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minix/servers/mfs/link.c
Ben Gras 41e9fedf87 Mostly bugfixes of bugs triggered by the test set. 
bugfixes:
 SYSTEM:
 . removed
        rc->p_priv->s_flags = 0;
   for the priv struct shared by all user processes in get_priv(). this
   should only be done once. doing a SYS_PRIV_USER in sys_privctl()
   caused the flags of all user processes to be reset, so they were no
   longer PREEMPTIBLE. this happened when RS executed a policy script.
   (this broke test1 in the test set)

 VFS/MFS:
 . chown can change the mode of a file, and chmod arguments are only
   part of the full file mode so the full filemode is slightly magic.
   changed these calls so that the final modes are returned to VFS, so
   that the vnode can be kept up-to-date.
   (this broke test11 in the test set)

 MFS:
 . lookup() checked for sizeof(string) instead of sizeof(user_path),
   truncating long path names
   (caught by test 23)
 . truncate functions neglected to update ctime
   (this broke test16)

 VFS:
 . corner case of an empty filename lookup caused fields of a request
   not to be filled in in the lookup functions, not making it clear
   that the lookup had failed, causing messages to garbage processes,
   causing strange failures.
   (caught by test 30)
 . trust v_size in vnode when doing reads or writes on non-special
   files, truncating i/o where necessary; this is necessary for pipes,
   as MFS can't tell when a pipe has been truncated without it being
   told explicitly each time.
   when the last reader/writer on a pipe closes, tell FS about
   the new size using truncate_vn().
   (this broke test 25, among others)
 . permission check for chdir() had disappeared; added a
   forbidden() call
   (caught by test 23)

new code, shouldn't change anything:
 . introduced RTS_SET, RTS_UNSET, and RTS_ISSET macro's, and their
   LOCK variants. These macros set and clear the p_rts_flags field,
   causing a lot of duplicated logic like

       old_flags = rp->p_rts_flags;            /* save value of the flags */
       rp->p_rts_flags &= ~NO_PRIV;
       if (old_flags != 0 && rp->p_rts_flags == 0) lock_enqueue(rp);

   to change into the simpler

       RTS_LOCK_UNSET(rp, NO_PRIV);

   so the macros take care of calling dequeue() and enqueue() (or lock_*()),
   as the case may be). This makes the code a bit more readable and a
   bit less fragile.
 . removed return code from do_clocktick in CLOCK as it currently
   never replies
 . removed some debug code from VFS
 . fixed grant debug message in device.c
 
preemptive checks, tests, changes:
 . added return code checks of receive() to SYSTEM and CLOCK
 . O_TRUNC should never arrive at MFS (added sanity check and removed
   O_TRUNC code)
 . user_path declared with PATH_MAX+1 to let it be null-terminated
 . checks in MFS to see if strings passed by VFS are null-terminated
 
 IS:
 . static irq name table thrown out
2007-02-01 17:50:02 +00:00

728 lines
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#include "fs.h"
#include <sys/stat.h>
#include <string.h>
#include <minix/com.h>
#include <minix/callnr.h>
#include "buf.h"
#include "inode.h"
#include "super.h"
#include <minix/vfsif.h>
#define SAME 1000
FORWARD _PROTOTYPE( int remove_dir, (struct inode *rldirp, struct inode *rip,
char dir_name[NAME_MAX]) );
FORWARD _PROTOTYPE( int unlink_file, (struct inode *dirp, struct inode *rip,
char file_name[NAME_MAX]) );
FORWARD _PROTOTYPE( off_t nextblock, (off_t pos, int zonesize) );
FORWARD _PROTOTYPE( void zeroblock_half, (struct inode *i, off_t p, int l));
FORWARD _PROTOTYPE( void zeroblock_range, (struct inode *i, off_t p, off_t h));
/* Args to zeroblock_half() */
#define FIRST_HALF 0
#define LAST_HALF 1
/*===========================================================================*
* fs_link *
*===========================================================================*/
PUBLIC int fs_link()
{
/* Perform the link(name1, name2) system call. */
struct inode *ip, *rip;
register int r;
char string[NAME_MAX];
struct inode *new_ip;
phys_bytes len;
caller_uid = fs_m_in.REQ_UID;
caller_gid = fs_m_in.REQ_GID;
len = MFS_MIN(fs_m_in.REQ_PATH_LEN, sizeof(string));
/* Copy the link name's last component */
r = sys_datacopy(FS_PROC_NR, (vir_bytes) fs_m_in.REQ_PATH,
SELF, (vir_bytes) string, (phys_bytes) len);
if (r != OK) return r;
MFS_NUL(string, len, sizeof(string));
/* Temporarily open the file. */
if ( (rip = get_inode(fs_dev, fs_m_in.REQ_LINKED_FILE)) == NIL_INODE) {
printf("MFS(%d) get_inode by fs_link() failed\n", SELF_E);
return(EINVAL);
}
/* Check to see if the file has maximum number of links already. */
r = OK;
if (rip->i_nlinks >= (rip->i_sp->s_version == V1 ? CHAR_MAX : SHRT_MAX))
r = EMLINK;
/* Only super_user may link to directories. */
if (r == OK)
if ( (rip->i_mode & I_TYPE) == I_DIRECTORY && caller_uid != SU_UID)
r = EPERM;
/* If error with 'name', return the inode. */
if (r != OK) {
put_inode(rip);
return(r);
}
/* Temporarily open the last dir */
if ( (ip = get_inode(fs_dev, fs_m_in.REQ_LINK_PARENT)) == NIL_INODE) {
printf("MFS(%d) get_inode by fs_link() failed\n", SELF_E);
return(EINVAL);
}
/* If 'name2' exists in full (even if no space) set 'r' to error. */
if (r == OK) {
if ( (new_ip = advance(&ip, string)) == NIL_INODE) {
r = err_code;
if (r == ENOENT) r = OK;
} else {
put_inode(new_ip);
r = EEXIST;
}
}
/* Try to link. */
if (r == OK)
r = search_dir(ip, string, &rip->i_num, ENTER);
/* If success, register the linking. */
if (r == OK) {
rip->i_nlinks++;
rip->i_update |= CTIME;
rip->i_dirt = DIRTY;
}
/* Done. Release both inodes. */
put_inode(rip);
put_inode(ip);
return(r);
}
/*===========================================================================*
* fs_unlink *
*===========================================================================*/
PUBLIC int fs_unlink()
{
/* Perform the unlink(name) or rmdir(name) system call. The code for these two
* is almost the same. They differ only in some condition testing. Unlink()
* may be used by the superuser to do dangerous things; rmdir() may not.
*/
register struct inode *rip;
struct inode *rldirp;
int r;
char string[NAME_MAX];
phys_bytes len;
caller_uid = fs_m_in.REQ_UID;
caller_gid = fs_m_in.REQ_GID;
/* Copy the last component */
len = MFS_MIN(fs_m_in.REQ_PATH_LEN, sizeof(string));
r = sys_datacopy(FS_PROC_NR, (vir_bytes) fs_m_in.REQ_PATH,
SELF, (vir_bytes) string, (phys_bytes) len);
if (r != OK) return r;
MFS_NUL(string, len, sizeof(string));
/* Temporarily open the dir. */
if ( (rldirp = get_inode(fs_dev, fs_m_in.REQ_INODE_NR)) == NIL_INODE) {
return(EINVAL);
}
/* The last directory exists. Does the file also exist? */
r = OK;
if ( (rip = advance(&rldirp, string)) == NIL_INODE) r = err_code;
/* If error, return inode. */
if (r != OK) {
/* Mount point? */
if (r == EENTERMOUNT || r == ELEAVEMOUNT)
r = EBUSY;
put_inode(rldirp);
return(r);
}
/* Now test if the call is allowed, separately for unlink() and rmdir(). */
if (fs_m_in.m_type == REQ_UNLINK) {
/* Only the su may unlink directories, but the su can unlink any dir.*/
if ( (rip->i_mode & I_TYPE) == I_DIRECTORY
&& caller_uid != SU_UID) r = EPERM;
/* Don't unlink a file if it is the root of a mounted file system. */
if (rip->i_num == ROOT_INODE) r = EBUSY;
/* Actually try to unlink the file; fails if parent is mode 0 etc. */
if (r == OK) r = unlink_file(rldirp, rip, string);
}
else {
r = remove_dir(rldirp, rip, string); /* call is RMDIR */
}
/* If unlink was possible, it has been done, otherwise it has not. */
put_inode(rip);
put_inode(rldirp);
return(r);
}
/*===========================================================================*
* fs_rdlink *
*===========================================================================*/
PUBLIC int fs_rdlink()
{
block_t b; /* block containing link text */
struct buf *bp; /* buffer containing link text */
register struct inode *rip; /* target inode */
register int r; /* return value */
int copylen;
copylen = fs_m_in.REQ_SLENGTH;
caller_uid = fs_m_in.REQ_UID;
caller_gid = fs_m_in.REQ_GID;
/* Temporarily open the file. */
if ( (rip = get_inode(fs_dev, fs_m_in.REQ_INODE_NR)) == NIL_INODE) {
return(EINVAL);
}
r = EACCES;
if (S_ISLNK(rip->i_mode) && (b = read_map(rip, (off_t) 0)) != NO_BLOCK) {
if (copylen <= 0) r = EINVAL;
else if (copylen < rip->i_size) r = ERANGE;
else {
if(rip->i_size < copylen) copylen = rip->i_size;
bp = get_block(rip->i_dev, b, NORMAL);
r = sys_vircopy(SELF, D, (vir_bytes) bp->b_data,
fs_m_in.REQ_WHO_E, D, (vir_bytes) fs_m_in.REQ_USER_ADDR,
(vir_bytes) copylen);
if (r == OK) r = copylen;
put_block(bp, DIRECTORY_BLOCK);
}
}
put_inode(rip);
return(r);
}
/*===========================================================================*
* remove_dir *
*===========================================================================*/
PRIVATE int remove_dir(rldirp, rip, dir_name)
struct inode *rldirp; /* parent directory */
struct inode *rip; /* directory to be removed */
char dir_name[NAME_MAX]; /* name of directory to be removed */
{
/* A directory file has to be removed. Five conditions have to met:
* - The file must be a directory
* - The directory must be empty (except for . and ..)
* - The final component of the path must not be . or ..
* - The directory must not be the root of a mounted file system (VFS)
* - The directory must not be anybody's root/working directory (VFS)
*/
int r;
/* search_dir checks that rip is a directory too. */
if ((r = search_dir(rip, "", (ino_t *) 0, IS_EMPTY)) != OK) return r;
if (strcmp(dir_name, ".") == 0 || strcmp(dir_name, "..") == 0)return(EINVAL);
if (rip->i_num == ROOT_INODE) return(EBUSY); /* can't remove 'root' */
/* Actually try to unlink the file; fails if parent is mode 0 etc. */
if ((r = unlink_file(rldirp, rip, dir_name)) != OK) return r;
/* Unlink . and .. from the dir. The super user can link and unlink any dir,
* so don't make too many assumptions about them.
*/
(void) unlink_file(rip, NIL_INODE, dot1);
(void) unlink_file(rip, NIL_INODE, dot2);
return(OK);
}
/*===========================================================================*
* unlink_file *
*===========================================================================*/
PRIVATE int unlink_file(dirp, rip, file_name)
struct inode *dirp; /* parent directory of file */
struct inode *rip; /* inode of file, may be NIL_INODE too. */
char file_name[NAME_MAX]; /* name of file to be removed */
{
/* Unlink 'file_name'; rip must be the inode of 'file_name' or NIL_INODE. */
ino_t numb; /* inode number */
int r;
/* If rip is not NIL_INODE, it is used to get faster access to the inode. */
if (rip == NIL_INODE) {
/* Search for file in directory and try to get its inode. */
err_code = search_dir(dirp, file_name, &numb, LOOK_UP);
if (err_code == OK) rip = get_inode(dirp->i_dev, (int) numb);
if (err_code != OK || rip == NIL_INODE) return(err_code);
} else {
dup_inode(rip); /* inode will be returned with put_inode */
}
r = search_dir(dirp, file_name, (ino_t *) 0, DELETE);
if (r == OK) {
rip->i_nlinks--; /* entry deleted from parent's dir */
rip->i_update |= CTIME;
rip->i_dirt = DIRTY;
}
put_inode(rip);
return(r);
}
/*===========================================================================*
* fs_rename *
*===========================================================================*/
PUBLIC int fs_rename()
{
/* Perform the rename(name1, name2) system call. */
struct inode *old_dirp, *old_ip; /* ptrs to old dir, file inodes */
struct inode *new_dirp, *new_ip; /* ptrs to new dir, file inodes */
struct inode *new_superdirp, *next_new_superdirp;
int r = OK; /* error flag; initially no error */
int odir, ndir; /* TRUE iff {old|new} file is dir */
int same_pdir; /* TRUE iff parent dirs are the same */
char old_name[NAME_MAX], new_name[NAME_MAX];
ino_t numb;
phys_bytes len;
int r1;
caller_uid = fs_m_in.REQ_UID;
caller_gid = fs_m_in.REQ_GID;
/* Copy the last component of the old name */
len = MFS_MIN(fs_m_in.REQ_PATH_LEN, sizeof(old_name));
r = sys_datacopy(FS_PROC_NR, (vir_bytes) fs_m_in.REQ_PATH,
SELF, (vir_bytes) old_name, (phys_bytes) len);
if (r != OK) return r;
MFS_NUL(old_name, len, sizeof(old_name));
/* Copy the last component of the new name */
len = MFS_MIN(fs_m_in.REQ_SLENGTH, sizeof(new_name));
r = sys_datacopy(FS_PROC_NR, (vir_bytes) fs_m_in.REQ_USER_ADDR,
SELF, (vir_bytes) new_name, (phys_bytes) len);
if (r != OK) return r;
MFS_NUL(new_name, len, sizeof(new_name));
/* Get old dir inode */
if ( (old_dirp = get_inode(fs_dev, fs_m_in.REQ_OLD_DIR)) == NIL_INODE)
return(err_code);
if ( (old_ip = advance(&old_dirp, old_name)) == NIL_INODE) r = err_code;
/* Get new dir inode */
if ( (new_dirp = get_inode(fs_dev, fs_m_in.REQ_NEW_DIR)) == NIL_INODE)
r = err_code;
new_ip = advance(&new_dirp, new_name); /* not required to exist */
if (old_ip != NIL_INODE)
odir = ((old_ip->i_mode & I_TYPE) == I_DIRECTORY); /* TRUE iff dir */
/* If it is ok, check for a variety of possible errors. */
if (r == OK) {
same_pdir = (old_dirp == new_dirp);
/* The old inode must not be a superdirectory of the new last dir. */
if (odir && !same_pdir) {
dup_inode(new_superdirp = new_dirp);
while (TRUE) { /* may hang in a file system loop */
if (new_superdirp == old_ip) {
put_inode(new_superdirp);
r = EINVAL;
break;
}
next_new_superdirp = advance(&new_superdirp, dot2);
put_inode(new_superdirp);
/*
if (next_new_superdirp == new_superdirp) {
put_inode(new_superdirp);
break;
}
*/
if (err_code == ELEAVEMOUNT) {
/* imitate that we are back at the root,
* cross device checked already on VFS */
/*next_new_superdirp = new_superdirp;*/
err_code = OK;
break;
}
new_superdirp = next_new_superdirp;
if (new_superdirp == NIL_INODE) {
/* Missing ".." entry. Assume the worst. */
r = EINVAL;
break;
}
}
/*put_inode(new_superdirp);*/
}
/* The old or new name must not be . or .. */
if (strcmp(old_name, ".")==0 || strcmp(old_name, "..")==0 ||
strcmp(new_name, ".")==0 || strcmp(new_name, "..")==0) {
r = EINVAL;
}
/* Both parent directories must be on the same device.
if (old_dirp->i_dev != new_dirp->i_dev) r = EXDEV; */
/* Parent dirs must be writable, searchable and on a writable device */
if ((r1 = forbidden(old_dirp, W_BIT | X_BIT)) != OK ||
(r1 = forbidden(new_dirp, W_BIT | X_BIT)) != OK) {
r = r1;
}
/* Some tests apply only if the new path exists. */
if (new_ip == NIL_INODE) {
/* don't rename a file with a file system mounted on it.
if (old_ip->i_dev != old_dirp->i_dev) r = EXDEV;*/
if (odir && new_dirp->i_nlinks >=
(new_dirp->i_sp->s_version == V1 ? CHAR_MAX : SHRT_MAX) &&
!same_pdir && r == OK) {
r = EMLINK;
}
}
else {
if (old_ip == new_ip) {
r = SAME; /* old=new */
}
/* has the old file or new file a file system mounted on it?
if (old_ip->i_dev != new_ip->i_dev) r = EXDEV;
*/
ndir = ((new_ip->i_mode & I_TYPE) == I_DIRECTORY); /* dir ? */
if (odir == TRUE && ndir == FALSE) {
r = ENOTDIR;
}
if (odir == FALSE && ndir == TRUE) {
r = EISDIR;
}
}
}
/* If a process has another root directory than the system root, we might
* "accidently" be moving it's working directory to a place where it's
* root directory isn't a super directory of it anymore. This can make
* the function chroot useless. If chroot will be used often we should
* probably check for it here.
*/
/* The rename will probably work. Only two things can go wrong now:
* 1. being unable to remove the new file. (when new file already exists)
* 2. being unable to make the new directory entry. (new file doesn't exists)
* [directory has to grow by one block and cannot because the disk
* is completely full].
*/
if (r == OK) {
if (new_ip != NIL_INODE) {
/* There is already an entry for 'new'. Try to remove it. */
if (odir)
r = remove_dir(new_dirp, new_ip, new_name);
else
r = unlink_file(new_dirp, new_ip, new_name);
}
/* if r is OK, the rename will succeed, while there is now an
* unused entry in the new parent directory.
*/
}
if (r == OK) {
/* If the new name will be in the same parent directory as the old one,
* first remove the old name to free an entry for the new name,
* otherwise first try to create the new name entry to make sure
* the rename will succeed.
*/
numb = old_ip->i_num; /* inode number of old file */
if (same_pdir) {
r = search_dir(old_dirp, old_name, (ino_t *) 0, DELETE);
/* shouldn't go wrong. */
if (r==OK) (void) search_dir(old_dirp, new_name, &numb, ENTER);
} else {
r = search_dir(new_dirp, new_name, &numb, ENTER);
if (r == OK)
(void) search_dir(old_dirp, old_name, (ino_t *) 0, DELETE);
}
}
/* If r is OK, the ctime and mtime of old_dirp and new_dirp have been marked
* for update in search_dir.
*/
if (r == OK && odir && !same_pdir) {
/* Update the .. entry in the directory (still points to old_dirp). */
numb = new_dirp->i_num;
(void) unlink_file(old_ip, NIL_INODE, dot2);
if (search_dir(old_ip, dot2, &numb, ENTER) == OK) {
/* New link created. */
new_dirp->i_nlinks++;
new_dirp->i_dirt = DIRTY;
}
}
/* Release the inodes. */
put_inode(old_dirp);
put_inode(old_ip);
put_inode(new_dirp);
put_inode(new_ip);
return(r == SAME ? OK : r);
}
/*===========================================================================*
* fs_trunc *
*===========================================================================*/
PUBLIC int fs_trunc()
{
struct inode *rip;
int r = OK;
caller_uid = fs_m_in.REQ_UID;
caller_gid = fs_m_in.REQ_GID;
/* Temporarily open the file. */
if ( (rip = get_inode(fs_dev, fs_m_in.REQ_INODE_NR)) == NIL_INODE) {
printf("MFS(%d) get_inode by fs_chmod() failed\n", SELF_E);
return(EINVAL);
}
if ( (rip->i_mode & I_TYPE) != I_REGULAR)
r = EINVAL;
else
r = truncate_inode(rip, fs_m_in.REQ_LENGTH);
put_inode(rip);
return r;
}
/*===========================================================================*
* fs_ftrunc *
*===========================================================================*/
PUBLIC int fs_ftrunc(void)
{
struct inode *rip;
off_t start, end;
int r;
if ( (rip = find_inode(fs_dev, fs_m_in.REQ_FD_INODE_NR))
== NIL_INODE) {
printf("FSfreesp: couldn't find inode %d\n",
fs_m_in.REQ_FD_INODE_NR);
return EINVAL;
}
start = fs_m_in.REQ_FD_START;
end = fs_m_in.REQ_FD_END;
if (end == 0) {
r = truncate_inode(rip, start);
}
else {
r = freesp_inode(rip, start, end);
}
return r;
}
/*===========================================================================*
* truncate_inode *
*===========================================================================*/
PUBLIC int truncate_inode(rip, newsize)
register struct inode *rip; /* pointer to inode to be truncated */
off_t newsize; /* inode must become this size */
{
/* Set inode to a certain size, freeing any zones no longer referenced
* and updating the size in the inode. If the inode is extended, the
* extra space is a hole that reads as zeroes.
*
* Nothing special has to happen to file pointers if inode is opened in
* O_APPEND mode, as this is different per fd and is checked when
* writing is done.
*/
zone_t zone_size;
int scale, file_type, waspipe;
dev_t dev;
file_type = rip->i_mode & I_TYPE; /* check to see if file is special */
if (file_type == I_CHAR_SPECIAL || file_type == I_BLOCK_SPECIAL)
return EINVAL;
if(newsize > rip->i_sp->s_max_size) /* don't let inode grow too big */
return EFBIG;
dev = rip->i_dev; /* device on which inode resides */
scale = rip->i_sp->s_log_zone_size;
zone_size = (zone_t) rip->i_sp->s_block_size << scale;
/* Pipes can shrink, so adjust size to make sure all zones are removed. */
waspipe = rip->i_pipe == I_PIPE; /* TRUE if this was a pipe */
if (waspipe) {
if(newsize != 0)
return EINVAL; /* Only truncate pipes to 0. */
rip->i_size = PIPE_SIZE(rip->i_sp->s_block_size);
}
/* Free the actual space if relevant. */
if(newsize < rip->i_size)
freesp_inode(rip, newsize, rip->i_size);
/* Next correct the inode size. */
if(!waspipe) rip->i_size = newsize;
else wipe_inode(rip); /* Pipes can only be truncated to 0. */
rip->i_update |= CTIME | MTIME;
rip->i_dirt = DIRTY;
return OK;
}
/*===========================================================================*
* freesp_inode *
*===========================================================================*/
PUBLIC int freesp_inode(rip, start, end)
register struct inode *rip; /* pointer to inode to be partly freed */
off_t start, end; /* range of bytes to free (end uninclusive) */
{
/* Cut an arbitrary hole in an inode. The caller is responsible for checking
* the reasonableness of the inode type of rip. The reason is this is that
* this function can be called for different reasons, for which different
* sets of inode types are reasonable. Adjusting the final size of the inode
* is to be done by the caller too, if wished.
*
* Consumers of this function currently are truncate_inode() (used to
* free indirect and data blocks for any type of inode, but also to
* implement the ftruncate() and truncate() system calls) and the F_FREESP
* fcntl().
*/
off_t p, e;
int zone_size, dev;
if(end > rip->i_size) /* freeing beyond end makes no sense */
end = rip->i_size;
if(end <= start) /* end is uninclusive, so start<end */
return EINVAL;
zone_size = rip->i_sp->s_block_size << rip->i_sp->s_log_zone_size;
dev = rip->i_dev; /* device on which inode resides */
/* If freeing doesn't cross a zone boundary, then we may only zero
* a range of the block.
*/
if(start/zone_size == (end-1)/zone_size) {
zeroblock_range(rip, start, end-start);
} else {
/* First zero unused part of partly used blocks. */
if(start%zone_size)
zeroblock_half(rip, start, LAST_HALF);
if(end%zone_size && end < rip->i_size)
zeroblock_half(rip, end, FIRST_HALF);
}
/* Now completely free the completely unused blocks.
* write_map() will free unused (double) indirect
* blocks too. Converting the range to zone numbers avoids
* overflow on p when doing e.g. 'p += zone_size'.
*/
e = end/zone_size;
if(end == rip->i_size && (end % zone_size)) e++;
for(p = nextblock(start, zone_size)/zone_size; p < e; p ++)
write_map(rip, p*zone_size, NO_ZONE, WMAP_FREE);
rip->i_update |= CTIME | MTIME;
rip->i_dirt = DIRTY;
return OK;
}
/*===========================================================================*
* nextblock *
*===========================================================================*/
PRIVATE off_t nextblock(pos, zone_size)
off_t pos;
int zone_size;
{
/* Return the first position in the next block after position 'pos'
* (unless this is the first position in the current block).
* This can be done in one expression, but that can overflow pos.
*/
off_t p;
p = (pos/zone_size)*zone_size;
if((pos % zone_size)) p += zone_size; /* Round up. */
return p;
}
/*===========================================================================*
* zeroblock_half *
*===========================================================================*/
PRIVATE void zeroblock_half(rip, pos, half)
struct inode *rip;
off_t pos;
int half;
{
/* Zero the upper or lower 'half' of a block that holds position 'pos'.
* half can be FIRST_HALF or LAST_HALF.
*
* FIRST_HALF: 0..pos-1 will be zeroed
* LAST_HALF: pos..blocksize-1 will be zeroed
*/
int offset, len;
/* Offset of zeroing boundary. */
offset = pos % rip->i_sp->s_block_size;
if(half == LAST_HALF) {
len = rip->i_sp->s_block_size - offset;
} else {
len = offset;
pos -= offset;
offset = 0;
}
zeroblock_range(rip, pos, len);
}
/*===========================================================================*
* zeroblock_range *
*===========================================================================*/
PRIVATE void zeroblock_range(rip, pos, len)
struct inode *rip;
off_t pos;
off_t len;
{
/* Zero a range in a block.
* This function is used to zero a segment of a block, either
* FIRST_HALF of LAST_HALF.
*
*/
block_t b;
struct buf *bp;
off_t offset;
if(!len) return; /* no zeroing to be done. */
if( (b = read_map(rip, pos)) == NO_BLOCK) return;
if( (bp = get_block(rip->i_dev, b, NORMAL)) == NIL_BUF)
panic(__FILE__, "zeroblock_range: no block", NO_NUM);
offset = pos % rip->i_sp->s_block_size;
if(offset + len > rip->i_sp->s_block_size)
panic(__FILE__, "zeroblock_range: len too long", len);
memset(bp->b_data + offset, 0, len);
bp->b_dirt = DIRTY;
put_block(bp, FULL_DATA_BLOCK);
}
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