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>

diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index a4b3817..75f8818 100644 (file)
--- 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 b3349a6..d45fb37 100644 (file)
--- 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 (file)
index 0000000..797b4cb
--- /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 (file)
index 0000000..074348a
--- /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 eb4b357..e830e0e 100644 (file)
--- 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;