minix3/fs/pfs/inode.c

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2020-02-21 00:59:27 +05:30
/* This file manages the inode table. There are procedures to allocate and
* deallocate inodes, acquire, erase, and release them, and read and write
* them from the disk.
*
* The entry points into this file are
* get_inode: search inode table for a given inode; if not there,
* read it
* put_inode: indicate that an inode is no longer needed in memory
* alloc_inode: allocate a new, unused inode
* wipe_inode: erase some fields of a newly allocated inode
* free_inode: mark an inode as available for a new file
* update_times: update atime, ctime, and mtime
* find_inode: retrieve pointer to inode in inode cache
*
*/
#include "fs.h"
#include "buf.h"
#include "inode.h"
#include <minix/vfsif.h>
static void addhash_inode(struct inode * const node);
static void unhash_inode(struct inode * const node);
/*===========================================================================*
* fs_putnode *
*===========================================================================*/
int fs_putnode(message *fs_m_in, message *fs_m_out)
{
/* Find the inode specified by the request message and decrease its counter.*/
struct inode *rip;
int count;
dev_t dev;
ino_t inum;
rip = find_inode(fs_m_in->m_vfs_fs_putnode.inode);
if(!rip) {
printf("%s:%d put_inode: inode #%llu not found\n", __FILE__,
__LINE__, fs_m_in->m_vfs_fs_putnode.inode);
panic("fs_putnode failed");
}
count = fs_m_in->m_vfs_fs_putnode.count;
if (count <= 0) {
printf("%s:%d put_inode: bad value for count: %d\n", __FILE__,
__LINE__, count);
panic("fs_putnode failed");
} else if(count > rip->i_count) {
printf("%s:%d put_inode: count too high: %d > %d\n", __FILE__,
__LINE__, count, rip->i_count);
panic("fs_putnode failed");
}
/* Decrease reference counter, but keep one reference; it will be consumed by
* put_inode(). */
rip->i_count -= count - 1;
dev = rip->i_dev;
inum = rip->i_num;
put_inode(rip);
if (rip->i_count == 0) put_block(dev, inum);
return(OK);
}
/*===========================================================================*
* init_inode_cache *
*===========================================================================*/
void init_inode_cache()
{
struct inode *rip;
struct inodelist *rlp;
/* init free/unused list */
TAILQ_INIT(&unused_inodes);
/* init hash lists */
for (rlp = &hash_inodes[0]; rlp < &hash_inodes[INODE_HASH_SIZE]; ++rlp)
LIST_INIT(rlp);
/* add free inodes to unused/free list */
for (rip = &inode[0]; rip < &inode[PFS_NR_INODES]; ++rip) {
rip->i_num = NO_ENTRY;
TAILQ_INSERT_HEAD(&unused_inodes, rip, i_unused);
}
/* Reserve the first inode (bit 0) to prevent it from being allocated later*/
if (alloc_bit() != NO_BIT) printf("PFS could not reserve NO_BIT\n");
busy = 0; /* This bit does not make the server 'in use/busy'. */
}
/*===========================================================================*
* addhash_inode *
*===========================================================================*/
static void addhash_inode(struct inode * const node)
{
int hashi = (int) (node->i_num & INODE_HASH_MASK);
/* insert into hash table */
LIST_INSERT_HEAD(&hash_inodes[hashi], node, i_hash);
}
/*===========================================================================*
* unhash_inode *
*===========================================================================*/
static void unhash_inode(struct inode * const node)
{
/* remove from hash table */
LIST_REMOVE(node, i_hash);
}
/*===========================================================================*
* get_inode *
*===========================================================================*/
struct inode *get_inode(
dev_t dev, /* device on which inode resides */
ino_t numb /* inode number */
)
{
/* Find the inode in the hash table. If it is not there, get a free inode
* load it from the disk if it's necessary and put on the hash list
*/
register struct inode *rip;
int hashi;
hashi = (int) (numb & INODE_HASH_MASK);
/* Search inode in the hash table */
LIST_FOREACH(rip, &hash_inodes[hashi], i_hash) {
if (rip->i_num == numb && rip->i_dev == dev) {
/* If unused, remove it from the unused/free list */
if (rip->i_count == 0) {
TAILQ_REMOVE(&unused_inodes, rip, i_unused);
}
++rip->i_count;
return(rip);
}
}
/* Inode is not on the hash, get a free one */
if (TAILQ_EMPTY(&unused_inodes)) {
err_code = ENFILE;
return(NULL);
}
rip = TAILQ_FIRST(&unused_inodes);
/* If not free unhash it */
if (rip->i_num != NO_ENTRY) unhash_inode(rip);
/* Inode is not unused any more */
TAILQ_REMOVE(&unused_inodes, rip, i_unused);
/* Load the inode. */
rip->i_dev = dev;
rip->i_num = numb;
rip->i_count = 1;
rip->i_update = 0; /* all the times are initially up-to-date */
/* Add to hash */
addhash_inode(rip);
return(rip);
}
/*===========================================================================*
* find_inode *
*===========================================================================*/
struct inode *find_inode(ino_t numb /* inode number */)
{
/* Find the inode specified by the inode and device number.
*/
struct inode *rip;
int hashi;
hashi = (int) (numb & INODE_HASH_MASK);
/* Search inode in the hash table */
LIST_FOREACH(rip, &hash_inodes[hashi], i_hash) {
if (rip->i_count > 0 && rip->i_num == numb) {
return(rip);
}
}
return(NULL);
}
/*===========================================================================*
* put_inode *
*===========================================================================*/
void put_inode(rip)
struct inode *rip; /* pointer to inode to be released */
{
/* The caller is no longer using this inode. If no one else is using it either
* write it back to the disk immediately. If it has no links, truncate it and
* return it to the pool of available inodes.
*/
if (rip == NULL) return; /* checking here is easier than in caller */
if (rip->i_count < 1)
panic("put_inode: i_count already below 1: %d", rip->i_count);
if (--rip->i_count == 0) { /* i_count == 0 means no one is using it now */
if (rip->i_nlinks == NO_LINK) { /* Are there links to this file? */
/* no links, free the inode. */
truncate_inode(rip, 0); /* return all the disk blocks */
rip->i_mode = I_NOT_ALLOC; /* clear I_TYPE field */
free_inode(rip);
} else {
truncate_inode(rip, (off_t) 0);
}
if (rip->i_nlinks == NO_LINK) {
/* free, put at the front of the LRU list */
unhash_inode(rip);
rip->i_num = NO_ENTRY;
rip->i_dev = NO_DEV;
rip->i_rdev = NO_DEV;
TAILQ_INSERT_HEAD(&unused_inodes, rip, i_unused);
} else {
/* unused, put at the back of the LRU (cache it) */
TAILQ_INSERT_TAIL(&unused_inodes, rip, i_unused);
}
}
}
/*===========================================================================*
* alloc_inode *
*===========================================================================*/
struct inode *alloc_inode(dev_t dev, mode_t bits, uid_t uid, gid_t gid)
{
/* Allocate a free inode on 'dev', and return a pointer to it. */
register struct inode *rip;
bit_t b;
ino_t i_num;
int print_oos_msg = 1;
b = alloc_bit();
if (b == NO_BIT) {
err_code = ENOSPC;
if (print_oos_msg)
printf("PipeFS is out of inodes\n");
print_oos_msg = 0; /* Don't repeat message */
return(NULL);
}
i_num = (ino_t) b;
print_oos_msg = 1;
/* Try to acquire a slot in the inode table. */
if ((rip = get_inode(dev, i_num)) == NULL) {
/* No inode table slots available. Free the inode if just allocated.*/
if (dev == NO_DEV) free_bit(b);
} else {
/* An inode slot is available. */
rip->i_mode = bits; /* set up RWX bits */
rip->i_nlinks = NO_LINK; /* initial no links */
rip->i_uid = uid; /* set file user id */
rip->i_gid = gid; /* ditto group id */
/* Fields not cleared already are cleared in wipe_inode(). They have
* been put there because truncate() needs to clear the same fields if
* the file happens to be open while being truncated. It saves space
* not to repeat the code twice.
*/
wipe_inode(rip);
}
return(rip);
}
/*===========================================================================*
* wipe_inode *
*===========================================================================*/
void wipe_inode(rip)
struct inode *rip; /* the inode to be erased */
{
/* Erase some fields in the inode. This function is called from alloc_inode()
* when a new inode is to be allocated, and from truncate(), when an existing
* inode is to be truncated.
*/
rip->i_size = 0;
rip->i_update = ATIME | CTIME | MTIME; /* update all times later */
}
/*===========================================================================*
* free_inode *
*===========================================================================*/
void free_inode(rip)
struct inode *rip;
{
/* Return an inode to the pool of unallocated inodes. */
bit_t b;
if (rip->i_num <= 0 || rip->i_num >= PFS_NR_INODES) return;
b = (bit_t) rip->i_num;
free_bit(b);
}
/*===========================================================================*
* update_times *
*===========================================================================*/
void update_times(rip)
struct inode *rip; /* pointer to inode to be read/written */
{
/* Various system calls are required by the standard to update atime, ctime,
* or mtime. Since updating a time requires sending a message to the clock
* task--an expensive business--the times are marked for update by setting
* bits in i_update. When a stat, fstat, or sync is done, or an inode is
* released, update_times() may be called to actually fill in the times.
*/
time_t cur_time;
cur_time = clock_time();
if (rip->i_update & ATIME) rip->i_atime = cur_time;
if (rip->i_update & CTIME) rip->i_ctime = cur_time;
if (rip->i_update & MTIME) rip->i_mtime = cur_time;
rip->i_update = 0; /* they are all up-to-date now */
}