minix/lib/libsffs/inode.c
David van Moolenbroek ef7b484e5c Create SFFS library out of HGFS
This Shared Folders File System library (libsffs) now contains all the
file system logic originally in HGFS. The actual HGFS server code is
now a stub that passes on all the work to libsffs. The libhgfs library
is changed accordingly.
2012-04-09 18:08:26 +02:00

301 lines
8.3 KiB
C

/* This file deals with inode management.
*
* The entry points into this file are:
* init_inode initialize the inode table, return the root inode
* find_inode find an inode based on its inode number
* get_inode increase the reference count of an inode
* put_inode decrease the reference count of an inode
* link_inode link an inode as a directory entry to another inode
* unlink_inode unlink an inode from its parent directory
* get_free_inode return a free inode object
* have_free_inode check whether there is a free inode available
* have_used_inode check whether any inode is still in use
* do_putnode perform the PUTNODE file system call
*
* Created:
* April 2009 (D.C. van Moolenbroek)
*/
#include "inc.h"
static struct inode inodes[NUM_INODES];
static TAILQ_HEAD(free_head, inode) free_list;
/*===========================================================================*
* init_inode *
*===========================================================================*/
struct inode *init_inode()
{
/* Initialize inode table. Return the root inode.
*/
struct inode *ino;
unsigned int index;
TAILQ_INIT(&free_list);
dprintf(("%s: %d inodes, %u bytes each, equals %u bytes\n",
sffs_name, NUM_INODES, sizeof(struct inode), sizeof(inodes)));
/* Mark all inodes except the root inode as free. */
for (index = 1; index < NUM_INODES; index++) {
ino = &inodes[index];
ino->i_parent = NULL;
LIST_INIT(&ino->i_child);
ino->i_num = index + 1;
ino->i_gen = (unsigned short)-1; /* aesthetics */
ino->i_ref = 0;
ino->i_flags = 0;
TAILQ_INSERT_TAIL(&free_list, ino, i_free);
}
/* Initialize and return the root inode. */
ino = &inodes[0];
ino->i_parent = ino; /* root inode is its own parent */
LIST_INIT(&ino->i_child);
ino->i_num = ROOT_INODE_NR;
ino->i_gen = 0; /* unused by root node */
ino->i_ref = 1; /* root inode is hereby in use */
ino->i_flags = I_DIR; /* root inode is a directory */
ino->i_name[0] = 0; /* root inode has empty name */
return ino;
}
/*===========================================================================*
* find_inode *
*===========================================================================*/
struct inode *find_inode(ino_nr)
ino_t ino_nr;
{
/* Get an inode based on its inode number. Do not increase its reference count.
*/
struct inode *ino;
int index;
/* Inode 0 (= index -1) is not a valid inode number. */
index = INODE_INDEX(ino_nr);
if (index < 0) {
printf("%s: VFS passed invalid inode number!\n", sffs_name);
return NULL;
}
assert(index < NUM_INODES);
ino = &inodes[index];
/* Make sure the generation number matches. */
if (INODE_GEN(ino_nr) != ino->i_gen) {
printf("%s: VFS passed outdated inode number!\n", sffs_name);
return NULL;
}
/* The VFS/FS protocol only uses referenced inodes. */
if (ino->i_ref == 0)
printf("%s: VFS passed unused inode!\n", sffs_name);
return ino;
}
/*===========================================================================*
* get_inode *
*===========================================================================*/
void get_inode(ino)
struct inode *ino;
{
/* Increase the given inode's reference count. If both reference and link
* count were zero before, remove the inode from the free list.
*/
dprintf(("%s: get_inode(%p) ['%s']\n", sffs_name, ino, ino->i_name));
/* (INUSE, CACHED) -> INUSE */
/* If this is the first reference, remove the node from the free list. */
if (ino->i_ref == 0 && !HAS_CHILDREN(ino))
TAILQ_REMOVE(&free_list, ino, i_free);
ino->i_ref++;
if (ino->i_ref == 0)
panic("inode reference count wrapped");
}
/*===========================================================================*
* put_inode *
*===========================================================================*/
void put_inode(ino)
struct inode *ino;
{
/* Decrease an inode's reference count. If this count has reached zero, close
* the inode's file handle, if any. If both reference and link count have
* reached zero, mark the inode as cached or free.
*/
dprintf(("%s: put_inode(%p) ['%s']\n", sffs_name, ino, ino->i_name));
assert(ino != NULL);
assert(ino->i_ref > 0);
ino->i_ref--;
/* If there are still references to this inode, we're done here. */
if (ino->i_ref > 0)
return;
/* Close any file handle associated with this inode. */
put_handle(ino);
/* Only add the inode to the free list if there are also no links to it. */
if (HAS_CHILDREN(ino))
return;
/* INUSE -> CACHED, DELETED -> FREE */
/* Add the inode to the head or tail of the free list, depending on whether
* it is also deleted (and therefore can never be reused as is).
*/
if (ino->i_parent == NULL)
TAILQ_INSERT_HEAD(&free_list, ino, i_free);
else
TAILQ_INSERT_TAIL(&free_list, ino, i_free);
}
/*===========================================================================*
* link_inode *
*===========================================================================*/
void link_inode(parent, ino)
struct inode *parent;
struct inode *ino;
{
/* Link an inode to a parent. If both reference and link count were zero
* before, remove the inode from the free list. This function should only be
* called from add_dentry().
*/
/* This can never happen, right? */
if (parent->i_ref == 0 && !HAS_CHILDREN(parent))
TAILQ_REMOVE(&free_list, parent, i_free);
LIST_INSERT_HEAD(&parent->i_child, ino, i_next);
ino->i_parent = parent;
}
/*===========================================================================*
* unlink_inode *
*===========================================================================*/
void unlink_inode(ino)
struct inode *ino;
{
/* Unlink an inode from its parent. If both reference and link count have
* reached zero, mark the inode as cached or free. This function should only
* be used from del_dentry().
*/
struct inode *parent;
parent = ino->i_parent;
LIST_REMOVE(ino, i_next);
if (parent->i_ref == 0 && !HAS_CHILDREN(parent)) {
if (parent->i_parent == NULL)
TAILQ_INSERT_HEAD(&free_list, parent, i_free);
else
TAILQ_INSERT_TAIL(&free_list, parent, i_free);
}
ino->i_parent = NULL;
}
/*===========================================================================*
* get_free_inode *
*===========================================================================*/
struct inode *get_free_inode()
{
/* Return a free inode object (with reference count 1), if available.
*/
struct inode *ino;
/* [CACHED -> FREE,] FREE -> DELETED */
/* If there are no inodes on the free list, we cannot satisfy the request. */
if (TAILQ_EMPTY(&free_list)) {
printf("%s: out of inodes!\n", sffs_name);
return NULL;
}
ino = TAILQ_FIRST(&free_list);
TAILQ_REMOVE(&free_list, ino, i_free);
assert(ino->i_ref == 0);
assert(!HAS_CHILDREN(ino));
/* If this was a cached inode, free it first. */
if (ino->i_parent != NULL)
del_dentry(ino);
assert(ino->i_parent == NULL);
/* Initialize a subset of its fields */
ino->i_gen++;
ino->i_ref = 1;
return ino;
}
/*===========================================================================*
* have_free_inode *
*===========================================================================*/
int have_free_inode()
{
/* Check whether there are any free inodes at the moment. Kind of lame, but
* this allows for easier error recovery in some places.
*/
return !TAILQ_EMPTY(&free_list);
}
/*===========================================================================*
* have_used_inode *
*===========================================================================*/
int have_used_inode()
{
/* Check whether any inodes are still in use, that is, any of the inodes have
* a reference count larger than zero.
*/
unsigned int index;
for (index = 0; index < NUM_INODES; index++)
if (inodes[index].i_ref > 0)
return TRUE;
return FALSE;
}
/*===========================================================================*
* do_putnode *
*===========================================================================*/
int do_putnode()
{
/* Decrease an inode's reference count.
*/
struct inode *ino;
int count;
if ((ino = find_inode(m_in.REQ_INODE_NR)) == NULL)
return EINVAL;
count = m_in.REQ_COUNT;
if (count <= 0 || count > ino->i_ref) return EINVAL;
ino->i_ref -= count - 1;
put_inode(ino);
return OK;
}