321d 100644 --- a/Documentation/mm/transhuge.rst +++ b/Documentation/mm/transhuge.rst @@ -122,7 +122,8 @@ pages: - 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. + ->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. |