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doc: mm: migration doesn't use FOLL_SPLIT anymore 

When demonstrating FOLL_SPLIT in transhuge document, migration is used
as an example.  But, since commit 94723aafb9 ("mm: unclutter THP
migration"), the way of THP migration is totally changed.  FOLL_SPLIT is
not used by migration anymore due to the change.

Remove the obsolete example to avoid confusion.

Cc: Michal Hocko <mhocko@suse.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
hifive-unleashed-5.2
Yang Shi 2019-04-19 04:17:04 +08:00 committed by Jonathan Corbet
parent d8e8bcc3d8
commit a496696ab5
1 changed files with 1 additions and 7 deletions
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8
Documentation/vm/transhuge.rst
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@ -55,13 +55,7 @@ prevent page from being split by anyone.
In case you can't handle compound pages if they're returned by
follow_page, the FOLL_SPLIT bit can be specified as parameter to
follow_page, so that it will split the hugepages before returning
them. Migration for example passes FOLL_SPLIT as parameter to
follow_page because it's not hugepage aware and in fact it can't work
at all on hugetlbfs (but it instead works fine on transparent
hugepages thanks to FOLL_SPLIT). migration simply can't deal with
hugepages being returned (as it's not only checking the pfn of the
page and pinning it during the copy but it pretends to migrate the
memory in regular page sizes and with regular pte/pmd mappings).
them.
Graceful fallback
=================