[PATCH 2/3] NFS support for btrfs - v3

David Woodhouse
2008-08-13T15:06:30Z

From: Balaji Rao <balajirrao@gmail.com>

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]

Signed-off-by: Balaji Rao <balajirrao@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
---

This replaces patch 2 of the sequence I sent out yesterday; the other
two patches remain the same.

Makefile | 2 +-
compat.h | 17 +++++
export.c | 200 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
export.h | 19 ++++++
super.c | 2 +
5 files changed, 239 insertions(+), 1 deletions(-)
create mode 100644 export.c
create mode 100644 export.h

diff --git a/Makefile b/Makefile
index a4b3817..75f8818 100644
--- a/Makefile
+++ b/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/compat.h b/compat.h
index b3349a6..d45fb37 100644
--- a/compat.h
+++ b/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/export.c b/export.c
new file mode 100644
index 0000000..1b8875c
--- /dev/null
+++ b/export.c
@@ -0,0 +1,200 @@
+#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_REF_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)
+ goto out;
+
+ btrfs_item_key_to_cpu(leaf, &key, slot);
+ if (key.objectid != dir->i_ino || key.type != BTRFS_INODE_REF_KEY)
+ goto out;
+
+ btrfs_free_path(path);
+ 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/export.h b/export.h
new file mode 100644
index 0000000..074348a
--- /dev/null
+++ b/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/super.c b/super.c
index eb4b357..e830e0e 100644
--- a/super.c
+++ b/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;
--
1.5.5.1

--
David Woodhouse Open Source Technology Centre
David.Woodhouse@intel.com Intel Corporation