nilfs2: make snapshots in checkpoint tree exportable

The previous export operations cannot handle multiple versions of
a filesystem if they belong to the same sb instance.

This adds a new type of file handle and extends export operations so
that they can get the inode specified by a checkpoint number as well
as an inode number and a generation number.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

5 files changed, 151 insertions, 71 deletions

diff --git a/fs/nilfs2/export.h b/fs/nilfs2/export.h
new file mode 100644
index 000000000000..a71cc412b651
--- /dev/null
+++ b/fs/nilfs2/export.h
@@ -0,0 +1,17 @@
+#ifndef NILFS_EXPORT_H
+#define NILFS_EXPORT_H
+
+#include <linux/exportfs.h>
+
+extern const struct export_operations nilfs_export_ops;
+
+struct nilfs_fid {
+        u64 cno;
+        u64 ino;
+        u32 gen;
+
+        u32 parent_gen;
+        u64 parent_ino;
+} __attribute__ ((packed));
+
+#endif
diff --git a/fs/nilfs2/namei.c b/fs/nilfs2/namei.c
index 1110d56a23f5..a65f46560fbe 100644
--- a/fs/nilfs2/namei.c
+++ b/fs/nilfs2/namei.c
@@ -40,7 +40,11 @@
 
 #include <linux/pagemap.h>
 #include "nilfs.h"
+#include "export.h"
 
+#define NILFS_FID_SIZE_NON_CONNECTABLE \
+        (offsetof(struct nilfs_fid, parent_gen) / 4)
+#define NILFS_FID_SIZE_CONNECTABLE      (sizeof(struct nilfs_fid) / 4)
 
 static inline int nilfs_add_nondir(struct dentry *dentry, struct inode *inode)
 {
@@ -77,23 +81,6 @@ nilfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
         return d_splice_alias(inode, dentry);
 }
 
-struct dentry *nilfs_get_parent(struct dentry *child)
-{
-        unsigned long ino;
-        struct inode *inode;
-        struct qstr dotdot = {.name = "..", .len = 2};
-
-        ino = nilfs_inode_by_name(child->d_inode, &dotdot);
-        if (!ino)
-                return ERR_PTR(-ENOENT);
-
-        inode = nilfs_iget(child->d_inode->i_sb,
-                           NILFS_I(child->d_inode)->i_root, ino);
-        if (IS_ERR(inode))
-                return ERR_CAST(inode);
-        return d_obtain_alias(inode);
-}
-
 /*
  * By the time this is called, we already have created
  * the directory cache entry for the new file, but it
@@ -469,6 +456,115 @@ out:
         return err;
 }
 
+/*
+ * Export operations
+ */
+static struct dentry *nilfs_get_parent(struct dentry *child)
+{
+        unsigned long ino;
+        struct inode *inode;
+        struct qstr dotdot = {.name = "..", .len = 2};
+        struct nilfs_root *root;
+
+        ino = nilfs_inode_by_name(child->d_inode, &dotdot);
+        if (!ino)
+                return ERR_PTR(-ENOENT);
+
+        root = NILFS_I(child->d_inode)->i_root;
+
+        inode = nilfs_iget(child->d_inode->i_sb, root, ino);
+        if (IS_ERR(inode))
+                return ERR_CAST(inode);
+
+        return d_obtain_alias(inode);
+}
+
+static struct dentry *nilfs_get_dentry(struct super_block *sb, u64 cno,
+                                       u64 ino, u32 gen)
+{
+        struct nilfs_root *root;
+        struct inode *inode;
+
+        if (ino < NILFS_FIRST_INO(sb) && ino != NILFS_ROOT_INO)
+                return ERR_PTR(-ESTALE);
+
+        root = nilfs_lookup_root(NILFS_SB(sb)->s_nilfs, cno);
+        if (!root)
+                return ERR_PTR(-ESTALE);
+
+        inode = nilfs_iget(sb, root, ino);
+        nilfs_put_root(root);
+
+        if (IS_ERR(inode))
+                return ERR_CAST(inode);
+        if (gen && inode->i_generation != gen) {
+                iput(inode);
+                return ERR_PTR(-ESTALE);
+        }
+        return d_obtain_alias(inode);
+}
+
+static struct dentry *nilfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
+                                         int fh_len, int fh_type)
+{
+        struct nilfs_fid *fid = (struct nilfs_fid *)fh;
+
+        if ((fh_len != NILFS_FID_SIZE_NON_CONNECTABLE &&
+             fh_len != NILFS_FID_SIZE_CONNECTABLE) ||
+            (fh_type != FILEID_NILFS_WITH_PARENT &&
+             fh_type != FILEID_NILFS_WITHOUT_PARENT))
+                return NULL;
+
+        return nilfs_get_dentry(sb, fid->cno, fid->ino, fid->gen);
+}
+
+static struct dentry *nilfs_fh_to_parent(struct super_block *sb, struct fid *fh,
+                                         int fh_len, int fh_type)
+{
+        struct nilfs_fid *fid = (struct nilfs_fid *)fh;
+
+        if (fh_len != NILFS_FID_SIZE_CONNECTABLE ||
+            fh_type != FILEID_NILFS_WITH_PARENT)
+                return NULL;
+
+        return nilfs_get_dentry(sb, fid->cno, fid->parent_ino, fid->parent_gen);
+}
+
+static int nilfs_encode_fh(struct dentry *dentry, __u32 *fh, int *lenp,
+                           int connectable)
+{
+        struct nilfs_fid *fid = (struct nilfs_fid *)fh;
+        struct inode *inode = dentry->d_inode;
+        struct nilfs_root *root = NILFS_I(inode)->i_root;
+        int type;
+
+        if (*lenp < NILFS_FID_SIZE_NON_CONNECTABLE ||
+            (connectable && *lenp < NILFS_FID_SIZE_CONNECTABLE))
+                return 255;
+
+        fid->cno = root->cno;
+        fid->ino = inode->i_ino;
+        fid->gen = inode->i_generation;
+
+        if (connectable && !S_ISDIR(inode->i_mode)) {
+                struct inode *parent;
+
+                spin_lock(&dentry->d_lock);
+                parent = dentry->d_parent->d_inode;
+                fid->parent_ino = parent->i_ino;
+                fid->parent_gen = parent->i_generation;
+                spin_unlock(&dentry->d_lock);
+
+                type = FILEID_NILFS_WITH_PARENT;
+                *lenp = NILFS_FID_SIZE_CONNECTABLE;
+        } else {
+                type = FILEID_NILFS_WITHOUT_PARENT;
+                *lenp = NILFS_FID_SIZE_NON_CONNECTABLE;
+        }
+
+        return type;
+}
+
 const struct inode_operations nilfs_dir_inode_operations = {
         .create         = nilfs_create,
         .lookup         = nilfs_lookup,
@@ -493,3 +589,10 @@ const struct inode_operations nilfs_symlink_inode_operations = {
         .follow_link    = page_follow_link_light,
         .put_link       = page_put_link,
 };
+
+const struct export_operations nilfs_export_ops = {
+        .encode_fh = nilfs_encode_fh,
+        .fh_to_dentry = nilfs_fh_to_dentry,
+        .fh_to_parent = nilfs_fh_to_parent,
+        .get_parent = nilfs_get_parent,
+};
diff --git a/fs/nilfs2/nilfs.h b/fs/nilfs2/nilfs.h
index 21d90c4b4e2d..aa7940f7ecf1 100644
--- a/fs/nilfs2/nilfs.h
+++ b/fs/nilfs2/nilfs.h
@@ -264,9 +264,6 @@ extern int nilfs_set_file_dirty(struct nilfs_sb_info *, struct inode *,
 extern int nilfs_mark_inode_dirty(struct inode *);
 extern void nilfs_dirty_inode(struct inode *);
 
-/* namei.c */
-extern struct dentry *nilfs_get_parent(struct dentry *);
-
 /* super.c */
 extern struct inode *nilfs_alloc_inode_common(struct the_nilfs *);
 extern struct inode *nilfs_alloc_inode(struct super_block *);
diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index a1c0e38a7706..adbf5826b837 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -48,10 +48,10 @@
 #include <linux/vfs.h>
 #include <linux/writeback.h>
 #include <linux/kobject.h>
-#include <linux/exportfs.h>
 #include <linux/seq_file.h>
 #include <linux/mount.h>
 #include "nilfs.h"
+#include "export.h"
 #include "mdt.h"
 #include "alloc.h"
 #include "btree.h"
@@ -556,56 +556,6 @@ static const struct super_operations nilfs_sops = {
         .show_options = nilfs_show_options
 };
 
-static struct inode *
-nilfs_nfs_get_inode(struct super_block *sb, u64 ino, u32 generation)
-{
-        struct inode *inode;
-        struct nilfs_root *root;
-
-        if (ino < NILFS_FIRST_INO(sb) && ino != NILFS_ROOT_INO &&
-            ino != NILFS_SKETCH_INO)
-                return ERR_PTR(-ESTALE);
-
-        root = nilfs_lookup_root(NILFS_SB(sb)->s_nilfs,
-                                 NILFS_CPTREE_CURRENT_CNO);
-        if (!root)
-                return ERR_PTR(-ESTALE);
-
-        /* new file handle type is required to export snapshots */
-        inode = nilfs_iget(sb, root, ino);
-        nilfs_put_root(root);
-        if (IS_ERR(inode))
-                return ERR_CAST(inode);
-        if (generation && inode->i_generation != generation) {
-                iput(inode);
-                return ERR_PTR(-ESTALE);
-        }
-
-        return inode;
-}
-
-static struct dentry *
-nilfs_fh_to_dentry(struct super_block *sb, struct fid *fid, int fh_len,
-                   int fh_type)
-{
-        return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
-                                    nilfs_nfs_get_inode);
-}
-
-static struct dentry *
-nilfs_fh_to_parent(struct super_block *sb, struct fid *fid, int fh_len,
-                   int fh_type)
-{
-        return generic_fh_to_parent(sb, fid, fh_len, fh_type,
-                                    nilfs_nfs_get_inode);
-}
-
-static const struct export_operations nilfs_export_ops = {
-        .fh_to_dentry = nilfs_fh_to_dentry,
-        .fh_to_parent = nilfs_fh_to_parent,
-        .get_parent = nilfs_get_parent,
-};
-
 enum {
         Opt_err_cont, Opt_err_panic, Opt_err_ro,
         Opt_barrier, Opt_nobarrier, Opt_snapshot, Opt_order, Opt_norecovery,
diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
index a9cd507f8cd2..28028988c862 100644
--- a/include/linux/exportfs.h
+++ b/include/linux/exportfs.h
@@ -67,6 +67,19 @@ enum fid_type {
          * 32 bit parent block number, 32 bit parent generation number
          */
         FILEID_UDF_WITH_PARENT = 0x52,
+
+        /*
+         * 64 bit checkpoint number, 64 bit inode number,
+         * 32 bit generation number.
+         */
+        FILEID_NILFS_WITHOUT_PARENT = 0x61,
+
+        /*
+         * 64 bit checkpoint number, 64 bit inode number,
+         * 32 bit generation number, 32 bit parent generation.
+         * 64 bit parent inode number.
+         */
+        FILEID_NILFS_WITH_PARENT = 0x62,
 };
 
 struct fid {