linux-kernel - [PATCH 04/21] ceph: ref counted buffer

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Date:	Tue, 22 Sep 2009 10:38:32 -0700
From:	Sage Weil <sage@...dream.net>
To:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org
Cc:	yehuda@...dream.net, Sage Weil <sage@...dream.net>
Subject: [PATCH 04/21] ceph: ref counted buffer

struct ceph_buffer is a simple ref-counted buffer.  We transparently
choose between kmalloc for small buffers and vmalloc for large ones.

This is used for allocating memory for xattr data, among other things.

Signed-off-by: Sage Weil <sage@...dream.net>
---
 fs/ceph/buffer.h |   83 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 83 insertions(+), 0 deletions(-)
 create mode 100644 fs/ceph/buffer.h

diff --git a/fs/ceph/buffer.h b/fs/ceph/buffer.h
new file mode 100644
index 0000000..128593d
--- /dev/null
+++ b/fs/ceph/buffer.h
@@ -0,0 +1,83 @@
+#ifndef __FS_CEPH_BUFFER_H
+#define __FS_CEPH_BUFFER_H
+
+#include <linux/mm.h>
+#include <linux/types.h>
+#include <linux/vmalloc.h>
+
+#include "ceph_debug.h"
+
+/*
+ * a simple reference counted buffer.
+ *
+ * use kmalloc for small sizes (<= one page), vmalloc for larger
+ * sizes.
+ */
+struct ceph_buffer {
+	atomic_t nref;
+	struct kvec vec;
+	size_t alloc_len;
+	bool is_vmalloc;
+};
+
+static inline struct ceph_buffer *ceph_buffer_new(gfp_t gfp)
+{
+	struct ceph_buffer *b;
+
+	b = kmalloc(sizeof(*b), gfp);
+	if (!b)
+		return NULL;
+	atomic_set(&b->nref, 1);
+	b->vec.iov_base = NULL;
+	b->vec.iov_len = 0;
+	b->alloc_len = 0;
+	return b;
+}
+
+static inline int ceph_buffer_alloc(struct ceph_buffer *b, int len, gfp_t gfp)
+{
+	if (len <= PAGE_SIZE) {
+		b->vec.iov_base = kmalloc(len, gfp);
+		b->is_vmalloc = false;
+	} else {
+		b->vec.iov_base = __vmalloc(len, gfp, PAGE_KERNEL);
+		b->is_vmalloc = true;
+	}
+	if (!b->vec.iov_base)
+		return -ENOMEM;
+	b->alloc_len = len;
+	b->vec.iov_len = len;
+	return 0;
+}
+
+static inline struct ceph_buffer *ceph_buffer_get(struct ceph_buffer *b)
+{
+	atomic_inc(&b->nref);
+	return b;
+}
+
+static inline void ceph_buffer_put(struct ceph_buffer *b)
+{
+	if (b && atomic_dec_and_test(&b->nref)) {
+		if (b->vec.iov_base) {
+			if (b->is_vmalloc)
+				vfree(b->vec.iov_base);
+			else
+				kfree(b->vec.iov_base);
+		}
+		kfree(b);
+	}
+}
+
+static inline struct ceph_buffer *ceph_buffer_new_alloc(int len, gfp_t gfp)
+{
+	struct ceph_buffer *b = ceph_buffer_new(gfp);
+
+	if (b && ceph_buffer_alloc(b, len, gfp) < 0) {
+		ceph_buffer_put(b);
+		b = NULL;
+	}
+	return b;
+}
+
+#endif
-- 
1.5.6.5

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