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>

2 files changed, 89 insertions, 0 deletions

diff --git a/fs/ceph/buffer.c b/fs/ceph/buffer.c
new file mode 100644
index 000000000000..cf9aaccef22b
--- /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
index 000000000000..16b1930acc45
--- /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