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authorVivek Kasireddy <vivek.kasireddy@intel.com>2024-06-24 08:36:09 +0200
committerAndrew Morton <akpm@linux-foundation.org>2024-07-13 00:52:09 +0200
commit6cc040542ba7b2c60e5119cd04d841fcf048c872 (patch)
treeeca76d8e135e644174758be21afff80b87b54e31 /mm/gup.c
parentmm/zswap: use only one pool in zswap (diff)
downloadlinux-6cc040542ba7b2c60e5119cd04d841fcf048c872.tar.xz
linux-6cc040542ba7b2c60e5119cd04d841fcf048c872.zip
mm/gup: introduce unpin_folio/unpin_folios helpers
Patch series "mm/gup: Introduce memfd_pin_folios() for pinning memfd folios", v16. Currently, some drivers (e.g, Udmabuf) that want to longterm-pin the pages/folios associated with a memfd, do so by simply taking a reference on them. This is not desirable because the pages/folios may reside in Movable zone or CMA block. Therefore, having drivers use memfd_pin_folios() API ensures that the folios are appropriately pinned via FOLL_PIN for longterm DMA. This patchset also introduces a few helpers and converts the Udmabuf driver to use folios and memfd_pin_folios() API to longterm-pin the folios for DMA. Two new Udmabuf selftests are also included to test the driver and the new API. This patch (of 9): 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. We should probably sanity check the folio as part of unpin similar to how it is done in unpin_user_page/unpin_user_pages but we cannot cleanly do that at the moment without also checking the subpage. Therefore, sanity checking needs to be added to these routines once we have a way to determine if any given folio is anon-exclusive (via a per folio AnonExclusive flag). Link: https://lkml.kernel.org/r/20240624063952.1572359-1-vivek.kasireddy@intel.com Link: https://lkml.kernel.org/r/20240624063952.1572359-2-vivek.kasireddy@intel.com Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com> Suggested-by: David Hildenbrand <david@redhat.com> Reviewed-by: David Hildenbrand <david@redhat.com> Acked-by: Dave Airlie <airlied@redhat.com> Acked-by: Gerd Hoffmann <kraxel@redhat.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Christoph Hellwig <hch@infradead.org> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Peter Xu <peterx@redhat.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Dongwon Kim <dongwon.kim@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Junxiao Chang <junxiao.chang@intel.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Christoph Hellwig <hch@lst.de> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Shuah Khan <shuah@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/gup.c')
-rw-r--r--mm/gup.c47
1 files changed, 47 insertions, 0 deletions
diff --git a/mm/gup.c b/mm/gup.c
index 2f46acefdee8..fd6a5b52a8f7 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -189,6 +189,19 @@ 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().
+ */
+void unpin_folio(struct folio *folio)
+{
+ gup_put_folio(folio, 1, FOLL_PIN);
+}
+EXPORT_SYMBOL_GPL(unpin_folio);
+
+/**
* folio_add_pin - Try to get an additional pin on a pinned folio
* @folio: The folio to be pinned
*
@@ -400,6 +413,40 @@ 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 gup_put_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;
+
+ 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_GPL(unpin_folios);
+
/*
* Set the MMF_HAS_PINNED if not set yet; after set it'll be there for the mm's
* lifecycle. Avoid setting the bit unless necessary, or it might cause write