Re: [PATCH v12 1/8] mm/gup: Introduce unpin_folio/unpin_folios helpers
On 02.04.24 15:52, David Hildenbrand wrote: On 25.02.24 08:56, Vivek Kasireddy wrote: These helpers are the folio versions of unpin_user_page/unpin_user_pages. They are currently only useful for unpinning folios pinned by memfd_pin_folios() or other associated routines. However, they could find new uses in the future, when more and more folio-only helpers are added to GUP. Cc: David Hildenbrand Cc: Matthew Wilcox Cc: Christoph Hellwig Cc: Jason Gunthorpe Cc: Peter Xu Suggested-by: David Hildenbrand Signed-off-by: Vivek Kasireddy --- include/linux/mm.h | 2 ++ mm/gup.c | 81 -- 2 files changed, 74 insertions(+), 9 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 6f4825d82965..36e4c2b22600 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1601,11 +1601,13 @@ static inline void put_page(struct page *page) #define GUP_PIN_COUNTING_BIAS (1U << 10) void unpin_user_page(struct page *page); +void unpin_folio(struct folio *folio); void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages, bool make_dirty); void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages, bool make_dirty); void unpin_user_pages(struct page **pages, unsigned long npages); +void unpin_folios(struct folio **folios, unsigned long nfolios); static inline bool is_cow_mapping(vm_flags_t flags) { diff --git a/mm/gup.c b/mm/gup.c index df83182ec72d..0a45eda6aaeb 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -30,6 +30,23 @@ struct follow_page_context { unsigned int page_mask; }; +static inline void sanity_check_pinned_folios(struct folio **folios, + unsigned long nfolios) +{ + if (!IS_ENABLED(CONFIG_DEBUG_VM)) + return; + + for (; nfolios; nfolios--, folios++) { + struct folio *folio = *folios; + + if (is_zero_folio(folio) || + !folio_test_anon(folio)) + continue; + + VM_BUG_ON_FOLIO(!PageAnonExclusive(&folio->page), folio); That change is wrong (and the split makes the check confusing). It could be that the first subpage is no longer exclusive, but the given (sanity_check_pinned_pages() ) subpage is exclusive for large folios. I suggest dropping that change, and instead, in unpin_folio()/unpin_folios(), reject any anon folios for now. So, replace the sanity_check_pinned_folios() in unpin_folio() / unpin_folios() by a VM_WARN_ON(folio_test_anon(folio)); After reading patch #2: drop both the sanity check and VM_WARN_ON() from unpin_folio()/unpin_folios(), and add a comment to the patch description that we cannot do the sanity checking without the subpage, and that we can reintroduce it once we have a single per-folio AnonExclusive bit. -- Cheers, David / dhildenb
Re: [PATCH v12 1/8] mm/gup: Introduce unpin_folio/unpin_folios helpers
On 25.02.24 08:56, Vivek Kasireddy wrote: These helpers are the folio versions of unpin_user_page/unpin_user_pages. They are currently only useful for unpinning folios pinned by memfd_pin_folios() or other associated routines. However, they could find new uses in the future, when more and more folio-only helpers are added to GUP. Cc: David Hildenbrand Cc: Matthew Wilcox Cc: Christoph Hellwig Cc: Jason Gunthorpe Cc: Peter Xu Suggested-by: David Hildenbrand Signed-off-by: Vivek Kasireddy --- include/linux/mm.h | 2 ++ mm/gup.c | 81 -- 2 files changed, 74 insertions(+), 9 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 6f4825d82965..36e4c2b22600 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1601,11 +1601,13 @@ static inline void put_page(struct page *page) #define GUP_PIN_COUNTING_BIAS (1U << 10) void unpin_user_page(struct page *page); +void unpin_folio(struct folio *folio); void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages, bool make_dirty); void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages, bool make_dirty); void unpin_user_pages(struct page **pages, unsigned long npages); +void unpin_folios(struct folio **folios, unsigned long nfolios); static inline bool is_cow_mapping(vm_flags_t flags) { diff --git a/mm/gup.c b/mm/gup.c index df83182ec72d..0a45eda6aaeb 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -30,6 +30,23 @@ struct follow_page_context { unsigned int page_mask; }; +static inline void sanity_check_pinned_folios(struct folio **folios, + unsigned long nfolios) +{ + if (!IS_ENABLED(CONFIG_DEBUG_VM)) + return; + + for (; nfolios; nfolios--, folios++) { + struct folio *folio = *folios; + + if (is_zero_folio(folio) || + !folio_test_anon(folio)) + continue; + + VM_BUG_ON_FOLIO(!PageAnonExclusive(&folio->page), folio); That change is wrong (and the split makes the check confusing). It could be that the first subpage is no longer exclusive, but the given (sanity_check_pinned_pages() ) subpage is exclusive for large folios. I suggest dropping that change, and instead, in unpin_folio()/unpin_folios(), reject any anon folios for now. So, replace the sanity_check_pinned_folios() in unpin_folio() / unpin_folios() by a VM_WARN_ON(folio_test_anon(folio)); It will all be better once we have a single anon-exclusive flag per folio (which I am working on), but in the meantime, we really don't expect code that called pin_user_pages() to call unpin_folios(). [...] +/** + * unpin_folio() - release a dma-pinned folio + * @folio: pointer to folio to be released + * + * Folios that were pinned via memfd_pin_folios() or other similar routines + * must be released either using unpin_folio() or unpin_folios(). This is so + * that such folios can be separately tracked and uniquely handled. I'd drop the last sentence; no need for apologies/explanations, this is simply how ;pinning works :) + */ +void unpin_folio(struct folio *folio) +{ + sanity_check_pinned_folios(&folio, 1); + gup_put_folio(folio, 1, FOLL_PIN); +} +EXPORT_SYMBOL(unpin_folio); Can we restrict that to EXPORT_SYMBOL_GPL for now? memfd_pin_folios() uses EXPORT_SYMBOL_GPL... + /** * folio_add_pin - Try to get an additional pin on a pinned folio * @folio: The folio to be pinned @@ -488,6 +516,41 @@ void unpin_user_pages(struct page **pages, unsigned long npages) } EXPORT_SYMBOL(unpin_user_pages); +/** + * unpin_folios() - release an array of gup-pinned folios. + * @folios: array of folios to be marked dirty and released. + * @nfolios: number of folios in the @folios array. + * + * For each folio in the @folios array, release the folio using unpin_folio(). + * + * Please see the unpin_folio() documentation for details. + */ +void unpin_folios(struct folio **folios, unsigned long nfolios) +{ + unsigned long i = 0, j; + + /* +* If this WARN_ON() fires, then the system *might* be leaking folios +* (by leaving them pinned), but probably not. More likely, gup/pup +* returned a hard -ERRNO error to the caller, who erroneously passed +* it here. +*/ + if (WARN_ON(IS_ERR_VALUE(nfolios))) + return; + + sanity_check_pinned_folios(folios, nfolios); + while (i < nfolios) { + for (j = i + 1; j < nfolios; j++) + if (folios[i] != folios[j]) + break; + + if (folios[i]) + gup_put_folio(folios[i], j - i, FOLL_PIN); + i = j; + } +} +EXPORT_SYMBOL(unpin_folios); Same thought here. -- Cheers, David / dhilde
[PATCH v12 1/8] mm/gup: Introduce unpin_folio/unpin_folios helpers
These helpers are the folio versions of unpin_user_page/unpin_user_pages. They are currently only useful for unpinning folios pinned by memfd_pin_folios() or other associated routines. However, they could find new uses in the future, when more and more folio-only helpers are added to GUP. Cc: David Hildenbrand Cc: Matthew Wilcox Cc: Christoph Hellwig Cc: Jason Gunthorpe Cc: Peter Xu Suggested-by: David Hildenbrand Signed-off-by: Vivek Kasireddy --- include/linux/mm.h | 2 ++ mm/gup.c | 81 -- 2 files changed, 74 insertions(+), 9 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 6f4825d82965..36e4c2b22600 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1601,11 +1601,13 @@ static inline void put_page(struct page *page) #define GUP_PIN_COUNTING_BIAS (1U << 10) void unpin_user_page(struct page *page); +void unpin_folio(struct folio *folio); void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages, bool make_dirty); void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages, bool make_dirty); void unpin_user_pages(struct page **pages, unsigned long npages); +void unpin_folios(struct folio **folios, unsigned long nfolios); static inline bool is_cow_mapping(vm_flags_t flags) { diff --git a/mm/gup.c b/mm/gup.c index df83182ec72d..0a45eda6aaeb 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -30,6 +30,23 @@ struct follow_page_context { unsigned int page_mask; }; +static inline void sanity_check_pinned_folios(struct folio **folios, + unsigned long nfolios) +{ + if (!IS_ENABLED(CONFIG_DEBUG_VM)) + return; + + for (; nfolios; nfolios--, folios++) { + struct folio *folio = *folios; + + if (is_zero_folio(folio) || + !folio_test_anon(folio)) + continue; + + VM_BUG_ON_FOLIO(!PageAnonExclusive(&folio->page), folio); + } +} + static inline void sanity_check_pinned_pages(struct page **pages, unsigned long npages) { @@ -52,15 +69,11 @@ static inline void sanity_check_pinned_pages(struct page **pages, struct page *page = *pages; struct folio *folio = page_folio(page); - if (is_zero_page(page) || - !folio_test_anon(folio)) - continue; - if (!folio_test_large(folio) || folio_test_hugetlb(folio)) - VM_BUG_ON_PAGE(!PageAnonExclusive(&folio->page), page); - else - /* Either a PTE-mapped or a PMD-mapped THP. */ - VM_BUG_ON_PAGE(!PageAnonExclusive(&folio->page) && - !PageAnonExclusive(page), page); + sanity_check_pinned_folios(&folio, 1); + + /* Either a PTE-mapped or a PMD-mapped THP. */ + if (folio_test_large(folio) && !folio_test_hugetlb(folio)) + VM_BUG_ON_PAGE(!PageAnonExclusive(page), page); } } @@ -276,6 +289,21 @@ void unpin_user_page(struct page *page) } EXPORT_SYMBOL(unpin_user_page); +/** + * unpin_folio() - release a dma-pinned folio + * @folio: pointer to folio to be released + * + * Folios that were pinned via memfd_pin_folios() or other similar routines + * must be released either using unpin_folio() or unpin_folios(). This is so + * that such folios can be separately tracked and uniquely handled. + */ +void unpin_folio(struct folio *folio) +{ + sanity_check_pinned_folios(&folio, 1); + gup_put_folio(folio, 1, FOLL_PIN); +} +EXPORT_SYMBOL(unpin_folio); + /** * folio_add_pin - Try to get an additional pin on a pinned folio * @folio: The folio to be pinned @@ -488,6 +516,41 @@ void unpin_user_pages(struct page **pages, unsigned long npages) } EXPORT_SYMBOL(unpin_user_pages); +/** + * unpin_folios() - release an array of gup-pinned folios. + * @folios: array of folios to be marked dirty and released. + * @nfolios: number of folios in the @folios array. + * + * For each folio in the @folios array, release the folio using unpin_folio(). + * + * Please see the unpin_folio() documentation for details. + */ +void unpin_folios(struct folio **folios, unsigned long nfolios) +{ + unsigned long i = 0, j; + + /* +* If this WARN_ON() fires, then the system *might* be leaking folios +* (by leaving them pinned), but probably not. More likely, gup/pup +* returned a hard -ERRNO error to the caller, who erroneously passed +* it here. +*/ + if (WARN_ON(IS_ERR_VALUE(nfolios))) + return; + + sanity_check_pinned_folios(folios, nfolios); + while (i < nfolios) { + for (j = i + 1; j < nfolios; j++) +