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 <david@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx>
---
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 / dhildenb
