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 currently used only for allocating memory for xattr data.

Signed-off-by: Sage Weil <sage@newdream.net>

diff --git a/fs/ceph/buffer.c b/fs/ceph/buffer.c
new file mode 100644 (file)
index 0000000..cf9aacc
--- /dev/null
+++ b/fs/ceph/buffer.c
@@ -0,0 +1,34 @@
+
+#include "ceph_debug.h"
+#include "buffer.h"
+
+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;
+}
+
+int ceph_buffer_alloc(struct ceph_buffer *b, int len, gfp_t gfp)
+{
+       b->vec.iov_base = kmalloc(len, gfp | __GFP_NOWARN);
+       if (b->vec.iov_base) {
+               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;
+}
+

diff --git a/fs/ceph/buffer.h b/fs/ceph/buffer.h
new file mode 100644 (file)
index 0000000..16b1930
--- /dev/null
+++ b/fs/ceph/buffer.h
@@ -0,0 +1,55 @@
+#ifndef __FS_CEPH_BUFFER_H
+#define __FS_CEPH_BUFFER_H
+
+#include <linux/mm.h>
+#include <linux/vmalloc.h>
+#include <linux/types.h>
+#include <linux/uio.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;
+};
+
+struct ceph_buffer *ceph_buffer_new(gfp_t gfp);
+int ceph_buffer_alloc(struct ceph_buffer *b, int len, gfp_t gfp);
+
+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