minix/servers/mfs/open.c

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#include "fs.h"
#include <sys/stat.h>
#include <string.h>
#include <minix/com.h>
#include "buf.h"
#include "inode.h"
#include "super.h"
#include <minix/vfsif.h>
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static struct inode *new_node(struct inode *ldirp, char *string, mode_t
bits, zone_t z0);
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/*===========================================================================*
* fs_create *
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*===========================================================================*/
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int fs_create()
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{
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size_t len;
int r;
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struct inode *ldirp;
struct inode *rip;
mode_t omode;
char lastc[MFS_NAME_MAX];
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/* Read request message */
omode = (mode_t) fs_m_in.REQ_MODE;
caller_uid = (uid_t) fs_m_in.REQ_UID;
caller_gid = (gid_t) fs_m_in.REQ_GID;
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/* Try to make the file. */
/* Copy the last component (i.e., file name) */
len = min( (unsigned) fs_m_in.REQ_PATH_LEN, sizeof(lastc));
err_code = sys_safecopyfrom(VFS_PROC_NR, (cp_grant_id_t) fs_m_in.REQ_GRANT,
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(vir_bytes) 0, (vir_bytes) lastc, len, D);
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if (err_code != OK) return err_code;
NUL(lastc, len, sizeof(lastc));
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/* Get last directory inode (i.e., directory that will hold the new inode) */
if ((ldirp = get_inode(fs_dev, (ino_t) fs_m_in.REQ_INODE_NR)) == NULL)
return(ENOENT);
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/* Create a new inode by calling new_node(). */
rip = new_node(ldirp, lastc, omode, NO_ZONE);
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r = err_code;
/* If an error occurred, release inode. */
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if (r != OK) {
put_inode(ldirp);
put_inode(rip);
return(r);
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}
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/* Reply message */
fs_m_out.RES_INODE_NR = rip->i_num;
fs_m_out.RES_MODE = rip->i_mode;
fs_m_out.RES_FILE_SIZE_LO = rip->i_size;
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/* These values are needed for the execution */
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fs_m_out.RES_UID = rip->i_uid;
fs_m_out.RES_GID = rip->i_gid;
/* Drop parent dir */
put_inode(ldirp);
return(OK);
}
/*===========================================================================*
* fs_mknod *
*===========================================================================*/
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int fs_mknod()
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{
struct inode *ip, *ldirp;
char lastc[MFS_NAME_MAX];
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phys_bytes len;
/* Copy the last component and set up caller's user and group id */
len = min( (unsigned) fs_m_in.REQ_PATH_LEN, sizeof(lastc));
err_code = sys_safecopyfrom(VFS_PROC_NR, (cp_grant_id_t) fs_m_in.REQ_GRANT,
(vir_bytes) 0, (vir_bytes) lastc, (size_t) len, D);
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if (err_code != OK) return err_code;
NUL(lastc, len, sizeof(lastc));
caller_uid = (uid_t) fs_m_in.REQ_UID;
caller_gid = (gid_t) fs_m_in.REQ_GID;
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/* Get last directory inode */
if((ldirp = get_inode(fs_dev, (ino_t) fs_m_in.REQ_INODE_NR)) == NULL)
return(ENOENT);
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/* Try to create the new node */
ip = new_node(ldirp, lastc, (mode_t) fs_m_in.REQ_MODE,
(zone_t) fs_m_in.REQ_DEV);
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put_inode(ip);
put_inode(ldirp);
return(err_code);
}
/*===========================================================================*
* fs_mkdir *
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*===========================================================================*/
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int fs_mkdir()
{
int r1, r2; /* status codes */
ino_t dot, dotdot; /* inode numbers for . and .. */
struct inode *rip, *ldirp;
char lastc[MFS_NAME_MAX]; /* last component */
phys_bytes len;
/* Copy the last component and set up caller's user and group id */
len = min( (unsigned) fs_m_in.REQ_PATH_LEN, sizeof(lastc));
err_code = sys_safecopyfrom(VFS_PROC_NR, (cp_grant_id_t) fs_m_in.REQ_GRANT,
(vir_bytes) 0, (vir_bytes) lastc, (size_t) len, D);
if(err_code != OK) return(err_code);
NUL(lastc, len, sizeof(lastc));
caller_uid = (uid_t) fs_m_in.REQ_UID;
caller_gid = (gid_t) fs_m_in.REQ_GID;
/* Get last directory inode */
if((ldirp = get_inode(fs_dev, (ino_t) fs_m_in.REQ_INODE_NR)) == NULL)
return(ENOENT);
/* Next make the inode. If that fails, return error code. */
rip = new_node(ldirp, lastc, (mode_t) fs_m_in.REQ_MODE, (zone_t) 0);
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if(rip == NULL || err_code == EEXIST) {
put_inode(rip); /* can't make dir: it already exists */
put_inode(ldirp);
return(err_code);
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}
/* Get the inode numbers for . and .. to enter in the directory. */
dotdot = ldirp->i_num; /* parent's inode number */
dot = rip->i_num; /* inode number of the new dir itself */
/* Now make dir entries for . and .. unless the disk is completely full. */
/* Use dot1 and dot2, so the mode of the directory isn't important. */
rip->i_mode = (mode_t) fs_m_in.REQ_MODE; /* set mode */
r1 = search_dir(rip, dot1, &dot, ENTER, IGN_PERM);/* enter . in the new dir*/
r2 = search_dir(rip, dot2, &dotdot, ENTER, IGN_PERM); /* enter .. in the new
dir */
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/* If both . and .. were successfully entered, increment the link counts. */
if (r1 == OK && r2 == OK) {
/* Normal case. It was possible to enter . and .. in the new dir. */
rip->i_nlinks++; /* this accounts for . */
ldirp->i_nlinks++; /* this accounts for .. */
IN_MARKDIRTY(ldirp); /* mark parent's inode as dirty */
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} else {
/* It was not possible to enter . or .. probably disk was full -
* links counts haven't been touched. */
if(search_dir(ldirp, lastc, NULL, DELETE, IGN_PERM) != OK)
panic("Dir disappeared: %ul", rip->i_num);
rip->i_nlinks--; /* undo the increment done in new_node() */
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}
IN_MARKDIRTY(rip); /* either way, i_nlinks has changed */
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put_inode(ldirp); /* return the inode of the parent dir */
put_inode(rip); /* return the inode of the newly made dir */
return(err_code); /* new_node() always sets 'err_code' */
}
/*===========================================================================*
* fs_slink *
*===========================================================================*/
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int fs_slink()
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{
phys_bytes len;
struct inode *sip; /* inode containing symbolic link */
struct inode *ldirp; /* directory containing link */
register int r; /* error code */
char string[MFS_NAME_MAX]; /* last component of the new dir's path name */
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struct buf *bp; /* disk buffer for link */
caller_uid = (uid_t) fs_m_in.REQ_UID;
caller_gid = (gid_t) fs_m_in.REQ_GID;
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/* Copy the link name's last component */
len = min( (unsigned) fs_m_in.REQ_PATH_LEN, sizeof(string));
r = sys_safecopyfrom(VFS_PROC_NR, (cp_grant_id_t) fs_m_in.REQ_GRANT,
(vir_bytes) 0, (vir_bytes) string, (size_t) len, D);
if (r != OK) return(r);
NUL(string, len, sizeof(string));
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/* Temporarily open the dir. */
if( (ldirp = get_inode(fs_dev, (ino_t) fs_m_in.REQ_INODE_NR)) == NULL)
return(EINVAL);
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/* Create the inode for the symlink. */
sip = new_node(ldirp, string, (mode_t) (I_SYMBOLIC_LINK | RWX_MODES),
(zone_t) 0);
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/* Allocate a disk block for the contents of the symlink.
* Copy contents of symlink (the name pointed to) into first disk block. */
if( (r = err_code) == OK) {
bp = new_block(sip, (off_t) 0);
if (bp == NULL)
r = err_code;
else
r = sys_safecopyfrom(VFS_PROC_NR,
(cp_grant_id_t) fs_m_in.REQ_GRANT3,
(vir_bytes) 0, (vir_bytes) bp->b_data,
(size_t) fs_m_in.REQ_MEM_SIZE, D);
if(bp != NULL && r == OK) {
bp->b_data[_MIN_BLOCK_SIZE-1] = '\0';
sip->i_size = (off_t) strlen(bp->b_data);
if(sip->i_size != fs_m_in.REQ_MEM_SIZE) {
/* This can happen if the user provides a buffer
* with a \0 in it. This can cause a lot of trouble
* when the symlink is used later. We could just use
* the strlen() value, but we want to let the user
* know he did something wrong. ENAMETOOLONG doesn't
* exactly describe the error, but there is no
* ENAMETOOWRONG.
*/
r = ENAMETOOLONG;
}
}
put_block(bp, DIRECTORY_BLOCK); /* put_block() accepts NULL. */
if(r != OK) {
sip->i_nlinks = NO_LINK;
if(search_dir(ldirp, string, NULL, DELETE, IGN_PERM) != OK)
panic("Symbolic link vanished");
}
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}
/* put_inode() accepts NULL as a noop, so the below are safe. */
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put_inode(sip);
put_inode(ldirp);
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return(r);
}
/*===========================================================================*
* new_node *
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*===========================================================================*/
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static struct inode *new_node(struct inode *ldirp,
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char *string, mode_t bits, zone_t z0)
{
/* New_node() is called by fs_open(), fs_mknod(), and fs_mkdir().
* In all cases it allocates a new inode, makes a directory entry for it in
* the ldirp directory with string name, and initializes it.
* It returns a pointer to the inode if it can do this;
* otherwise it returns NULL. It always sets 'err_code'
* to an appropriate value (OK or an error code).
*
* The parsed path rest is returned in 'parsed' if parsed is nonzero. It
* has to hold at least MFS_NAME_MAX bytes.
*/
register struct inode *rip;
register int r;
if (ldirp->i_nlinks == NO_LINK) { /* Dir does not actually exist */
err_code = ENOENT;
return(NULL);
}
/* Get final component of the path. */
rip = advance(ldirp, string, IGN_PERM);
if (S_ISDIR(bits) && (ldirp->i_nlinks >= LINK_MAX)) {
/* New entry is a directory, alas we can't give it a ".." */
put_inode(rip);
err_code = EMLINK;
return(NULL);
}
if ( rip == NULL && err_code == ENOENT) {
/* Last path component does not exist. Make new directory entry. */
if ( (rip = alloc_inode((ldirp)->i_dev, bits)) == NULL) {
/* Can't creat new inode: out of inodes. */
return(NULL);
}
/* Force inode to the disk before making directory entry to make
* the system more robust in the face of a crash: an inode with
* no directory entry is much better than the opposite.
*/
rip->i_nlinks++;
rip->i_zone[0] = z0; /* major/minor device numbers */
rw_inode(rip, WRITING); /* force inode to disk now */
/* New inode acquired. Try to make directory entry. */
if((r=search_dir(ldirp, string, &rip->i_num, ENTER, IGN_PERM)) != OK) {
rip->i_nlinks--; /* pity, have to free disk inode */
IN_MARKDIRTY(rip); /* dirty inodes are written out */
put_inode(rip); /* this call frees the inode */
err_code = r;
return(NULL);
}
} else if (err_code == EENTERMOUNT || err_code == ELEAVEMOUNT) {
r = EEXIST;
} else {
/* Either last component exists, or there is some problem. */
if (rip != NULL)
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r = EEXIST;
else
r = err_code;
}
/* The caller has to return the directory inode (*ldirp). */
err_code = r;
return(rip);
}
/*===========================================================================*
* fs_inhibread *
*===========================================================================*/
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int fs_inhibread()
{
struct inode *rip;
if((rip = find_inode(fs_dev, (ino_t) fs_m_in.REQ_INODE_NR)) == NULL)
return(EINVAL);
/* inhibit read ahead */
rip->i_seek = ISEEK;
return(OK);
}