Patch submitted by hoefnix. Ref. https://groups.google.com/d/msg/minix-dev/sHQDVJRyx1c/eJjrYOqk5bgJ Change-Id: I2fcdf4cf119ef252ccc7df06849baf37ffd08440
184 lines
5.1 KiB
C
184 lines
5.1 KiB
C
/* This file contains directory entry management and the name lookup hashtable.
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*
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* The entry points into this file are:
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* init_dentry initialize the directory entry name lookup hashtable
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* lookup_dentry find an inode based on parent directory and name
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* add_dentry add an inode as directory entry to a parent directory
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* del_dentry delete an inode from its parent directory
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*
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* Created:
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* April 2009 (D.C. van Moolenbroek)
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*/
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#include "inc.h"
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static LIST_HEAD(hash_head, inode) hash_table[NUM_HASH_SLOTS];
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static void del_one_dentry(struct inode *ino);
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static unsigned int hash_dentry(struct inode *parent, char *name);
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/*===========================================================================*
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* init_dentry *
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*===========================================================================*/
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void init_dentry(void)
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{
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/* Initialize the names hashtable.
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*/
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int i;
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for (i = 0; i < NUM_HASH_SLOTS; i++)
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LIST_INIT(&hash_table[i]);
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}
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/*===========================================================================*
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* lookup_dentry *
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*===========================================================================*/
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struct inode *lookup_dentry(struct inode *parent, char *name)
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{
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/* Given a directory inode and a component name, look up the inode associated
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* with that directory entry. Return the inode (with increased reference
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* count) if found, or NULL otherwise.
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*/
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struct inode *ino;
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unsigned int slot;
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assert(IS_DIR(parent));
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slot = hash_dentry(parent, name);
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LIST_FOREACH(ino, &hash_table[slot], i_hash) {
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if (compare_name(ino->i_name, name) == TRUE)
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break;
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}
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if (ino == NULL)
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return NULL;
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get_inode(ino);
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return ino;
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}
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/*===========================================================================*
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* add_dentry *
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*===========================================================================*/
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void add_dentry(struct inode *parent, char *name, struct inode *ino)
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{
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/* Add an entry to a parent inode, in the form of a new inode, with the given
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* name. An entry with this name must not already exist.
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*/
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unsigned int slot;
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assert(IS_DIR(parent));
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assert(parent->i_ref > 0);
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assert(ino->i_ref > 0);
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assert(name[0]);
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assert(strlen(name) <= NAME_MAX);
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link_inode(parent, ino);
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strlcpy(ino->i_name, name, sizeof(ino->i_name));
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/* hash_add(ino); */
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slot = hash_dentry(parent, ino->i_name);
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LIST_INSERT_HEAD(&hash_table[slot], ino, i_hash);
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}
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/*===========================================================================*
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* del_one_dentry *
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*===========================================================================*/
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static void del_one_dentry(struct inode *ino)
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{
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/* This inode has become inaccessible by name. Disassociate it from its parent
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* and remove it from the names hash table.
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*/
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/* There can and must be exactly one root inode, so don't delete it! */
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if (IS_ROOT(ino))
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return;
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/* INUSE -> DELETED, CACHED -> FREE */
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/* Remove the entry from the hashtable.
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* Decrease parent's refcount, possibly adding it to the free list.
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* Do not touch open handles. Do not add to the free list.
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*/
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assert(ino->i_parent != NULL);
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/* hash_del(ino); */
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LIST_REMOVE(ino, i_hash);
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ino->i_name[0] = 0;
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unlink_inode(ino);
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}
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/*===========================================================================*
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* del_dentry *
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*===========================================================================*/
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void del_dentry(struct inode *ino)
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{
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/* Disassociate an inode from its parent, effectively deleting it. Recursively
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* delete all its children as well, fragmenting the deleted branch into single
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* inodes.
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*/
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LIST_HEAD(work_list, inode) work_list;
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struct inode *child;
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del_one_dentry(ino);
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/* Quick way out: one directory entry that itself has no children. */
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if (!HAS_CHILDREN(ino))
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return;
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/* Recursively delete all children of the inode as well.
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* Iterative version: this is potentially 128 levels deep.
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*/
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LIST_INIT(&work_list);
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LIST_INSERT_HEAD(&work_list, ino, i_next);
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do {
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ino = LIST_FIRST(&work_list);
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LIST_REMOVE(ino, i_next);
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assert(IS_DIR(ino));
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while (!LIST_EMPTY(&ino->i_child)) {
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child = LIST_FIRST(&ino->i_child);
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LIST_REMOVE(child, i_next);
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del_one_dentry(child);
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if (HAS_CHILDREN(child))
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LIST_INSERT_HEAD(&work_list, child, i_next);
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}
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} while (!LIST_EMPTY(&work_list));
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}
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/*===========================================================================*
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* hash_dentry *
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*===========================================================================*/
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static unsigned int hash_dentry(struct inode *parent, char *name)
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{
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/* Generate a hash value for a given name. Normalize the name first, so that
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* different variations of the name will result in the same hash value.
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*/
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unsigned int val;
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char buf[NAME_MAX+1], *p;
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dprintf(("%s: hash_dentry for '%s'\n", sffs_name, name));
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normalize_name(buf, name);
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/* djb2 string hash algorithm, XOR variant */
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val = 5381;
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for (p = buf; *p; p++)
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val = ((val << 5) + val) ^ *p;
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/* Mix with inode number: typically, many file names occur in several
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* different directories.
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*/
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return (val ^ parent->i_num) % NUM_HASH_SLOTS;
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}
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