[PATCH 04/21] ceph: ref counted buffer

Sage Weil
2009-09-22T17:46:44Z

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@newdream.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