The patch titled
Subject: mm-gup-introduce-memfd_pin_folios-for-pinning-memfd-folios-fix-fix
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-gup-stop-abusing-try_grab_folio-fix.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-gup-stop-abusing-try_grab_folio-fix.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Yang Shi <shy828301@xxxxxxxxx>
Subject: mm-gup-introduce-memfd_pin_folios-for-pinning-memfd-folios-fix-fix
Date: Fri, 28 Jun 2024 18:58:14 -0700
fix implicit declaration of function try_grab_folio_fast
Link: https://lkml.kernel.org/r/CAHbLzkowMSso-4Nufc9hcMehQsK9PNz3OSu-+eniU-2Mm-xjhA@xxxxxxxxxxxxxx
Signed-off-by: Yang Shi <shy828301@xxxxxxxxx>
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-kbuild-all/202406290729.21FzkVlI-lkp@xxxxxxxxx/
Cc: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx> (v6)
Cc: Dave Airlie <airlied@xxxxxxxxxx>
Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/gup.c | 192 ++++++++++++++++++++++++++---------------------------
1 file changed, 96 insertions(+), 96 deletions(-)
--- a/mm/gup.c~mm-gup-stop-abusing-try_grab_folio-fix
+++ a/mm/gup.c
@@ -427,6 +427,102 @@ static int record_subpages(struct page *
return nr;
}
+
+/**
+ * try_grab_folio_fast() - Attempt to get or pin a folio in fast path.
+ * @page: pointer to page to be grabbed
+ * @refs: the value to (effectively) add to the folio's refcount
+ * @flags: gup flags: these are the FOLL_* flag values.
+ *
+ * "grab" names in this file mean, "look at flags to decide whether to use
+ * FOLL_PIN or FOLL_GET behavior, when incrementing the folio's refcount.
+ *
+ * Either FOLL_PIN or FOLL_GET (or neither) must be set, but not both at the
+ * same time. (That's true throughout the get_user_pages*() and
+ * pin_user_pages*() APIs.) Cases:
+ *
+ * FOLL_GET: folio's refcount will be incremented by @refs.
+ *
+ * FOLL_PIN on large folios: folio's refcount will be incremented by
+ * @refs, and its pincount will be incremented by @refs.
+ *
+ * FOLL_PIN on single-page folios: folio's refcount will be incremented by
+ * @refs * GUP_PIN_COUNTING_BIAS.
+ *
+ * Return: The folio containing @page (with refcount appropriately
+ * incremented) for success, or NULL upon failure. If neither FOLL_GET
+ * nor FOLL_PIN was set, that's considered failure, and furthermore,
+ * a likely bug in the caller, so a warning is also emitted.
+ *
+ * It uses add ref unless zero to elevate the folio refcount and must be called
+ * in fast path only.
+ */
+static struct folio *try_grab_folio_fast(struct page *page, int refs,
+ unsigned int flags)
+{
+ struct folio *folio;
+
+ /* Raise warn if it is not called in fast GUP */
+ VM_WARN_ON_ONCE(!irqs_disabled());
+
+ if (WARN_ON_ONCE((flags & (FOLL_GET | FOLL_PIN)) == 0))
+ return NULL;
+
+ if (unlikely(!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page)))
+ return NULL;
+
+ if (flags & FOLL_GET)
+ return try_get_folio(page, refs);
+
+ /* FOLL_PIN is set */
+
+ /*
+ * Don't take a pin on the zero page - it's not going anywhere
+ * and it is used in a *lot* of places.
+ */
+ if (is_zero_page(page))
+ return page_folio(page);
+
+ folio = try_get_folio(page, refs);
+ if (!folio)
+ return NULL;
+
+ /*
+ * Can't do FOLL_LONGTERM + FOLL_PIN gup fast path if not in a
+ * right zone, so fail and let the caller fall back to the slow
+ * path.
+ */
+ if (unlikely((flags & FOLL_LONGTERM) &&
+ !folio_is_longterm_pinnable(folio))) {
+ if (!put_devmap_managed_folio_refs(folio, refs))
+ folio_put_refs(folio, refs);
+ return NULL;
+ }
+
+ /*
+ * When pinning a large folio, use an exact count to track it.
+ *
+ * However, be sure to *also* increment the normal folio
+ * refcount field at least once, so that the folio really
+ * is pinned. That's why the refcount from the earlier
+ * try_get_folio() is left intact.
+ */
+ if (folio_test_large(folio))
+ atomic_add(refs, &folio->_pincount);
+ else
+ folio_ref_add(folio,
+ refs * (GUP_PIN_COUNTING_BIAS - 1));
+ /*
+ * Adjust the pincount before re-checking the PTE for changes.
+ * This is essentially a smp_mb() and is paired with a memory
+ * barrier in folio_try_share_anon_rmap_*().
+ */
+ smp_mb__after_atomic();
+
+ node_stat_mod_folio(folio, NR_FOLL_PIN_ACQUIRED, refs);
+
+ return folio;
+}
#endif /* CONFIG_ARCH_HAS_HUGEPD || CONFIG_HAVE_GUP_FAST */
#ifdef CONFIG_ARCH_HAS_HUGEPD
@@ -2715,102 +2811,6 @@ EXPORT_SYMBOL(get_user_pages_unlocked);
* This code is based heavily on the PowerPC implementation by Nick Piggin.
*/
#ifdef CONFIG_HAVE_GUP_FAST
-/**
- * try_grab_folio_fast() - Attempt to get or pin a folio in fast path.
- * @page: pointer to page to be grabbed
- * @refs: the value to (effectively) add to the folio's refcount
- * @flags: gup flags: these are the FOLL_* flag values.
- *
- * "grab" names in this file mean, "look at flags to decide whether to use
- * FOLL_PIN or FOLL_GET behavior, when incrementing the folio's refcount.
- *
- * Either FOLL_PIN or FOLL_GET (or neither) must be set, but not both at the
- * same time. (That's true throughout the get_user_pages*() and
- * pin_user_pages*() APIs.) Cases:
- *
- * FOLL_GET: folio's refcount will be incremented by @refs.
- *
- * FOLL_PIN on large folios: folio's refcount will be incremented by
- * @refs, and its pincount will be incremented by @refs.
- *
- * FOLL_PIN on single-page folios: folio's refcount will be incremented by
- * @refs * GUP_PIN_COUNTING_BIAS.
- *
- * Return: The folio containing @page (with refcount appropriately
- * incremented) for success, or NULL upon failure. If neither FOLL_GET
- * nor FOLL_PIN was set, that's considered failure, and furthermore,
- * a likely bug in the caller, so a warning is also emitted.
- *
- * It uses add ref unless zero to elevate the folio refcount and must be called
- * in fast path only.
- */
-static struct folio *try_grab_folio_fast(struct page *page, int refs,
- unsigned int flags)
-{
- struct folio *folio;
-
- /* Raise warn if it is not called in fast GUP */
- VM_WARN_ON_ONCE(!irqs_disabled());
-
- if (WARN_ON_ONCE((flags & (FOLL_GET | FOLL_PIN)) == 0))
- return NULL;
-
- if (unlikely(!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page)))
- return NULL;
-
- if (flags & FOLL_GET)
- return try_get_folio(page, refs);
-
- /* FOLL_PIN is set */
-
- /*
- * Don't take a pin on the zero page - it's not going anywhere
- * and it is used in a *lot* of places.
- */
- if (is_zero_page(page))
- return page_folio(page);
-
- folio = try_get_folio(page, refs);
- if (!folio)
- return NULL;
-
- /*
- * Can't do FOLL_LONGTERM + FOLL_PIN gup fast path if not in a
- * right zone, so fail and let the caller fall back to the slow
- * path.
- */
- if (unlikely((flags & FOLL_LONGTERM) &&
- !folio_is_longterm_pinnable(folio))) {
- if (!put_devmap_managed_folio_refs(folio, refs))
- folio_put_refs(folio, refs);
- return NULL;
- }
-
- /*
- * When pinning a large folio, use an exact count to track it.
- *
- * However, be sure to *also* increment the normal folio
- * refcount field at least once, so that the folio really
- * is pinned. That's why the refcount from the earlier
- * try_get_folio() is left intact.
- */
- if (folio_test_large(folio))
- atomic_add(refs, &folio->_pincount);
- else
- folio_ref_add(folio,
- refs * (GUP_PIN_COUNTING_BIAS - 1));
- /*
- * Adjust the pincount before re-checking the PTE for changes.
- * This is essentially a smp_mb() and is paired with a memory
- * barrier in folio_try_share_anon_rmap_*().
- */
- smp_mb__after_atomic();
-
- node_stat_mod_folio(folio, NR_FOLL_PIN_ACQUIRED, refs);
-
- return folio;
-}
-
/*
* Used in the GUP-fast path to determine whether GUP is permitted to work on
* a specific folio.
_
Patches currently in -mm which might be from shy828301@xxxxxxxxx are
mm-gup-stop-abusing-try_grab_folio-fix.patch
