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minix/servers/mfs/link.c
Ben Gras bd3cde4571 Move primary cache code to libminixfs. 
Add primary cache management feature to libminixfs as mfs and ext2
currently do separately, remove cache code from mfs and ext2, and make
them use the libminixfs interface. This makes all fields of the buf
struct private to libminixfs and FS clients aren't supposed to access
them at all. Only the opaque 'void *data' field (the FS block contents,
used to be called bp) is to be accessed by the FS client.

The main purpose is to implement the interface to the 2ndary vm cache
just once, get rid of some code duplication, and add a little
abstraction to reduce the code inertia of the whole caching business.

Some minor sanity checking and prohibition done by mfs in this code
as removed from the generic primary cache code as a result:
        - checking all inodes are not in use when allocating/resizing
          the cache
        - checking readonly filesystems aren't written to
        - checking the superblock isn't written to on mounted filesystems

The minixfslib code relies on fs_blockstats() in the client filesystem to
return some FS usage information.
2012-10-23 19:48:38 +02:00

707 lines
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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>
#define SAME 1000
static int freesp_inode(struct inode *rip, off_t st, off_t end);
static int remove_dir(struct inode *rldirp, struct inode *rip, char
dir_name[MFS_NAME_MAX]);
static int unlink_file(struct inode *dirp, struct inode *rip, char
file_name[MFS_NAME_MAX]);
static off_t nextblock(off_t pos, int zone_size);
static void zerozone_half(struct inode *rip, off_t pos, int half, int
zone_size);
static void zerozone_range(struct inode *rip, off_t pos, off_t len);
/* Args to zerozone_half() */
#define FIRST_HALF 0
#define LAST_HALF 1
/*===========================================================================*
* fs_link *
*===========================================================================*/
int fs_link()
{
/* Perform the link(name1, name2) system call. */
struct inode *ip, *rip;
register int r;
char string[MFS_NAME_MAX];
struct inode *new_ip;
phys_bytes len;
len = min( (unsigned) fs_m_in.REQ_PATH_LEN, sizeof(string));
/* Copy the link name's last component */
r = sys_safecopyfrom(VFS_PROC_NR, (cp_grant_id_t) fs_m_in.REQ_GRANT,
(vir_bytes) 0, (vir_bytes) string, (size_t) len);
if (r != OK) return r;
NUL(string, len, sizeof(string));
/* Temporarily open the file. */
if( (rip = get_inode(fs_dev, (ino_t) fs_m_in.REQ_INODE_NR)) == NULL)
return(EINVAL);
/* Check to see if the file has maximum number of links already. */
r = OK;
if(rip->i_nlinks >= LINK_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, (ino_t) fs_m_in.REQ_DIR_INO)) == NULL) {
put_inode(rip);
return(EINVAL);
}
if (ip->i_nlinks == NO_LINK) { /* Dir does not actually exist */
put_inode(rip);
put_inode(ip);
return(ENOENT);
}
/* If 'name2' exists in full (even if no space) set 'r' to error. */
if((new_ip = advance(ip, string, IGN_PERM)) == NULL) {
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, IGN_PERM);
/* If success, register the linking. */
if(r == OK) {
rip->i_nlinks++;
rip->i_update |= CTIME;
IN_MARKDIRTY(rip);
}
/* Done. Release both inodes. */
put_inode(rip);
put_inode(ip);
return(r);
}
/*===========================================================================*
* fs_unlink *
*===========================================================================*/
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[MFS_NAME_MAX];
phys_bytes len;
/* Copy the 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);
if (r != OK) return r;
NUL(string, len, sizeof(string));
/* Temporarily open the dir. */
if( (rldirp = get_inode(fs_dev, (ino_t) fs_m_in.REQ_INODE_NR)) == NULL)
return(EINVAL);
/* The last directory exists. Does the file also exist? */
rip = advance(rldirp, string, IGN_PERM);
r = err_code;
/* If error, return inode. */
if(r != OK) {
/* Mount point? */
if (r == EENTERMOUNT || r == ELEAVEMOUNT) {
put_inode(rip);
r = EBUSY;
}
put_inode(rldirp);
return(r);
}
if(rip->i_sp->s_rd_only) {
r = EROFS;
} else if(fs_m_in.m_type == REQ_UNLINK) {
/* Now test if the call is allowed, separately for unlink() and rmdir(). */
/* Only the su may unlink directories, but the su can unlink any
* dir.*/
if( (rip->i_mode & I_TYPE) == I_DIRECTORY) r = EPERM;
/* 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 *
*===========================================================================*/
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 */
size_t copylen;
copylen = min( (size_t) fs_m_in.REQ_MEM_SIZE, UMAX_FILE_POS);
/* Temporarily open the file. */
if( (rip = get_inode(fs_dev, (ino_t) fs_m_in.REQ_INODE_NR)) == NULL)
return(EINVAL);
if(!S_ISLNK(rip->i_mode))
r = EACCES;
else if ((b = read_map(rip, (off_t) 0)) == NO_BLOCK)
r = EIO;
else {
/* Passed all checks */
/* We can safely cast to unsigned, because copylen is guaranteed to be
below max file size */
copylen = min( copylen, (unsigned) rip->i_size);
bp = get_block(rip->i_dev, b, NORMAL);
r = sys_safecopyto(VFS_PROC_NR, (cp_grant_id_t) fs_m_in.REQ_GRANT,
(vir_bytes) 0, (vir_bytes) b_data(bp),
(size_t) copylen);
put_block(bp, DIRECTORY_BLOCK);
if (r == OK)
fs_m_out.RES_NBYTES = copylen;
}
put_inode(rip);
return(r);
}
/*===========================================================================*
* remove_dir *
*===========================================================================*/
static int remove_dir(rldirp, rip, dir_name)
struct inode *rldirp; /* parent directory */
struct inode *rip; /* directory to be removed */
char dir_name[MFS_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, "", NULL, IS_EMPTY, IGN_PERM)) != 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, NULL, dot1);
(void) unlink_file(rip, NULL, dot2);
return(OK);
}
/*===========================================================================*
* unlink_file *
*===========================================================================*/
static int unlink_file(dirp, rip, file_name)
struct inode *dirp; /* parent directory of file */
struct inode *rip; /* inode of file, may be NULL too. */
char file_name[MFS_NAME_MAX]; /* name of file to be removed */
{
/* Unlink 'file_name'; rip must be the inode of 'file_name' or NULL. */
ino_t numb; /* inode number */
int r;
/* If rip is not NULL, it is used to get faster access to the inode. */
if (rip == NULL) {
/* Search for file in directory and try to get its inode. */
err_code = search_dir(dirp, file_name, &numb, LOOK_UP, IGN_PERM);
if (err_code == OK) rip = get_inode(dirp->i_dev, (int) numb);
if (err_code != OK || rip == NULL) return(err_code);
} else {
dup_inode(rip); /* inode will be returned with put_inode */
}
r = search_dir(dirp, file_name, NULL, DELETE, IGN_PERM);
if (r == OK) {
rip->i_nlinks--; /* entry deleted from parent's dir */
rip->i_update |= CTIME;
IN_MARKDIRTY(rip);
}
put_inode(rip);
return(r);
}
/*===========================================================================*
* fs_rename *
*===========================================================================*/
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[MFS_NAME_MAX], new_name[MFS_NAME_MAX];
ino_t numb;
phys_bytes len;
/* Copy the last component of the old name */
len = min( (unsigned) fs_m_in.REQ_REN_LEN_OLD, sizeof(old_name));
r = sys_safecopyfrom(VFS_PROC_NR, (cp_grant_id_t) fs_m_in.REQ_REN_GRANT_OLD,
(vir_bytes) 0, (vir_bytes) old_name, (size_t) len);
if (r != OK) return r;
NUL(old_name, len, sizeof(old_name));
/* Copy the last component of the new name */
len = min( (unsigned) fs_m_in.REQ_REN_LEN_NEW, sizeof(new_name));
r = sys_safecopyfrom(VFS_PROC_NR, (cp_grant_id_t) fs_m_in.REQ_REN_GRANT_NEW,
(vir_bytes) 0, (vir_bytes) new_name, (size_t) len);
if (r != OK) return r;
NUL(new_name, len, sizeof(new_name));
/* Get old dir inode */
if( (old_dirp = get_inode(fs_dev, (ino_t) fs_m_in.REQ_REN_OLD_DIR)) == NULL)
return(err_code);
old_ip = advance(old_dirp, old_name, IGN_PERM);
r = err_code;
if (r == EENTERMOUNT || r == ELEAVEMOUNT) {
put_inode(old_ip);
old_ip = NULL;
if (r == EENTERMOUNT) r = EXDEV; /* should this fail at all? */
else if (r == ELEAVEMOUNT) r = EINVAL; /* rename on dot-dot */
}
if (old_ip == NULL) {
put_inode(old_dirp);
return(r);
}
/* Get new dir inode */
if( (new_dirp = get_inode(fs_dev, (ino_t) fs_m_in.REQ_REN_NEW_DIR)) == NULL) {
put_inode(old_ip);
put_inode(old_dirp);
return(err_code);
} else {
if (new_dirp->i_nlinks == NO_LINK) { /* Dir does not actually exist */
put_inode(old_ip);
put_inode(old_dirp);
put_inode(new_dirp);
return(ENOENT);
}
}
new_ip = advance(new_dirp, new_name, IGN_PERM); /* not required to exist */
/* However, if the check failed because the file does exist, don't continue.
* Note that ELEAVEMOUNT is covered by the dot-dot check later. */
if(err_code == EENTERMOUNT) {
put_inode(new_ip);
new_ip = NULL;
r = EBUSY;
}
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,
IGN_PERM);
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 */
put_inode(next_new_superdirp);
err_code = OK;
break;
}
new_superdirp = next_new_superdirp;
if(new_superdirp == NULL) {
/* Missing ".." entry. Assume the worst. */
r = EINVAL;
break;
}
}
}
/* 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; */
/* Some tests apply only if the new path exists. */
if(new_ip == NULL) {
/* 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 >= LINK_MAX &&
!same_pdir && r == OK) {
r = EMLINK;
}
} else {
if(old_ip == new_ip) r = SAME; /* old=new */
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 != NULL) {
/* 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, NULL, DELETE, IGN_PERM);
/* shouldn't go wrong. */
if(r == OK)
(void) search_dir(old_dirp, new_name, &numb, ENTER,
IGN_PERM);
} else {
r = search_dir(new_dirp, new_name, &numb, ENTER, IGN_PERM);
if(r == OK)
(void) search_dir(old_dirp, old_name, NULL, DELETE,
IGN_PERM);
}
}
/* 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, NULL, dot2);
if(search_dir(old_ip, dot2, &numb, ENTER, IGN_PERM) == OK) {
/* New link created. */
new_dirp->i_nlinks++;
IN_MARKDIRTY(new_dirp);
}
}
/* 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_ftrunc *
*===========================================================================*/
int fs_ftrunc(void)
{
struct inode *rip;
off_t start, end;
int r;
if( (rip = find_inode(fs_dev, (ino_t) fs_m_in.REQ_INODE_NR)) == NULL)
return(EINVAL);
if(rip->i_sp->s_rd_only) {
r = EROFS;
} else {
start = fs_m_in.REQ_TRC_START_LO;
end = fs_m_in.REQ_TRC_END_LO;
if (end == 0)
r = truncate_inode(rip, start);
else
r = freesp_inode(rip, start, end);
}
return(r);
}
/*===========================================================================*
* truncate_inode *
*===========================================================================*/
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.
*/
int r;
mode_t file_type;
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);
/* Free the actual space if truncating. */
if (newsize < rip->i_size) {
if ((r = freesp_inode(rip, newsize, rip->i_size)) != OK)
return(r);
}
/* Clear the rest of the last zone if expanding. */
if (newsize > rip->i_size) clear_zone(rip, rip->i_size, 0);
/* Next correct the inode size. */
rip->i_size = newsize;
rip->i_update |= CTIME | MTIME;
IN_MARKDIRTY(rip);
return(OK);
}
/*===========================================================================*
* freesp_inode *
*===========================================================================*/
static 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, r;
int zero_last, zero_first;
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;
/* If freeing doesn't cross a zone boundary, then we may only zero
* a range of the zone, unless we are freeing up that entire zone.
*/
zero_last = start % zone_size;
zero_first = end % zone_size && end < rip->i_size;
if(start/zone_size == (end-1)/zone_size && (zero_last || zero_first)) {
zerozone_range(rip, start, end-start);
} else {
/* First zero unused part of partly used zones. */
if(zero_last)
zerozone_half(rip, start, LAST_HALF, zone_size);
if(zero_first)
zerozone_half(rip, end, FIRST_HALF, zone_size);
/* Now completely free the completely unused zones.
* 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 ++) {
if((r = write_map(rip, p*zone_size, NO_ZONE, WMAP_FREE)) != OK)
return(r);
}
}
rip->i_update |= CTIME | MTIME;
IN_MARKDIRTY(rip);
return(OK);
}
/*===========================================================================*
* nextblock *
*===========================================================================*/
static 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);
}
/*===========================================================================*
* zerozone_half *
*===========================================================================*/
static void zerozone_half(rip, pos, half, zone_size)
struct inode *rip;
off_t pos;
int half;
int zone_size;
{
/* Zero the upper or lower 'half' of a zone that holds position 'pos'.
* half can be FIRST_HALF or LAST_HALF.
*
* FIRST_HALF: 0..pos-1 will be zeroed
* LAST_HALF: pos..zone_size-1 will be zeroed
*/
off_t offset, len;
/* Offset of zeroing boundary. */
offset = pos % zone_size;
if(half == LAST_HALF) {
len = zone_size - offset;
} else {
len = offset;
pos -= offset;
}
zerozone_range(rip, pos, len);
}
/*===========================================================================*
* zerozone_range *
*===========================================================================*/
static void zerozone_range(rip, pos, len)
struct inode *rip;
off_t pos;
off_t len;
{
/* Zero an arbitrary byte range in a zone, possibly spanning multiple blocks.
*/
block_t b;
struct buf *bp;
off_t offset;
unsigned short block_size;
size_t bytes;
block_size = rip->i_sp->s_block_size;
if(!len) return; /* no zeroing to be done. */
if( (b = read_map(rip, pos)) == NO_BLOCK) return;
while (len > 0) {
if( (bp = get_block(rip->i_dev, b, NORMAL)) == NULL)
panic("zerozone_range: no block");
offset = pos % block_size;
bytes = block_size - offset;
if (bytes > (size_t) len)
bytes = len;
memset(b_data(bp) + offset, 0, bytes);
MARKDIRTY(bp);
put_block(bp, FULL_DATA_BLOCK);
pos += bytes;
len -= bytes;
b++;
}
}
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