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/* This file contains the procedures that look up path names in the directory
* system and determine the inode number that goes with a given path name.
*/
#include "fs.h"
#include <assert.h>
#include <string.h>
#include "buf.h"
#include "inode.h"
#include "super.h"
/*===========================================================================*
* fs_lookup *
*===========================================================================*/
int fs_lookup(ino_t dir_nr, char *name, struct fsdriver_node *node,
int *is_mountpt)
{
struct inode *dirp, *rip;
/* Find the starting inode. */
if ((dirp = find_inode(fs_dev, dir_nr)) == NULL)
return EINVAL;
/* Look up the directory entry. */
if ((rip = advance(dirp, name)) == NULL)
return err_code;
/* On success, leave the resulting inode open and return its details. */
node->fn_ino_nr = rip->i_num;
node->fn_mode = rip->i_mode;
node->fn_size = rip->i_size;
node->fn_uid = rip->i_uid;
node->fn_gid = rip->i_gid;
/* This is only valid for block and character specials. But it doesn't
* cause any harm to always set the device field. */
node->fn_dev = (dev_t) rip->i_zone[0];
*is_mountpt = rip->i_mountpoint;
return OK;
}
/*===========================================================================*
* advance *
*===========================================================================*/
struct inode *advance(dirp, string)
struct inode *dirp; /* inode for directory to be searched */
const char *string; /* component name to look for */
{
/* Given a directory and a component of a path, look up the component in
* the directory, find the inode, open it, and return a pointer to its inode
* slot.
*/
ino_t numb;
struct inode *rip;
assert(dirp != NULL);
/* If 'string' is empty, return an error. */
if (string[0] == '\0') {
err_code = ENOENT;
return(NULL);
}
/* If dir has been removed return ENOENT. */
if (dirp->i_nlinks == NO_LINK) {
err_code = ENOENT;
return(NULL);
}
/* If 'string' is not present in the directory, signal error. */
if ( (err_code = search_dir(dirp, string, &numb, LOOK_UP)) != OK) {
return(NULL);
}
/* The component has been found in the directory. Get inode. */
if ( (rip = get_inode(dirp->i_dev, (int) numb)) == NULL) {
assert(err_code != OK);
return(NULL);
}
assert(err_code == OK);
return(rip);
}
/*===========================================================================*
* search_dir *
*===========================================================================*/
int search_dir(ldir_ptr, string, numb, flag)
register struct inode *ldir_ptr; /* ptr to inode for dir to search */
const char *string; /* component to search for */
ino_t *numb; /* pointer to inode number */
int flag; /* LOOK_UP, ENTER, DELETE or IS_EMPTY */
{
/* This function searches the directory whose inode is pointed to by 'ldip':
* if (flag == ENTER) enter 'string' in the directory with inode # '*numb';
* if (flag == DELETE) delete 'string' from the directory;
* if (flag == LOOK_UP) search for 'string' and return inode # in 'numb';
* if (flag == IS_EMPTY) return OK if only . and .. in dir else ENOTEMPTY;
*
* This function, and this function alone, implements name truncation,
* by simply considering only the first MFS_NAME_MAX bytes from 'string'.
*/
register struct direct *dp = NULL;
register struct buf *bp = NULL;
int i, r, e_hit, t, match;
off_t pos;
unsigned new_slots, old_slots;
struct super_block *sp;
int extended = 0;
/* If 'ldir_ptr' is not a pointer to a dir inode, error. */
if ( (ldir_ptr->i_mode & I_TYPE) != I_DIRECTORY) {
return(ENOTDIR);
}
if((flag == DELETE || flag == ENTER) && ldir_ptr->i_sp->s_rd_only)
return EROFS;
/* Step through the directory one block at a time. */
old_slots = (unsigned) (ldir_ptr->i_size/DIR_ENTRY_SIZE);
new_slots = 0;
e_hit = FALSE;
match = 0; /* set when a string match occurs */
pos = 0;
if (flag == ENTER && ldir_ptr->i_last_dpos < ldir_ptr->i_size) {
pos = ldir_ptr->i_last_dpos;
new_slots = (unsigned) (pos/DIR_ENTRY_SIZE);
}
for (; pos < ldir_ptr->i_size; pos += ldir_ptr->i_sp->s_block_size) {
assert(ldir_ptr->i_dev != NO_DEV);
/* Since directories don't have holes, 'b' cannot be NO_BLOCK. */
bp = get_block_map(ldir_ptr, pos);
assert(ldir_ptr->i_dev != NO_DEV);
assert(bp != NULL);
/* Search a directory block. */
for (dp = &b_dir(bp)[0];
dp < &b_dir(bp)[NR_DIR_ENTRIES(ldir_ptr->i_sp->s_block_size)];
dp++) {
if (++new_slots > old_slots) { /* not found, but room left */
if (flag == ENTER) e_hit = TRUE;
break;
}
/* Match occurs if string found. */
if (flag != ENTER && dp->mfs_d_ino != NO_ENTRY) {
if (flag == IS_EMPTY) {
/* If this test succeeds, dir is not empty. */
if (strcmp(dp->mfs_d_name, "." ) != 0 &&
strcmp(dp->mfs_d_name, "..") != 0)
match = 1;
} else {
if (strncmp(dp->mfs_d_name, string,
sizeof(dp->mfs_d_name)) == 0){
match = 1;
}
}
}
if (match) {
/* LOOK_UP or DELETE found what it wanted. */
r = OK;
if (flag == IS_EMPTY) r = ENOTEMPTY;
else if (flag == DELETE) {
/* Save d_ino for recovery. */
t = MFS_NAME_MAX - sizeof(ino_t);
*((ino_t *) &dp->mfs_d_name[t]) = dp->mfs_d_ino;
dp->mfs_d_ino = NO_ENTRY; /* erase entry */
MARKDIRTY(bp);
ldir_ptr->i_update |= CTIME | MTIME;
IN_MARKDIRTY(ldir_ptr);
if (pos < ldir_ptr->i_last_dpos)
ldir_ptr->i_last_dpos = pos;
} else {
sp = ldir_ptr->i_sp; /* 'flag' is LOOK_UP */
*numb = (ino_t) conv4(sp->s_native,
(int) dp->mfs_d_ino);
}
put_block(bp);
return(r);
}
/* Check for free slot for the benefit of ENTER. */
if (flag == ENTER && dp->mfs_d_ino == 0) {
e_hit = TRUE; /* we found a free slot */
break;
}
}
/* The whole block has been searched or ENTER has a free slot. */
if (e_hit) break; /* e_hit set if ENTER can be performed now */
put_block(bp); /* otherwise, continue searching dir */
}
/* The whole directory has now been searched. */
if (flag != ENTER) {
return(flag == IS_EMPTY ? OK : ENOENT);
}
/* When ENTER next time, start searching for free slot from
* i_last_dpos. It gives some performance improvement (3-5%).
*/
ldir_ptr->i_last_dpos = pos;
/* This call is for ENTER. If no free slot has been found so far, try to
* extend directory.
*/
if (e_hit == FALSE) { /* directory is full and no room left in last block */
new_slots++; /* increase directory size by 1 entry */
if (new_slots == 0) return(EFBIG); /* dir size limited by slot count */
if ( (bp = new_block(ldir_ptr, ldir_ptr->i_size)) == NULL)
return(err_code);
dp = &b_dir(bp)[0];
extended = 1;
}
/* 'bp' now points to a directory block with space. 'dp' points to slot. */
(void) memset(dp->mfs_d_name, 0, (size_t) MFS_NAME_MAX); /* clear entry */
for (i = 0; i < MFS_NAME_MAX && string[i]; i++) dp->mfs_d_name[i] = string[i];
sp = ldir_ptr->i_sp;
dp->mfs_d_ino = conv4(sp->s_native, (int) *numb);
MARKDIRTY(bp);
put_block(bp);
ldir_ptr->i_update |= CTIME | MTIME; /* mark mtime for update later */
IN_MARKDIRTY(ldir_ptr);
if (new_slots > old_slots) {
ldir_ptr->i_size = (off_t) new_slots * DIR_ENTRY_SIZE;
/* Send the change to disk if the directory is extended. */
if (extended) rw_inode(ldir_ptr, WRITING);
}
return(OK);
}
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