/
lfs.py
197 lines (141 loc) · 4.46 KB
/
lfs.py
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import cython
from disk import *
import errno
import time
import z3
class LFS(object):
SUPERBLOCK = 0
SB_OFF_BALLOC = 0
SB_OFF_IALLOC = 1
SB_OFF_IMAP = 2
I_OFF_MTIME = 0
I_OFF_MODE = 1
I_OFF_DATA = 4
def __init__(self, disk):
self._disk = disk
self._sb = None
self._imap = None
def read(self, ino, block):
self._begin()
bid = self._imap[ino]
r = self._disk.read(bid)
self._commit(False)
return r
def _begin(self):
assert self._sb is None
assert self._imap is None
self._sb = self._disk.read(self.SUPERBLOCK)
self._imap = self._disk.read(self._sb[self.SB_OFF_IMAP])
def _balloc(self):
a = self._sb[self.SB_OFF_BALLOC]
self._sb[self.SB_OFF_BALLOC] += 1
# Allocator returned a new block
assertion(0 < (a + 1))
return a
def _ialloc(self):
a = self._sb[self.SB_OFF_IALLOC]
self._sb[self.SB_OFF_IALLOC] += 1
# we have a free inode..
assertion(a < 512)
return a
def _commit(self, write=True):
assert self._sb is not None
assert self._imap is not None
if write:
a = self._balloc()
self._disk.write(a, self._imap)
self._disk.flush()
self._sb[self.SB_OFF_IMAP] = a
self._disk.write(self.SUPERBLOCK, self._sb)
self._disk.flush()
self._sb = None
self._imap = None
def _set_map(self, ino, bid):
self._imap[Extract(8, 0, ino)] = bid
def _get_map(self, ino):
return self._imap[Extract(8, 0, ino)]
########
def dir_lookup(self, blk, name):
res = -errno.ENOENT
for i in range(2):
oname = blk[self.I_OFF_DATA + i * 2]
oino = blk[self.I_OFF_DATA + i * 2 + 1]
res = If(And(oname == name, 0 < oino), oino, res)
return res
def dir_find_empty(self, blk):
res = BitVecVal(-errno.ENOSPC, 64)
for i in range(2):
res = If(blk[self.I_OFF_DATA + i * 2] == 0, i, res)
return res
def get_attr(self, ino):
s = Stat(0, 0, 0)
self._begin()
blk = self._get_map(ino)
blk = self._disk.read(blk)
s.bsize = 0
s.mode = blk[self.I_OFF_MODE]
s.mtime = blk[self.I_OFF_MTIME]
self._commit(False)
return s
def lookup(self, parent, name):
self._begin()
parent_blkno = self._get_map(parent)
parent_blk = self._disk.read(parent_blkno)
ino = self.dir_lookup(parent_blk, name)
self._commit(False)
return ino
def exists(self, parent, name):
return 0 < self.lookup(parent, name)
def mknod(self, parent, name, mode, mtime):
# check if the file exists
if self.exists(parent, name):
assertion(False)
return BitVecVal(-errno.EEXIST, 64)
self._begin()
parent_blkno = self._get_map(parent)
parent_blk = self._disk.read(parent_blkno)
ino = self._ialloc()
blkno = self._balloc()
eoff = self.dir_find_empty(parent_blk)
if eoff < 0:
self._commit(False)
return eoff
# write new inode
inodeblk = ConstBlock(0)
inodeblk[self.I_OFF_MTIME] = mtime
inodeblk[self.I_OFF_MODE] = mode
self._disk.write(blkno, inodeblk)
# update parent directory
parent_blk[self.I_OFF_DATA + 2 * Extract(8, 0, eoff)] = name
parent_blk[self.I_OFF_DATA + 2 * Extract(8, 0, eoff) + 1] = ino
new_parent_blkno = self._balloc()
self._disk.write(new_parent_blkno, parent_blk)
# update the imap
self._set_map(ino, blkno)
self._set_map(parent, new_parent_blkno)
self._commit()
return ino
def crash(self, mach):
return self.__class__(self._disk.crash(mach))
def mkfs(disk):
sb = disk._disk.read(0)
if sb[0] == 0:
sb[LFS.SB_OFF_BALLOC] = 3
sb[LFS.SB_OFF_IALLOC] = 2
sb[LFS.SB_OFF_IMAP] = 1
disk._disk.write(0, sb)
imap = ConstBlock(0)
imap[1] = 2
disk._disk.write(1, imap)
def create_lfs(*args):
disk = AsyncDisk('/tmp/foo.img')
lfs = LFS(disk)
mkfs(lfs)
return lfs
if __name__ == '__main__':
lfs = create_lfs()
print lfs.lookup(1, 16)
print lfs.get_attr(4)
print lfs.mknod(1, 20, 2000, 2000)
print lfs.lookup(1, 20)
print lfs.get_attr(4)