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Subject[PATCH 16/19] ceph: nfs re-export support
Date
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 | 145 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 145 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..78c5699
--- /dev/null
+++ b/fs/ceph/export.c
@@ -0,0 +1,145 @@
+#include <linux/exportfs.h>
+
+#include "super.h"
+#include "ceph_debug.h"
+
+int ceph_debug_export = -1;
+#define DOUT_MASK DOUT_MASK_EXPORT
+#define DOUT_VAR ceph_debug_export
+#define DOUT_PREFIX "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,
+ len, (char *)fh, 0, NULL,
+ NULL, USE_ANY_MDS);
+ if (IS_ERR(req))
+ return ERR_PTR(PTR_ERR(req));
+ err = ceph_mdsc_do_request(mdsc, 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


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