From 1101fb8f89e5fc548c4d0ad66750e98980291815 Mon Sep 17 00:00:00 2001 From: David Howells Date: Fri, 26 May 2023 22:41:41 +0100 Subject: [PATCH] mm: Provide a function to get an additional pin on a page Provide a function to get an additional pin on a page that we already have a pin on. This will be used in fs/direct-io.c when dispatching multiple bios to a page we've extracted from a user-backed iter rather than redoing the extraction. Signed-off-by: David Howells cc: Christoph Hellwig cc: David Hildenbrand cc: Lorenzo Stoakes cc: Andrew Morton cc: Jens Axboe cc: Al Viro cc: Matthew Wilcox cc: Jan Kara cc: Jeff Layton cc: Jason Gunthorpe cc: Logan Gunthorpe cc: Hillf Danton cc: Christian Brauner cc: Linus Torvalds cc: linux-fsdevel@vger.kernel.org cc: linux-block@vger.kernel.org cc: linux-kernel@vger.kernel.org cc: linux-mm@kvack.org Reviewed-by: Christoph Hellwig Acked-by: David Hildenbrand Link: https://lore.kernel.org/r/20230526214142.958751-3-dhowells@redhat.com Signed-off-by: Jens Axboe --- include/linux/mm.h | 1 + mm/gup.c | 27 +++++++++++++++++++++++++++ 2 files changed, 28 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index 3c2f6b4..200068d 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2405,6 +2405,7 @@ int get_user_pages_fast(unsigned long start, int nr_pages, unsigned int gup_flags, struct page **pages); int pin_user_pages_fast(unsigned long start, int nr_pages, unsigned int gup_flags, struct page **pages); +void folio_add_pin(struct folio *folio); int account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc); int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc, diff --git a/mm/gup.c b/mm/gup.c index ad28261d..0814576 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -275,6 +275,33 @@ void unpin_user_page(struct page *page) } EXPORT_SYMBOL(unpin_user_page); +/** + * folio_add_pin - Try to get an additional pin on a pinned folio + * @folio: The folio to be pinned + * + * Get an additional pin on a folio we already have a pin on. Makes no change + * if the folio is a zero_page. + */ +void folio_add_pin(struct folio *folio) +{ + if (is_zero_folio(folio)) + return; + + /* + * Similar to try_grab_folio(): be sure to *also* increment the normal + * page refcount field at least once, so that the page really is + * pinned. + */ + if (folio_test_large(folio)) { + WARN_ON_ONCE(atomic_read(&folio->_pincount) < 1); + folio_ref_inc(folio); + atomic_inc(&folio->_pincount); + } else { + WARN_ON_ONCE(folio_ref_count(folio) < GUP_PIN_COUNTING_BIAS); + folio_ref_add(folio, GUP_PIN_COUNTING_BIAS); + } +} + static inline struct folio *gup_folio_range_next(struct page *start, unsigned long npages, unsigned long i, unsigned int *ntails) { -- 2.7.4