linux-kernel - [PATCH 10/11] x86/xen: open code alloc_vm_area in arch_gnttab

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Date:   Thu, 24 Sep 2020 15:58:52 +0200
From:   Christoph Hellwig <hch@....de>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Matthew Auld <matthew.auld@...el.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Minchan Kim <minchan@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Nitin Gupta <ngupta@...are.org>, x86@...nel.org,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-mm@...ck.org
Subject: [PATCH 10/11] x86/xen: open code alloc_vm_area in arch_gnttab_valloc

Replace the last call to alloc_vm_area with an open coded version using
an iterator in struct gnttab_vm_area instead of the triple indirection
magic in alloc_vm_area.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 arch/x86/xen/grant-table.c | 27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/arch/x86/xen/grant-table.c b/arch/x86/xen/grant-table.c
index 4988e19598c8a5..1e681bf62561a0 100644
--- a/arch/x86/xen/grant-table.c
+++ b/arch/x86/xen/grant-table.c
@@ -25,6 +25,7 @@
 static struct gnttab_vm_area {
 	struct vm_struct *area;
 	pte_t **ptes;
+	int idx;
 } gnttab_shared_vm_area, gnttab_status_vm_area;
 
 int arch_gnttab_map_shared(unsigned long *frames, unsigned long nr_gframes,
@@ -90,19 +91,31 @@ void arch_gnttab_unmap(void *shared, unsigned long nr_gframes)
 	}
 }
 
+static int gnttab_apply(pte_t *pte, unsigned long addr, void *data)
+{
+	struct gnttab_vm_area *area = data;
+
+	area->ptes[area->idx++] = pte;
+	return 0;
+}
+
 static int arch_gnttab_valloc(struct gnttab_vm_area *area, unsigned nr_frames)
 {
 	area->ptes = kmalloc_array(nr_frames, sizeof(*area->ptes), GFP_KERNEL);
 	if (area->ptes == NULL)
 		return -ENOMEM;
-
-	area->area = alloc_vm_area(PAGE_SIZE * nr_frames, area->ptes);
-	if (area->area == NULL) {
-		kfree(area->ptes);
-		return -ENOMEM;
-	}
-
+	area->area = get_vm_area(PAGE_SIZE * nr_frames, VM_IOREMAP);
+	if (!area->area)
+		goto out_free_ptes;
+	if (apply_to_page_range(&init_mm, (unsigned long)area->area->addr,
+			PAGE_SIZE * nr_frames, gnttab_apply, area))
+		goto out_free_vm_area;
 	return 0;
+out_free_vm_area:
+	free_vm_area(area->area);
+out_free_ptes:
+	kfree(area->ptes);
+	return -ENOMEM;
 }
 
 static void arch_gnttab_vfree(struct gnttab_vm_area *area)
-- 
2.28.0