// Allocate a page to hold the disk block
int
map_block(uint32_t blockno)
{
if (block_is_mapped(blockno))
return 0;
return sys_page_alloc(0, diskaddr(blockno), PTE_U|PTE_P|PTE_W);
}
// Set *blk to point at the filebno'th block in file 'f'.
// Allocate the block if it doesn't yet exist.
// Returns 0 on success, < 0 on error.
int
file_get_block(struct File *f, uint32_t filebno, char **blk)
{
int r;
uint32_t diskbno;
// Read in the block, leaving the pointer in *blk.
// Hint: Use file_map_block and read_block.
// LAB 5: Your code here.
r = file_map_block(f, filebno, &diskbno, 1);
if (r)
return r;
// If the block is already mapped we return it
// instead of reading the block from disk again.
// XXX: I'm not sure whether this is the right
// thing to do, however, looks like lab5 says
// to do that (p. 7).
if (block_is_mapped(diskbno)) {
if (blk)
*blk = diskaddr(diskbno);
return 0;
}
return read_block(diskbno, blk);
}
// Make sure a particular disk block is loaded into memory.
// Returns 0 on success, or a negative error code on error.
//
// If blk != 0, set *blk to the address of the block in memory.
//
// Hint: Use diskaddr, map_block, and ide_read.
static int
read_block(uint32_t blockno, char **blk)
{
int r;
char *addr;
if (super && blockno >= super->s_nblocks)
panic("reading non-existent block %08x\n", blockno);
if (bitmap && block_is_free(blockno))
panic("reading free block %08x\n", blockno);
// LAB 5: Your code here.
addr = diskaddr(blockno);
if (block_is_mapped(blockno)) {
goto succeeded;
}
// now that the block is not in memory, allocate memory and read it in.
if ((r = map_block(blockno)) < 0)
return r;
if ((r = ide_read(blockno * BLKSECTS, addr, BLKSECTS)) < 0)
return r;
succeeded:
if (blk)
*blk = addr;
return 0;
}
// Flush the contents and metadata of file f out to disk.
// Loop over all the blocks in file.
// Translate the file block number into a disk block number
// and then check whether that disk block is dirty. If so, write it out.
void
file_flush(struct File *f)
{
int i;
uint32_t *pdiskbno;
for (i = 0; i < (f->f_size + BLKSIZE - 1) / BLKSIZE; i++) {
if (file_block_walk(f, i, &pdiskbno, 0) < 0 ||
pdiskbno == NULL || *pdiskbno == 0)
continue;
flush_block(diskaddr(*pdiskbno));
}
flush_block(f);
if (f->f_indirect)
flush_block(diskaddr(f->f_indirect));
}
// Make sure a particular disk block is loaded into memory.
// Returns 0 on success, or a negative error code on error.
//
// If blk != 0, set *blk to the address of the block in memory.
//
// Hint: Use diskaddr, map_block, and ide_read.
static int
read_block(uint32_t blockno, char **blk)
{
int r;
char *addr;
if (super && blockno >= super->s_nblocks)
panic("reading non-existent block %08x\n", blockno);
if (bitmap && block_is_free(blockno))
panic("reading free block %08x\n", blockno);
addr = diskaddr(blockno);
if(!block_is_mapped(blockno)){
if((r = map_block(blockno)) < 0)
return r;
r = ide_read(blockno*BLKSECTS, (void *)addr, BLKSECTS);
if(r < 0)
return r;
}
if(blk)
*blk = addr;
return 0;
}
// Set *blk to the address in memory where the filebno'th
// block of file 'f' would be mapped.
//
// Returns 0 on success, < 0 on error. Errors are:
// -E_NO_DISK if a block needed to be allocated but the disk is full.
// -E_INVAL if filebno is out of range.
//
// Hint: Use file_block_walk and alloc_block.
int
file_get_block(struct File *f, uint32_t filebno, char **blk)
{
// code for lab 5- M.G
// panic("file_get_block not implemented");
uint32_t *ppdiskbno;
uint32_t new_block_no;
int return_value;
if ((return_value = file_block_walk(f, filebno, &ppdiskbno,true)) < 0)
{
return return_value;
}
if (!*ppdiskbno)
{
if ((new_block_no = alloc_block()) < 0)
{
return -E_NO_DISK;
}
*ppdiskbno = new_block_no;
}
*blk = diskaddr(*ppdiskbno);
return 0;
}
// Read and validate the file system bitmap.
//
// Read all the bitmap blocks into memory.
// Set the "bitmap" pointer to point at the beginning of the first
// bitmap block.
//
// Check that all reserved blocks -- 0, 1, and the bitmap blocks themselves --
// are all marked as in-use
// (for each block i, assert(!block_is_free(i))).
//
// Hint: Assume that the superblock has already been loaded into
// memory (in variable 'super'). Check out super->s_nblocks.
void
read_bitmap(void)
{
int r;
uint32_t i;
// Read the bitmap into memory.
// The bitmap consists of one or more blocks. A single bitmap block
// contains the in-use bits for BLKBITSIZE blocks. There are
// super->s_nblocks blocks in the disk altogether.
// Set 'bitmap' to point to the first address in the bitmap.
// Hint: Use read_block.
// LAB 5: Your code here.
// bitmap blocks start at block 2.
for (i = 0; i < (super->s_nblocks - 1) / BLKBITSIZE + 1; i++) {
if ((r = read_block(i + 2, NULL)) < 0)
panic("read_block for bitmap %d failed: %e.\n", i, r);
}
bitmap = (uint32_t *) diskaddr(2);
// Make sure the reserved and root blocks are marked in-use.
assert(!block_is_free(0));
assert(!block_is_free(1));
assert(bitmap);
// Make sure that the bitmap blocks are marked in-use.
// LAB 5: Your code here.
for (i = 0; i < super->s_nblocks / BLKBITSIZE; i++)
assert(!block_is_free(i + 2));
cprintf("read_bitmap is good\n");
}
static int
file_block_walk(struct File *f, uint32_t filebno, uint32_t **ppdiskbno, bool alloc)
{
if (filebno >= NDIRECT + NINDIRECT) {
return -E_INVAL;
}
uint32_t nblock = f->f_size / BLKSIZE;
if (filebno > nblock) {
return -E_NOT_FOUND;
}
if (filebno < NDIRECT) {
*ppdiskbno = &f->f_direct[filebno];
return 0;
}
else {
if(!f->f_indirect) {
return -E_NOT_FOUND;
}
uint32_t* index = (uint32_t*)diskaddr(f->f_indirect);
*ppdiskbno = &index[filebno - NDIRECT] ;
}
return 0;
// LAB 5: Your code here.
// panic("file_block_walk not implemented");
}
// Make sure a particular disk block is loaded into memory.
// Returns 0 on success, or a negative error code on error.
//
// If blk != 0, set *blk to the address of the block in memory.
//
// Hint: Use diskaddr, map_block, and ide_read.
static int
read_block(uint32_t blockno, char **blk)
{
int r;
char *addr;
if (super && blockno >= super->s_nblocks)
panic("reading non-existent block %08x\n", blockno);
if (bitmap && block_is_free(blockno))
panic("reading free block %08x\n", blockno);
// LAB 5: Your code here.
r = map_block(blockno);
if (r)
return r;
addr = diskaddr(blockno);
r = ide_read(blockno * BLKSECTS, addr, BLKSECTS);
if (r)
return r;
if (blk)
*blk = addr;
return sys_page_map(0, addr, 0, addr, vpt[VPN(addr)] & PTE_USER);
}
// Sync the entire file system. A big hammer.
void
fs_sync(void)
{
int i;
for (i = 1; i < super->s_nblocks; i++)
flush_block(diskaddr(i));
}
int
fs_rmdir(const char *path)
{
struct inode *dir;
struct dirent *dent;
uint32_t nblock, i, j;
char *blk;
int r;
if ((r = inode_open(path, &dir)) < 0)
return r;
if (dir == diskaddr(super->s_root))
return -EPERM;
if (!S_ISDIR(dir->i_mode))
return -ENOTDIR;
nblock = dir->i_size / BLKSIZE;
for (i = 0; i < nblock; i++) {
if ((r = inode_get_block(dir, i, &blk)) < 0)
return r;
dent = (struct dirent *)blk;
for (j = 0; j < BLKDIRENTS; ++j)
if (dent[j].d_name[0] != '\0')
return -ENOTEMPTY;
}
return inode_unlink(path);
}
// Make sure a particular disk block is loaded into memory.
// Returns 0 on success, or a negative error code on error.
//
// If blk != 0, set *blk to the address of the block in memory.
//
// Hint: Use diskaddr, map_block, and ide_read.
static int
read_block(uint32_t blockno, char **blk)
{
int r;
char *addr;
if (super && blockno >= super->s_nblocks)
panic("reading non-existent block %08x\n", blockno);
if (bitmap && block_is_free(blockno))
panic("reading free block %08x\n", blockno);
// LAB 5: Your code here.
addr = diskaddr(blockno);
int error = map_block(blockno);
if(error<0) return error;
int secno = blockno*BLKSECTS;
error = ide_read(secno, addr, (size_t)BLKSECTS);
if(error) return error;
if(blk) *blk = addr;
// panic("read_block not implemented");
return 0;
}
// Copy the current contents of the block out to disk.
// Then clear the PTE_D bit using sys_page_map.
// Hint: Use ide_write.
// Hint: Use the PTE_USER constant when calling sys_page_map.
void
write_block(uint32_t blockno)
{
char *addr;
if (!block_is_mapped(blockno))
panic("write unmapped block %08x", blockno);
// Write the disk block and clear PTE_D.
// LAB 5: Your code here.
// We will use the VM hardware to keep track of whether a
// disk block has been modified since it was last read from
// or written to disk. To see whether a block needs writing,
// we can just look to see if the PTE_D "dirty" bit is set
// in the vpt entry.
addr = diskaddr(blockno);
if(!va_is_dirty(addr)) return;
int error;
int secno = blockno*BLKSECTS;
error = ide_write(secno, addr, BLKSECTS);
if(error<0) panic("write block error on writing");
int env_id = sys_getenvid();
error = sys_page_map(env_id, addr,
env_id, addr, ((PTE_U|PTE_P|PTE_W) & ~PTE_D));
if(error<0) panic("write block error on clearing PTE_D");
// panic("write_block not implemented");
}
// Search the bitmap for a free block and allocate it. When you
// allocate a block, immediately flush the changed bitmap block
// to disk.
//
// Return block number allocated on success,
// -E_NO_DISK if we are out of blocks.
//
// Hint: use free_block as an example for manipulating the bitmap.
int
alloc_block(void)
{
// The bitmap consists of one or more blocks. A single bitmap block
// contains the in-use bits for BLKBITSIZE blocks. There are
// super->s_nblocks blocks in the disk altogether.
// code for lab 5 -M.G
// panic("alloc_block not implemented");
uint32_t i,j;
for (i = 0; i < super->s_nblocks/32; i++)
{
for (j = 0; j < 32; j++)
{
uint32_t mark_bit = (1 << j);
if (bitmap[i] & mark_bit)
{
bitmap[i] &= ~mark_bit;
flush_block(diskaddr((i * 32 | j)/BLKBITSIZE + 2));
return (i * 32) | j;
}
}
}
return -E_NO_DISK;
}
// Find the disk block number slot for the 'filebno'th block in file 'f'.
// Set '*ppdiskbno' to point to that slot.
// The slot will be one of the f->f_direct[] entries,
// or an entry in the indirect block.
// When 'alloc' is set, this function will allocate an indirect block
// if necessary.
//
// Returns:
// 0 on success (but note that *ppdiskbno might equal 0).
// -E_NOT_FOUND if the function needed to allocate an indirect block, but
// alloc was 0.
// -E_NO_DISK if there's no space on the disk for an indirect block.
// -E_INVAL if filebno is out of range (it's >= NDIRECT + NINDIRECT).
//
// Analogy: This is like pgdir_walk for files.
// Hint: Don't forget to clear any block you allocate.
static int
file_block_walk(struct File *f, uint32_t filebno, uint32_t **ppdiskbno, bool alloc)
{
// LAB 5: Your code here.
//panic("file_block_walk not implemented");
int result;
if(filebno >= NDIRECT+NINDIRECT)
{
return -E_INVAL;
}
if(filebno < NDIRECT)
{
if(ppdiskbno)
{
*ppdiskbno=(f->f_direct+filebno);
}
return 0;
}
if(!f->f_indirect && !alloc)
{
return -E_NOT_FOUND;
}
if(!f->f_indirect)
{
if((result=alloc_block()) < 0)
{
return -E_NO_DISK;
}
f->f_indirect=result;
memset(diskaddr(result), 0, BLKSIZE);
flush_block(diskaddr(result));
}
if(ppdiskbno)
{
*ppdiskbno=(uint32_t *)diskaddr(f->f_indirect)+filebno-NDIRECT;
}
return 0;
}
// Find the disk block number slot for the 'filebno'th block in file 'f'.
// Set '*ppdiskbno' to point to that slot.
// The slot will be one of the f->f_direct[] entries,
// or an entry in the indirect block.
// When 'alloc' is set, this function will allocate an indirect block
// if necessary.
//
// Returns:
// 0 on success (but note that *ppdiskbno might equal 0).
// -E_NOT_FOUND if the function needed to allocate an indirect block, but
// alloc was 0.
// -E_NO_DISK if there's no space on the disk for an indirect block.
// -E_INVAL if filebno is out of range (it's >= NDIRECT + NINDIRECT).
//
// Analogy: This is like pgdir_walk for files.
// Hint: Don't forget to clear any block you allocate.
static int
file_block_walk(struct File *f, uint32_t filebno, uint32_t **ppdiskbno, bool alloc)
{
// Lab 5 ex 4
// LAB 5: Your code here.
if(!f || !ppdiskbno)
return -E_INVAL;
int new_block;
void *blk_addr;
uint32_t * index;
if(filebno >= (NDIRECT + NINDIRECT))
return -E_INVAL;
if(filebno < 10)
{
*ppdiskbno = &(f->f_direct[filebno]);
return 0;
}
else
{
filebno -= 10;
if(f->f_indirect)
{
blk_addr = diskaddr((uint64_t)(f->f_indirect));
index = (uint32_t *) blk_addr;
*ppdiskbno = (index + filebno);
return 0;
}
else
{
if(alloc == 0)
return -E_NOT_FOUND;
new_block = alloc_block();
if(new_block == -E_NO_DISK)
return -E_NO_DISK;
f->f_indirect = (uint32_t)new_block;
blk_addr = diskaddr((uint64_t)(f->f_indirect));
index = (uint32_t *) blk_addr;
*ppdiskbno = (index + filebno);
return 0;
}
}
//panic("file_block_walk not implemented");
}
void
bc_init(void)
{
struct Super super;
set_pgfault_handler(bc_pgfault);
// cache the super block by reading it once
memmove(&super, diskaddr(1), sizeof super);
}
static void print_block_list()
{
cprintf("\n");
cprintf("==============block usage list==============\n");
int i;
for (i=0; i<MAXBLK; ++i)
if (plist[i].valid)
cprintf("+block at %x, used %d times, last used at time %d\n", diskaddr(i), plist[i].count, plist[i].tstamp);
cprintf("++++++++++++++++++end list++++++++++++++++++\n");
}
// Initialize the file system
void
fs_init(void)
{
static_assert(sizeof(struct File) == 256);
// Find a JOS disk. Use the second IDE disk (number 1) if availabl
if (ide_probe_disk1())
ide_set_disk(1);
else
ide_set_disk(0);
bc_init();
// Set "super" to point to the super block.
super = diskaddr(1);
check_super();
// Set "bitmap" to the beginning of the first bitmap block.
bitmap = diskaddr(2);
check_bitmap();
}
// Find the disk block number slot for the 'filebno'th block in file 'f'.
// Set '*ppdiskbno' to point to that slot.
// The slot will be one of the f->f_direct[] entries,
// or an entry in the indirect block.
// When 'alloc' is set, this function will allocate an indirect block
// if necessary.
//
// Returns:
// 0 on success (but note that *ppdiskbno might equal 0).
// -E_NOT_FOUND if the function needed to allocate an indirect block, but
// alloc was 0.
// -E_NO_DISK if there's no space on the disk for an indirect block.
// -E_INVAL if filebno is out of range (it's >= NDIRECT + NINDIRECT).
//
// Analogy: This is like pgdir_walk for files.
// Hint: Don't forget to clear any block you allocate.
static int
file_block_walk(struct File *f, uint32_t filebno, uint32_t **ppdiskbno, bool alloc)
{
// code for lab 5-M.G
// panic("file_block_walk not implemented");
uint32_t new_block_no;
if (filebno < NDIRECT)
{
*ppdiskbno = &f->f_direct[filebno];
}
else if (filebno < (NDIRECT + NINDIRECT))
{
if (!f->f_indirect)
{
if (alloc == false)
{
return -E_NOT_FOUND;
}
else
{
if ((new_block_no = alloc_block()) < 0)
{
return -E_NO_DISK;
}
f->f_indirect = new_block_no;
memset(diskaddr(new_block_no), 0, BLKSIZE);
}
}
*ppdiskbno = &((uintptr_t *) diskaddr(f->f_indirect))[filebno - NDIRECT];
}
else
{
return -E_INVAL;
}
return 0;
}
// Find the disk block number slot for the 'filebno'th block in file 'f'.
// Set '*ppdiskbno' to point to that slot.
// The slot will be one of the f->f_direct[] entries,
// or an entry in the indirect block.
// When 'alloc' is set, this function will allocate an indirect block
// if necessary.
//
// Returns:
// 0 on success (but note that *ppdiskbno might equal 0).
// -E_NOT_FOUND if the function needed to allocate an indirect block, but
// alloc was 0.
// -E_NO_DISK if there's no space on the disk for an indirect block.
// -E_INVAL if filebno is out of range (it's >= NDIRECT + NINDIRECT).
//
// Analogy: This is like pgdir_walk for files.
// Hint: Don't forget to clear any block you allocate.
static int
file_block_walk(struct File *f, uint32_t filebno, uint32_t **ppdiskbno, bool alloc)
{
// LAB 5: Your code here.
// panic("file_block_walk not implemented");
if (!f) panic("file not exist!\n");
if (filebno >= NDIRECT + NINDIRECT) return -E_INVAL;
if (filebno < NDIRECT) {
*ppdiskbno = &(f->f_direct[filebno]);
return 0;
}
if (!f->f_indirect) {
if (!alloc) return -E_NOT_FOUND;
int n;
if ((n = alloc_block()) < 0) return n;
f->f_indirect = n;
memset(diskaddr(n), 0, BLKSIZE);
}
*ppdiskbno = (uint32_t*)(diskaddr(f->f_indirect) + 4 * (filebno - NDIRECT));
return 0;
}
int
main(int argc, char **argv)
{
struct fuse_args args = FUSE_ARGS_INIT(0, NULL);
const char *imgname = NULL, *mntpoint = NULL;
char fsname_buf[17 + PATH_MAX];
int r, fd;
fuse_opt_add_arg(&args, argv[0]);
if (argc < 2)
panic("missing image or mountpoint parameter, see help");
for (r = 1; r < argc; r++) {
if (imgname == NULL && argv[r][0] != '-' && strcmp(argv[r - 1], "-o") != 0) {
imgname = argv[r];
} else if(mntpoint == NULL && argv[r][0] != '-' && strcmp(argv[r - 1], "-o") != 0) {
mntpoint = argv[r];
fuse_opt_add_arg(&args, argv[r]);
} else {
fuse_opt_add_arg(&args, argv[r]);
}
}
// Use a fsname (which shows up in df) in the style of sshfs, another
// FUSE-based file system, with format "fsname#fslocation".
snprintf(fsname_buf, sizeof(fsname_buf), "-ofsname=CS202fs#%s", imgname);
fuse_opt_add_arg(&args, "-s"); // Always run single-threaded.
fuse_opt_add_arg(&args, "-odefault_permissions"); // Kernel handles access.
fuse_opt_add_arg(&args, fsname_buf); // Set the filesystem name.
if (imgname == NULL) {
fuse_opt_parse(&args, NULL, fs_opts, fs_parse_opt);
return -1;
} else {
struct inode *dirroot;
map_disk_image(imgname, mntpoint);
// Make sure the superblock fields are sane.
assert(super->s_magic == FS_MAGIC);
assert(super->s_root != 0);
// Guarantee that the root directory has proper permissions.
// This is vital so that we can unmount the disk.
dirroot = diskaddr(super->s_root);
dirroot->i_mode = S_IFDIR | 0777;
fuse_opt_parse(&args, NULL, fs_opts, fs_parse_opt);
return fuse_main(args.argc, args.argv, &fs_oper, NULL);
}
}
// Make sure this block is unmapped.
void
unmap_block(uint32_t blockno)
{
int r;
if (!block_is_mapped(blockno))
return;
assert(block_is_free(blockno) || !block_is_dirty(blockno));
if ((r = sys_page_unmap(0, diskaddr(blockno))) < 0)
panic("unmap_block: sys_mem_unmap: %e", r);
assert(!block_is_mapped(blockno));
}
int
fs_chmod(const char *path, mode_t mode)
{
struct inode *ino;
int r;
if ((r = inode_open(path, &ino)) < 0)
return r;
if (ino == diskaddr(super->s_root))
return -EPERM;
ino->i_mode = mode;
ino->i_ctime = time(NULL);
flush_block(ino);
return 0;
}
// Allocate a block -- first find a free block in the bitmap,
// then map it into memory.
int
alloc_block(void)
{
int r, bno;
if ((r = alloc_block_num()) < 0)
return r;
bno = r;
if ((r = map_block(bno)) < 0) {
free_block(bno);
return r;
}
memset(diskaddr(bno), 0, BLKSIZE);
return bno;
}
// Set *blk to the address in memory where the filebno'th
// block of file 'f' would be mapped.
//
// Returns 0 on success, < 0 on error. Errors are:
// -E_NO_DISK if a block needed to be allocated but the disk is full.
// -E_INVAL if filebno is out of range.
//
// Hint: Use file_block_walk and alloc_block.
int
file_get_block(struct File *f, uint32_t filebno, char **blk)
{
// LAB 5: Your code here.
int r;
uint32_t *ppdiskbno;
if ((r = file_block_walk(f, filebno, &ppdiskbno, 1)) < 0)
return r;
if (!*ppdiskbno)
{
if ((r = alloc_block()) < 0)
return r;
*ppdiskbno = r;
}
*blk = (char *) diskaddr(*ppdiskbno);
return 0;
}
// Set *blk to the address in memory where the filebno'th
// block of file 'f' would be mapped.
//
// Returns 0 on success, < 0 on error. Errors are:
// -E_NO_DISK if a block needed to be allocated but the disk is full.
// -E_INVAL if filebno is out of range.
//
int
file_get_block(struct File *f, uint32_t filebno, char **blk)
{
if (filebno >= NDIRECT + NINDIRECT) {
return -E_INVAL;
}
uint32_t *ppdiskbno;
int r = file_block_walk(f, filebno, &ppdiskbno, false);
if (r < 0)
return r;
if (!*ppdiskbno)
return -E_NO_DISK;
*blk = (char*)diskaddr(*ppdiskbno);
return 0;
// LAB 5: Your code here.
//panic("file_block_walk not implemented");
}
// Copy the current contents of the block out to disk.
// Then clear the PTE_D bit using sys_page_map.
// Hint: Use ide_write.
// Hint: Use the PTE_USER constant when calling sys_page_map.
void
write_block(uint32_t blockno)
{
int r;
char *addr;
if (!block_is_mapped(blockno))
panic("write unmapped block %08x", blockno);
// Write the disk block and clear PTE_D.
// LAB 5: Your code here.
addr = diskaddr(blockno);
if ((r = ide_write(blockno * BLKSECTS, addr, BLKSECTS)) < 0)
panic("write_block: ide_write failed: %e.\n", r);
if ((r = sys_page_map(0, addr, 0, addr, PTE_USER)) < 0)
panic("write_block: sys_page_map failed: %e.\n", r);
}
// Search the bitmap for a free block and allocate it. When you
// allocate a block, immediately flush the changed bitmap block
// to disk.
//
// Return block number allocated on success,
// -E_NO_DISK if we are out of blocks.
//
// Hint: use free_block as an example for manipulating the bitmap.
int
alloc_block(void)
{
// The bitmap consists of one or more blocks. A single bitmap block
// contains the in-use bits for BLKBITSIZE blocks. There are
// super->s_nblocks blocks in the disk altogether.
// LAB 5: Your code here.
uint32_t blockno;
for(blockno = 1; blockno < super->s_nblocks; blockno++)
if(block_is_free(blockno))
{
bitmap[blockno/32] ^= (1<<(blockno%32));
flush_block(diskaddr(2));
assert(!block_is_free(blockno));
return blockno;
}
return -E_NO_DISK;
}
int
fs_chown(const char *path, uid_t uid, gid_t gid)
{
struct inode *ino;
int r;
if ((r = inode_open(path, &ino)) < 0)
return r;
if (ino == diskaddr(super->s_root))
return -EPERM;
if (uid != -1)
ino->i_owner = uid;
if (gid != -1)
ino->i_group = gid;
ino->i_ctime = time(NULL);
flush_block(ino);
return 0;
}