mm: extend rmap flags arguments for folio_add_new_anon_rmap

Patch series "mm: clarify folio_add_new_anon_rmap() and
__folio_add_anon_rmap()", v2.

This patchset is preparatory work for mTHP swapin.

folio_add_new_anon_rmap() assumes that new anon rmaps are always
exclusive.  However, this assumption doesn’t hold true for cases like
do_swap_page(), where a new anon might be added to the swapcache and is
not necessarily exclusive.

The patchset extends the rmap flags to allow folio_add_new_anon_rmap() to
handle both exclusive and non-exclusive new anon folios.  The
do_swap_page() function is updated to use this extended API with rmap
flags.  Consequently, all new anon folios now consistently use
folio_add_new_anon_rmap().  The special case for !folio_test_anon() in
__folio_add_anon_rmap() can be safely removed.

In conclusion, new anon folios always use folio_add_new_anon_rmap(),
regardless of exclusivity.  Old anon folios continue to use
__folio_add_anon_rmap() via folio_add_anon_rmap_pmd() and
folio_add_anon_rmap_ptes().


This patch (of 3):

In the case of a swap-in, a new anonymous folio is not necessarily
exclusive.  This patch updates the rmap flags to allow a new anonymous
folio to be treated as either exclusive or non-exclusive.  To maintain the
existing behavior, we always use EXCLUSIVE as the default setting.

[[email protected]: cleanup and constifications per David and akpm]
[[email protected]: fix missing doc for flags of folio_add_new_anon_rmap()]
  Link: https://lkml.kernel.org/r/[email protected]
[[email protected]: enhance doc for extend rmap flags arguments for folio_add_new_anon_rmap]
  Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Barry Song <[email protected]>
Suggested-by: David Hildenbrand <[email protected]>
Tested-by: Shuai Yuan <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Cc: Baolin Wang <[email protected]>
Cc: Chris Li <[email protected]>
Cc: "Huang, Ying" <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Ryan Roberts <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Yang Shi <[email protected]>
Cc: Yosry Ahmed <[email protected]>
Cc: Yu Zhao <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions