linux-kernel - [PATCH 1/3] mm/vmalloc: add vfree

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Date:   Tue, 8 Nov 2016 18:05:43 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Christoph Hellwig <hch@....de>
CC:     Andrew Morton <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
        <linux-rt-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        "Andrey Ryabinin" <aryabinin@...tuozzo.com>,
        Andy Lutomirski <luto@...nel.org>,
        "Joel Fernandes" <joelaf@...gle.com>,
        Jisheng Zhang <jszhang@...vell.com>,
        "Chris Wilson" <chris@...is-wilson.co.uk>,
        John Dias <joaodias@...gle.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, <x86@...nel.org>
Subject: [PATCH 1/3] mm/vmalloc: add vfree_atomic()

We are going to use sleeping lock for freeing vmap. However some
vfree() users want to free memory from atomic (but not from interrupt)
context. For this we add vfree_atomic() - deferred variation of vfree()
which can be used in any atomic context (except NMIs).

Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Joel Fernandes <joelaf@...gle.com>
Cc: Christoph Hellwig <hch@....de>
Cc: Jisheng Zhang <jszhang@...vell.com>
Cc: Chris Wilson <chris@...is-wilson.co.uk>
Cc: John Dias <joaodias@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: x86@...nel.org
---
 include/linux/vmalloc.h |  1 +
 mm/vmalloc.c            | 36 ++++++++++++++++++++++++++++++------
 2 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 3d9d786..d68edff 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -82,6 +82,7 @@ extern void *__vmalloc_node_range(unsigned long size, unsigned long align,
 			const void *caller);
 
 extern void vfree(const void *addr);
+extern void vfree_atomic(const void *addr);
 
 extern void *vmap(struct page **pages, unsigned int count,
 			unsigned long flags, pgprot_t prot);
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 719ced3..b0edc67 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1471,7 +1471,33 @@ static void __vunmap(const void *addr, int deallocate_pages)
 	kfree(area);
 	return;
 }
- 
+
+static inline void __vfree_deferred(const void *addr)
+{
+	struct vfree_deferred *p = this_cpu_ptr(&vfree_deferred);
+
+	if (llist_add((struct llist_node *)addr, &p->list))
+		schedule_work(&p->wq);
+}
+
+/**
+ *	vfree_atomic  -  release memory allocated by vmalloc()
+ *	@addr:		memory base address
+ *
+ *	This one is just like vfree() but can be called in any atomic context
+ *	except NMIs.
+ */
+void vfree_atomic(const void *addr)
+{
+	BUG_ON(in_nmi());
+
+	kmemleak_free(addr);
+
+	if (!addr)
+		return;
+	__vfree_deferred(addr);
+}
+
 /**
  *	vfree  -  release memory allocated by vmalloc()
  *	@addr:		memory base address
@@ -1494,11 +1520,9 @@ void vfree(const void *addr)
 
 	if (!addr)
 		return;
-	if (unlikely(in_interrupt())) {
-		struct vfree_deferred *p = this_cpu_ptr(&vfree_deferred);
-		if (llist_add((struct llist_node *)addr, &p->list))
-			schedule_work(&p->wq);
-	} else
+	if (unlikely(in_interrupt()))
+		__vfree_deferred(addr);
+	else
 		__vunmap(addr, 1);
 }
 EXPORT_SYMBOL(vfree);
-- 
2.7.3