Some efforts to adding better support for readdir

README

@@ -46,7 +46,7 @@ MM0 is the systm task that implements memory management. It contains memory and
 page allocators. It implements demand paging by managing page faults, physical
 pages and their file/task associations.
 
-FS0 is the system task implements a simple, modern virtual filesystem layer.
+FS0 is the system task that implements a simple, modern virtual filesystem layer.
 Since it abstracts the low-level filesystem details, it is a relatively easy job
 to port a new filesystem to be used under FS0.
 

tasks/fs0/include/fs.h

@@ -47,7 +47,7 @@ struct file_ops {
 struct vnode_ops {
 	vnode_op_t create;
 	struct vnode *(*lookup)(struct vnode *root, char *path);
-	void * (*readdir)(struct vnode *v, void *dirbuf);
+	void *(*readdir)(struct vnode *v, void *dirbuf);
 	vnode_op_t link;
 	vnode_op_t unlink;
 	vnode_op_t mkdir;
@@ -97,6 +97,7 @@ struct vnode {
 	struct file_ops fops;		/* File-related operations on this vnode */
 	struct list_head dentries;	/* Dirents that refer to this vnode */
 	struct list_head state_list;	/* List for vnode's dirty/clean state */
+	struct list_head cache_list;	/* For adding the vnode to vnode cache */
 	u32 type;			/* Vnode type, dev? socket? dir? ... */
 	u32 mode;			/* Permissions */
 	u32 owner;			/* Owner */

tasks/fs0/include/memfs/memfs.h

@@ -75,8 +75,9 @@ struct memfs_superblock {
 
 #define MEMFS_DNAME_MAX			32
 struct memfs_dentry {
-	u32 inum;	/* Inode number */
-	u32 nlength;	/* Name length */
+	u32 inum;			/* Inode number */
+	u32 offset;			/* Dentry offset in its buffer */
+	u32 rlength;			/* Record length */
 	u8  name[MEMFS_DNAME_MAX];	/* Name string */
 };
 

tasks/fs0/include/vfs.h

@@ -6,6 +6,17 @@
 #include <l4/lib/list.h>
 #include <memfs/memfs.h>
 
+/* Buffer to keep directory content. This is the only vnode content
+ * that fs0 maintains. All other file data is in mm0 page cache.
+ */
+struct dirbuf {
+	struct list_head list;
+	unsigned long bufsize;
+	u8 *buffer;
+};
+extern struct list_head vnode_cache;
+extern struct list_head dentry_cache;
+
 /*
  * FIXME:
  * These ought to be strings and split/comparison functions should
@@ -58,12 +69,16 @@ static inline struct vnode *vfs_alloc_vnode(void)
 
 	INIT_LIST_HEAD(&v->dentries);
 	INIT_LIST_HEAD(&v->state_list);
+	INIT_LIST_HEAD(&v->cache_list);
+	list_add(&v->cache_list, &vnode_cache);
 
 	return v;
 }
 
 static inline void vfs_free_vnode(struct vnode *v)
 {
+	BUG(); /* Are the dentries freed ??? */
+	list_del(&v->cache_list);
 	kfree(v);
 }
 
@@ -84,6 +99,7 @@ extern struct vfs_mountpoint vfs_root;
 
 int vfs_mount_root(struct superblock *sb);
 struct vnode *generic_vnode_lookup(struct vnode *thisnode, char *path);
-struct vnode *vfs_lookup(struct superblock *sb, char *path);
+struct vnode *vfs_lookup_bypath(struct superblock *sb, char *path);
+struct vnode *vfs_lookup_byvnum(struct superblock *sb, unsigned long vnum);
 
 #endif /* __VFS_H__ */

tasks/fs0/main.c

@@ -16,6 +16,19 @@
 #include <syscalls.h>
 #include <task.h>
 
+/*
+ * TODO:
+ * - Have a dentry cache searchable by name
+ * - Have a vnode cache searchable by vnum (and name?)
+ * - fs-specific readdir would read contents by page range, and add vnodes/dentries
+ *   to their caches, while populating the directory vnode being read.
+ * - Have 2 vfs_lookup() flavors, one that searches a path, one that searches a vnum.
+ * - dirbuf is either allocated by low-level readdir, or else by a higher level, i.e.
+ *   either high-level vfs code, or the mm0 page cache.
+ * - readdir provides a posix-compliant dirent structure list in dirbuf.
+ * - memfs dentries should be identical to posix struct dirents.
+ */
+
 /* Synchronise with pager via a `wait' tagged ipc with destination as pager */
 void wait_pager(l4id_t partner)
 {

tasks/fs0/src/init.c

@@ -75,6 +75,8 @@ int initialise(void)
 	memfs_format_filesystem(rootdev_blocks);
 
 	INIT_LIST_HEAD(&vm_file_list);
+	INIT_LIST_HEAD(&vnode_cache);
+	INIT_LIST_HEAD(&dentry_cache);
 
 	/* Search for a filesystem on the root device */
 	BUG_ON(IS_ERR(root_sb = vfs_probe_filesystems(rootdev_blocks)));

tasks/fs0/src/syscalls.c

@@ -91,6 +91,7 @@ int sys_read(l4id_t sender, int fd, void *buf, int count)
 int sys_readdir(l4id_t sender, int fd, void *buf, int count)
 {
 	struct vnode *v;
+	struct tcb *t;
 
 	/* Get the task */
 	BUG_ON(!(t = find_task(sender)));
@@ -104,7 +105,7 @@ int sys_readdir(l4id_t sender, int fd, void *buf, int count)
 
 	/* Simply read its contents */
 	v->ops.readdir(v, buf, count);
-`
+
 	return 0;
 }
 

tasks/fs0/src/vfs.c

@@ -6,12 +6,49 @@
 #include <fs.h>
 #include <vfs.h>
 
-struct vnode *vfs_lookup(struct superblock *sb, char *path)
+struct list_head vnode_cache;
+struct list_head dentry_cache;
+
+/*
+ * Vnodes in the vnode cache have 2 keys. One is their dentry names, the other
+ * is their vnum. This one checks the vnode cache by the given vnum first.
+ * If nothing is found, it reads the vnode from disk into cache.
+ */
+struct vnode *vfs_lookup_byvnum(struct superblock *sb, unsigned long vnum)
+{
+	struct vnode *v;
+
+	/* Check the vnode cache by vnum */
+	list_for_each_entry(v, vnode_cache, cache_list)
+		if (v->vnum == vnum)
+			return v;
+
+	/* Otherwise ask the filesystem:
+	 * TODO:
+	 * vfs_alloc_vnode() -> This should also add the empty vnode to vnode cache.
+	 * read_vnode() -> read it from filesystem.
+	 * return what's read.
+	 */
+}
+
+/*
+ * Vnodes in the vnode cache have 2 keys. One is their dentry name, the
+ * other is their vnum. This one checks the vnode cache by the path first.
+ * If nothing is found, it reads the vnode from disk into the cache.
+ */
+struct vnode *vfs_lookup_bypath(struct superblock *sb, char *path)
 {
 	/* If it's just / we already got it. */
 	if (!strcmp(path, "/"))
 		return sb->root;
 
+	/* TODO: Check the vnode cache by path component
+	 *
+	 * This should split the path into components and compare
+	 * each of them with each vnode's dentry list.
+	 */
+
+	/* It's not in the cache, look it up from filesystem. */
 	return sb->root->ops.lookup(sb->root, path);
 }
 
@@ -28,7 +65,7 @@ struct vfs_mountpoint vfs_root;
 int vfs_mount_root(struct superblock *sb)
 {
 	/* Lookup the root vnode of this superblock */
-	vfs_root.pivot = vfs_lookup(sb, "/");
+	vfs_root.pivot = vfs_lookup_bypath(sb, "/");
 	vfs_root.sb = sb;
 
 	return 0;