NFS support for btrfs - v3

Date: Mon, 21 Jul 2008 02:01:56 +0530
Here's an implementation of NFS support for btrfs. It relies on the
fixes which are going in to 2.6.28 for the NFS readdir/lookup deadlock.

This uses the btrfs_iget helper introduced previously.

[dwmw2: Tidy up a little, switch to d_obtain_alias() w/compat routine,
	change fh_type,	store parent's root object ID where needed,
	fix some get_parent() and fs_to_dentry() bugs]

Signed-off-by: Balaji Rao <balajirrao@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

5 files changed, 247 insertions, 1 deletions

diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index a4b38177abdb..75f8818cbfee 100644
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -7,7 +7,7 @@ btrfs-y := super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
            transaction.o bit-radix.o inode.o file.o tree-defrag.o \
            extent_map.o sysfs.o struct-funcs.o xattr.o ordered-data.o \
            extent_io.o volumes.o async-thread.o ioctl.o locking.o orphan.o \
-           ref-cache.o
+           ref-cache.o export.o
 
 btrfs-$(CONFIG_FS_POSIX_ACL)    += acl.o
 else
diff --git a/fs/btrfs/compat.h b/fs/btrfs/compat.h
index b3349a66999d..d45fb37887bc 100644
--- a/fs/btrfs/compat.h
+++ b/fs/btrfs/compat.h
@@ -5,6 +5,23 @@
 #define trylock_page(page) (!TestSetPageLocked(page))
 #endif
 
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(2,6,27)
+static inline struct dentry *d_obtain_alias(struct inode *inode)
+{
+        struct dentry *d;
+
+        if (!inode)
+                return NULL;
+        if (IS_ERR(inode))
+                return ERR_CAST(inode);
+
+        d = d_alloc_anon(inode);
+        if (!d)
+                iput(inode);
+        return d;
+}
+#endif
+
 /*
  * Even if AppArmor isn't enabled, it still has different prototypes.
  * Add more distro/version pairs here to declare which has AppArmor applied.
diff --git a/fs/btrfs/export.c b/fs/btrfs/export.c
new file mode 100644
index 000000000000..797b4cbc3786
--- /dev/null
+++ b/fs/btrfs/export.c
@@ -0,0 +1,208 @@
+#include <linux/fs.h>
+#include <linux/types.h>
+#include "ctree.h"
+#include "disk-io.h"
+#include "btrfs_inode.h"
+#include "print-tree.h"
+#include "export.h"
+#include "compat.h"
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,28)
+#define FILEID_BTRFS_WITHOUT_PARENT             0x4d
+#define FILEID_BTRFS_WITH_PARENT                0x4e
+#define FILEID_BTRFS_WITH_PARENT_ROOT           0x4f
+#endif
+
+#define BTRFS_FID_SIZE_NON_CONNECTABLE          (offsetof(struct btrfs_fid, parent_objectid)/4)
+#define BTRFS_FID_SIZE_CONNECTABLE              (offsetof(struct btrfs_fid, parent_root_objectid)/4)
+#define BTRFS_FID_SIZE_CONNECTABLE_ROOT         (sizeof(struct btrfs_fid)/4)
+
+static int btrfs_encode_fh(struct dentry *dentry, u32 *fh, int *max_len,
+                           int connectable)
+{
+        struct btrfs_fid *fid = (struct btrfs_fid *)fh;
+        struct inode *inode = dentry->d_inode;
+        int len = *max_len;
+        int type;
+
+        if ((len < BTRFS_FID_SIZE_NON_CONNECTABLE) ||
+            (connectable && len < BTRFS_FID_SIZE_CONNECTABLE))
+                return 255;
+
+        len  = BTRFS_FID_SIZE_NON_CONNECTABLE;
+        type = FILEID_BTRFS_WITHOUT_PARENT;
+
+        fid->objectid = BTRFS_I(inode)->location.objectid;
+        fid->root_objectid = BTRFS_I(inode)->root->objectid;
+        fid->gen = inode->i_generation;
+
+        if (connectable && !S_ISDIR(inode->i_mode)) {
+                struct inode *parent;
+                u64 parent_root_id;
+
+                spin_lock(&dentry->d_lock);
+
+                parent = dentry->d_parent->d_inode;
+                fid->parent_objectid = BTRFS_I(parent)->location.objectid;
+                fid->parent_gen = parent->i_generation;
+                parent_root_id = BTRFS_I(parent)->root->objectid;
+
+                spin_unlock(&dentry->d_lock);
+
+                if (parent_root_id != fid->root_objectid) {
+                        fid->parent_root_objectid = parent_root_id;
+                        len = BTRFS_FID_SIZE_CONNECTABLE_ROOT;
+                        type = FILEID_BTRFS_WITH_PARENT_ROOT;
+                } else {
+                        len = BTRFS_FID_SIZE_CONNECTABLE;
+                        type = FILEID_BTRFS_WITH_PARENT;
+                }
+        }
+
+        *max_len = len;
+        return type;
+}
+
+static struct dentry *btrfs_get_dentry(struct super_block *sb, u64 objectid,
+                                       u64 root_objectid, u32 generation)
+{
+        struct btrfs_root *root;
+        struct inode *inode;
+        struct dentry *result;
+        struct btrfs_key key;
+
+        key.objectid = objectid;
+        btrfs_set_key_type(&key, BTRFS_INODE_ITEM_KEY);
+        key.offset = 0;
+
+        root = btrfs_lookup_fs_root(btrfs_sb(sb)->fs_info, root_objectid);
+        inode = btrfs_iget(sb, &key, root, NULL);
+        if (IS_ERR(inode))
+                return (void *)inode;
+
+        if (generation != inode->i_generation) {
+                iput(inode);
+                return ERR_PTR(-ESTALE);
+        }
+
+        result = d_obtain_alias(inode);
+        if (!result)
+                return ERR_PTR(-ENOMEM);
+
+        return result;
+}
+
+static struct dentry *btrfs_fh_to_parent(struct super_block *sb, struct fid *fh,
+                                         int fh_len, int fh_type)
+{
+        struct btrfs_fid *fid = (struct btrfs_fid *) fh;
+        u64 objectid, root_objectid;
+        u32 generation;
+
+        if (fh_type == FILEID_BTRFS_WITH_PARENT) {
+                if (fh_len !=  BTRFS_FID_SIZE_CONNECTABLE)
+                        return NULL;
+                root_objectid = fid->root_objectid;
+        } else if (fh_type == FILEID_BTRFS_WITH_PARENT_ROOT) {
+                if (fh_len != BTRFS_FID_SIZE_CONNECTABLE_ROOT)
+                        return NULL;
+                root_objectid = fid->parent_root_objectid;
+        } else
+                return NULL;
+
+        objectid = fid->parent_objectid;
+        generation = fid->parent_gen;
+
+        return btrfs_get_dentry(sb, objectid, root_objectid, generation);
+}
+
+static struct dentry *btrfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
+                                         int fh_len, int fh_type)
+{
+        struct btrfs_fid *fid = (struct btrfs_fid *) fh;
+        u64 objectid, root_objectid;
+        u32 generation;
+
+        if ((fh_type != FILEID_BTRFS_WITH_PARENT ||
+             fh_len != BTRFS_FID_SIZE_CONNECTABLE) &&
+            (fh_type != FILEID_BTRFS_WITH_PARENT_ROOT ||
+             fh_len != BTRFS_FID_SIZE_CONNECTABLE_ROOT) &&
+            (fh_type != FILEID_BTRFS_WITHOUT_PARENT ||
+             fh_len != BTRFS_FID_SIZE_NON_CONNECTABLE))
+                return NULL;
+
+        objectid = fid->objectid;
+        root_objectid = fid->root_objectid;
+        generation = fid->gen;
+
+        return btrfs_get_dentry(sb, objectid, root_objectid, generation);
+}
+
+static struct dentry *btrfs_get_parent(struct dentry *child)
+{
+        struct inode *dir = child->d_inode;
+        struct inode *inode;
+        struct dentry *parent;
+        struct btrfs_root *root = BTRFS_I(dir)->root;
+        struct btrfs_key key;
+        struct btrfs_path *path;
+        struct extent_buffer *leaf;
+        u32 nritems;
+        int slot;
+        u64 objectid;
+        int ret;
+
+        path = btrfs_alloc_path();
+
+        key.objectid = dir->i_ino;
+        btrfs_set_key_type(&key, BTRFS_INODE_REF_KEY);
+        key.offset = 0;
+        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+        BUG_ON(ret == 0);
+        ret = 0;
+
+        leaf = path->nodes[0];
+        slot = path->slots[0];
+        nritems = btrfs_header_nritems(leaf);
+        if (slot >= nritems) {
+                ret = btrfs_next_leaf(root, path);
+                if (ret) {
+                        btrfs_free_path(path);
+                        goto out;
+                }
+                leaf = path->nodes[0];
+                slot = path->slots[0];
+        }
+
+        btrfs_free_path(path);
+
+        btrfs_item_key_to_cpu(leaf, &key, slot);
+        if (key.objectid != dir->i_ino || key.type != BTRFS_INODE_REF_KEY)
+                goto out;
+
+        objectid = key.offset;
+
+        /* Build a new key for the inode item */
+        key.objectid = objectid;
+        btrfs_set_key_type(&key, BTRFS_INODE_ITEM_KEY);
+        key.offset = 0;
+
+        inode = btrfs_iget(root->fs_info->sb, &key, root, NULL);
+
+        parent = d_obtain_alias(inode);
+        if (!parent)
+                parent = ERR_PTR(-ENOMEM);
+
+        return parent;
+
+out:
+        btrfs_free_path(path);
+        return ERR_PTR(-EINVAL);
+}
+
+const struct export_operations btrfs_export_ops = {
+        .encode_fh      = btrfs_encode_fh,
+        .fh_to_dentry   = btrfs_fh_to_dentry,
+        .fh_to_parent   = btrfs_fh_to_parent,
+        .get_parent     = btrfs_get_parent,
+};
diff --git a/fs/btrfs/export.h b/fs/btrfs/export.h
new file mode 100644
index 000000000000..074348a95841
--- /dev/null
+++ b/fs/btrfs/export.h
@@ -0,0 +1,19 @@
+#ifndef BTRFS_EXPORT_H
+#define BTRFS_EXPORT_H
+
+#include <linux/exportfs.h>
+
+extern const struct export_operations btrfs_export_ops;
+
+struct btrfs_fid {
+        u64 objectid;
+        u64 root_objectid;
+        u32 gen;
+
+        u64 parent_objectid;
+        u32 parent_gen;
+
+        u64 parent_root_objectid;
+} __attribute__ ((packed));
+
+#endif
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index eb4b357d05e1..e830e0ed409a 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -46,6 +46,7 @@
 #include "xattr.h"
 #include "volumes.h"
 #include "version.h"
+#include "export.h"
 
 #define BTRFS_SUPER_MAGIC 0x9123683E
 
@@ -303,6 +304,7 @@ static int btrfs_fill_super(struct super_block * sb,
         sb->s_maxbytes = MAX_LFS_FILESIZE;
         sb->s_magic = BTRFS_SUPER_MAGIC;
         sb->s_op = &btrfs_super_ops;
+        sb->s_export_op = &btrfs_export_ops;
         sb->s_xattr = btrfs_xattr_handlers;
         sb->s_time_gran = 1;
         sb->s_flags |= MS_POSIXACL;