296 lines
8.3 KiB
C
296 lines
8.3 KiB
C
/* This file deals with inode management.
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*
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* The entry points into this file are:
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* init_inode initialize the inode table, return the root inode
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* find_inode find an inode based on its inode number
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* get_inode increase the reference count of an inode
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* put_inode decrease the reference count of an inode
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* link_inode link an inode as a directory entry to another inode
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* unlink_inode unlink an inode from its parent directory
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* get_free_inode return a free inode object
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* have_free_inode check whether there is a free inode available
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* have_used_inode check whether any inode is still in use
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* do_putnode perform the PUTNODE file system call
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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 struct inode inodes[NUM_INODES];
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static TAILQ_HEAD(free_head, inode) free_list;
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/*===========================================================================*
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* init_inode *
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*===========================================================================*/
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struct inode *init_inode(void)
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{
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/* Initialize inode table. Return the root inode.
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*/
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struct inode *ino;
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unsigned int index;
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TAILQ_INIT(&free_list);
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dprintf(("%s: %d inodes, %u bytes each, equals %u bytes\n",
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sffs_name, NUM_INODES, sizeof(struct inode), sizeof(inodes)));
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/* Mark all inodes except the root inode as free. */
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for (index = 1; index < NUM_INODES; index++) {
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ino = &inodes[index];
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ino->i_parent = NULL;
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LIST_INIT(&ino->i_child);
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ino->i_num = index + 1;
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ino->i_gen = (unsigned short)-1; /* aesthetics */
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ino->i_ref = 0;
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ino->i_flags = 0;
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TAILQ_INSERT_TAIL(&free_list, ino, i_free);
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}
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/* Initialize and return the root inode. */
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ino = &inodes[0];
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ino->i_parent = ino; /* root inode is its own parent */
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LIST_INIT(&ino->i_child);
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ino->i_num = ROOT_INODE_NR;
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ino->i_gen = 0; /* unused by root node */
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ino->i_ref = 1; /* root inode is hereby in use */
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ino->i_flags = I_DIR; /* root inode is a directory */
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ino->i_name[0] = 0; /* root inode has empty name */
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return ino;
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}
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/*===========================================================================*
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* find_inode *
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*===========================================================================*/
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struct inode *find_inode(ino_t ino_nr)
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{
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/* Get an inode based on its inode number. Do not increase its reference count.
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*/
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struct inode *ino;
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int index;
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/* Inode 0 (= index -1) is not a valid inode number. */
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index = INODE_INDEX(ino_nr);
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if (index < 0) {
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printf("%s: VFS passed invalid inode number!\n", sffs_name);
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return NULL;
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}
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assert(index < NUM_INODES);
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ino = &inodes[index];
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/* Make sure the generation number matches. */
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if (INODE_GEN(ino_nr) != ino->i_gen) {
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printf("%s: VFS passed outdated inode number!\n", sffs_name);
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return NULL;
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}
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/* The VFS/FS protocol only uses referenced inodes. */
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if (ino->i_ref == 0)
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printf("%s: VFS passed unused inode!\n", sffs_name);
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return ino;
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}
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/*===========================================================================*
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* get_inode *
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*===========================================================================*/
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void get_inode(struct inode *ino)
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{
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/* Increase the given inode's reference count. If both reference and link
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* count were zero before, remove the inode from the free list.
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*/
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dprintf(("%s: get_inode(%p) ['%s']\n", sffs_name, ino, ino->i_name));
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/* (INUSE, CACHED) -> INUSE */
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/* If this is the first reference, remove the node from the free list. */
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if (ino->i_ref == 0 && !HAS_CHILDREN(ino))
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TAILQ_REMOVE(&free_list, ino, i_free);
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ino->i_ref++;
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if (ino->i_ref == 0)
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panic("inode reference count wrapped");
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}
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/*===========================================================================*
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* put_inode *
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*===========================================================================*/
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void put_inode(struct inode *ino)
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{
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/* Decrease an inode's reference count. If this count has reached zero, close
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* the inode's file handle, if any. If both reference and link count have
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* reached zero, mark the inode as cached or free.
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*/
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dprintf(("%s: put_inode(%p) ['%s']\n", sffs_name, ino, ino->i_name));
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assert(ino != NULL);
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assert(ino->i_ref > 0);
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ino->i_ref--;
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/* If there are still references to this inode, we're done here. */
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if (ino->i_ref > 0)
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return;
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/* Close any file handle associated with this inode. */
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put_handle(ino);
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/* Only add the inode to the free list if there are also no links to it. */
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if (HAS_CHILDREN(ino))
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return;
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/* INUSE -> CACHED, DELETED -> FREE */
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/* Add the inode to the head or tail of the free list, depending on whether
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* it is also deleted (and therefore can never be reused as is).
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*/
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if (ino->i_parent == NULL)
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TAILQ_INSERT_HEAD(&free_list, ino, i_free);
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else
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TAILQ_INSERT_TAIL(&free_list, ino, i_free);
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}
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/*===========================================================================*
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* link_inode *
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*===========================================================================*/
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void link_inode(struct inode *parent, struct inode *ino)
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{
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/* Link an inode to a parent. If both reference and link count were zero
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* before, remove the inode from the free list. This function should only be
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* called from add_dentry().
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*/
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/* This can never happen, right? */
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if (parent->i_ref == 0 && !HAS_CHILDREN(parent))
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TAILQ_REMOVE(&free_list, parent, i_free);
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LIST_INSERT_HEAD(&parent->i_child, ino, i_next);
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ino->i_parent = parent;
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}
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/*===========================================================================*
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* unlink_inode *
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*===========================================================================*/
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void unlink_inode(struct inode *ino)
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{
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/* Unlink an inode from its parent. If both reference and link count have
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* reached zero, mark the inode as cached or free. This function should only
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* be used from del_dentry().
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*/
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struct inode *parent;
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parent = ino->i_parent;
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LIST_REMOVE(ino, i_next);
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if (parent->i_ref == 0 && !HAS_CHILDREN(parent)) {
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if (parent->i_parent == NULL)
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TAILQ_INSERT_HEAD(&free_list, parent, i_free);
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else
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TAILQ_INSERT_TAIL(&free_list, parent, i_free);
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}
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ino->i_parent = NULL;
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}
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/*===========================================================================*
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* get_free_inode *
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*===========================================================================*/
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struct inode *get_free_inode(void)
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{
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/* Return a free inode object (with reference count 1), if available.
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*/
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struct inode *ino;
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/* [CACHED -> FREE,] FREE -> DELETED */
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/* If there are no inodes on the free list, we cannot satisfy the request. */
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if (TAILQ_EMPTY(&free_list)) {
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printf("%s: out of inodes!\n", sffs_name);
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return NULL;
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}
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ino = TAILQ_FIRST(&free_list);
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TAILQ_REMOVE(&free_list, ino, i_free);
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assert(ino->i_ref == 0);
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assert(!HAS_CHILDREN(ino));
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/* If this was a cached inode, free it first. */
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if (ino->i_parent != NULL)
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del_dentry(ino);
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assert(ino->i_parent == NULL);
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/* Initialize a subset of its fields */
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ino->i_gen++;
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ino->i_ref = 1;
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return ino;
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}
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/*===========================================================================*
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* have_free_inode *
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*===========================================================================*/
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int have_free_inode(void)
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{
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/* Check whether there are any free inodes at the moment. Kind of lame, but
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* this allows for easier error recovery in some places.
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*/
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return !TAILQ_EMPTY(&free_list);
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}
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/*===========================================================================*
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* have_used_inode *
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*===========================================================================*/
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int have_used_inode(void)
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{
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/* Check whether any inodes are still in use, that is, any of the inodes have
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* a reference count larger than zero.
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*/
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unsigned int index;
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for (index = 0; index < NUM_INODES; index++)
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if (inodes[index].i_ref > 0)
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return TRUE;
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return FALSE;
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}
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/*===========================================================================*
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* do_putnode *
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*===========================================================================*/
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int do_putnode(void)
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{
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/* Decrease an inode's reference count.
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*/
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struct inode *ino;
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int count;
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if ((ino = find_inode(m_in.m_vfs_fs_putnode.inode)) == NULL)
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return EINVAL;
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count = m_in.m_vfs_fs_putnode.count;
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if (count <= 0 || count > ino->i_ref) return EINVAL;
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ino->i_ref -= count - 1;
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put_inode(ino);
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return OK;
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}
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