Implement [hard]link operation.

Also:
- include "." and ".." in list of invalid directory entry names
- move dirent name validation to dbfs_dir_append()
- dbfs_inode_free(NULL) is now supported

4 files changed, 72 insertions, 14 deletions

diff --git a/dbfs-backend.c b/dbfs-backend.c
index b4d7c44..34c9fc3 100644
--- a/dbfs-backend.c
+++ b/dbfs-backend.c
@@ -339,6 +339,19 @@ static int dbfs_dir_find_last(struct dbfs_dirent *de, void *userdata)
 	return 0;
 }
 
+static int dbfs_name_validate(const char *name)
+{
+	if (strchr(name, '/'))
+		return -EINVAL;
+	if (!g_utf8_validate(name, -1, NULL))
+		return -EINVAL;
+	if (!strcmp(name, "."))
+		return -EINVAL;
+	if (!strcmp(name, ".."))
+		return -EINVAL;
+	return 0;
+}
+
 static int dbfs_dir_append(guint64 parent, guint64 ino_n, const char *name)
 {
 	struct dbfs_dirscan_info di;
@@ -348,6 +361,10 @@ static int dbfs_dir_append(guint64 parent, guint64 ino_n, const char *name)
 	unsigned int dir_size, namelen;
 	void *p;
 
+	rc = dbfs_name_validate(name);
+	if (rc)
+		return rc;
+
 	/* read parent directory from database */
 	rc = dbfs_dir_read(parent, &val);
 	if (rc)
@@ -449,6 +466,30 @@ int dbfs_symlink_write(guint64 ino, const char *link)
 	return gfs->meta->put(gfs->meta, NULL, &key, &val, 0) ? -EIO : 0;
 }
 
+int dbfs_link(struct dbfs_inode *ino, guint64 ino_n, guint64 parent,
+	      const char *name)
+{
+	guint32 nlink;
+	int rc;
+
+	/* make sure it doesn't exist yet */
+	rc = dbfs_dir_append(parent, ino_n, name);
+	if (rc)
+		return rc;
+
+	/* increment link count */
+	nlink = GUINT32_FROM_LE(ino->raw_inode->nlink);
+	nlink++;
+	ino->raw_inode->nlink = GUINT32_TO_LE(nlink);
+
+	/* write inode; if fails, undo directory modification */
+	rc = dbfs_inode_write(ino);
+	if (rc)
+		dbfs_dirent_del(parent, name);
+
+	return rc;
+}
+
 int dbfs_unlink(guint64 parent, const char *name, unsigned long flags)
 {
 	struct dbfs_inode *ino;
@@ -497,15 +538,6 @@ out:
 	return rc;
 }
 
-static int dbfs_name_validate(const char *name)
-{
-	if (strchr(name, '/'))
-		return -EINVAL;
-	if (!g_utf8_validate(name, -1, NULL))
-		return -EINVAL;
-	return 0;
-}
-
 int dbfs_mknod(guint64 parent, const char *name, guint32 mode, guint64 rdev,
 	       struct dbfs_inode **ino_out)
 {
@@ -516,10 +548,6 @@ int dbfs_mknod(guint64 parent, const char *name, guint32 mode, guint64 rdev,
 
 	*ino_out = NULL;
 
-	rc = dbfs_name_validate(name);
-	if (rc)
-		return rc;
-
 	rc = dbfs_inode_next(&ino);
 	if (rc)
 		return rc;
diff --git a/dbfs.c b/dbfs.c
index 6ad725a..10a7906 100644
--- a/dbfs.c
+++ b/dbfs.c
@@ -215,6 +215,32 @@ static void dbfs_op_unlink(fuse_req_t req, fuse_ino_t parent, const char *name)
 	fuse_reply_err(req, rc ? -rc : 0);
 }
 
+static void dbfs_op_link(fuse_req_t req, fuse_ino_t ino_n, fuse_ino_t parent,
+			 const char *newname)
+{
+	struct dbfs_inode *ino;
+	int rc;
+
+	/* read inode from database */
+	rc = dbfs_inode_read(ino_n, &ino);
+	if (rc) {
+		fuse_reply_err(req, ENOENT);
+		return;
+	}
+
+	/* attempt to create hard link */
+	rc = dbfs_link(ino, ino_n, parent, newname);
+	if (rc)
+		goto err_out;
+
+	dbfs_reply_ino(req, ino);
+	return;
+
+err_out:
+	dbfs_inode_free(ino);
+	fuse_reply_err(req, -rc);
+}
+
 static int dbfs_chk_empty(struct dbfs_dirent *de, void *userdata)
 {
 	if ((GUINT16_FROM_LE(de->namelen) == 1) && (!memcmp(de->name, ".", 1)))
@@ -390,7 +416,7 @@ static struct fuse_lowlevel_ops dbfs_ops = {
 	.rmdir		= dbfs_op_rmdir,
 	.symlink	= dbfs_op_symlink,
 	.rename		= NULL,
-	.link		= NULL,
+	.link		= dbfs_op_link,
 	.open		= NULL,
 	.read		= NULL,
 	.write		= NULL,
diff --git a/dbfs.h b/dbfs.h
index 0803156..220a02f 100644
--- a/dbfs.h
+++ b/dbfs.h
@@ -86,6 +86,7 @@ extern int dbfs_dir_read(guint64 ino, DBT *val);
 extern int dbfs_symlink_read(guint64 ino, DBT *val);
 extern int dbfs_dir_foreach(void *dir, dbfs_dir_actor_t func, void *userdata);
 extern int dbfs_dir_lookup(guint64 parent, const char *name, guint64 *ino);
+extern int dbfs_link(struct dbfs_inode *ino, guint64 ino_n, guint64 parent, const char *name);
 extern int dbfs_unlink(guint64 parent, const char *name, unsigned long flags);
 extern void dbfs_init(void *userdata);
 extern void dbfs_exit(void *userdata);
diff --git a/libdbfs.c b/libdbfs.c
index 9b4d878..d51fa35 100644
--- a/libdbfs.c
+++ b/libdbfs.c
@@ -151,6 +151,9 @@ void dbfs_free(struct dbfs *fs)
 
 void dbfs_inode_free(struct dbfs_inode *ino)
 {
+	if (!ino)		/* permit dbfs_inode_free(NULL) */
+		return;
+
 	free(ino->raw_inode);
 	g_free(ino);
 }