minix/servers/ext2/link.c

727 lines
22 KiB
C
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/* Created (MFS based):
* February 2010 (Evgeniy Ivanov)
*/
#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>
#include <sys/param.h>
#define SAME 1000
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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[NAME_MAX + 1]);
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static int unlink_file(struct inode *dirp, struct inode *rip, char
file_name[NAME_MAX + 1]);
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static off_t nextblock(off_t pos, int blocksize);
static void zeroblock_half(struct inode *i, off_t p, int l);
static 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 *
*===========================================================================*/
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int fs_link()
{
/* Perform the link(name1, name2) system call. */
struct inode *ip, *rip;
register int r;
char string[NAME_MAX + 1];
struct inode *new_ip;
phys_bytes len;
/* Copy the link name's last component */
len = fs_m_in.m_vfs_fs_link.path_len; /* including trailing '\0' */
if (len > NAME_MAX + 1 || len > EXT2_NAME_MAX + 1)
return(ENAMETOOLONG);
r = sys_safecopyfrom(VFS_PROC_NR, fs_m_in.m_vfs_fs_link.grant, 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, fs_m_in.m_vfs_fs_link.inode)) == NULL)
return(EINVAL);
/* Check to see if the file has maximum number of links already. */
r = OK;
if (rip->i_links_count >= USHRT_MAX)
r = EMLINK;
if(rip->i_links_count >= 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, fs_m_in.m_vfs_fs_link.dir_ino)) == NULL) {
put_inode(rip);
return(EINVAL);
}
if (ip->i_links_count == 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,
rip->i_mode & I_TYPE);
/* If success, register the linking. */
if(r == OK) {
rip->i_links_count++;
rip->i_update |= CTIME;
rip->i_dirt = IN_DIRTY;
}
/* Done. Release both inodes. */
put_inode(rip);
put_inode(ip);
return(r);
}
/*===========================================================================*
* fs_unlink *
*===========================================================================*/
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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 + 1];
phys_bytes len;
/* Copy the last component */
len = fs_m_in.m_vfs_fs_unlink.path_len; /* including trailing '\0' */
if (len > NAME_MAX + 1 || len > EXT2_NAME_MAX + 1)
return(ENAMETOOLONG);
r = sys_safecopyfrom(VFS_PROC_NR, fs_m_in.m_vfs_fs_unlink.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, fs_m_in.m_vfs_fs_unlink.inode)) == 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);
}
/* 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) 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 *
*===========================================================================*/
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int fs_rdlink()
{
struct buf *bp = NULL; /* buffer containing link text */
char* link_text; /* either bp->b_data or rip->i_block */
register struct inode *rip; /* target inode */
register int r; /* return value */
size_t copylen;
copylen = min(fs_m_in.m_vfs_fs_rdlink.mem_size, UMAX_FILE_POS);
/* Temporarily open the file. */
if( (rip = get_inode(fs_dev, fs_m_in.m_vfs_fs_rdlink.inode)) == NULL)
return(EINVAL);
if (rip->i_size >= MAX_FAST_SYMLINK_LENGTH) {
/* normal symlink */
if(!(bp = get_block_map(rip, 0))) {
r = EIO;
} else {
link_text = b_data(bp);
r = OK;
}
} else {
/* fast symlink, stored in inode */
link_text = (char*) rip->i_block;
r = OK;
}
if (r == OK) {
/* 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);
r = sys_safecopyto(VFS_PROC_NR, fs_m_in.m_vfs_fs_rdlink.grant,
(vir_bytes) 0, (vir_bytes) link_text,
(size_t) copylen);
put_block(bp, DIRECTORY_BLOCK);
if (r == OK)
fs_m_out.m_fs_vfs_rdlink.nbytes = copylen;
}
put_inode(rip);
return(r);
}
/*===========================================================================*
* remove_dir *
*===========================================================================*/
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static int remove_dir(rldirp, rip, dir_name)
struct inode *rldirp; /* parent directory */
struct inode *rip; /* directory to be removed */
char dir_name[NAME_MAX + 1]; /* 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, 0)) != 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 *
*===========================================================================*/
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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[NAME_MAX + 1]; /* 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, 0);
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, 0);
if (r == OK) {
rip->i_links_count--; /* entry deleted from parent's dir */
rip->i_update |= CTIME;
rip->i_dirt = IN_DIRTY;
}
put_inode(rip);
return(r);
}
/*===========================================================================*
* fs_rename *
*===========================================================================*/
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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 = 0; /* TRUE iff parent dirs are the same */
char old_name[NAME_MAX + 1], new_name[NAME_MAX + 1];
ino_t numb;
phys_bytes len;
/* Copy the last component of the old name */
len = fs_m_in.m_vfs_fs_rename.len_old; /* including trailing '\0' */
if (len > NAME_MAX + 1 || len > EXT2_NAME_MAX + 1)
return(ENAMETOOLONG);
r = sys_safecopyfrom(VFS_PROC_NR, fs_m_in.m_vfs_fs_rename.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 = fs_m_in.m_vfs_fs_rename.len_new; /* including trailing '\0' */
if (len > NAME_MAX + 1 || len > EXT2_NAME_MAX + 1)
return(ENAMETOOLONG);
r = sys_safecopyfrom(VFS_PROC_NR, fs_m_in.m_vfs_fs_rename.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, fs_m_in.m_vfs_fs_rename.dir_old)) == 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 */
} else if (old_ip == NULL) {
return(err_code);
}
/* Get new dir inode */
if ((new_dirp = get_inode(fs_dev, fs_m_in.m_vfs_fs_rename.dir_new)) == NULL){
put_inode(old_ip);
put_inode(old_dirp);
return(err_code);
} else {
if (new_dirp->i_links_count == NO_LINK) { /* Dir does not 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;
}
if(old_ip != NULL)
odir = ((old_ip->i_mode & I_TYPE) == I_DIRECTORY); /* TRUE iff dir */
else
odir = FALSE;
/* 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_links_count >= SHRT_MAX ||
new_dirp->i_links_count >= 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, 0);
/* shouldn't go wrong. */
if(r == OK)
(void) search_dir(old_dirp, new_name, &numb, ENTER, IGN_PERM,
old_ip->i_mode & I_TYPE);
} else {
r = search_dir(new_dirp, new_name, &numb, ENTER, IGN_PERM,
old_ip->i_mode & I_TYPE);
if(r == OK) {
(void) search_dir(old_dirp, old_name, NULL,
DELETE, IGN_PERM, 0);
}
}
}
/* 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, I_DIRECTORY) == OK) {
/* New link created. */
new_dirp->i_links_count++;
new_dirp->i_dirt = IN_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_ftrunc *
*===========================================================================*/
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int fs_ftrunc(void)
{
struct inode *rip;
off_t start, end;
int r;
if( (rip = find_inode(fs_dev, fs_m_in.m_vfs_fs_ftrunc.inode)) == NULL)
return(EINVAL);
start = fs_m_in.m_vfs_fs_ftrunc.trc_start;
end = fs_m_in.m_vfs_fs_ftrunc.trc_end;
if (end == 0)
r = truncate_inode(rip, start);
else
r = freesp_inode(rip, start, end);
return(r);
}
/*===========================================================================*
* truncate_inode *
*===========================================================================*/
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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 blocks 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;
discard_preallocated_blocks(rip);
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 block if expanding. */
if (newsize > rip->i_size) zeroblock_half(rip, rip->i_size, LAST_HALF);
/* Next correct the inode size. */
rip->i_size = newsize;
rip->i_update |= CTIME | MTIME;
rip->i_dirt = IN_DIRTY;
return(OK);
}
/*===========================================================================*
* freesp_inode *
*===========================================================================*/
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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 r;
unsigned short block_size = rip->i_sp->s_block_size;
int zero_last, zero_first;
discard_preallocated_blocks(rip);
if (rip->i_blocks == 0) {
/* Either hole or symlink. Freeing fast symlink using
* write_map() causes segfaults since it doesn't use any
* blocks, but uses i_block[] to store target.
*/
return(OK);
}
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);
/* If freeing doesn't cross a block boundary, then we may only zero
* a range of the block.
*/
zero_last = start % block_size;
zero_first = end % block_size && end < rip->i_size;
if (start/block_size == (end-1)/block_size && (zero_last || zero_first)) {
zeroblock_range(rip, start, end-start);
} else {
/* First zero unused part of partly used blocks. */
if (zero_last)
zeroblock_half(rip, start, LAST_HALF);
if (zero_first)
zeroblock_half(rip, end, FIRST_HALF);
/* Now completely free the completely unused blocks.
* write_map() will free unused indirect
* blocks too. Converting the range to block numbers avoids
* overflow on p when doing e.g. 'p += block_size'.
*/
e = end / block_size;
if (end == rip->i_size && (end % block_size))
e++;
for (p = nextblock(start, block_size)/block_size; p < e; p++) {
if ((r = write_map(rip, p*block_size, NO_BLOCK, WMAP_FREE)) != OK)
return(r);
}
}
rip->i_update |= CTIME | MTIME;
rip->i_dirt = IN_DIRTY;
return(OK);
}
/*===========================================================================*
* nextblock *
*===========================================================================*/
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static off_t nextblock(pos, block_size)
off_t pos;
unsigned short block_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 / block_size) * block_size;
if (pos % block_size) p += block_size; /* Round up. */
return(p);
}
/*===========================================================================*
* zeroblock_half *
*===========================================================================*/
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static 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
*/
off_t 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;
}
zeroblock_range(rip, pos, len);
}
/*===========================================================================*
* zeroblock_range *
*===========================================================================*/
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static 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.
*/
struct buf *bp;
off_t offset;
if (!len) return; /* no zeroing to be done. */
if (!(bp = get_block_map(rip, rounddown(pos, rip->i_sp->s_block_size))))
panic("zeroblock_range: no block");
offset = pos % rip->i_sp->s_block_size;
if (offset + len > rip->i_sp->s_block_size)
panic("zeroblock_range: len too long: %lld", len);
memset(b_data(bp) + offset, 0, len);
lmfs_markdirty(bp);
put_block(bp, FULL_DATA_BLOCK);
}