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mm: add largest_zero_folio() routine

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The callers of mm_get_huge_zero_folio() have access to a mm struct and the
lifetime of the huge_zero_folio is tied to the lifetime of the mm struct.

largest_zero_folio() will give access to huge_zero_folio when
PERSISTENT_HUGE_ZERO_FOLIO config option is enabled for callers that do
not want to tie the lifetime to a mm struct.  This is very useful for
filesystem and block layers where the request completions can be async and
there is no guarantee on the mm struct lifetime.

This function will return a ZERO_PAGE folio if PERSISTENT_HUGE_ZERO_FOLIO
is disabled or if we failed to allocate a huge_zero_folio during early
init.

Link: https://lkml.kernel.org/r/20250811084113.647267-5-kernel@pankajraghav.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Co-developed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: "Darrick J. Wong" <djwong@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Luis Chamberalin <mcgrof@kernel.org>
Cc: Mariano Pache <npache@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Kiryl Shutsemau <kirill@shutemov.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Pankaj Raghav
2025-08-11 10:41:12 +02:00
committed by Andrew Morton
parent 2d8bd8049e
commit 415a0fd62f
1 changed files with 22 additions and 0 deletions
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22
include/linux/huge_mm.h
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@@ -714,4 +714,26 @@ static inline int split_folio_to_order(struct folio *folio, int new_order)
return split_folio_to_list_to_order(folio, NULL, new_order);
}
/**
* largest_zero_folio - Get the largest zero size folio available
*
* This function shall be used when mm_get_huge_zero_folio() cannot be
* used as there is no appropriate mm lifetime to tie the huge zero folio
* from the caller.
*
* Deduce the size of the folio with folio_size instead of assuming the
* folio size.
*
* Return: pointer to PMD sized zero folio if CONFIG_PERSISTENT_HUGE_ZERO_FOLIO
* is enabled or a single page sized zero folio
*/
static inline struct folio *largest_zero_folio(void)
{
struct folio *folio = get_persistent_huge_zero_folio();
if (folio)
return folio;
return page_folio(ZERO_PAGE(0));
}
#endif /* _LINUX_HUGE_MM_H */