ceph: nfs re-export support

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>

1 files changed, 223 insertions, 0 deletions

diff --git a/fs/ceph/export.c b/fs/ceph/export.c
new file mode 100644
index 000000000000..fc68e39cbad6
--- /dev/null
+++ b/fs/ceph/export.c
@@ -0,0 +1,223 @@
+#include "ceph_debug.h"
+
+#include <linux/exportfs.h>
+#include <asm/unaligned.h>
+
+#include "super.h"
+
+/*
+ * NFS export support
+ *
+ * NFS re-export of a ceph mount is, at present, only semireliable.
+ * The basic issue is that the Ceph architectures doesn't lend itself
+ * well to generating filehandles that will remain valid forever.
+ *
+ * So, we do our best.  If you're lucky, your inode will be in the
+ * client's cache.  If it's not, and you have a connectable fh, then
+ * the MDS server may be able to find it for you.  Otherwise, you get
+ * ESTALE.
+ *
+ * There are ways to this more reliable, but in the non-connectable fh
+ * case, we won't every work perfectly, and in the connectable case,
+ * some changes are needed on the MDS side to work better.
+ */
+
+/*
+ * Basic fh
+ */
+struct ceph_nfs_fh {
+        u64 ino;
+} __attribute__ ((packed));
+
+/*
+ * Larger 'connectable' fh that includes parent ino and name hash.
+ * Use this whenever possible, as it works more reliably.
+ */
+struct ceph_nfs_confh {
+        u64 ino, parent_ino;
+        u32 parent_name_hash;
+} __attribute__ ((packed));
+
+static int ceph_encode_fh(struct dentry *dentry, u32 *rawfh, int *max_len,
+                          int connectable)
+{
+        struct ceph_nfs_fh *fh = (void *)rawfh;
+        struct ceph_nfs_confh *cfh = (void *)rawfh;
+        struct dentry *parent = dentry->d_parent;
+        struct inode *inode = dentry->d_inode;
+        int type;
+
+        /* don't re-export snaps */
+        if (ceph_snap(inode) != CEPH_NOSNAP)
+                return -EINVAL;
+
+        if (*max_len >= sizeof(*cfh)) {
+                dout("encode_fh %p connectable\n", dentry);
+                cfh->ino = ceph_ino(dentry->d_inode);
+                cfh->parent_ino = ceph_ino(parent->d_inode);
+                cfh->parent_name_hash = parent->d_name.hash;
+                *max_len = sizeof(*cfh);
+                type = 2;
+        } else if (*max_len > sizeof(*fh)) {
+                if (connectable)
+                        return -ENOSPC;
+                dout("encode_fh %p\n", dentry);
+                fh->ino = ceph_ino(dentry->d_inode);
+                *max_len = sizeof(*fh);
+                type = 1;
+        } else {
+                return -ENOSPC;
+        }
+        return type;
+}
+
+/*
+ * convert regular fh to dentry
+ *
+ * FIXME: we should try harder by querying the mds for the ino.
+ */
+static struct dentry *__fh_to_dentry(struct super_block *sb,
+                                     struct ceph_nfs_fh *fh)
+{
+        struct inode *inode;
+        struct dentry *dentry;
+        struct ceph_vino vino;
+        int err;
+
+        dout("__fh_to_dentry %llx\n", fh->ino);
+        vino.ino = fh->ino;
+        vino.snap = CEPH_NOSNAP;
+        inode = ceph_find_inode(sb, vino);
+        if (!inode)
+                return ERR_PTR(-ESTALE);
+
+        dentry = d_obtain_alias(inode);
+        if (!dentry) {
+                pr_err("fh_to_dentry %llx -- inode %p but ENOMEM\n",
+                       fh->ino, inode);
+                iput(inode);
+                return ERR_PTR(-ENOMEM);
+        }
+        err = ceph_init_dentry(dentry);
+
+        if (err < 0) {
+                iput(inode);
+                return ERR_PTR(err);
+        }
+        dout("__fh_to_dentry %llx %p dentry %p\n", fh->ino, inode, dentry);
+        return dentry;
+}
+
+/*
+ * convert connectable fh to dentry
+ */
+static struct dentry *__cfh_to_dentry(struct super_block *sb,
+                                      struct ceph_nfs_confh *cfh)
+{
+        struct ceph_mds_client *mdsc = &ceph_client(sb)->mdsc;
+        struct inode *inode;
+        struct dentry *dentry;
+        struct ceph_vino vino;
+        int err;
+
+        dout("__cfh_to_dentry %llx (%llx/%x)\n",
+             cfh->ino, cfh->parent_ino, cfh->parent_name_hash);
+
+        vino.ino = cfh->ino;
+        vino.snap = CEPH_NOSNAP;
+        inode = ceph_find_inode(sb, vino);
+        if (!inode) {
+                struct ceph_mds_request *req;
+
+                req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_LOOKUPHASH,
+                                               USE_ANY_MDS);
+                if (IS_ERR(req))
+                        return ERR_PTR(PTR_ERR(req));
+
+                req->r_ino1 = vino;
+                req->r_ino2.ino = cfh->parent_ino;
+                req->r_ino2.snap = CEPH_NOSNAP;
+                req->r_path2 = kmalloc(16, GFP_NOFS);
+                snprintf(req->r_path2, 16, "%d", cfh->parent_name_hash);
+                req->r_num_caps = 1;
+                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);
+        }
+
+        dentry = d_obtain_alias(inode);
+        if (!dentry) {
+                pr_err("cfh_to_dentry %llx -- inode %p but ENOMEM\n",
+                       cfh->ino, inode);
+                iput(inode);
+                return ERR_PTR(-ENOMEM);
+        }
+        err = ceph_init_dentry(dentry);
+        if (err < 0) {
+                iput(inode);
+                return ERR_PTR(err);
+        }
+        dout("__cfh_to_dentry %llx %p dentry %p\n", cfh->ino, inode, dentry);
+        return dentry;
+}
+
+static struct dentry *ceph_fh_to_dentry(struct super_block *sb, struct fid *fid,
+                                        int fh_len, int fh_type)
+{
+        if (fh_type == 1)
+                return __fh_to_dentry(sb, (struct ceph_nfs_fh *)fid->raw);
+        else
+                return __cfh_to_dentry(sb, (struct ceph_nfs_confh *)fid->raw);
+}
+
+/*
+ * get parent, if possible.
+ *
+ * FIXME: we could do better by querying the mds to discover the
+ * parent.
+ */
+static struct dentry *ceph_fh_to_parent(struct super_block *sb,
+                                         struct fid *fid,
+                                        int fh_len, int fh_type)
+{
+        struct ceph_nfs_confh *cfh = (void *)fid->raw;
+        struct ceph_vino vino;
+        struct inode *inode;
+        struct dentry *dentry;
+        int err;
+
+        if (fh_type == 1)
+                return ERR_PTR(-ESTALE);
+
+        pr_debug("fh_to_parent %llx/%d\n", cfh->parent_ino,
+                 cfh->parent_name_hash);
+
+        vino.ino = cfh->ino;
+        vino.snap = CEPH_NOSNAP;
+        inode = ceph_find_inode(sb, vino);
+        if (!inode)
+                return ERR_PTR(-ESTALE);
+
+        dentry = d_obtain_alias(inode);
+        if (!dentry) {
+                pr_err("fh_to_parent %llx -- inode %p but ENOMEM\n",
+                       cfh->ino, inode);
+                iput(inode);
+                return ERR_PTR(-ENOMEM);
+        }
+        err = ceph_init_dentry(dentry);
+        if (err < 0) {
+                iput(inode);
+                return ERR_PTR(err);
+        }
+        dout("fh_to_parent %llx %p dentry %p\n", cfh->ino, inode, dentry);
+        return dentry;
+}
+
+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,
+};