[PATCH 16/20] ceph: nfs re-export support

[Sage Weil <sage@newdream.net>]

Basic NFS re-export support is included.  This mostly works.  However,
Ceph's MDS design precludes the ability to generate a (small)
filehandle that will be valid forever, so this is of limited utility.

Signed-off-by: Sage Weil <sage@newdream.net>
---
 fs/ceph/export.c |  143 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 143 insertions(+), 0 deletions(-)
 create mode 100644 fs/ceph/export.c

diff --git a/fs/ceph/export.c b/fs/ceph/export.c
new file mode 100644
index 0000000..6c5b484
--- /dev/null
+++ b/fs/ceph/export.c
@@ -0,0 +1,143 @@
+#include <linux/exportfs.h>
+
+#include "super.h"
+#include "ceph_debug.h"
+
+int ceph_debug_export __read_mostly = -1;
+#define DOUT_MASK DOUT_MASK_EXPORT
+#define DOUT_VAR ceph_debug_export
+
+/*
+ * fh is N tuples of
+ *  <ino, parent's d_name.hash>
+ *
+ * This is only a semi-reliable strategy.  The fundamental issue is
+ * that ceph doesn't not have a way to locate an arbitrary inode by
+ * ino.  Keeping a few parents in the handle increases the probability
+ * that we'll find it in one of the MDS caches, but it is by no means
+ * a guarantee.
+ *
+ * Also, the FINDINODE request is currently directed at a single MDS.
+ * It should probably try all MDS's before giving up.  For a single MDS
+ * system that isn't a problem.
+ *
+ * In the meantime, this works reasonably well for basic usage.
+ */
+
+#define IPSZ (sizeof(struct ceph_inopath_item) / sizeof(u32))
+
+static int ceph_encode_fh(struct dentry *dentry, u32 *rawfh, int *max_len,
+		   int connectable)
+{
+	int type = 1;
+	struct ceph_inopath_item *fh =
+		(struct ceph_inopath_item *)rawfh;
+	int max = *max_len / IPSZ;
+	int len;
+
+	dout(10, "encode_fh %p max_len %d u32s (%d inopath items)%s\n", dentry,
+	     *max_len, max, connectable ? " connectable" : "");
+
+	if (max < 1 || (connectable && max < 2))
+		return -ENOSPC;
+
+	/*
+	 * pretty sure this is racy.  caller holds dentry->d_lock, but
+	 * not parents'.
+	 */
+	fh[0].ino = cpu_to_le64(ceph_vino(dentry->d_inode).ino);
+	fh[0].dname_hash = cpu_to_le32(dentry->d_name.hash);
+	len = 1;
+	while (len < max) {
+		dentry = dentry->d_parent;
+		if (!dentry)
+			break;
+		fh[len].ino = cpu_to_le64(ceph_vino(dentry->d_inode).ino);
+		fh[len].dname_hash = cpu_to_le32(dentry->d_name.hash);
+		len++;
+		type = 2;
+		if (IS_ROOT(dentry))
+			break;
+	}
+
+	*max_len = len * IPSZ;
+	return type;
+}
+
+static struct dentry *__fh_to_dentry(struct super_block *sb,
+			      struct ceph_inopath_item *fh, int len)
+{
+	struct ceph_mds_client *mdsc = &ceph_client(sb)->mdsc;
+	struct inode *inode;
+	struct dentry *dentry;
+	int err;
+	struct ceph_vino vino = {
+		.ino = le64_to_cpu(fh[0].ino),
+		.snap = CEPH_NOSNAP,   /* FIXME */
+	};
+	u32 hash = le32_to_cpu(fh[0].dname_hash);
+
+	inode = ceph_find_inode(sb, vino);
+	if (!inode) {
+		struct ceph_mds_request *req;
+		derr(10, "fh_to_dentry %llx.%x -- no inode\n", vino.ino, hash);
+		req = ceph_mdsc_create_request(mdsc,
+					       CEPH_MDS_OP_FINDINODE,
+					       NULL, NULL,
+					       (char *)fh, (void *)&len,
+					       USE_ANY_MDS);
+		if (IS_ERR(req))
+			return ERR_PTR(PTR_ERR(req));
+		err = ceph_mdsc_do_request(mdsc, NULL, req);
+		ceph_mdsc_put_request(req);
+		inode = ceph_find_inode(sb, vino);
+		if (!inode)
+			return ERR_PTR(err ? err : -ESTALE);
+	}
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 28)
+	dentry = d_obtain_alias(inode);
+#else
+	dentry = d_alloc_anon(inode);
+#endif
+	if (!dentry) {
+		derr(10, "fh_to_dentry %llx.%x -- inode %p but ENOMEM\n",
+		     vino.ino,
+		     hash, inode);
+		iput(inode);
+		return ERR_PTR(-ENOMEM);
+	}
+	dout(10, "fh_to_dentry %llx.%x -- inode %p dentry %p\n", vino.ino,
+	     hash, inode, dentry);
+	return dentry;
+
+}
+
+static struct dentry *ceph_fh_to_dentry(struct super_block *sb, struct fid *fid,
+				 int fh_len, int fh_type)
+{
+	u32 *fh = fid->raw;
+	return __fh_to_dentry(sb, (struct ceph_inopath_item *)fh, fh_len/IPSZ);
+}
+
+static struct dentry *ceph_fh_to_parent(struct super_block *sb, struct fid *fid,
+				 int fh_len, int fh_type)
+{
+	u32 *fh = fid->raw;
+	u64 ino = *(u64 *)fh;
+	u32 hash = fh[2];
+
+	derr(10, "fh_to_parent %llx.%x\n", ino, hash);
+
+	if (fh_len < 6)
+		return ERR_PTR(-ESTALE);
+
+	return __fh_to_dentry(sb, (struct ceph_inopath_item *)fh + 1,
+			      fh_len/IPSZ - 1);
+}
+
+const struct export_operations ceph_export_ops = {
+	.encode_fh = ceph_encode_fh,
+	.fh_to_dentry = ceph_fh_to_dentry,
+	.fh_to_parent = ceph_fh_to_parent,
+};
-- 
1.5.6.5