On 12/26/22 09:44, Lorenzo Stoakes wrote:
> We now pass folios to these functions, so update the documentation
> accordingly.
>
> Additionally, correct the outdated reference to __pagevec_lru_add_fn(), the
> referenced action occurs in __munlock_folio() directly now.
>
> Signed-off-by: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
With:
> ---
> Documentation/mm/unevictable-lru.rst | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/mm/unevictable-lru.rst b/Documentation/mm/unevictable-lru.rst
> index 4a0e158aa9ce..153629e0c100 100644
> --- a/Documentation/mm/unevictable-lru.rst
> +++ b/Documentation/mm/unevictable-lru.rst
> @@ -308,22 +308,22 @@ do end up getting faulted into this VM_LOCKED VMA, they will be handled in the
> fault path - which is also how mlock2()'s MLOCK_ONFAULT areas are handled.
>
> For each PTE (or PMD) being faulted into a VMA, the page add rmap function
> -calls mlock_vma_page(), which calls mlock_page() when the VMA is VM_LOCKED
> +calls mlock_vma_page(), which calls mlock_folio() when the VMA is VM_LOCKED
> (unless it is a PTE mapping of a part of a transparent huge page). Or when
> it is a newly allocated anonymous page, lru_cache_add_inactive_or_unevictable()
Think it would be more appropriate now: ^ folio_add_lru_vma()
> -calls mlock_new_page() instead: similar to mlock_page(), but can make better
> +calls mlock_new_folio() instead: similar to mlock_folio(), but can make better
> judgments, since this page is held exclusively and known not to be on LRU yet.
>
> -mlock_page() sets PageMlocked immediately, then places the page on the CPU's
PG_mlocked?
> -mlock pagevec, to batch up the rest of the work to be done under lru_lock by
> -__mlock_page(). __mlock_page() sets PageUnevictable, initializes mlock_count
PG_unevictable
ditto below
> +mlock_folio() sets PageMlocked immediately, then places the page on the CPU's
> +mlock folio batch, to batch up the rest of the work to be done under lru_lock by
> +__mlock_folio(). __mlock_folio() sets PageUnevictable, initializes mlock_count
> and moves the page to unevictable state ("the unevictable LRU", but with
> mlock_count in place of LRU threading). Or if the page was already PageLRU
> and PageUnevictable and PageMlocked, it simply increments the mlock_count.
>
> But in practice that may not work ideally: the page may not yet be on an LRU, or
> it may have been temporarily isolated from LRU. In such cases the mlock_count
> -field cannot be touched, but will be set to 0 later when __pagevec_lru_add_fn()
> +field cannot be touched, but will be set to 0 later when __munlock_folio()
> returns the page to "LRU". Races prohibit mlock_count from being set to 1 then:
> rather than risk stranding a page indefinitely as unevictable, always err with
> mlock_count on the low side, so that when munlocked the page will be rescued to
