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From: John Hubbard <jhubbard@nvidia.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>,
	dri-devel@lists.freedesktop.org, David Airlie <airlied@linux.ie>,
	John Hubbard <jhubbard@nvidia.com>,
	intel-gfx@lists.freedesktop.org,
	LKML <linux-kernel@vger.kernel.org>,
	Chris Wilson <chris@chris-wilson.co.uk>,
	linux-mm@kvack.org, Souptick Joarder <jrdr.linux@gmail.com>,
	Matthew Auld <matthew.auld@intel.com>
Subject: [Intel-gfx] [PATCH v2 3/4] mm/gup: introduce pin_user_pages_fast_only()
Date: Thu, 21 May 2020 22:19:30 -0700
Message-ID: <20200522051931.54191-4-jhubbard@nvidia.com> (raw)
In-Reply-To: <20200522051931.54191-1-jhubbard@nvidia.com>

This is the FOLL_PIN equivalent of __get_user_pages_fast(),
except with a more descriptive name, and gup_flags instead of
a boolean "write" in the argument list.

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 include/linux/mm.h |  2 ++
 mm/gup.c           | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 84b601cab699..98be7289d7e9 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1820,6 +1820,8 @@ extern int mprotect_fixup(struct vm_area_struct *vma,
  */
 int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
 			  struct page **pages);
+int pin_user_pages_fast_only(unsigned long start, int nr_pages,
+			     unsigned int gup_flags, struct page **pages);
 /*
  * per-process(per-mm_struct) statistics.
  */
diff --git a/mm/gup.c b/mm/gup.c
index 4564b0dc7d0b..6fa9b2016a53 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2859,6 +2859,42 @@ int pin_user_pages_fast(unsigned long start, int nr_pages,
 }
 EXPORT_SYMBOL_GPL(pin_user_pages_fast);
 
+/*
+ * This is the FOLL_PIN equivalent of __get_user_pages_fast(). Behavior is the
+ * same, except that this one sets FOLL_PIN instead of FOLL_GET.
+ *
+ * The API rules are the same, too: no negative values may be returned.
+ */
+int pin_user_pages_fast_only(unsigned long start, int nr_pages,
+			     unsigned int gup_flags, struct page **pages)
+{
+	int nr_pinned;
+
+	/*
+	 * FOLL_GET and FOLL_PIN are mutually exclusive. Note that the API
+	 * rules require returning 0, rather than -errno:
+	 */
+	if (WARN_ON_ONCE(gup_flags & FOLL_GET))
+		return 0;
+	/*
+	 * FOLL_FAST_ONLY is required in order to match the API description of
+	 * this routine: no fall back to regular ("slow") GUP.
+	 */
+	gup_flags |= (FOLL_PIN | FOLL_FAST_ONLY);
+	nr_pinned = internal_get_user_pages_fast(start, nr_pages, gup_flags,
+						 pages);
+	/*
+	 * This routine is not allowed to return negative values. However,
+	 * internal_get_user_pages_fast() *can* return -errno. Therefore,
+	 * correct for that here:
+	 */
+	if (nr_pinned < 0)
+		nr_pinned = 0;
+
+	return nr_pinned;
+}
+EXPORT_SYMBOL_GPL(pin_user_pages_fast_only);
+
 /**
  * pin_user_pages_remote() - pin pages of a remote process (task != current)
  *
-- 
2.26.2

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  parent reply index

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-22  5:19 [Intel-gfx] [PATCH v2 0/4] mm/gup, drm/i915: refactor gup_fast, convert to pin_user_pages() John Hubbard
2020-05-22  5:19 ` [Intel-gfx] [PATCH v2 1/4] mm/gup: move __get_user_pages_fast() down a few lines in gup.c John Hubbard
2020-05-22  5:19 ` [Intel-gfx] [PATCH v2 2/4] mm/gup: refactor and de-duplicate gup_fast() code John Hubbard
2020-05-22  5:19 ` John Hubbard [this message]
2020-05-22  5:19 ` [Intel-gfx] [PATCH v2 4/4] drm/i915: convert get_user_pages() --> pin_user_pages() John Hubbard
2020-05-23  9:41 ` [Intel-gfx] [PATCH v2 0/4] mm/gup, drm/i915: refactor gup_fast, convert to pin_user_pages() Chris Wilson
2020-05-23 22:33   ` John Hubbard
2020-05-23 18:35 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for " Patchwork
2020-05-23 18:37 ` [Intel-gfx] ✗ Fi.CI.SPARSE: " Patchwork
2020-05-23 20:34 ` [Intel-gfx] ✓ Fi.CI.BAT: success " Patchwork
2020-05-23 21:35 ` [Intel-gfx] ✗ Fi.CI.IGT: failure " Patchwork

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