nfs: make nfs_path() work without vfsmount

part 3: now we have everything to get nfs_path() just by dentry -
just follow to (disconnected) root and pick the rest of the thing
there.

Start killing propagation of struct vfsmount * on the paths that
used to bring it to nfs_path().
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/nfs/internal.h

@@ -163,10 +163,10 @@ static inline void nfs_fs_proc_exit(void)
 
 /* nfs4namespace.c */
 #ifdef CONFIG_NFS_V4
-extern struct vfsmount *nfs_do_refmount(const struct vfsmount *mnt_parent, struct dentry *dentry);
+extern struct vfsmount *nfs_do_refmount(struct super_block *sb, struct dentry *dentry);
 #else
 static inline
-struct vfsmount *nfs_do_refmount(const struct vfsmount *mnt_parent, struct dentry *dentry)
+struct vfsmount *nfs_do_refmount(struct super_block *sb, struct dentry *dentry)
 {
 	return ERR_PTR(-ENOENT);
 }
@@ -247,9 +247,7 @@ extern void nfs_sb_active(struct super_block *sb);
 extern void nfs_sb_deactive(struct super_block *sb);
 
 /* namespace.c */
-extern char *nfs_path(const char *base,
-		      const struct dentry *droot,
-		      const struct dentry *dentry,
+extern char *nfs_path(char **p, struct dentry *dentry,
 		      char *buffer, ssize_t buflen);
 extern struct vfsmount *nfs_d_automount(struct path *path);
 
@@ -290,12 +288,11 @@ extern int _nfs4_call_sync_session(struct nfs_server *server,
 /*
  * Determine the device name as a string
  */
-static inline char *nfs_devname(const struct vfsmount *mnt_parent,
-				const struct dentry *dentry,
+static inline char *nfs_devname(struct dentry *dentry,
 				char *buffer, ssize_t buflen)
 {
-	return nfs_path(mnt_parent->mnt_devname, mnt_parent->mnt_root,
-			dentry, buffer, buflen);
+	char *dummy;
+	return nfs_path(&dummy, dentry, buffer, buflen);
 }
 
 /*

fs/nfs/namespace.c

@@ -25,33 +25,31 @@ static LIST_HEAD(nfs_automount_list);
 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
 int nfs_mountpoint_expiry_timeout = 500 * HZ;
 
-static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent,
-					const struct dentry *dentry,
+static struct vfsmount *nfs_do_submount(struct super_block *sb,
+					struct dentry *dentry,
 					struct nfs_fh *fh,
 					struct nfs_fattr *fattr);
 
 /*
  * nfs_path - reconstruct the path given an arbitrary dentry
- * @base - arbitrary string to prepend to the path
- * @droot - pointer to root dentry for mountpoint
+ * @base - used to return pointer to the end of devname part of path
  * @dentry - pointer to dentry
  * @buffer - result buffer
  * @buflen - length of buffer
  *
- * Helper function for constructing the path from the
- * root dentry to an arbitrary hashed dentry.
+ * Helper function for constructing the server pathname
+ * by arbitrary hashed dentry.
  *
  * This is mainly for use in figuring out the path on the
- * server side when automounting on top of an existing partition.
+ * server side when automounting on top of an existing partition
+ * and in generating /proc/mounts and friends.
  */
-char *nfs_path(const char *base,
-	       const struct dentry *droot,
-	       const struct dentry *dentry,
-	       char *buffer, ssize_t buflen)
+char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen)
 {
 	char *end;
 	int namelen;
 	unsigned seq;
+	const char *base;
 
 rename_retry:
 	end = buffer+buflen;
@@ -60,7 +58,10 @@ char *nfs_path(const char *base,
 
 	seq = read_seqbegin(&rename_lock);
 	rcu_read_lock();
-	while (!IS_ROOT(dentry) && dentry != droot) {
+	while (1) {
+		spin_lock(&dentry->d_lock);
+		if (IS_ROOT(dentry))
+			break;
 		namelen = dentry->d_name.len;
 		buflen -= namelen + 1;
 		if (buflen < 0)
@@ -68,27 +69,47 @@ char *nfs_path(const char *base,
 		end -= namelen;
 		memcpy(end, dentry->d_name.name, namelen);
 		*--end = '/';
+		spin_unlock(&dentry->d_lock);
 		dentry = dentry->d_parent;
 	}
+	if (read_seqretry(&rename_lock, seq)) {
+		spin_unlock(&dentry->d_lock);
 		rcu_read_unlock();
-	if (read_seqretry(&rename_lock, seq))
 		goto rename_retry;
+	}
 	if (*end != '/') {
-		if (--buflen < 0)
+		if (--buflen < 0) {
+			spin_unlock(&dentry->d_lock);
+			rcu_read_unlock();
 			goto Elong;
+		}
 		*--end = '/';
 	}
+	*p = end;
+	base = dentry->d_fsdata;
+	if (!base) {
+		spin_unlock(&dentry->d_lock);
+		rcu_read_unlock();
+		WARN_ON(1);
+		return end;
+	}
 	namelen = strlen(base);
 	/* Strip off excess slashes in base string */
 	while (namelen > 0 && base[namelen - 1] == '/')
 		namelen--;
 	buflen -= namelen;
-	if (buflen < 0)
+	if (buflen < 0) {
+		spin_lock(&dentry->d_lock);
+		rcu_read_unlock();
 		goto Elong;
+	}
 	end -= namelen;
 	memcpy(end, base, namelen);
+	spin_unlock(&dentry->d_lock);
+	rcu_read_unlock();
 	return end;
 Elong_unlock:
+	spin_lock(&dentry->d_lock);
 	rcu_read_unlock();
 	if (read_seqretry(&rename_lock, seq))
 		goto rename_retry;
@@ -143,9 +164,9 @@ struct vfsmount *nfs_d_automount(struct path *path)
 	}
 
 	if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL)
-		mnt = nfs_do_refmount(path->mnt, path->dentry);
+		mnt = nfs_do_refmount(path->mnt->mnt_sb, path->dentry);
 	else
-		mnt = nfs_do_submount(path->mnt, path->dentry, fh, fattr);
+		mnt = nfs_do_submount(path->mnt->mnt_sb, path->dentry, fh, fattr);
 	if (IS_ERR(mnt))
 		goto out;
 
@@ -209,19 +230,19 @@ static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
 
 /**
  * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
- * @mnt_parent - mountpoint of parent directory
+ * @sb - superblock of parent directory
  * @dentry - parent directory
  * @fh - filehandle for new root dentry
  * @fattr - attributes for new root inode
  *
  */
-static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent,
-					const struct dentry *dentry,
+static struct vfsmount *nfs_do_submount(struct super_block *sb,
+					struct dentry *dentry,
 					struct nfs_fh *fh,
 					struct nfs_fattr *fattr)
 {
 	struct nfs_clone_mount mountdata = {
-		.sb = mnt_parent->mnt_sb,
+		.sb = sb,
 		.dentry = dentry,
 		.fh = fh,
 		.fattr = fattr,
@@ -237,11 +258,11 @@ static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent,
 			dentry->d_name.name);
 	if (page == NULL)
 		goto out;
-	devname = nfs_devname(mnt_parent, dentry, page, PAGE_SIZE);
+	devname = nfs_devname(dentry, page, PAGE_SIZE);
 	mnt = (struct vfsmount *)devname;
 	if (IS_ERR(devname))
 		goto free_page;
-	mnt = nfs_do_clone_mount(NFS_SB(mnt_parent->mnt_sb), devname, &mountdata);
+	mnt = nfs_do_clone_mount(NFS_SB(sb), devname, &mountdata);
 free_page:
 	free_page((unsigned long)page);
 out:

fs/nfs/nfs4namespace.c

@@ -54,33 +54,29 @@ static inline char *nfs4_pathname_string(const struct nfs4_pathname *pathname,
 /*
  * Determine the mount path as a string
  */
-static char *nfs4_path(const struct vfsmount *mnt_parent,
-		       const struct dentry *dentry,
-		       char *buffer, ssize_t buflen)
+static char *nfs4_path(struct dentry *dentry, char *buffer, ssize_t buflen)
 {
-	const char *srvpath;
-
-	srvpath = strchr(mnt_parent->mnt_devname, ':');
-	if (srvpath)
-		srvpath++;
-	else
-		srvpath = mnt_parent->mnt_devname;
-
-	return nfs_path(srvpath, mnt_parent->mnt_root, dentry, buffer, buflen);
+	char *limit;
+	char *path = nfs_path(&limit, dentry, buffer, buflen);
+	if (!IS_ERR(path)) {
+		char *colon = strchr(path, ':');
+		if (colon && colon < limit)
+			path = colon + 1;
+	}
+	return path;
 }
 
 /*
  * Check that fs_locations::fs_root [RFC3530 6.3] is a prefix for what we
  * believe to be the server path to this dentry
  */
-static int nfs4_validate_fspath(const struct vfsmount *mnt_parent,
-				const struct dentry *dentry,
+static int nfs4_validate_fspath(struct dentry *dentry,
 				const struct nfs4_fs_locations *locations,
 				char *page, char *page2)
 {
 	const char *path, *fs_path;
 
-	path = nfs4_path(mnt_parent, dentry, page, PAGE_SIZE);
+	path = nfs4_path(dentry, page, PAGE_SIZE);
 	if (IS_ERR(path))
 		return PTR_ERR(path);
 
@@ -165,20 +161,20 @@ static struct vfsmount *try_location(struct nfs_clone_mount *mountdata,
 
 /**
  * nfs_follow_referral - set up mountpoint when hitting a referral on moved error
- * @mnt_parent - mountpoint of parent directory
+ * @sb - superblock of parent directory
  * @dentry - parent directory
  * @locations - array of NFSv4 server location information
  *
  */
-static struct vfsmount *nfs_follow_referral(const struct vfsmount *mnt_parent,
-					    const struct dentry *dentry,
+static struct vfsmount *nfs_follow_referral(struct super_block *sb,
+					    struct dentry *dentry,
 					    const struct nfs4_fs_locations *locations)
 {
 	struct vfsmount *mnt = ERR_PTR(-ENOENT);
 	struct nfs_clone_mount mountdata = {
-		.sb = mnt_parent->mnt_sb,
+		.sb = sb,
 		.dentry = dentry,
-		.authflavor = NFS_SB(mnt_parent->mnt_sb)->client->cl_auth->au_flavor,
+		.authflavor = NFS_SB(sb)->client->cl_auth->au_flavor,
 	};
 	char *page = NULL, *page2 = NULL;
 	int loc, error;
@@ -198,7 +194,7 @@ static struct vfsmount *nfs_follow_referral(const struct vfsmount *mnt_parent,
 		goto out;
 
 	/* Ensure fs path is a prefix of current dentry path */
-	error = nfs4_validate_fspath(mnt_parent, dentry, locations, page, page2);
+	error = nfs4_validate_fspath(dentry, locations, page, page2);
 	if (error < 0) {
 		mnt = ERR_PTR(error);
 		goto out;
@@ -225,11 +221,10 @@ static struct vfsmount *nfs_follow_referral(const struct vfsmount *mnt_parent,
 
 /*
  * nfs_do_refmount - handle crossing a referral on server
- * @mnt_parent - mountpoint of referral
  * @dentry - dentry of referral
  *
  */
-struct vfsmount *nfs_do_refmount(const struct vfsmount *mnt_parent, struct dentry *dentry)
+struct vfsmount *nfs_do_refmount(struct super_block *sb, struct dentry *dentry)
 {
 	struct vfsmount *mnt = ERR_PTR(-ENOMEM);
 	struct dentry *parent;
@@ -262,7 +257,7 @@ struct vfsmount *nfs_do_refmount(const struct vfsmount *mnt_parent, struct dentr
 	    fs_locations->fs_path.ncomponents <= 0)
 		goto out_free;
 
-	mnt = nfs_follow_referral(mnt_parent, dentry, fs_locations);
+	mnt = nfs_follow_referral(sb, dentry, fs_locations);
 out_free:
 	__free_page(page);
 	kfree(fs_locations);

fs/nfs/super.c

@@ -2771,16 +2771,15 @@ static struct vfsmount *nfs_do_root_mount(struct file_system_type *fs_type,
 	return root_mnt;
 }
 
-static void nfs_fix_devname(const struct path *path, struct vfsmount *mnt)
+static void nfs_fix_devname(struct dentry *dentry, struct vfsmount *mnt)
 {
 	char *page = (char *) __get_free_page(GFP_KERNEL);
 	char *devname, *tmp;
+	char *dummy;
 
 	if (page == NULL)
 		return;
-	devname = nfs_path(path->mnt->mnt_devname,
-			path->mnt->mnt_root, path->dentry,
-			page, PAGE_SIZE);
+	devname = nfs_path(&dummy, dentry, page, PAGE_SIZE);
 	if (IS_ERR(devname))
 		goto out_freepage;
 	tmp = kstrdup(devname, GFP_KERNEL);
@@ -2894,7 +2893,7 @@ static int nfs_follow_remote_path(struct vfsmount *root_mnt,
 	mnt_target->mnt_root = dget(nd->path.dentry);
 
 	/* Correct the device pathname */
-	nfs_fix_devname(&nd->path, mnt_target);
+	nfs_fix_devname(nd->path.dentry, mnt_target);
 
 	path_put(&nd->path);
 	kfree(nd);