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[unix-history] / usr / src / sys / ufs / ffs / ufs_lookup.c
/* ufs_lookup.c 4.38 83/05/18 */
#include "../h/param.h"
#include "../h/systm.h"
#include "../h/inode.h"
#include "../h/fs.h"
#include "../h/mount.h"
#include "../h/dir.h"
#include "../h/user.h"
#include "../h/buf.h"
#include "../h/conf.h"
#include "../h/uio.h"
#include "../h/nami.h"
struct buf *blkatoff();
int dirchk = 0;
/*
* Convert a pathname into a pointer to a locked inode,
* with side effects usable in creating and removing files.
* This is a very central and rather complicated routine.
*
* The func argument gives the routine which returns successive
* characters of the name to be translated.
*
* The flag argument is (LOOKUP, CREATE, DELETE) depending on whether
* the name is to be (looked up, created, deleted). If flag has
* LOCKPARENT or'ed into it and the target of the pathname exists,
* namei returns both the target and its parent directory locked.
* If the file system is not maintained in a strict tree hierarchy,
* this can result in a deadlock situation. When creating and
* LOCKPARENT is specified, the target may not be ".". When deleting
* and LOCKPARENT is specified, the target may be ".", but the caller
* must check to insure it does an irele and iput instead of two iputs.
*
* The follow argument is 1 when symbolic links are to be followed
* when they occur at the end of the name translation process.
*
* Overall outline:
*
* copy in name
* get starting directory
* dirloop:
* check accessibility of directory
* dirloop2:
* copy next component of name to u.u_dent
* handle degenerate case where name is null string
* search for name in directory, to found or notfound
* notfound:
* if creating, return locked directory, leaving info on avail. slots
* else return error
* found:
* if at end of path and deleting, return information to allow delete
* if at end of path and rewriting (create and LOCKPARENT), lock targe
* inode and return info to allow rewrite
* if .. and on mounted filesys, look in mount table for parent
* if symbolic link, massage name in buffer and continue at dirloop
* if more components of name, do next level at dirloop
* return the answer as locked inode
*
* NOTE: (LOOKUP | LOCKPARENT) currently returns the parent inode,
* but unlocked.
*/
struct inode *
namei(func, flag, follow)
int (*func)(), flag, follow;
{
register char *cp; /* pointer into pathname argument */
/* these variables refer to things which must be freed or unlocked */
register struct inode *dp = 0; /* the directory we are searching */
register struct fs *fs; /* file system that directory is in */
register struct buf *bp = 0; /* a buffer of directory entries */
register struct direct *ep; /* the current directory entry */
int entryoffsetinblock; /* offset of ep in bp's buffer */
register struct buf *nbp; /* buffer storing path name argument */
/* these variables hold information about the search for a slot */
enum {NONE, COMPACT, FOUND} slotstatus;
int slotoffset = -1; /* offset of area with free space */
int slotsize; /* size of area at slotoffset */
int slotfreespace; /* amount of space free in slot */
int slotneeded; /* size of the entry we're seeking */
/* */
int dirsize;
int prevoff; /* u.u_offset of previous entry */
int nlink = 0; /* number of symbolic links taken */
struct inode *pdp; /* saved dp during symlink work */
int i;
int lockparent;
lockparent = flag & LOCKPARENT;
flag &= ~LOCKPARENT;
/*
* Get a buffer for the name to be translated, and copy the
* name into the buffer.
*/
nbp = geteblk(MAXPATHLEN);
for (cp = nbp->b_un.b_addr; *cp = (*func)(); ) {
if ((*cp&0377) == ('/'|0200) || (*cp&0200) && flag != 2) {
u.u_error = EPERM;
goto bad;
}
cp++;
if (cp >= nbp->b_un.b_addr + MAXPATHLEN) {
u.u_error = ENOENT;
goto bad;
}
}
if (u.u_error)
goto bad;
/*
* Get starting directory.
*/
cp = nbp->b_un.b_addr;
if (*cp == '/') {
while (*cp == '/')
cp++;
if ((dp = u.u_rdir) == NULL)
dp = rootdir;
} else
dp = u.u_cdir;
fs = dp->i_fs;
ilock(dp);
dp->i_count++;
u.u_pdir = (struct inode *)0xc0000000; /* illegal */
/*
* We come to dirloop to search a new directory.
* The directory must be locked so that it can be
* iput, and fs must be already set to dp->i_fs.
*/
dirloop:
/*
* Check accessiblity of directory.
*/
if ((dp->i_mode&IFMT) != IFDIR) {
u.u_error = ENOTDIR;
goto bad;
}
if (access(dp, IEXEC))
goto bad;
dirloop2:
/*
* Copy next component of name to u.u_dent.
*/
for (i = 0; *cp != 0 && *cp != '/'; cp++) {
if (i >= MAXNAMLEN) {
u.u_error = ENOENT;
goto bad;
}
u.u_dent.d_name[i++] = *cp;
}
u.u_dent.d_namlen = i;
u.u_dent.d_name[i] = 0;
/*
* Check for degenerate name (e.g. / or "")
* which is a way of talking about a directory,
* e.g. like "/." or ".".
*/
if (u.u_dent.d_name[0] == 0) {
if (flag || lockparent) {
u.u_error = ENOENT;
goto bad;
}
brelse(nbp);
return (dp);
}
/*
* Suppress search for slots unless creating
* file and at end of pathname, in which case
* we watch for a place to put the new file in
* case it doesn't already exist.
*/
slotstatus = FOUND;
if (flag == CREATE && *cp == 0) {
slotstatus = NONE;
slotfreespace = 0;
slotneeded = DIRSIZ(&u.u_dent);
}
dirsize = roundup(dp->i_size, DIRBLKSIZ);
u.u_offset = 0;
while (u.u_offset < dirsize) {
/*
* If offset is on a block boundary,
* read the next directory block.
* Release previous if it exists.
*/
if (blkoff(fs, u.u_offset) == 0) {
if (bp != NULL)
brelse(bp);
bp = blkatoff(dp, u.u_offset, (char **)0);
if (bp == 0)
goto bad;
entryoffsetinblock = 0;
}
/*
* If still looking for a slot, and at a DIRBLKSIZE
* boundary, have to start looking for free space
* again.
*/
if (slotstatus == NONE &&
(entryoffsetinblock&(DIRBLKSIZ-1)) == 0) {
slotoffset = -1;
slotfreespace = 0;
}
/*
* Get pointer to next entry, and do consistency checking:
* record length must be multiple of 4
* record length must not be zero
* entry must fit in rest of this DIRBLKSIZ block
* record must be large enough to contain name
* When dirchk is set we also check:
* name is not longer than MAXNAMLEN
* name must be as long as advertised, and null terminated
* Checking last two conditions is done only when dirchk is
* set, to save time.
*/
ep = (struct direct *)(bp->b_un.b_addr + entryoffsetinblock);
i = DIRBLKSIZ - (entryoffsetinblock & (DIRBLKSIZ - 1));
if ((ep->d_reclen & 0x3) || ep->d_reclen == 0 ||
ep->d_reclen > i || DIRSIZ(ep) > ep->d_reclen ||
dirchk && (ep->d_namlen > MAXNAMLEN || dirbadname(ep))) {
dirbad(dp, "mangled entry");
u.u_offset += i;
entryoffsetinblock += i;
continue;
}
/*
* If an appropriate sized slot has not yet been found,
* check to see if one is available. Also accumulate space
* in the current block so that we can determine if
* compaction is viable.
*/
if (slotstatus != FOUND) {
int size = ep->d_reclen;
if (ep->d_ino != 0)
size -= DIRSIZ(ep);
if (size > 0) {
if (size >= slotneeded) {
slotstatus = FOUND;
slotoffset = u.u_offset;
slotsize = ep->d_reclen;
} else if (slotstatus == NONE) {
slotfreespace += size;
if (slotoffset == -1)
slotoffset = u.u_offset;
if (slotfreespace >= slotneeded) {
slotstatus = COMPACT;
slotsize =
u.u_offset+ep->d_reclen -
slotoffset;
}
}
}
}
/*
* Check for a name match.
*/
if (ep->d_ino) {
if (ep->d_namlen == u.u_dent.d_namlen &&
!bcmp(u.u_dent.d_name, ep->d_name, ep->d_namlen))
goto found;
}
prevoff = u.u_offset;
u.u_offset += ep->d_reclen;
entryoffsetinblock += ep->d_reclen;
}
/* notfound: */
/*
* If creating, and at end of pathname and current
* directory has not been removed, then can consider
* allowing file to be created.
*/
if (flag == CREATE && *cp == 0 && dp->i_nlink != 0) {
/*
* Access for write is interpreted as allowing
* creation of files in the directory.
*/
if (access(dp, IWRITE))
goto bad;
/*
* Return an indication of where the new directory
* entry should be put. If we didn't find a slot,
* then set u.u_count to 0 indicating that the
* new slot belongs at the end of the directory.
* If we found a slot, then the new entry can be
* put in the range [u.u_offset..u.u_offset+u.u_count)
*/
if (slotstatus == NONE)
u.u_count = 0;
else {
u.u_offset = slotoffset;
u.u_count = slotsize;
}
dp->i_flag |= IUPD|ICHG;
if (bp)
brelse(bp);
brelse(nbp);
/*
* We return with the directory locked, so that
* the parameters we set up above will still be
* valid if we actually decide to do a direnter().
* We return NULL to indicate that the entry doesn't
* currently exist, leaving a pointer to the (locked)
* directory inode in u.u_pdir.
*/
u.u_pdir = dp;
return (NULL);
}
u.u_error = ENOENT;
goto bad;
found:
/*
* Check that directory length properly reflects presence
* of this entry.
*/
if (entryoffsetinblock + DIRSIZ(ep) > dp->i_size) {
dirbad(dp, "i_size too small");
dp->i_size = entryoffsetinblock + DIRSIZ(ep);
dp->i_flag |= IUPD|ICHG;
}
/*
* Found component in pathname; save directory
* entry in u.u_dent, and release directory buffer.
*/
bcopy((caddr_t)ep, (caddr_t)&u.u_dent, (u_int)DIRSIZ(ep));
brelse(bp);
bp = NULL;
/*
* If deleting, and at end of pathname, return
* parameters which can be used to remove file.
* If the lockparent flag isn't set, we return only
* the directory (in u.u_pdir), otherwise we go
* on and lock the inode, being careful with ".".
*/
if (flag == DELETE && *cp == 0) {
/*
* Write access to directory required to delete files.
*/
if (access(dp, IWRITE))
goto bad;
u.u_pdir = dp; /* for dirremove() */
/*
* Return pointer to current entry in u.u_offset,
* and distance past previous entry (if there
* is a previous entry in this block) in u.u_count.
* Save directory inode pointer in u.u_pdir for dirremove().
*/
if ((u.u_offset&(DIRBLKSIZ-1)) == 0)
u.u_count = 0;
else
u.u_count = u.u_offset - prevoff;
if (lockparent) {
if (dp->i_number == u.u_dent.d_ino)
dp->i_count++;
else {
dp = iget(dp->i_dev, fs, u.u_dent.d_ino);
if (dp == NULL) {
iput(u.u_pdir);
goto bad;
}
}
}
brelse(nbp);
return (dp);
}
/*
* Special handling for ".." allowing chdir out of mounted
* file system: indirect .. in root inode to reevaluate
* in directory file system was mounted on.
*/
if (u.u_dent.d_name[0] == '.' && u.u_dent.d_name[1] == '.' &&
u.u_dent.d_name[2] == '\0') {
if (dp == u.u_rdir)
u.u_dent.d_ino = dp->i_number;
else if (u.u_dent.d_ino == ROOTINO &&
dp->i_number == ROOTINO) {
for (i = 1; i < NMOUNT; i++)
if (mount[i].m_bufp != NULL &&
mount[i].m_dev == dp->i_dev) {
iput(dp);
dp = mount[i].m_inodp;
ilock(dp);
dp->i_count++;
fs = dp->i_fs;
cp -= 2; /* back over .. */
goto dirloop2;
}
}
}
/*
* If rewriting (rename), return the inode and the
* information required to rewrite the present directory
* Must get inode of directory entry to verify it's a
* regular file, or empty directory.
*/
if ((flag == CREATE && lockparent) && *cp == 0) {
if (access(dp, IWRITE))
goto bad;
u.u_pdir = dp; /* for dirrewrite() */
/*
* Careful about locking second inode.
* This can only occur if the target is ".".
*/
if (dp->i_number == u.u_dent.d_ino) {
u.u_error = EISDIR; /* XXX */
goto bad;
}
dp = iget(dp->i_dev, fs, u.u_dent.d_ino);
if (dp == NULL) {
iput(u.u_pdir);
goto bad;
}
brelse(nbp);
return (dp);
}
/*
* Check for symbolic link, which may require us to massage the
* name before we continue translation. We do not `iput' the
* directory because we may need it again if the symbolic link
* is relative to the current directory. Instead we save it
* unlocked as "pdp". We must get the target inode before unlocking
* the directory to insure that the inode will not be removed
* before we get it. We prevent deadlock by always fetching
* inodes from the root, moving down the directory tree. Thus
* when following backward pointers ".." we must unlock the
* parent directory before getting the requested directory.
* There is a potential race condition here if both the current
* and parent directories are removed before the `iget' for the
* inode associated with ".." returns. We hope that this occurs
* infrequently since we cannot avoid this race condition without
* implementing a sophisticated deadlock detection algorithm.
* Note also that this simple deadlock detection scheme will not
* work if the file system has any hard links other than ".."
* that point backwards in the directory structure.
*/
pdp = dp;
if (bcmp(u.u_dent.d_name, "..", 3) == 0) {
iunlock(pdp); /* race to get the inode */
dp = iget(dp->i_dev, fs, u.u_dent.d_ino);
if (dp == NULL)
goto bad2;
} else if (dp->i_number == u.u_dent.d_ino) {
dp->i_count++; /* we want ourself, ie "." */
} else {
dp = iget(dp->i_dev, fs, u.u_dent.d_ino);
iunlock(pdp);
if (dp == NULL)
goto bad2;
}
fs = dp->i_fs;
/*
* Check for symbolic link
*/
if ((dp->i_mode & IFMT) == IFLNK && (follow || *cp == '/')) {
u_int pathlen = strlen(cp) + 1;
if (dp->i_size + pathlen >= MAXPATHLEN - 1 ||
++nlink > MAXSYMLINKS) {
u.u_error = ELOOP;
goto bad2;
}
ovbcopy(cp, nbp->b_un.b_addr + dp->i_size, pathlen);
u.u_error =
rdwri(UIO_READ, dp, nbp->b_un.b_addr, (int)dp->i_size,
0, 1, (int *)0);
if (u.u_error)
goto bad2;
cp = nbp->b_un.b_addr;
iput(dp);
if (*cp == '/') {
irele(pdp);
while (*cp == '/')
cp++;
if ((dp = u.u_rdir) == NULL)
dp = rootdir;
ilock(dp);
dp->i_count++;
} else {
dp = pdp;
ilock(dp);
}
fs = dp->i_fs;
goto dirloop;
}
/*
* Not a symbolic link. If more pathname,
* continue at next component, else return.
*/
if (*cp == '/') {
while (*cp == '/')
cp++;
irele(pdp);
goto dirloop;
}
brelse(nbp);
if (lockparent)
u.u_pdir = pdp;
else
irele(pdp);
return (dp);
bad2:
irele(pdp);
bad:
if (bp)
brelse(bp);
if (dp)
iput(dp);
brelse(nbp);
return (NULL);
}
dirbad(ip, how)
struct inode *ip;
char *how;
{
printf("%s: bad dir ino %d at offset %d: %s\n",
ip->i_fs->fs_fsmnt, ip->i_number, u.u_offset, how);
}
dirbadname(ep)
register struct direct *ep;
{
register int i;
for (i = 0; i < ep->d_namlen; i++)
if (ep->d_name[i] == 0)
return (1);
return (ep->d_name[i]);
}
/*
* Write a directory entry after a call to namei, using the parameters
* which it left in the u. area. The argument ip is the inode which
* the new directory entry will refer to. The u. area field u.u_pdir is
* a pointer to the directory to be written, which was left locked by
* namei. Remaining parameters (u.u_offset, u.u_count) indicate
* how the space for the new entry is to be gotten.
*/
direnter(ip)
struct inode *ip;
{
register struct direct *ep, *nep;
struct buf *bp;
int loc, spacefree, error = 0;
u_int dsize;
int newentrysize;
char *dirbuf;
u.u_dent.d_ino = ip->i_number;
u.u_segflg = 1;
newentrysize = DIRSIZ(&u.u_dent);
if (u.u_count == 0) {
/*
* If u.u_count is 0, then namei could find no space in the
* directory. In this case u.u_offset will be on a directory
* block boundary and we will write the new entry into a fresh
* block.
*/
if (u.u_offset&(DIRBLKSIZ-1))
panic("wdir: newblk");
u.u_dent.d_reclen = DIRBLKSIZ;
error = rdwri(UIO_WRITE, u.u_pdir, (caddr_t)&u.u_dent,
newentrysize, u.u_offset, 1, (int *)0);
iput(u.u_pdir);
return (error);
}
/*
* If u.u_count is non-zero, then namei found space for the
* new entry in the range u.u_offset to u.u_offset+u.u_count.
* in the directory. To use this space, we may have to compact
* the entries located there, by copying them together towards
* the beginning of the block, leaving the free space in
* one usable chunk at the end.
*/
/*
* Increase size of directory if entry eats into new space.
* This should never push the size past a new multiple of
* DIRBLKSIZE.
*/
if (u.u_offset + u.u_count > u.u_pdir->i_size)
u.u_pdir->i_size = u.u_offset + u.u_count;
/*
* Get the block containing the space for the new directory
* entry. Should return error by result instead of u.u_error.
*/
bp = blkatoff(u.u_pdir, u.u_offset, (char **)&dirbuf);
if (bp == 0) {
iput(u.u_pdir);
return (u.u_error);
}
/*
* Find space for the new entry. In the simple case, the
* entry at offset base will have the space. If it does
* not, then namei arranged that compacting the region
* u.u_offset to u.u_offset+u.u_count would yield the space.
*/
ep = (struct direct *)dirbuf;
dsize = DIRSIZ(ep);
spacefree = ep->d_reclen - dsize;
for (loc = ep->d_reclen; loc < u.u_count; ) {
nep = (struct direct *)(dirbuf + loc);
if (ep->d_ino) {
/* trim the existing slot */
ep->d_reclen = dsize;
ep = (struct direct *)((char *)ep + dsize);
} else {
/* overwrite; nothing there; header is ours */
spacefree += dsize;
}
dsize = DIRSIZ(nep);
spacefree += nep->d_reclen - dsize;
loc += nep->d_reclen;
bcopy((caddr_t)nep, (caddr_t)ep, dsize);
}
/*
* Update the pointer fields in the previous entry (if any),
* copy in the new entry, and write out the block.
*/
if (ep->d_ino == 0) {
if (spacefree + dsize < newentrysize)
panic("wdir: compact1");
u.u_dent.d_reclen = spacefree + dsize;
} else {
if (spacefree < newentrysize)
panic("wdir: compact2");
u.u_dent.d_reclen = spacefree;
ep->d_reclen = dsize;
ep = (struct direct *)((char *)ep + dsize);
}
bcopy((caddr_t)&u.u_dent, (caddr_t)ep, (u_int)newentrysize);
bwrite(bp);
u.u_pdir->i_flag |= IUPD|ICHG;
iput(u.u_pdir);
return (error);
}
/*
* Remove a directory entry after a call to namei, using the
* parameters which it left in the u. area. The u. entry
* u_offset contains the offset into the directory of the
* entry to be eliminated. The u_count field contains the
* size of the previous record in the directory. If this
* is 0, the first entry is being deleted, so we need only
* zero the inode number to mark the entry as free. If the
* entry isn't the first in the directory, we must reclaim
* the space of the now empty record by adding the record size
* to the size of the previous entry.
*/
dirremove()
{
register struct inode *dp = u.u_pdir;
register struct buf *bp;
struct direct *ep;
if (u.u_count == 0) {
/*
* First entry in block: set d_ino to zero.
*/
u.u_dent.d_ino = 0;
(void) rdwri(UIO_WRITE, dp, (caddr_t)&u.u_dent,
(int)DIRSIZ(&u.u_dent), u.u_offset, 1, (int *)0);
} else {
/*
* Collapse new free space into previous entry.
*/
bp = blkatoff(dp, (int)(u.u_offset - u.u_count), (char **)&ep);
if (bp == 0)
return (0);
ep->d_reclen += u.u_dent.d_reclen;
bwrite(bp);
dp->i_flag |= IUPD|ICHG;
}
return (1);
}
/*
* Rewrite an existing directory entry to point at the inode
* supplied. The parameters describing the directory entry are
* set up by a call to namei.
*/
dirrewrite(dp, ip)
struct inode *dp, *ip;
{
u.u_dent.d_ino = ip->i_number;
u.u_error = rdwri(UIO_WRITE, dp, (caddr_t)&u.u_dent,
(int)DIRSIZ(&u.u_dent), u.u_offset, 1, (int *)0);
iput(dp);
}
/*
* Return buffer with contents of block "offset"
* from the beginning of directory "ip". If "res"
* is non-zero, fill it in with a pointer to the
* remaining space in the directory.
*/
struct buf *
blkatoff(ip, offset, res)
struct inode *ip;
off_t offset;
char **res;
{
register struct fs *fs = ip->i_fs;
daddr_t lbn = lblkno(fs, offset);
int base = blkoff(fs, offset);
int bsize = blksize(fs, ip, lbn);
daddr_t bn = fsbtodb(fs, bmap(ip, lbn, B_WRITE, base, bsize));
register struct buf *bp;
if (u.u_error)
return (0);
bp = bread(ip->i_dev, bn, bsize);
if (bp->b_flags & B_ERROR) {
brelse(bp);
return (0);
}
if (res)
*res = bp->b_un.b_addr + base;
return (bp);
}
/*
* Check if a directory is empty or not.
* Inode supplied must be locked.
*/
dirempty(ip)
register struct inode *ip;
{
register off_t off;
struct direct dbuf;
register struct direct *dp = &dbuf;
int error, count;
for (off = 0; off < ip->i_size; off += dp->d_reclen) {
error = rdwri(UIO_READ, ip, (caddr_t)dp,
sizeof (struct direct), off, 1, &count);
count = sizeof (struct direct) - count;
#define MINDIRSIZ (sizeof (struct direct) - (MAXNAMLEN + 1))
if (error || count < MINDIRSIZ || count < DIRSIZ(dp))
return (0);
if (dp->d_ino == 0)
continue;
if (dp->d_name[0] != '.')
return (0);
if (dp->d_namlen == 1 ||
(dp->d_namlen == 2 && dp->d_name[1] == '.'))
continue;
return (0);
}
return (1);
}
Continuous source code history from original PDP-7 UNIX to FreeBSD 2, the first fully unencumbered FreeBSD release.