X-Git-Url: https://scm.lunaixsky.com/lunaix-os.git/blobdiff_plain/4769a870917b98723690aa336d12d0656769528b..fac3bbf2b2634f4f15cb33ece3acfa39db1433df:/lunaix-os/kernel/fs/vfs.c

diff --git a/lunaix-os/kernel/fs/vfs.c b/lunaix-os/kernel/fs/vfs.c
index 09539c9..53d21d8 100644
--- a/lunaix-os/kernel/fs/vfs.c
+++ b/lunaix-os/kernel/fs/vfs.c
@@ -1,7 +1,24 @@
+/**
+ * @file vfs.c
+ * @author Lunaixsky (zelong56@gmail.com)
+ * @brief Lunaix virtual file system - an abstraction layer for all file system.
+ * @version 0.1
+ * @date 2022-07-24
+ *
+ * @copyright Copyright (c) 2022
+ *
+ */
+
 #include <klibc/string.h>
+#include <lunaix/dirent.h>
+#include <lunaix/foptions.h>
 #include <lunaix/fs.h>
 #include <lunaix/mm/cake.h>
+#include <lunaix/mm/page.h>
 #include <lunaix/mm/valloc.h>
+#include <lunaix/process.h>
+#include <lunaix/spike.h>
+#include <lunaix/syscall.h>
 
 #define PATH_DELIM '/'
 #define DNODE_HASHTABLE_BITS 10
@@ -9,47 +26,53 @@
 #define DNODE_HASH_MASK (DNODE_HASHTABLE_SIZE - 1)
 #define DNODE_HASHBITS (32 - DNODE_HASHTABLE_BITS)
 
-#define VFS_ETOOLONG -1
-#define VFS_ENOFS -2
-
 static struct cake_pile* dnode_pile;
 static struct cake_pile* inode_pile;
+static struct cake_pile* file_pile;
 static struct cake_pile* superblock_pile;
-static struct cake_pile* name_pile;
+static struct cake_pile* fd_pile;
 
 static struct v_superblock* root_sb;
 static struct hbucket* dnode_cache;
 
 static int fs_id = 0;
 
+struct hstr vfs_ddot = HSTR("..", 2);
+struct hstr vfs_dot = HSTR(".", 1);
+struct hstr vfs_empty = HSTR("", 0);
+
 struct v_dnode*
-__new_dnode();
+vfs_d_alloc();
 
 void
-__free_dnode(struct v_dnode* dnode);
+vfs_d_free(struct v_dnode* dnode);
 
 struct v_superblock*
-__new_superblock();
+vfs_sb_alloc();
 
 void
-__free_superblock(struct v_superblock* sb);
+vfs_sb_free(struct v_superblock* sb);
 
 void
 vfs_init()
 {
-    // 为他们专门创建一个蛋糕堆，而不使用valloc，这样我们可以最小化内部碎片的产生
-    dnode_pile = cake_new_pile("dnode", sizeof(struct v_dnode), 1, 0);
-    inode_pile = cake_new_pile("inode", sizeof(struct v_inode), 1, 0);
-    name_pile = cake_new_pile("dname", VFS_NAME_MAXLEN, 1, 0);
+    // 为他们专门创建一个蛋糕堆，而不使用valloc，这样我们可以最小化内碎片的产生
+    dnode_pile = cake_new_pile("dnode_cache", sizeof(struct v_dnode), 1, 0);
+    inode_pile = cake_new_pile("inode_cache", sizeof(struct v_inode), 1, 0);
+    file_pile = cake_new_pile("file_cache", sizeof(struct v_file), 1, 0);
+    fd_pile = cake_new_pile("fd_cache", sizeof(struct v_fd), 1, 0);
     superblock_pile =
-      cake_new_pile("superblock", sizeof(struct v_superblock), 1, 0);
+      cake_new_pile("sb_cache", sizeof(struct v_superblock), 1, 0);
 
-    dnode_cache = valloc(DNODE_HASHTABLE_SIZE * sizeof(struct hbucket));
+    dnode_cache = vzalloc(DNODE_HASHTABLE_SIZE * sizeof(struct hbucket));
 
-    // 挂载Lunaix的根文件系统，TwiFS！
-    struct filesystem* rootfs = fsm_get("twifs");
-    root_sb = __new_superblock();
-    rootfs->mount(root_sb, NULL);
+    hstr_rehash(&vfs_ddot, HSTR_FULL_HASH);
+    hstr_rehash(&vfs_dot, HSTR_FULL_HASH);
+
+    // 创建一个根superblock，用来蕴含我们的根目录。
+    root_sb = vfs_sb_alloc();
+    root_sb->root = vfs_d_alloc();
+    root_sb->root->inode = vfs_i_alloc();
 }
 
 inline struct hbucket*
@@ -65,6 +88,13 @@ __dcache_get_bucket(struct v_dnode* parent, unsigned int hash)
 struct v_dnode*
 vfs_dcache_lookup(struct v_dnode* parent, struct hstr* str)
 {
+    if (!str->len || HSTR_EQ(str, &vfs_dot))
+        return parent;
+
+    if (HSTR_EQ(str, &vfs_ddot)) {
+        return parent->parent ? parent->parent : parent;
+    }
+
     struct hbucket* slot = __dcache_get_bucket(parent, str->hash);
 
     struct v_dnode *pos, *n;
@@ -85,13 +115,21 @@ vfs_dcache_add(struct v_dnode* parent, struct v_dnode* dnode)
 }
 
 int
-vfs_walk(struct v_dnode* start, const char* path, struct v_dnode** dentry)
+__vfs_walk(struct v_dnode* start,
+           const char* path,
+           struct v_dnode** dentry,
+           struct hstr* component,
+           int walk_options)
 {
     int errno = 0;
     int i = 0, j = 0;
 
-    if (path[0] == PATH_DELIM) {
-        start = start->super_block->root;
+    if (path[0] == PATH_DELIM || !start) {
+        if ((walk_options & VFS_WALK_FSRELATIVE) && start) {
+            start = start->super_block->root;
+        } else {
+            start = root_sb->root;
+        }
         i++;
     }
 
@@ -101,34 +139,61 @@ vfs_walk(struct v_dnode* start, const char* path, struct v_dnode** dentry)
     char name_content[VFS_NAME_MAXLEN];
     struct hstr name = HSTR(name_content, 0);
 
-    char current, lookahead;
-    do {
-        current = path[i++];
+    char current = path[i++], lookahead;
+    while (current) {
         lookahead = path[i++];
         if (current != PATH_DELIM) {
             if (j >= VFS_NAME_MAXLEN - 1) {
-                errno = VFS_ETOOLONG;
-                goto error;
+                return ENAMETOOLONG;
+            }
+            if (!VFS_VALID_CHAR(current)) {
+                return EINVAL;
             }
             name_content[j++] = current;
             if (lookahead) {
-                continue;
+                goto cont;
             }
         }
 
+        // handling cases like /^.*(\/+).*$/
+        if (lookahead == PATH_DELIM) {
+            goto cont;
+        }
+
         name_content[j] = 0;
-        hstr_rehash(&name, 32);
+        name.len = j;
+        hstr_rehash(&name, HSTR_FULL_HASH);
+
+        if (!lookahead && (walk_options & VFS_WALK_PARENT)) {
+            if (component) {
+                component->hash = name.hash;
+                component->len = j;
+                strcpy(component->value, name_content);
+            }
+            break;
+        }
 
         dnode = vfs_dcache_lookup(current_level, &name);
 
         if (!dnode) {
-            dnode = __new_dnode();
+            dnode = vfs_d_alloc();
+            dnode->name = HHSTR(valloc(VFS_NAME_MAXLEN), j, name.hash);
+
             strcpy(dnode->name.value, name_content);
-            dnode->name.hash = name.hash;
-            dnode->name.len = j;
 
-            if ((errno =
-                   dnode->inode->ops.dir_lookup(current_level->inode, dnode))) {
+            errno =
+              current_level->inode->ops.dir_lookup(current_level->inode, dnode);
+
+            if (errno == ENOENT && (walk_options & VFS_WALK_MKPARENT)) {
+                if (!current_level->inode->ops.mkdir) {
+                    errno = ENOTSUP;
+                } else {
+                    errno = current_level->inode->ops.mkdir(
+                      current_level->inode, dnode);
+                }
+            }
+
+            if (errno) {
                 goto error;
             }
 
@@ -140,29 +205,99 @@ vfs_walk(struct v_dnode* start, const char* path, struct v_dnode** dentry)
 
         j = 0;
         current_level = dnode;
-    } while (lookahead);
+    cont:
+        current = lookahead;
+    };
 
-    *dentry = dnode;
+    *dentry = current_level;
     return 0;
 
 error:
-    __free_dnode(dnode);
+    vfree(dnode->name.value);
+    vfs_d_free(dnode);
+    *dentry = NULL;
+    return errno;
+}
+
+#define VFS_MAX_SYMLINK 16
+
+int
+vfs_walk(struct v_dnode* start,
+         const char* path,
+         struct v_dnode** dentry,
+         struct hstr* component,
+         int options)
+{
+    struct v_dnode* interim;
+    char* pathname = path;
+    int errno = __vfs_walk(start, path, &interim, component, options);
+    int counter = 0;
+
+    while (!errno) {
+        if (counter >= VFS_MAX_SYMLINK) {
+            errno = ELOOP;
+            continue;
+        }
+        if ((interim->inode->itype & VFS_IFSYMLINK) &&
+            !(options & VFS_WALK_NOFOLLOW) &&
+            interim->inode->ops.read_symlink) {
+            errno = interim->inode->ops.read_symlink(interim->inode, &pathname);
+            if (errno) {
+                break;
+            }
+        } else {
+            break;
+        }
+        errno = __vfs_walk(start, pathname, &interim, component, options);
+        counter++;
+    }
+
+    *dentry = errno ? 0 : interim;
+
+    return errno;
+}
+
+int
+vfs_mount(const char* target, const char* fs_name, bdev_t device)
+{
+    int errno;
+    struct v_dnode* mnt;
+
+    if (!(errno = vfs_walk(NULL, target, &mnt, NULL, 0))) {
+        errno = vfs_mount_at(fs_name, device, mnt);
+    }
+
     return errno;
 }
 
 int
-vfs_mount(const char* fs_name, bdev_t device, struct v_dnode* mnt_point)
+vfs_unmount(const char* target)
+{
+    int errno;
+    struct v_dnode* mnt;
+
+    if (!(errno = vfs_walk(NULL, target, &mnt, NULL, 0))) {
+        errno = vfs_unmount_at(mnt);
+    }
+
+    return errno;
+}
+
+int
+vfs_mount_at(const char* fs_name, bdev_t device, struct v_dnode* mnt_point)
 {
     struct filesystem* fs = fsm_get(fs_name);
     if (!fs)
-        return VFS_ENOFS;
-    struct v_superblock* sb = __new_superblock();
+        return ENODEV;
+    struct v_superblock* sb = vfs_sb_alloc();
     sb->dev = device;
     sb->fs_id = fs_id++;
 
     int errno = 0;
     if (!(errno = fs->mount(sb, mnt_point))) {
         sb->fs = fs;
+        sb->root = mnt_point;
+        mnt_point->super_block = sb;
         llist_append(&root_sb->sb_list, &sb->sb_list);
     }
 
@@ -170,52 +305,717 @@ vfs_mount(const char* fs_name, bdev_t device, struct v_dnode* mnt_point)
 }
 
 int
-vfs_unmount(const int fs_id)
+vfs_unmount_at(struct v_dnode* mnt_point)
 {
     int errno = 0;
-    struct v_superblock *pos, *n;
-    llist_for_each(pos, n, &root_sb->sb_list, sb_list)
-    {
-        if (pos->fs_id != fs_id) {
-            continue;
-        }
-        if (!(errno = pos->fs->unmount(pos))) {
-            llist_delete(&pos->sb_list);
-            __free_superblock(pos);
+    struct v_superblock* sb = mnt_point->super_block;
+    if (!sb) {
+        return EINVAL;
+    }
+    if (!(errno = sb->fs->unmount(sb))) {
+        struct v_dnode* fs_root = sb->root;
+        llist_delete(&fs_root->siblings);
+        llist_delete(&sb->sb_list);
+        vfs_sb_free(sb);
+    }
+    return errno;
+}
+
+int
+vfs_open(struct v_dnode* dnode, struct v_file** file)
+{
+    if (!dnode->inode || !dnode->inode->ops.open) {
+        return ENOTSUP;
+    }
+
+    struct v_inode* inode = dnode->inode;
+    struct v_file* vfile = cake_grab(file_pile);
+    memset(vfile, 0, sizeof(*vfile));
+
+    vfile->dnode = dnode;
+    vfile->inode = inode;
+    vfile->ref_count = 1;
+    vfile->ops = inode->default_fops;
+    inode->open_count++;
+
+    if ((inode->itype & VFS_IFFILE) && !inode->pg_cache) {
+        struct pcache* pcache = vzalloc(sizeof(struct pcache));
+        pcache_init(pcache);
+        inode->pg_cache = pcache;
+    }
+
+    int errno = inode->ops.open(inode, vfile);
+    if (errno) {
+        cake_release(file_pile, vfile);
+    } else {
+        *file = vfile;
+    }
+    return errno;
+}
+
+int
+vfs_link(struct v_dnode* to_link, struct v_dnode* name)
+{
+    int errno;
+    if (to_link->super_block->root != name->super_block->root) {
+        errno = EXDEV;
+    } else if (!to_link->inode->ops.link) {
+        errno = ENOTSUP;
+    } else if (!(errno = to_link->inode->ops.link(to_link->inode, name))) {
+        name->inode = to_link->inode;
+        to_link->inode->link_count++;
+    }
+
+    return errno;
+}
+
+int
+vfs_close(struct v_file* file)
+{
+    int errno = 0;
+    if (!file->ops.close || !(errno = file->ops.close(file))) {
+        if (file->inode->open_count) {
+            file->inode->open_count--;
         }
-        break;
+        pcache_commit_all(file);
+        cake_release(file_pile, file);
+    }
+    return errno;
+}
+
+int
+vfs_fsync(struct v_file* file)
+{
+    int errno = ENOTSUP;
+    pcache_commit_all(file);
+    if (file->ops.sync) {
+        errno = file->ops.sync(file);
+    }
+    if (!errno && file->inode->ops.sync) {
+        return file->inode->ops.sync(file->inode);
     }
     return errno;
 }
 
+int
+vfs_alloc_fdslot(int* fd)
+{
+    for (size_t i = 0; i < VFS_MAX_FD; i++) {
+        if (!__current->fdtable->fds[i]) {
+            *fd = i;
+            return 0;
+        }
+    }
+    return EMFILE;
+}
+
 struct v_superblock*
-__new_superblock()
+vfs_sb_alloc()
 {
     struct v_superblock* sb = cake_grab(superblock_pile);
     memset(sb, 0, sizeof(*sb));
     llist_init_head(&sb->sb_list);
-    sb->root = __new_dnode();
+    return sb;
 }
 
 void
-__free_superblock(struct v_superblock* sb)
+vfs_sb_free(struct v_superblock* sb)
 {
-    __free_dnode(sb->root);
     cake_release(superblock_pile, sb);
 }
 
 struct v_dnode*
-__new_dnode()
+vfs_d_alloc()
 {
     struct v_dnode* dnode = cake_grab(dnode_pile);
-    dnode->inode = cake_grab(inode_pile);
-    dnode->name.value = cake_grab(name_pile);
+    memset(dnode, 0, sizeof(*dnode));
+    llist_init_head(&dnode->children);
+    dnode->name = vfs_empty;
+    return dnode;
 }
 
 void
-__free_dnode(struct v_dnode* dnode)
+vfs_d_free(struct v_dnode* dnode)
 {
-    cake_release(inode_pile, dnode->inode);
-    cake_release(name_pile, dnode->name.value);
+    if (dnode->ops.destruct) {
+        dnode->ops.destruct(dnode);
+    }
     cake_release(dnode_pile, dnode);
+}
+
+struct v_inode*
+vfs_i_alloc()
+{
+    struct v_inode* inode = cake_grab(inode_pile);
+    memset(inode, 0, sizeof(*inode));
+    return inode;
+}
+
+void
+vfs_i_free(struct v_inode* inode)
+{
+    cake_release(inode_pile, inode);
+}
+
+/* ---- System call definition and support ---- */
+
+#define FLOCATE_CREATE_EMPTY 1
+
+#define DO_STATUS(errno) SYSCALL_ESTATUS(__current->k_status = errno)
+#define DO_STATUS_OR_RETURN(errno) ({ errno < 0 ? DO_STATUS(errno) : errno; })
+
+int
+__vfs_try_locate_file(const char* path,
+                      struct v_dnode** fdir,
+                      struct v_dnode** file,
+                      int options)
+{
+    char name_str[VFS_NAME_MAXLEN];
+    struct hstr name = HSTR(name_str, 0);
+    int errno;
+    if ((errno = vfs_walk(NULL, path, fdir, &name, VFS_WALK_PARENT))) {
+        return errno;
+    }
+
+    errno = vfs_walk(*fdir, name.value, file, NULL, 0);
+    if (errno != ENOENT || !(options & FLOCATE_CREATE_EMPTY)) {
+        return errno;
+    }
+
+    if (!(errno = (*fdir)->inode->ops.create((*fdir)->inode))) {
+        struct v_dnode* file_new;
+        file_new = vfs_d_alloc();
+        file_new->name = HHSTR(valloc(VFS_NAME_MAXLEN), name.len, name.hash);
+        strcpy(file_new->name.value, name_str);
+        *file = file_new;
+
+        llist_append(&(*fdir)->children, &file_new->siblings);
+    }
+
+    return errno;
+}
+
+int
+__file_cached_read(struct v_file* file, void* buf, size_t len, size_t fpos)
+{
+    return pcache_read(file, buf, len, fpos);
+}
+
+int
+vfs_do_open(const char* path, int options)
+{
+    int errno, fd;
+    struct v_dnode *dentry, *file;
+    struct v_file* ofile = 0;
+
+    errno = __vfs_try_locate_file(path, &dentry, &file, 0);
+
+    if (errno != ENOENT && (options & FO_CREATE)) {
+        errno = dentry->inode->ops.create(dentry->inode);
+    }
+
+    if (!errno && (errno = vfs_open(file, &ofile))) {
+        return errno;
+    }
+
+    struct v_inode* o_inode = ofile->inode;
+    if (!(o_inode->itype & VFS_IFSEQDEV) && !(options & FO_DIRECT)) {
+        // XXX Change here accordingly when signature of pcache_r/w changed.
+        ofile->ops.read = pcache_read;
+        ofile->ops.write = pcache_write;
+    }
+
+    if (!errno && !(errno = vfs_alloc_fdslot(&fd))) {
+        struct v_fd* fd_s = vzalloc(sizeof(*fd_s));
+        ofile->f_pos = ofile->inode->fsize & -((options & FO_APPEND) != 0);
+        fd_s->file = ofile;
+        fd_s->flags = options;
+        __current->fdtable->fds[fd] = fd_s;
+        return fd;
+    }
+
+    return errno;
+}
+
+__DEFINE_LXSYSCALL2(int, open, const char*, path, int, options)
+{
+    int errno = vfs_do_open(path, options);
+    return DO_STATUS_OR_RETURN(errno);
+}
+
+#define TEST_FD(fd) (fd >= 0 && fd < VFS_MAX_FD)
+#define GET_FD(fd, fd_s) (TEST_FD(fd) && (fd_s = __current->fdtable->fds[fd]))
+
+__DEFINE_LXSYSCALL1(int, close, int, fd)
+{
+    struct v_fd* fd_s;
+    int errno = 0;
+    if (!GET_FD(fd, fd_s)) {
+        errno = EBADF;
+        goto done_err;
+    }
+
+    if (fd_s->file->ref_count > 1) {
+        fd_s->file->ref_count--;
+    } else if ((errno = vfs_close(fd_s->file))) {
+        goto done_err;
+    }
+
+    vfree(fd_s);
+    __current->fdtable->fds[fd] = 0;
+
+done_err:
+    return DO_STATUS(errno);
+}
+
+void
+__vfs_readdir_callback(struct dir_context* dctx,
+                       const char* name,
+                       const int len,
+                       const int dtype)
+{
+    struct dirent* dent = (struct dirent*)dctx->cb_data;
+    strncpy(dent->d_name, name, DIRENT_NAME_MAX_LEN);
+    dent->d_nlen = len;
+    dent->d_type = dtype;
+}
+
+__DEFINE_LXSYSCALL2(int, readdir, int, fd, struct dirent*, dent)
+{
+    struct v_fd* fd_s;
+    int errno;
+    if (!GET_FD(fd, fd_s)) {
+        errno = EBADF;
+    } else if (!(fd_s->file->inode->itype & VFS_IFDIR)) {
+        errno = ENOTDIR;
+    } else {
+        struct dir_context dctx =
+          (struct dir_context){ .cb_data = dent,
+                                .index = dent->d_offset,
+                                .read_complete_callback =
+                                  __vfs_readdir_callback };
+        if (dent->d_offset == 0) {
+            __vfs_readdir_callback(&dctx, vfs_dot.value, vfs_dot.len, 0);
+        } else if (dent->d_offset == 1) {
+            __vfs_readdir_callback(&dctx, vfs_ddot.value, vfs_ddot.len, 0);
+        } else {
+            dctx.index -= 2;
+            if ((errno = fd_s->file->ops.readdir(fd_s->file, &dctx))) {
+                goto done;
+            }
+        }
+        errno = 0;
+        dent->d_offset++;
+    }
+
+done:
+    return DO_STATUS(errno);
+}
+
+__DEFINE_LXSYSCALL1(int, mkdir, const char*, path)
+{
+    struct v_dnode *parent, *dir;
+    struct hstr component = HSTR(valloc(VFS_NAME_MAXLEN), 0);
+    int errno = vfs_walk(NULL, path, &parent, &component, VFS_WALK_PARENT);
+    if (errno) {
+        goto done;
+    }
+
+    if ((parent->super_block->fs->types & FSTYPE_ROFS)) {
+        errno = ENOTSUP;
+    } else if (!parent->inode->ops.mkdir) {
+        errno = ENOTSUP;
+    } else if (!(parent->inode->itype & VFS_IFDIR)) {
+        errno = ENOTDIR;
+    } else {
+        dir = vfs_d_alloc();
+        dir->name = component;
+        if (!(errno = parent->inode->ops.mkdir(parent->inode, dir))) {
+            llist_append(&parent->children, &dir->siblings);
+        } else {
+            vfs_d_free(dir);
+            vfree(component.value);
+        }
+    }
+
+done:
+    return DO_STATUS(errno);
+}
+
+__DEFINE_LXSYSCALL3(int, read, int, fd, void*, buf, size_t, count)
+{
+    int errno = 0;
+    struct v_fd* fd_s;
+    if (!GET_FD(fd, fd_s)) {
+        errno = EBADF;
+        goto done;
+    }
+
+    struct v_file* file = fd_s->file;
+    if ((file->inode->itype & VFS_IFDIR)) {
+        errno = EISDIR;
+        goto done;
+    }
+
+    errno = file->ops.read(file, buf, count, file->f_pos);
+
+    if (errno > 0) {
+        file->f_pos += errno;
+        return errno;
+    }
+
+done:
+    return DO_STATUS(errno);
+}
+
+__DEFINE_LXSYSCALL3(int, write, int, fd, void*, buf, size_t, count)
+{
+    int errno = 0;
+    struct v_fd* fd_s;
+    if (!GET_FD(fd, fd_s)) {
+        errno = EBADF;
+        goto done;
+    }
+
+    struct v_file* file = fd_s->file;
+    if ((file->inode->itype & VFS_IFDIR)) {
+        errno = EISDIR;
+        goto done;
+    }
+
+    errno = file->ops.write(file, buf, count, file->f_pos);
+
+    if (errno > 0) {
+        file->f_pos += errno;
+        return errno;
+    }
+
+done:
+    return DO_STATUS(errno);
+}
+
+__DEFINE_LXSYSCALL3(int, lseek, int, fd, int, offset, int, options)
+{
+    int errno = 0;
+    struct v_fd* fd_s;
+    if (!GET_FD(fd, fd_s)) {
+        errno = EBADF;
+    } else {
+        struct v_file* file = fd_s->file;
+        size_t fpos = file->f_pos;
+        switch (options) {
+            case FSEEK_CUR:
+                fpos = (size_t)((int)file->f_pos + offset);
+                break;
+            case FSEEK_END:
+                fpos = (size_t)((int)file->inode->fsize + offset);
+                break;
+            case FSEEK_SET:
+                fpos = offset;
+                break;
+        }
+        if (!file->ops.seek || !(errno = file->ops.seek(file, fpos))) {
+            file->f_pos = fpos;
+        }
+    }
+
+    return DO_STATUS(errno);
+}
+
+int
+vfs_get_path(struct v_dnode* dnode, char* buf, size_t size, int depth)
+{
+    if (!dnode) {
+        return 0;
+    }
+
+    if (depth > 64) {
+        return ELOOP;
+    }
+
+    size_t len = vfs_get_path(dnode->parent, buf, size, depth + 1);
+
+    if (len >= size) {
+        return len;
+    }
+
+    size_t cpy_size = MIN(dnode->name.len, size - len);
+    strncpy(buf + len, dnode->name.value, cpy_size);
+    len += cpy_size;
+
+    if (len < size) {
+        buf[len++] = PATH_DELIM;
+    }
+
+    return len;
+}
+
+int
+vfs_readlink(struct v_dnode* dnode, char* buf, size_t size)
+{
+    char* link;
+    if (dnode->inode->ops.read_symlink) {
+        int errno = dnode->inode->ops.read_symlink(dnode->inode, &link);
+        strncpy(buf, link, size);
+        return errno;
+    }
+    return 0;
+}
+
+__DEFINE_LXSYSCALL3(int, realpathat, int, fd, char*, buf, size_t, size)
+{
+    int errno;
+    struct v_fd* fd_s;
+    if (!GET_FD(fd, fd_s)) {
+        errno = EBADF;
+    } else {
+        struct v_dnode* dnode;
+        errno = vfs_get_path(fd_s->file->dnode, buf, size, 0);
+    }
+
+    if (errno >= 0) {
+        return errno;
+    }
+
+    return DO_STATUS(errno);
+}
+
+__DEFINE_LXSYSCALL3(int, readlink, const char*, path, char*, buf, size_t, size)
+{
+    int errno;
+    struct v_dnode* dnode;
+    if (!(errno = vfs_walk(NULL, path, &dnode, NULL, VFS_WALK_NOFOLLOW))) {
+        errno = vfs_readlink(dnode, buf, size);
+    }
+
+    if (errno >= 0) {
+        return errno;
+    }
+
+    return DO_STATUS(errno);
+}
+
+__DEFINE_LXSYSCALL4(int,
+                    readlinkat,
+                    int,
+                    dirfd,
+                    const char*,
+                    pathname,
+                    char*,
+                    buf,
+                    size_t,
+                    size)
+{
+    int errno;
+    struct v_fd* fd_s;
+    if (!GET_FD(dirfd, fd_s)) {
+        errno = EBADF;
+    } else {
+        struct v_dnode* dnode;
+        if (!(errno = vfs_walk(fd_s->file->dnode,
+                               pathname,
+                               &dnode,
+                               NULL,
+                               VFS_WALK_NOFOLLOW))) {
+            errno = vfs_readlink(fd_s->file->dnode, buf, size);
+        }
+    }
+
+    if (errno >= 0) {
+        return errno;
+    }
+
+    return DO_STATUS(errno);
+}
+
+__DEFINE_LXSYSCALL1(int, rmdir, const char*, pathname)
+{
+    int errno;
+    struct v_dnode* dnode;
+    if ((errno = vfs_walk(NULL, pathname, &dnode, NULL, 0))) {
+        goto done;
+    }
+    if ((dnode->super_block->fs->types & FSTYPE_ROFS)) {
+        errno = EROFS;
+        goto done;
+    }
+
+    if (dnode->inode->open_count) {
+        errno = EBUSY;
+        goto done;
+    }
+
+    if ((dnode->inode->itype & VFS_IFDIR)) {
+        errno = dnode->inode->ops.rmdir(dnode->inode);
+    } else {
+        errno = ENOTDIR;
+    }
+
+done:
+    return DO_STATUS(errno);
+}
+
+int
+__vfs_do_unlink(struct v_inode* inode)
+{
+    int errno;
+    if (inode->open_count) {
+        errno = EBUSY;
+    } else if (!(inode->itype & VFS_IFDIR)) {
+        // TODO handle symbolic link and type other than regular file
+        errno = inode->ops.unlink(inode);
+        if (!errno) {
+            inode->link_count--;
+        }
+    } else {
+        errno = EISDIR;
+    }
+
+    return errno;
+}
+
+__DEFINE_LXSYSCALL1(int, unlink, const char*, pathname)
+{
+    int errno;
+    struct v_dnode* dnode;
+    if ((errno = vfs_walk(NULL, pathname, &dnode, NULL, 0))) {
+        goto done;
+    }
+    if ((dnode->super_block->fs->types & FSTYPE_ROFS)) {
+        errno = EROFS;
+        goto done;
+    }
+
+    errno = __vfs_do_unlink(dnode->inode);
+
+done:
+    return DO_STATUS(errno);
+}
+
+__DEFINE_LXSYSCALL2(int, unlinkat, int, fd, const char*, pathname)
+{
+    int errno;
+    struct v_fd* fd_s;
+    if (!GET_FD(fd, fd_s)) {
+        errno = EBADF;
+    } else {
+        struct v_dnode* dnode;
+        if (!(errno = vfs_walk(fd_s->file->dnode, pathname, &dnode, NULL, 0))) {
+            errno = __vfs_do_unlink(dnode->inode);
+        }
+    }
+
+done:
+    return DO_STATUS(errno);
+}
+
+__DEFINE_LXSYSCALL2(int, link, const char*, oldpath, const char*, newpath)
+{
+    int errno;
+    struct v_dnode *dentry, *to_link, *name_dentry, *name_file;
+
+    errno = __vfs_try_locate_file(oldpath, &dentry, &to_link, 0);
+    if (!errno) {
+        errno = __vfs_try_locate_file(
+          newpath, &name_dentry, &name_file, FLOCATE_CREATE_EMPTY);
+        if (!errno) {
+            errno = EEXIST;
+        } else if (name_file) {
+            errno = vfs_link(to_link, name_file);
+        }
+    }
+    return DO_STATUS(errno);
+}
+
+__DEFINE_LXSYSCALL1(int, fsync, int, fildes)
+{
+    int errno;
+    struct v_fd* fd_s;
+    if (!GET_FD(fildes, fd_s)) {
+        errno = EBADF;
+    } else {
+        errno = vfs_fsync(fd_s->file);
+    }
+
+    return DO_STATUS(errno);
+}
+
+int
+__vfs_dup_fd(struct v_fd* old, struct v_fd** new)
+{
+    int errno = 0;
+    struct v_fd* copied = cake_grab(fd_pile);
+
+    memcpy(copied, old, sizeof(struct v_fd));
+    old->file->ref_count++;
+
+    return errno;
+}
+
+__DEFINE_LXSYSCALL2(int, dup2, int, oldfd, int, newfd)
+{
+    if (newfd == oldfd) {
+        return newfd;
+    }
+
+    int errno;
+    struct v_fd *oldfd_s, *newfd_s;
+    if (!GET_FD(oldfd, oldfd_s) || TEST_FD(newfd)) {
+        errno = EBADF;
+        goto done;
+    }
+    newfd_s = __current->fdtable->fds[newfd];
+    if (newfd_s && (errno = vfs_close(newfd_s))) {
+        goto done;
+    }
+
+    if (!(errno = __vfs_dup_fd(oldfd_s, &newfd_s))) {
+        __current->fdtable->fds[newfd] = newfd_s;
+        return newfd;
+    }
+
+done:
+    return DO_STATUS(errno);
+}
+
+__DEFINE_LXSYSCALL1(int, dup, int, oldfd)
+{
+    int errno, newfd;
+    struct v_fd *oldfd_s, *newfd_s;
+    if (!GET_FD(oldfd, oldfd_s)) {
+        errno = EBADF;
+    } else if (!(errno = vfs_alloc_fdslot(&newfd)) &&
+               !(errno = __vfs_dup_fd(oldfd_s, &newfd_s))) {
+        __current->fdtable->fds[newfd] = newfd_s;
+        return newfd;
+    }
+
+    return DO_STATUS(errno);
+}
+
+__DEFINE_LXSYSCALL2(int,
+                    symlink,
+                    const char*,
+                    pathname,
+                    const char*,
+                    link_target)
+{
+    int errno;
+    struct v_dnode* dnode;
+    if ((errno = vfs_walk(NULL, pathname, &dnode, NULL, 0))) {
+        goto done;
+    }
+    if ((dnode->super_block->fs->types & FSTYPE_ROFS)) {
+        errno = EROFS;
+        goto done;
+    }
+    if (!dnode->inode->ops.symlink) {
+        errno = ENOTSUP;
+        goto done;
+    }
+
+    errno = dnode->inode->ops.symlink(dnode->inode, link_target);
+
+done:
+    return DO_STATUS(errno);
 }
\ No newline at end of file