feat: ability to evict dnode and inode cache

[lunaix-os.git] / lunaix-os / kernel / fs / vfs.c

diff --git a/lunaix-os/kernel/fs/vfs.c b/lunaix-os/kernel/fs/vfs.c
index 0fbf6529df93295f851e13b690f827479daa5d69..8edc9fd6126eb05d9f15c18d38ab4356fa71bfd8 100644 (file)
--- a/lunaix-os/kernel/fs/vfs.c
+++ b/lunaix-os/kernel/fs/vfs.c
@@ -9,6 +9,39 @@
  *
  */
 
  *
  */
 

+// Welcome to The Mountain O'Shit! :)
+
+/*
+ TODO vfs & device todos checklist
+
+    It is overseen by Twilight Sparkle ;)
+
+ 1. Get inodes hooked into lru (CHECKED)
+ 2. Get dnodes hooked into lru (CHECKED)
+ 3. Get inodes properly hashed so they can be reused by underling fs (CHECKED)
+ 4. (lru) Add a callback function (or destructor) for eviction. (CHECKED)
+        [good idea] or a constructor/destructor pattern in cake allocator ?
+ 5. (mount) Figure out a way to identify a busy mount point before unmount
+            maybe a unified mount_point structure that maintain a referencing
+            counter on any dnodes within the subtree? Such a counter will only
+            increament if a file is opened or a dnode is being used as working
+            directory and decreamenting conversely.
+ 6. (mount) Ability to track all mount points (including sub-mounts)
+            so we can be confident to clean up everything when we unmount.
+ 7. (mount) Figure out a way to acquire the device represented by a dnode.
+            so it can be used to mount. (e.g. we wish to get `struct device*`
+            out of the dnode at /dev/sda)
+            [tip] we should pay attention at twifs and add a private_data field
+            under struct v_dnode?
+ 8. (mount) Then, we should refactor on mount/unmount mechanism.
+ 9. (mount) (future) Ability to mount any thing? e.g. Linux can mount a disk
+                    image file using a so called "loopback" pseudo device. Maybe
+                    we can do similar thing in Lunaix? A block device emulation
+                    above the regular file when we mount it on.
+ 10. (device) device number (dev_t) allocation
+            [good idea] <class>:<subclass>:<uniq_id> composition
+*/
+

 #include <klibc/string.h>
 #include <lunaix/dirent.h>
 #include <lunaix/foptions.h>
 #include <klibc/string.h>
 #include <lunaix/dirent.h>
 #include <lunaix/foptions.h>


@@ -20,11 +53,27 @@
 #include <lunaix/spike.h>
 #include <lunaix/syscall.h>
 
 #include <lunaix/spike.h>
 #include <lunaix/syscall.h>
 

+#include <lunaix/fs/twifs.h>
+

 #define PATH_DELIM '/'
 #define PATH_DELIM '/'

-#define DNODE_HASHTABLE_BITS 10
-#define DNODE_HASHTABLE_SIZE (1 << DNODE_HASHTABLE_BITS)
-#define DNODE_HASH_MASK (DNODE_HASHTABLE_SIZE - 1)
-#define DNODE_HASHBITS (32 - DNODE_HASHTABLE_BITS)
+#define HASHTABLE_BITS 10
+#define HASHTABLE_SIZE (1 << HASHTABLE_BITS)
+#define HASH_MASK (HASHTABLE_SIZE - 1)
+#define HASHBITS (32 - HASHTABLE_BITS)
+
+#define unlock_inode(inode) mutex_unlock(&inode->lock)
+#define lock_inode(inode)                                                      \
+    ({                                                                         \
+        mutex_lock(&inode->lock);                                              \
+        lru_use_one(inode_lru, &inode->lru);                                   \
+    })
+
+#define unlock_dnode(dnode) mutex_unlock(&dnode->lock)
+#define lock_dnode(dnode)                                                      \
+    ({                                                                         \
+        mutex_lock(&dnode->lock);                                              \
+        lru_use_one(dnode_lru, &dnode->lru);                                   \
+    })

 
 static struct cake_pile* dnode_pile;
 static struct cake_pile* inode_pile;
 
 static struct cake_pile* dnode_pile;
 static struct cake_pile* inode_pile;


@@ -33,26 +82,26 @@ static struct cake_pile* superblock_pile;
 static struct cake_pile* fd_pile;
 
 static struct v_superblock* root_sb;
 static struct cake_pile* fd_pile;
 
 static struct v_superblock* root_sb;

-static struct hbucket* dnode_cache;
+static struct hbucket *dnode_cache, *inode_cache;

 
 

-static int fs_id = 0;
+static struct lru_zone *dnode_lru, *inode_lru;

 
 struct hstr vfs_ddot = HSTR("..", 2);
 struct hstr vfs_dot = HSTR(".", 1);
 struct hstr vfs_empty = HSTR("", 0);
 
 
 struct hstr vfs_ddot = HSTR("..", 2);
 struct hstr vfs_dot = HSTR(".", 1);
 struct hstr vfs_empty = HSTR("", 0);
 

-struct v_dnode*
-vfs_d_alloc();
-
-void
-vfs_d_free(struct v_dnode* dnode);
-

 struct v_superblock*
 vfs_sb_alloc();
 
 void
 vfs_sb_free(struct v_superblock* sb);
 
 struct v_superblock*
 vfs_sb_alloc();
 
 void
 vfs_sb_free(struct v_superblock* sb);
 

+static int
+__vfs_try_evict_dnode(struct lru_node* obj);
+
+static int
+__vfs_try_evict_inode(struct lru_node* obj);
+

 void
 vfs_init()
 {
 void
 vfs_init()
 {


@@ -64,7 +113,11 @@ vfs_init()
     superblock_pile =
       cake_new_pile("sb_cache", sizeof(struct v_superblock), 1, 0);
 
     superblock_pile =
       cake_new_pile("sb_cache", sizeof(struct v_superblock), 1, 0);
 

-    dnode_cache = vzalloc(DNODE_HASHTABLE_SIZE * sizeof(struct hbucket));
+    dnode_cache = vzalloc(HASHTABLE_SIZE * sizeof(struct hbucket));
+    inode_cache = vzalloc(HASHTABLE_SIZE * sizeof(struct hbucket));
+
+    dnode_lru = lru_new_zone(__vfs_try_evict_dnode);
+    inode_lru = lru_new_zone(__vfs_try_evict_inode);

 
     hstr_rehash(&vfs_ddot, HSTR_FULL_HASH);
     hstr_rehash(&vfs_dot, HSTR_FULL_HASH);
 
     hstr_rehash(&vfs_ddot, HSTR_FULL_HASH);
     hstr_rehash(&vfs_dot, HSTR_FULL_HASH);


@@ -75,13 +128,15 @@ vfs_init()
 }
 
 inline struct hbucket*
 }
 
 inline struct hbucket*

-__dcache_get_bucket(struct v_dnode* parent, unsigned int hash)
+__dcache_hash(struct v_dnode* parent, uint32_t* hash)

 {
 {

+    uint32_t _hash = *hash;

     // 与parent的指针值做加法，来减小碰撞的可能性。
     // 与parent的指针值做加法，来减小碰撞的可能性。

-    hash += (uint32_t)parent;
+    _hash += (uint32_t)parent;

     // 确保低位更加随机
     // 确保低位更加随机

-    hash = hash ^ (hash >> DNODE_HASHBITS);
-    return &dnode_cache[hash & DNODE_HASH_MASK];
+    _hash = _hash ^ (_hash >> HASHBITS);
+    *hash = _hash;
+    return &dnode_cache[_hash & HASH_MASK];

 }
 
 struct v_dnode*
 }
 
 struct v_dnode*


@@ -94,12 +149,13 @@ vfs_dcache_lookup(struct v_dnode* parent, struct hstr* str)
         return parent->parent ? parent->parent : parent;
     }
 
         return parent->parent ? parent->parent : parent;
     }
 

-    struct hbucket* slot = __dcache_get_bucket(parent, str->hash);
+    uint32_t hash = str->hash;
+    struct hbucket* slot = __dcache_hash(parent, &hash);

 
     struct v_dnode *pos, *n;
     hashtable_bucket_foreach(slot, pos, n, hash_list)
     {
 
     struct v_dnode *pos, *n;
     hashtable_bucket_foreach(slot, pos, n, hash_list)
     {

-        if (pos->name.hash == str->hash) {
+        if (pos->name.hash == hash) {

             return pos;
         }
     }
             return pos;
         }
     }


@@ -109,16 +165,39 @@ vfs_dcache_lookup(struct v_dnode* parent, struct hstr* str)
 void
 vfs_dcache_add(struct v_dnode* parent, struct v_dnode* dnode)
 {
 void
 vfs_dcache_add(struct v_dnode* parent, struct v_dnode* dnode)
 {

-    struct hbucket* bucket = __dcache_get_bucket(parent, dnode->name.hash);
+    atomic_fetch_add(&dnode->ref_count, 1);
+    dnode->parent = parent;
+    llist_append(&parent->children, &dnode->siblings);
+    struct hbucket* bucket = __dcache_hash(parent, &dnode->name.hash);

     hlist_add(&bucket->head, &dnode->hash_list);
 }
 
     hlist_add(&bucket->head, &dnode->hash_list);
 }
 

+void
+vfs_dcache_remove(struct v_dnode* dnode)
+{
+    assert(dnode->ref_count == 1);
+
+    llist_delete(&dnode->siblings);
+    hlist_delete(&dnode->hash_list);
+
+    dnode->parent = NULL;
+    atomic_fetch_sub(&dnode->ref_count, 1);
+}
+
+void
+vfs_dcache_rehash(struct v_dnode* new_parent, struct v_dnode* dnode)
+{
+    hstr_rehash(&dnode->name, HSTR_FULL_HASH);
+    vfs_dcache_remove(dnode);
+    vfs_dcache_add(new_parent, dnode);
+}
+

 int
 int

-vfs_walk(struct v_dnode* start,
-         const char* path,
-         struct v_dnode** dentry,
-         struct hstr* component,
-         int walk_options)
+__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;
 {
     int errno = 0;
     int i = 0, j = 0;


@@ -146,7 +225,7 @@ vfs_walk(struct v_dnode* start,
                 return ENAMETOOLONG;
             }
             if (!VFS_VALID_CHAR(current)) {
                 return ENAMETOOLONG;
             }
             if (!VFS_VALID_CHAR(current)) {

-                return VFS_EINVLD;
+                return EINVAL;

             }
             name_content[j++] = current;
             if (lookahead) {
             }
             name_content[j++] = current;
             if (lookahead) {


@@ -159,6 +238,8 @@ vfs_walk(struct v_dnode* start,
             goto cont;
         }
 
             goto cont;
         }
 

+        lock_dnode(current_level);
+

         name_content[j] = 0;
         name.len = j;
         hstr_rehash(&name, HSTR_FULL_HASH);
         name_content[j] = 0;
         name.len = j;
         hstr_rehash(&name, HSTR_FULL_HASH);


@@ -169,6 +250,7 @@ vfs_walk(struct v_dnode* start,
                 component->len = j;
                 strcpy(component->value, name_content);
             }
                 component->len = j;
                 strcpy(component->value, name_content);
             }

+            unlock_dnode(current_level);

             break;
         }
 
             break;
         }
 


@@ -176,10 +258,15 @@ vfs_walk(struct v_dnode* start,
 
         if (!dnode) {
             dnode = vfs_d_alloc();
 
         if (!dnode) {
             dnode = vfs_d_alloc();

-            dnode->name = HSTR(valloc(VFS_NAME_MAXLEN), j);
-            dnode->name.hash = name.hash;

 
 

-            strcpy(dnode->name.value, name_content);
+            if (!dnode) {
+                errno = ENOMEM;
+                goto error;
+            }
+
+            hstrcpy(&dnode->name, &name);
+
+            lock_inode(current_level->inode);

 
             errno =
               current_level->inode->ops.dir_lookup(current_level->inode, dnode);
 
             errno =
               current_level->inode->ops.dir_lookup(current_level->inode, dnode);


@@ -193,16 +280,19 @@ vfs_walk(struct v_dnode* start,
                 }
             }
 
                 }
             }
 

+            unlock_inode(current_level->inode);
+

             if (errno) {
             if (errno) {

-                goto error;
+                unlock_dnode(current_level);
+                vfree(dnode->name.value);
+                goto cleanup;

             }
 
             vfs_dcache_add(current_level, dnode);
             }
 
             vfs_dcache_add(current_level, dnode);

-
-            dnode->parent = current_level;
-            llist_append(&current_level->children, &dnode->siblings);

         }
 
         }
 

+        unlock_dnode(current_level);
+

         j = 0;
         current_level = dnode;
     cont:
         j = 0;
         current_level = dnode;
     cont:


@@ -212,20 +302,61 @@ vfs_walk(struct v_dnode* start,
     *dentry = current_level;
     return 0;
 
     *dentry = current_level;
     return 0;
 

-error:
-    vfree(dnode->name.value);
+cleanup:

     vfs_d_free(dnode);
     vfs_d_free(dnode);

+error:

     *dentry = NULL;
     return errno;
 }
 
     *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;
+    const char* pathname = path;
+    int errno = __vfs_walk(start, path, &interim, component, options);
+    int counter = 0;
+
+    while (!errno && interim->inode && (options & VFS_WALK_NOFOLLOW)) {
+        if (counter >= VFS_MAX_SYMLINK) {
+            errno = ELOOP;
+            continue;
+        }
+        if ((interim->inode->itype & VFS_IFSYMLINK) &&
+            interim->inode->ops.read_symlink) {
+
+            lock_inode(interim->inode);
+            errno = interim->inode->ops.read_symlink(interim->inode, &pathname);
+            unlock_inode(interim->inode);
+
+            if (errno) {
+                break;
+            }
+        } else {
+            break;
+        }
+        errno = __vfs_walk(start, pathname, &interim, component, options);
+        counter++;
+    }
+
+    *dentry = errno ? 0 : interim;
+
+    return errno;
+}
+

 int
 int

-vfs_mount(const char* target, const char* fs_name, bdev_t device)
+vfs_mount(const char* target, const char* fs_name, struct device* device)

 {
     int errno;
     struct v_dnode* mnt;
 
 {
     int errno;
     struct v_dnode* mnt;
 

-    if (!(errno = vfs_walk(NULL, target, &mnt, NULL, 0))) {
+    if (!(errno = vfs_walk(__current->cwd, target, &mnt, NULL, 0))) {

         errno = vfs_mount_at(fs_name, device, mnt);
     }
 
         errno = vfs_mount_at(fs_name, device, mnt);
     }
 


@@ -238,7 +369,7 @@ vfs_unmount(const char* target)
     int errno;
     struct v_dnode* mnt;
 
     int errno;
     struct v_dnode* mnt;
 

-    if (!(errno = vfs_walk(NULL, target, &mnt, NULL, 0))) {
+    if (!(errno = vfs_walk(__current->cwd, target, &mnt, NULL, 0))) {

         errno = vfs_unmount_at(mnt);
     }
 
         errno = vfs_unmount_at(mnt);
     }
 


@@ -246,14 +377,22 @@ vfs_unmount(const char* target)
 }
 
 int
 }
 
 int

-vfs_mount_at(const char* fs_name, bdev_t device, struct v_dnode* mnt_point)
+vfs_mount_at(const char* fs_name,
+             struct device* device,
+             struct v_dnode* mnt_point)

 {
 {

+    if (mnt_point->inode && !(mnt_point->inode->itype & VFS_IFDIR)) {
+        return ENOTDIR;
+    }
+

     struct filesystem* fs = fsm_get(fs_name);
     struct filesystem* fs = fsm_get(fs_name);

-    if (!fs)
-        return VFS_ENOFS;
+    if (!fs) {
+        return ENODEV;
+    }
+

     struct v_superblock* sb = vfs_sb_alloc();
     sb->dev = device;
     struct v_superblock* sb = vfs_sb_alloc();
     sb->dev = device;

-    sb->fs_id = fs_id++;
+    sb->fs_id = fs->fs_id;

 
     int errno = 0;
     if (!(errno = fs->mount(sb, mnt_point))) {
 
     int errno = 0;
     if (!(errno = fs->mount(sb, mnt_point))) {


@@ -269,16 +408,24 @@ vfs_mount_at(const char* fs_name, bdev_t device, struct v_dnode* mnt_point)
 int
 vfs_unmount_at(struct v_dnode* mnt_point)
 {
 int
 vfs_unmount_at(struct v_dnode* mnt_point)
 {

+    // FIXME deal with the detached dcache subtree

     int errno = 0;
     struct v_superblock* sb = mnt_point->super_block;
     if (!sb) {
     int errno = 0;
     struct v_superblock* sb = mnt_point->super_block;
     if (!sb) {

-        return VFS_EBADMNT;
+        return EINVAL;
+    }
+
+    if (sb->root != mnt_point) {
+        return EINVAL;

     }
     }

+

     if (!(errno = sb->fs->unmount(sb))) {
         struct v_dnode* fs_root = sb->root;
     if (!(errno = sb->fs->unmount(sb))) {
         struct v_dnode* fs_root = sb->root;

-        llist_delete(&fs_root->siblings);
+        vfs_dcache_remove(fs_root);
+

         llist_delete(&sb->sb_list);
         vfs_sb_free(sb);
         llist_delete(&sb->sb_list);
         vfs_sb_free(sb);

+        vfs_d_free(fs_root);

     }
     return errno;
 }
     }
     return errno;
 }


@@ -290,34 +437,72 @@ vfs_open(struct v_dnode* dnode, struct v_file** file)
         return ENOTSUP;
     }
 
         return ENOTSUP;
     }
 

+    struct v_inode* inode = dnode->inode;

     struct v_file* vfile = cake_grab(file_pile);
     memset(vfile, 0, sizeof(*vfile));
 
     vfile->dnode = dnode;
     struct v_file* vfile = cake_grab(file_pile);
     memset(vfile, 0, sizeof(*vfile));
 
     vfile->dnode = dnode;

-    vfile->inode = dnode->inode;
-    dnode->inode->open_count++;
+    vfile->inode = inode;
+    vfile->ref_count = ATOMIC_VAR_INIT(1);
+    vfile->ops = inode->default_fops;
+
+    if ((inode->itype & VFS_IFFILE) && !inode->pg_cache) {
+        struct pcache* pcache = vzalloc(sizeof(struct pcache));
+        pcache_init(pcache);
+        pcache->master = inode;
+        inode->pg_cache = pcache;
+    }

 
 

-    int errno = dnode->inode->ops.open(dnode->inode, vfile);
+    int errno = inode->ops.open(inode, vfile);

     if (errno) {
         cake_release(file_pile, vfile);
     } else {
     if (errno) {
         cake_release(file_pile, vfile);
     } else {

+        atomic_fetch_add(&dnode->ref_count, 1);
+        inode->open_count++;
+

         *file = vfile;
     }
         *file = vfile;
     }

+

     return errno;
 }
 
     return errno;
 }
 

+void
+vfs_assign_inode(struct v_dnode* assign_to, struct v_inode* inode)
+{
+    if (assign_to->inode) {
+        assign_to->inode->link_count--;
+    }
+    assign_to->inode = inode;
+    inode->link_count++;
+}
+

 int
 int

-vfs_close(struct v_file* file)
+vfs_link(struct v_dnode* to_link, struct v_dnode* name)

 {
 {

-    if (!file->ops.close) {
-        return ENOTSUP;
+    int errno;
+
+    lock_inode(to_link->inode);
+    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))) {
+        vfs_assign_inode(name, to_link->inode);

     }
     }

+    unlock_inode(to_link->inode);

 
 

-    int errno = file->ops.close(file);
-    if (!errno) {
-        if (file->inode->open_count) {
-            file->inode->open_count--;
-        }
+    return errno;
+}
+
+int
+vfs_close(struct v_file* file)
+{
+    int errno = 0;
+    if (!file->ops.close || !(errno = file->ops.close(file))) {
+        atomic_fetch_sub(&file->dnode->ref_count, 1);
+        file->inode->open_count--;
+
+        pcache_commit_all(file->inode);

         cake_release(file_pile, file);
     }
     return errno;
         cake_release(file_pile, file);
     }
     return errno;


@@ -326,13 +511,16 @@ vfs_close(struct v_file* file)
 int
 vfs_fsync(struct v_file* file)
 {
 int
 vfs_fsync(struct v_file* file)
 {

+    lock_inode(file->inode);
+

     int errno = ENOTSUP;
     int errno = ENOTSUP;

+    pcache_commit_all(file->inode);

     if (file->ops.sync) {
     if (file->ops.sync) {

-        errno = file->ops.sync(file);
-    }
-    if (!errno && file->inode->ops.sync) {
-        return file->inode->ops.sync(file->inode);
+        errno = file->ops.sync(file->inode);

     }
     }

+
+    unlock_inode(file->inode);
+

     return errno;
 }
 
     return errno;
 }
 


@@ -363,104 +551,245 @@ vfs_sb_free(struct v_superblock* sb)
     cake_release(superblock_pile, sb);
 }
 
     cake_release(superblock_pile, sb);
 }
 

+static int
+__vfs_try_evict_dnode(struct lru_node* obj)
+{
+    struct v_dnode* dnode = container_of(obj, struct v_dnode, lru);
+
+    if (!dnode->ref_count) {
+        vfs_d_free(dnode);
+        return 1;
+    }
+    return 0;
+}
+
+static int
+__vfs_try_evict_inode(struct lru_node* obj)
+{
+    struct v_inode* inode = container_of(obj, struct v_inode, lru);
+
+    if (!inode->link_count && !inode->open_count) {
+        vfs_i_free(inode);
+        return 1;
+    }
+    return 0;
+}
+

 struct v_dnode*
 vfs_d_alloc()
 {
     struct v_dnode* dnode = cake_grab(dnode_pile);
 struct v_dnode*
 vfs_d_alloc()
 {
     struct v_dnode* dnode = cake_grab(dnode_pile);

+    if (!dnode) {
+        lru_evict_half(dnode_lru);
+
+        if (!(dnode = cake_grab(dnode_pile))) {
+            return NULL;
+        }
+    }
+

     memset(dnode, 0, sizeof(*dnode));
     llist_init_head(&dnode->children);
     memset(dnode, 0, sizeof(*dnode));
     llist_init_head(&dnode->children);

-    dnode->name = vfs_empty;
+    llist_init_head(&dnode->siblings);
+    mutex_init(&dnode->lock);
+
+    dnode->ref_count = ATOMIC_VAR_INIT(0);
+    dnode->name = HHSTR(vzalloc(VFS_NAME_MAXLEN), 0, 0);
+
+    lru_use_one(dnode_lru, &dnode->lru);
+

     return dnode;
 }
 
 void
 vfs_d_free(struct v_dnode* dnode)
 {
     return dnode;
 }
 
 void
 vfs_d_free(struct v_dnode* dnode)
 {

-    if (dnode->ops.destruct) {
-        dnode->ops.destruct(dnode);
+    assert(dnode->ref_count == 0);
+
+    if (dnode->inode) {
+        assert(dnode->inode->link_count > 0);
+        dnode->inode->link_count--;
+    }
+
+    // Make sure the children de-referencing their parent.
+    // With lru presented, the eviction will be propagated over the entire
+    // detached subtree eventually
+    struct v_dnode *pos, *n;
+    llist_for_each(pos, n, &dnode->children, siblings)
+    {
+        vfs_dcache_remove(pos);

     }
     }

+
+    vfree(dnode->name.value);

     cake_release(dnode_pile, dnode);
 }
 
 struct v_inode*
     cake_release(dnode_pile, dnode);
 }
 
 struct v_inode*

-vfs_i_alloc()
+vfs_i_alloc(dev_t device_id, uint32_t inode_id)

 {
 {

-    struct v_inode* inode = cake_grab(inode_pile);
-    memset(inode, 0, sizeof(*inode));
+    // 我们这里假设每个文件系统与设备是一一对应（毕竟一个分区不可能有两个不同的文件系统）
+    // 而每个文件系统所产生的 v_inode 缓存必须要和其他文件系统产生的区分开来。
+    // 这也就是说，每个 v_inode 的 id
+    // 必须要由设备ID，和该虚拟inode缓存所对应的物理inode
+    // 相对于其所在的文件系统的id，进行组成！
+    inode_id = hash_32(inode_id ^ (-device_id), HASH_SIZE_BITS);
+    inode_id = (inode_id >> HASHBITS) ^ inode_id;
+
+    struct hbucket* slot = &inode_cache[inode_id & HASH_MASK];
+    struct v_inode *pos, *n;
+    hashtable_bucket_foreach(slot, pos, n, hash_list)
+    {
+        if (pos->id == inode_id) {
+            goto done;
+        }
+    }
+
+    if (!(pos = cake_grab(inode_pile))) {
+        lru_evict_half(inode_lru);
+        if (!(pos = cake_grab(inode_pile))) {
+            return NULL;
+        }
+    }
+
+    memset(pos, 0, sizeof(*pos));
+
+    pos->id = inode_id;

 
 

-    return inode;
+    mutex_init(&pos->lock);
+
+    hlist_add(&slot->head, &pos->hash_list);
+
+done:
+    lru_use_one(inode_lru, &pos->lru);
+    return pos;

 }
 
 void
 vfs_i_free(struct v_inode* inode)
 {
 }
 
 void
 vfs_i_free(struct v_inode* inode)
 {

+    hlist_delete(&inode->hash_list);

     cake_release(inode_pile, inode);
 }
 
 /* ---- System call definition and support ---- */
 
     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; })
+
+#define TEST_FD(fd) (fd >= 0 && fd < VFS_MAX_FD)
+
+int
+__vfs_getfd(int fd, struct v_fd** fd_s)
+{
+    if (TEST_FD(fd) && (*fd_s = __current->fdtable->fds[fd])) {
+        return 0;
+    }
+    return EBADF;
+}
+

 int
 int

-__vfs_do_open(struct v_file** file_out, const char* path, int options)
+__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);
 {
     char name_str[VFS_NAME_MAXLEN];
     struct hstr name = HSTR(name_str, 0);

-    struct v_dnode *dentry, *file;

     int errno;
     int errno;

-    if ((errno = vfs_walk(NULL, path, &dentry, &name, VFS_WALK_PARENT))) {
-        return ENOENT;
+    if ((errno =
+           vfs_walk(__current->cwd, 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;

     }
 
     }
 

-    vfs_walk(dentry, name.value, &file, NULL, 0);
+    struct v_dnode* parent = *fdir;
+    struct v_dnode* file_new = vfs_d_alloc();

 
 

-    struct v_file* opened_file = 0;
-    if (!file) {
-        if ((options & FO_CREATE)) {
-            errno = dentry->inode->ops.create(dentry->inode, opened_file);
-        } else {
-            errno = ENOENT;
-        }
+    if (!file_new) {
+        return ENOMEM;
+    }
+
+    hstrcpy(&file_new->name, &name);
+
+    lock_dnode(parent);
+
+    if (!(errno = parent->inode->ops.create(parent->inode, file_new))) {
+        *file = file_new;
+
+        vfs_dcache_add(parent, file_new);
+        llist_append(&parent->children, &file_new->siblings);

     } else {
     } else {

-        errno = vfs_open(file, &opened_file);
+        vfs_d_free(file_new);

     }
 
     }
 

-    *file_out = opened_file;
+    unlock_dnode(parent);
+

     return errno;
 }
 
     return errno;
 }
 

-__DEFINE_LXSYSCALL2(int, open, const char*, path, int, options)
+int
+vfs_do_open(const char* path, int options)

 {
 {

-    struct v_file* opened_file;
-    int errno = __vfs_do_open(&opened_file, path, options), fd;
+    int errno, fd;
+    struct v_dnode *dentry, *file;
+    struct v_file* ofile = 0;
+
+    errno = __vfs_try_locate_file(
+      path, &dentry, &file, (options & FO_CREATE) ? FLOCATE_CREATE_EMPTY : 0);
+
+    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));
 
     if (!errno && !(errno = vfs_alloc_fdslot(&fd))) {
         struct v_fd* fd_s = vzalloc(sizeof(*fd_s));

-        fd_s->file = opened_file;
-        fd_s->pos = opened_file->inode->fsize & -((options & FO_APPEND) != 0);
+        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;
     }
 
         __current->fdtable->fds[fd] = fd_s;
         return fd;
     }
 

-    __current->k_status = errno;
-    return SYSCALL_ESTATUS(errno);
+    return errno;

 }
 
 }
 

-#define GET_FD(fd, fd_s)                                                       \
-    (fd >= 0 && fd < VFS_MAX_FD && (fd_s = __current->fdtable->fds[fd]))
+__DEFINE_LXSYSCALL2(int, open, const char*, path, int, options)
+{
+    int errno = vfs_do_open(path, options);
+    return DO_STATUS_OR_RETURN(errno);
+}

 
 __DEFINE_LXSYSCALL1(int, close, int, fd)
 {
     struct v_fd* fd_s;
 
 __DEFINE_LXSYSCALL1(int, close, int, fd)
 {
     struct v_fd* fd_s;

-    int errno;
-    if (!GET_FD(fd, fd_s)) {
-        errno = EBADF;
-    } else if (!(errno = vfs_close(fd_s->file))) {
-        vfree(fd_s);
-        __current->fdtable->fds[fd] = 0;
+    int errno = 0;
+    if ((errno = __vfs_getfd(fd, &fd_s))) {
+        goto done_err;

     }
 
     }
 

-    __current->k_status = errno;
+    if (fd_s->file->ref_count > 1) {
+        fd_s->file->ref_count--;
+    } else if ((errno = vfs_close(fd_s->file))) {
+        goto done_err;
+    }

 
 

-    return SYSCALL_ESTATUS(errno);
+    vfree(fd_s);
+    __current->fdtable->fds[fd] = 0;
+
+done_err:
+    return DO_STATUS(errno);

 }
 
 void
 }
 
 void


@@ -479,9 +808,16 @@ __DEFINE_LXSYSCALL2(int, readdir, int, fd, struct dirent*, dent)
 {
     struct v_fd* fd_s;
     int errno;
 {
     struct v_fd* fd_s;
     int errno;

-    if (!GET_FD(fd, fd_s)) {
-        errno = EBADF;
-    } else if (!(fd_s->file->inode->itype & VFS_INODE_TYPE_DIR)) {
+
+    if ((errno = __vfs_getfd(fd, &fd_s))) {
+        goto done;
+    }
+
+    struct v_inode* inode = fd_s->file->inode;
+
+    lock_inode(inode);
+
+    if (!(fd_s->file->inode->itype & VFS_IFDIR)) {

         errno = ENOTDIR;
     } else {
         struct dir_context dctx =
         errno = ENOTDIR;
     } else {
         struct dir_context dctx =


@@ -495,7 +831,8 @@ __DEFINE_LXSYSCALL2(int, readdir, int, fd, struct dirent*, dent)
             __vfs_readdir_callback(&dctx, vfs_ddot.value, vfs_ddot.len, 0);
         } else {
             dctx.index -= 2;
             __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))) {
+            if ((errno = fd_s->file->ops.readdir(inode, &dctx))) {
+                unlock_inode(inode);

                 goto done;
             }
         }
                 goto done;
             }
         }


@@ -503,109 +840,114 @@ __DEFINE_LXSYSCALL2(int, readdir, int, fd, struct dirent*, dent)
         dent->d_offset++;
     }
 
         dent->d_offset++;
     }
 

+    unlock_inode(inode);
+

 done:
 done:

-    __current->k_status = errno;
-    return SYSCALL_ESTATUS(errno);
+    return DO_STATUS(errno);

 }
 
 }
 

-__DEFINE_LXSYSCALL1(int, mkdir, const char*, path)
+__DEFINE_LXSYSCALL3(int, read, int, fd, void*, buf, size_t, count)

 {
 {

-    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) {
+    int errno = 0;
+    struct v_fd* fd_s;
+    if ((errno = __vfs_getfd(fd, &fd_s))) {

         goto done;
     }
 
         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_INODE_TYPE_DIR)) {
-        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);
-        }
+    struct v_file* file = fd_s->file;
+    if ((file->inode->itype & VFS_IFDIR)) {
+        errno = EISDIR;
+        goto done;

     }
 
     }
 

-done:
-    __current->k_status = errno;
-    return SYSCALL_ESTATUS(errno);
-}
+    lock_inode(file->inode);

 
 

-__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;
-    } else {
-        struct v_file* file = fd_s->file;
-        file->f_pos = fd_s->pos;
-        if ((errno = file->ops.read(file, buf, count)) >= 0) {
-            fd_s->pos += errno;
-        }
+    file->inode->atime = clock_unixtime();
+
+    __SYSCALL_INTERRUPTIBLE(
+      { errno = file->ops.read(file->inode, buf, count, file->f_pos); })
+
+    if (errno > 0) {
+        file->f_pos += errno;
+        unlock_inode(file->inode);
+        return errno;

     }
 
     }
 

-    __current->k_status = errno;
-    return SYSCALL_ESTATUS(errno);
+    unlock_inode(file->inode);
+
+done:
+    return DO_STATUS(errno);

 }
 
 __DEFINE_LXSYSCALL3(int, write, int, fd, void*, buf, size_t, count)
 {
     int errno = 0;
     struct v_fd* fd_s;
 }
 
 __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;
-    } else {
-        struct v_file* file = fd_s->file;
-        file->f_pos = fd_s->pos;
-        if ((errno = file->ops.write(file, buf, count)) >= 0) {
-            fd_s->pos += errno;
-        }
+    if ((errno = __vfs_getfd(fd, &fd_s))) {
+        goto done;

     }
 
     }
 

-    __current->k_status = errno;
-    return SYSCALL_ESTATUS(errno);
+    struct v_file* file = fd_s->file;
+    if ((file->inode->itype & VFS_IFDIR)) {
+        errno = EISDIR;
+        goto done;
+    }
+
+    lock_inode(file->inode);
+
+    file->inode->mtime = clock_unixtime();
+
+    __SYSCALL_INTERRUPTIBLE(
+      { errno = file->ops.write(file->inode, buf, count, file->f_pos); })
+
+    if (errno > 0) {
+        file->f_pos += errno;
+        unlock_inode(file->inode);
+        return errno;
+    }
+
+    unlock_inode(file->inode);
+
+done:
+    return DO_STATUS(errno);

 }
 
 __DEFINE_LXSYSCALL3(int, lseek, int, fd, int, offset, int, options)
 {
     int errno = 0;
     struct v_fd* fd_s;
 }
 
 __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 {
-        size_t fpos = fd_s->file->f_pos;
-        switch (options) {
-            case FSEEK_CUR:
-                fpos = (size_t)((int)fd_s->file->f_pos + offset);
-                break;
-            case FSEEK_END:
-                fpos = (size_t)((int)fd_s->file->inode->fsize + offset);
-                break;
-            case FSEEK_SET:
-                fpos = offset;
-                break;
+    if ((errno = __vfs_getfd(fd, &fd_s))) {
+        goto done;
+    }

 
 

-            default:
-                break;
-        }
-        fd_s->pos = fpos;
+    struct v_file* file = fd_s->file;
+
+    lock_inode(file->inode);
+
+    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->inode, fpos))) {
+        file->f_pos = fpos;

     }
 
     }
 

-    __current->k_status = errno;
-    return SYSCALL_ESTATUS(errno);
+    unlock_inode(file->inode);
+
+done:
+    return DO_STATUS(errno);

 }
 
 int
 }
 
 int

-vfs_readlink(struct v_dnode* dnode, char* buf, size_t size, int depth)
+vfs_get_path(struct v_dnode* dnode, char* buf, size_t size, int depth)

 {
     if (!dnode) {
         return 0;
 {
     if (!dnode) {
         return 0;


@@ -615,7 +957,7 @@ vfs_readlink(struct v_dnode* dnode, char* buf, size_t size, int depth)
         return ELOOP;
     }
 
         return ELOOP;
     }
 

-    size_t len = vfs_readlink(dnode->parent, buf, size, depth + 1);
+    size_t len = vfs_get_path(dnode->parent, buf, size, depth + 1);

 
     if (len >= size) {
         return len;
 
     if (len >= size) {
         return len;


@@ -632,20 +974,56 @@ vfs_readlink(struct v_dnode* dnode, char* buf, size_t size, int depth)
     return len;
 }
 
     return len;
 }
 

-__DEFINE_LXSYSCALL3(int, readlink, const char*, path, char*, buf, size_t, size)
+int
+vfs_readlink(struct v_dnode* dnode, char* buf, size_t size)

 {
 {

-    int errno;
-    struct v_dnode* dnode;
-    if (!(errno = vfs_walk(NULL, path, &dnode, NULL, 0))) {
-        errno = vfs_readlink(dnode, buf, size, 0);
-    }
+    const char* link;
+    struct v_inode* inode = dnode->inode;
+    if (inode->ops.read_symlink) {
+        lock_inode(inode);

 
 

-    if (errno >= 0) {
+        int errno = inode->ops.read_symlink(inode, &link);
+        strncpy(buf, link, size);
+
+        unlock_inode(inode);

         return errno;
     }
         return errno;
     }

-
-    __current->k_status = errno;
-    return SYSCALL_ESTATUS(errno);
+    return 0;
+}
+
+__DEFINE_LXSYSCALL3(int, realpathat, int, fd, char*, buf, size_t, size)
+{
+    int errno;
+    struct v_fd* fd_s;
+    if ((errno = __vfs_getfd(fd, &fd_s))) {
+        goto done;
+    }
+
+    struct v_dnode* dnode;
+    errno = vfs_get_path(fd_s->file->dnode, buf, size, 0);
+
+    if (errno >= 0) {
+        return errno;
+    }
+
+done:
+    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(__current->cwd, path, &dnode, NULL, VFS_WALK_NOFOLLOW))) {
+        errno = vfs_readlink(dnode, buf, size);
+    }
+
+    if (errno >= 0) {
+        return errno;
+    }
+
+    return DO_STATUS(errno);

 }
 
 __DEFINE_LXSYSCALL4(int,
 }
 
 __DEFINE_LXSYSCALL4(int,


@@ -661,64 +1039,150 @@ __DEFINE_LXSYSCALL4(int,
 {
     int errno;
     struct v_fd* fd_s;
 {
     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, 0))) {
-            errno = vfs_readlink(fd_s->file->dnode, buf, size, 0);
-        }
+    if ((errno = __vfs_getfd(dirfd, &fd_s))) {
+        goto done;
+    }
+
+    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;
     }
 
     }
 
     if (errno >= 0) {
         return errno;
     }
 

-    __current->k_status = errno;
-    return SYSCALL_ESTATUS(errno);
+done:
+    return DO_STATUS(errno);

 }
 
 }
 

+/*
+    NOTE
+    When we perform operation that could affect the layout of
+    directory (i.e., rename, mkdir, rmdir). We must lock the parent dir
+    whenever possible. This will blocking any ongoing path walking to reach
+    it hence avoid any partial state.
+*/
+

 __DEFINE_LXSYSCALL1(int, rmdir, const char*, pathname)
 {
     int errno;
     struct v_dnode* dnode;
 __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 ((errno = vfs_walk(__current->cwd, pathname, &dnode, NULL, 0))) {
+        return DO_STATUS(errno);

     }
     }

+
+    lock_dnode(dnode);
+

     if ((dnode->super_block->fs->types & FSTYPE_ROFS)) {
         errno = EROFS;
         goto done;
     }
 
     if ((dnode->super_block->fs->types & FSTYPE_ROFS)) {
         errno = EROFS;
         goto done;
     }
 

-    if (dnode->inode->open_count) {
+    if (dnode->ref_count > 1 || dnode->inode->open_count) {

         errno = EBUSY;
         goto done;
     }
 
         errno = EBUSY;
         goto done;
     }
 

-    if (dnode->inode->itype == VFS_INODE_TYPE_DIR) {
-        errno = dnode->inode->ops.rmdir(dnode->inode);
+    if (!llist_empty(&dnode->children)) {
+        errno = ENOTEMPTY;
+        goto done;
+    }
+
+    struct v_dnode* parent = dnode->parent;
+
+    if (!parent) {
+        errno = EINVAL;
+        goto done;
+    }
+
+    lock_dnode(parent);
+    lock_inode(parent->inode);
+
+    if ((dnode->inode->itype & VFS_IFDIR)) {
+        errno = parent->inode->ops.rmdir(parent->inode, dnode);
+        if (!errno) {
+            vfs_dcache_remove(dnode);
+        }

     } else {
         errno = ENOTDIR;
     }
 
     } else {
         errno = ENOTDIR;
     }
 

+    unlock_inode(parent->inode);
+    unlock_dnode(parent);
+

 done:
 done:

-    __current->k_status = errno;
-    return SYSCALL_ESTATUS(errno);
+    unlock_dnode(dnode);
+    return DO_STATUS(errno);
+}
+
+__DEFINE_LXSYSCALL1(int, mkdir, const char*, path)
+{
+    int errno = 0;
+    struct v_dnode *parent, *dir = vfs_d_alloc();
+
+    if (!dir) {
+        errno = ENOMEM;
+        goto done;
+    }
+
+    if ((errno = vfs_walk(
+           __current->cwd, path, &parent, &dir->name, VFS_WALK_PARENT))) {
+        goto done;
+    }
+
+    lock_dnode(parent);
+    lock_inode(parent->inode);
+
+    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 if (!(errno = parent->inode->ops.mkdir(parent->inode, dir))) {
+        llist_append(&parent->children, &dir->siblings);
+        goto cleanup;
+    }
+
+    vfs_d_free(dir);
+
+cleanup:
+    unlock_inode(parent->inode);
+    unlock_dnode(parent);
+done:
+    return DO_STATUS(errno);

 }
 
 int
 }
 
 int

-__vfs_do_unlink(struct v_inode* inode)
+__vfs_do_unlink(struct v_dnode* dnode)

 {
 {

+    struct v_inode* inode = dnode->inode;
+
+    if (dnode->ref_count > 1) {
+        return EBUSY;
+    }
+
+    lock_inode(inode);
+

     int errno;
     if (inode->open_count) {
         errno = EBUSY;
     int errno;
     if (inode->open_count) {
         errno = EBUSY;

-    } else if (inode->itype != VFS_INODE_TYPE_DIR) {
-        // TODO handle symbolic link and type other than regular file
+    } else if (!(inode->itype & VFS_IFDIR)) {
+        // The underlying unlink implementation should handle
+        //  symlink case

         errno = inode->ops.unlink(inode);
         errno = inode->ops.unlink(inode);

+        if (!errno) {
+            vfs_dcache_remove(dnode);
+            vfs_d_free(dnode);
+        }

     } else {
         errno = EISDIR;
     }
 
     } else {
         errno = EISDIR;
     }
 

+    unlock_inode(inode);
+

     return errno;
 }
 
     return errno;
 }
 


@@ -726,7 +1190,7 @@ __DEFINE_LXSYSCALL1(int, unlink, const char*, pathname)
 {
     int errno;
     struct v_dnode* dnode;
 {
     int errno;
     struct v_dnode* dnode;

-    if ((errno = vfs_walk(NULL, pathname, &dnode, NULL, 0))) {
+    if ((errno = vfs_walk(__current->cwd, pathname, &dnode, NULL, 0))) {

         goto done;
     }
     if ((dnode->super_block->fs->types & FSTYPE_ROFS)) {
         goto done;
     }
     if ((dnode->super_block->fs->types & FSTYPE_ROFS)) {


@@ -734,27 +1198,382 @@ __DEFINE_LXSYSCALL1(int, unlink, const char*, pathname)
         goto done;
     }
 
         goto done;
     }
 

-    errno = __vfs_do_unlink(dnode->inode);
+    errno = __vfs_do_unlink(dnode);

 
 done:
 
 done:

-    __current->k_status = errno;
-    return SYSCALL_ESTATUS(errno);
+    return DO_STATUS(errno);

 }
 
 __DEFINE_LXSYSCALL2(int, unlinkat, int, fd, const char*, pathname)
 {
     int errno;
     struct v_fd* fd_s;
 }
 
 __DEFINE_LXSYSCALL2(int, unlinkat, int, fd, const char*, pathname)
 {
     int errno;
     struct v_fd* fd_s;

-    if (!GET_FD(fd, fd_s)) {
+    if ((errno = __vfs_getfd(fd, &fd_s))) {
+        goto done;
+    }
+
+    struct v_dnode* dnode;
+    if (!(errno = vfs_walk(fd_s->file->dnode, pathname, &dnode, NULL, 0))) {
+        errno = __vfs_do_unlink(dnode);
+    }
+
+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 (!(errno = __vfs_getfd(fildes, &fd_s))) {
+        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));
+
+    atomic_fetch_add(&old->file->ref_count, 1);
+
+    *new = copied;
+
+    return errno;
+}
+
+int
+vfs_dup2(int oldfd, int newfd)
+{
+    if (newfd == oldfd) {
+        return newfd;
+    }
+
+    int errno;
+    struct v_fd *oldfd_s, *newfd_s;
+    if ((errno = __vfs_getfd(oldfd, &oldfd_s))) {
+        goto done;
+    }
+
+    if (!TEST_FD(newfd)) {

         errno = EBADF;
         errno = EBADF;

+        goto done;
+    }
+
+    newfd_s = __current->fdtable->fds[newfd];
+    if (newfd_s && (errno = vfs_close(newfd_s->file))) {
+        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_LXSYSCALL2(int, dup2, int, oldfd, int, newfd)
+{
+    return vfs_dup2(oldfd, newfd);
+}
+
+__DEFINE_LXSYSCALL1(int, dup, int, oldfd)
+{
+    int errno, newfd;
+    struct v_fd *oldfd_s, *newfd_s;
+    if ((errno = __vfs_getfd(oldfd, &oldfd_s))) {
+        goto done;
+    }
+
+    if (!(errno = vfs_alloc_fdslot(&newfd)) &&
+        !(errno = vfs_dup_fd(oldfd_s, &newfd_s))) {
+        __current->fdtable->fds[newfd] = newfd_s;
+        return newfd;
+    }
+
+done:
+    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(__current->cwd, pathname, &dnode, NULL, 0))) {
+        goto done;
+    }
+    if ((dnode->super_block->fs->types & FSTYPE_ROFS)) {
+        errno = EROFS;
+        goto done;
+    }
+    if (!dnode->inode->ops.set_symlink) {
+        errno = ENOTSUP;
+        goto done;
+    }
+
+    lock_inode(dnode->inode);
+
+    errno = dnode->inode->ops.set_symlink(dnode->inode, link_target);
+
+    unlock_inode(dnode->inode);
+
+done:
+    return DO_STATUS(errno);
+}
+
+int
+__vfs_do_chdir(struct v_dnode* dnode)
+{
+    int errno = 0;
+
+    lock_dnode(dnode);
+
+    if (!(dnode->inode->itype & VFS_IFDIR)) {
+        errno = ENOTDIR;
+        goto done;
+    }
+
+    if (__current->cwd) {
+        atomic_fetch_add(&__current->cwd->ref_count, 1);
+    }
+
+    atomic_fetch_sub(&dnode->ref_count, 1);
+    __current->cwd = dnode;
+
+    unlock_dnode(dnode);
+
+done:
+    return errno;
+}
+
+__DEFINE_LXSYSCALL1(int, chdir, const char*, path)
+{
+    struct v_dnode* dnode;
+    int errno = 0;
+
+    if ((errno = vfs_walk(__current->cwd, path, &dnode, NULL, 0))) {
+        goto done;
+    }
+
+    errno = __vfs_do_chdir(dnode);
+
+done:
+    return DO_STATUS(errno);
+}
+
+__DEFINE_LXSYSCALL1(int, fchdir, int, fd)
+{
+    struct v_fd* fd_s;
+    int errno = 0;
+
+    if ((errno = __vfs_getfd(fd, &fd_s))) {
+        goto done;
+    }
+
+    errno = __vfs_do_chdir(fd_s->file->dnode);
+
+done:
+    return DO_STATUS(errno);
+}
+
+__DEFINE_LXSYSCALL2(char*, getcwd, char*, buf, size_t, size)
+{
+    int errno = 0;
+    char* ret_ptr = 0;
+    if (size < 2) {
+        errno = ERANGE;
+        goto done;
+    }
+
+    size_t len = 0;
+
+    if (!__current->cwd) {
+        *buf = PATH_DELIM;
+        len = 1;

     } else {
     } else {

-        struct v_dnode* dnode;
-        if (!(errno = vfs_walk(fd_s->file->dnode, pathname, &dnode, NULL, 0))) {
-            errno = __vfs_do_unlink(dnode->inode);
+        len = vfs_get_path(__current->cwd, buf, size, 0);
+        if (len == size) {
+            errno = ERANGE;
+            goto done;

         }
     }
 
         }
     }
 

+    buf[len + 1] = '\0';
+
+    ret_ptr = buf;
+

 done:
     __current->k_status = errno;
 done:
     __current->k_status = errno;

-    return SYSCALL_ESTATUS(errno);
+    return ret_ptr;
+}
+
+int
+vfs_do_rename(struct v_dnode* current, struct v_dnode* target)
+{
+    if (current->inode->id == target->inode->id) {
+        // hard link
+        return 0;
+    }
+
+    if (current->ref_count > 1 || target->ref_count > 1) {
+        return EBUSY;
+    }
+
+    if (current->super_block != target->super_block) {
+        return EXDEV;
+    }
+
+    int errno = 0;
+
+    struct v_dnode* oldparent = current->parent;
+    struct v_dnode* newparent = target->parent;
+
+    lock_dnode(current);
+    lock_dnode(target);
+    if (oldparent)
+        lock_dnode(oldparent);
+    if (newparent)
+        lock_dnode(newparent);
+
+    if (!llist_empty(&target->children)) {
+        errno = ENOTEMPTY;
+        unlock_dnode(target);
+        goto cleanup;
+    }
+
+    if ((errno = current->inode->ops.rename(current->inode, current, target))) {
+        unlock_dnode(target);
+        goto cleanup;
+    }
+
+    // re-position current
+    hstrcpy(&current->name, &target->name);
+    vfs_dcache_rehash(newparent, current);
+
+    // detach target
+    vfs_dcache_remove(target);
+
+    unlock_dnode(target);
+
+cleanup:
+    unlock_dnode(current);
+    if (oldparent)
+        unlock_dnode(oldparent);
+    if (newparent)
+        unlock_dnode(newparent);
+
+    return errno;
+}
+
+__DEFINE_LXSYSCALL2(int, rename, const char*, oldpath, const char*, newpath)
+{
+    struct v_dnode *cur, *target_parent, *target;
+    struct hstr name = HSTR(valloc(VFS_NAME_MAXLEN), 0);
+    int errno = 0;
+
+    if ((errno = vfs_walk(__current->cwd, oldpath, &cur, NULL, 0))) {
+        goto done;
+    }
+
+    if ((errno = vfs_walk(
+           __current->cwd, newpath, &target_parent, &name, VFS_WALK_PARENT))) {
+        goto done;
+    }
+
+    errno = vfs_walk(target_parent, name.value, &target, NULL, 0);
+    if (errno == ENOENT) {
+        target = vfs_d_alloc();
+    } else if (errno) {
+        goto done;
+    }
+
+    if (!target) {
+        errno = ENOMEM;
+        goto done;
+    }
+
+    hstrcpy(&target->name, &name);
+
+    if (!(errno = vfs_do_rename(cur, target))) {
+        vfs_d_free(target);
+    }
+
+done:
+    vfree(name.value);
+    return DO_STATUS(errno);
+}
+
+__DEFINE_LXSYSCALL3(int,
+                    mount,
+                    const char*,
+                    source,
+                    const char*,
+                    target,
+                    const char*,
+                    fstype)
+{
+    struct v_dnode *dev, *mnt;
+    int errno = 0;
+
+    if ((errno = vfs_walk(__current->cwd, source, &dev, NULL, 0))) {
+        goto done;
+    }
+
+    if ((errno = vfs_walk(__current->cwd, target, &mnt, NULL, 0))) {
+        goto done;
+    }
+
+    if (!(dev->inode->itype & VFS_IFVOLDEV)) {
+        errno = ENOTDEV;
+        goto done;
+    }
+
+    if (mnt->ref_count > 1) {
+        errno = EBUSY;
+        goto done;
+    }
+
+    // FIXME should not touch the underlying fs!
+    struct device* device =
+      (struct device*)((struct twifs_node*)dev->inode->data)->data;
+
+    errno = vfs_mount_at(fstype, device, mnt);
+
+done:
+    return DO_STATUS(errno);
+}
+
+__DEFINE_LXSYSCALL1(int, unmount, const char*, target)
+{
+    return vfs_unmount(target);

 }
\ No newline at end of file
 }
\ No newline at end of file