Exemplo n.º 1
0
Arquivo: bio.c Projeto: Hooman3/minix
/*
 * Perform block I/O, on "dev", starting from offset "pos", for a total of
 * "bytes" bytes.  Reading, writing, and peeking are highly similar, and thus,
 * this function implements all of them.  The "call" parameter indicates the
 * call type (one of FSC_READ, FSC_WRITE, FSC_PEEK).  For read and write calls,
 * "data" will identify the user buffer to use; for peek calls, "data" is set
 * to NULL.  In all cases, this function returns the number of bytes
 * successfully transferred, 0 on end-of-file conditions, and a negative error
 * code if no bytes could be transferred due to an error.  Dirty data is not
 * flushed immediately, and thus, a successful write only indicates that the
 * data have been taken in by the cache (for immediate I/O, a character device
 * would have to be used, but MINIX3 no longer supports this), which may be
 * follwed later by silent failures, including undetected end-of-file cases.
 * In particular, write requests may or may not return 0 (EOF) immediately when
 * writing at or beyond the block device's size. i Since block I/O takes place
 * at block granularity, block-unaligned writes have to read a block from disk
 * before updating it, and that is the only possible source of actual I/O
 * errors for write calls.
 * TODO: reconsider the buffering-only approach, or see if we can at least
 * somehow throw accurate EOF errors without reading in each block first.
 */
ssize_t
lmfs_bio(dev_t dev, struct fsdriver_data * data, size_t bytes, off_t pos,
	int call)
{
	block_t block, blocks_left;
	size_t block_size, off, block_off, chunk;
	struct buf *bp;
	int r, write, how;

	if (dev == NO_DEV)
		return EINVAL;

	block_size = lmfs_fs_block_size();
	write = (call == FSC_WRITE);

	assert(block_size > 0);

	/* FIXME: block_t is 32-bit, so we have to impose a limit here. */
	if (pos < 0 || pos / block_size > UINT32_MAX || bytes > SSIZE_MAX)
		return EINVAL;

	off = 0;
	block = pos / block_size;
	block_off = (size_t)(pos % block_size);
	blocks_left = howmany(block_off + bytes, block_size);

	lmfs_reset_rdwt_err();
	r = OK;

	for (off = 0; off < bytes; off += chunk) {
		chunk = block_size - block_off;
		if (chunk > bytes - off)
			chunk = bytes - off;

		/*
		 * For read requests, help the block driver form larger I/O
		 * requests.
		 */
		if (!write)
			block_prefetch(dev, block, blocks_left);

		/*
		 * Do not read the block from disk if we will end up
		 * overwriting all of its contents.
		 */
		how = (write && chunk == block_size) ? NO_READ : NORMAL;

		bp = lmfs_get_block(dev, block, how);
		assert(bp);

		r = lmfs_rdwt_err();

		if (r == OK && data != NULL) {
			assert(lmfs_dev(bp) != NO_DEV);

			if (write) {
				r = fsdriver_copyin(data, off,
				    (char *)bp->data + block_off, chunk);

				/*
				 * Mark the block as dirty even if the copy
				 * failed, since the copy may in fact have
				 * succeeded partially.  This is an interface
				 * issue that should be resolved at some point,
				 * but for now we do not want the cache to be
				 * desynchronized from the disk contents.
				 */
				lmfs_markdirty(bp);
			} else
				r = fsdriver_copyout(data, off,
				    (char *)bp->data + block_off, chunk);
		}

		lmfs_put_block(bp, FULL_DATA_BLOCK);

		if (r != OK)
			break;

		block++;
		block_off = 0;
		blocks_left--;
	}

	/*
	 * If we were not able to do any I/O, return the error (or EOF, even
	 * for writes).  Otherwise, return how many bytes we did manage to
	 * transfer.
	 */
	if (r != OK && off == 0)
		return (r == END_OF_FILE) ? 0 : r;

	return off;
}
Exemplo n.º 2
0
Arquivo: read.c Projeto: Hooman3/minix
ssize_t fs_read(ino_t ino_nr, struct fsdriver_data *data, size_t bytes,
	off_t pos, int __unused call)
{
	size_t off, chunk, block_size, cum_io;
	off_t f_size;
	struct inode *i_node;
	struct buf *bp;
	int r;

	/* Try to get inode according to its index. */
	if ((i_node = find_inode(ino_nr)) == NULL)
		return EINVAL; /* No inode found. */

	f_size = i_node->i_stat.st_size;
	if (pos >= f_size)
		return 0; /* EOF */

	/* Limit the request to the remainder of the file size. */
	if ((off_t)bytes > f_size - pos)
		bytes = (size_t)(f_size - pos);

	block_size = v_pri.logical_block_size_l;
	cum_io = 0;

	lmfs_reset_rdwt_err();
	r = OK;

	/* Split the transfer into chunks that don't span two blocks. */
	while (bytes > 0) {
		off = pos % block_size;

		chunk = block_size - off;
		if (chunk > bytes)
			chunk = bytes;

		/* Read 'chunk' bytes. */
		bp = read_extent_block(i_node->extent, pos / block_size);
		if (bp == NULL)
			panic("bp not valid in rw_chunk; this can't happen");

		r = fsdriver_copyout(data, cum_io, b_data(bp)+off, chunk);

		lmfs_put_block(bp, FULL_DATA_BLOCK);

		if (r != OK)
			break;  /* EOF reached. */
		if (lmfs_rdwt_err() < 0)
			break;

		/* Update counters and pointers. */
		bytes -= chunk;		/* Bytes yet to be read. */
		cum_io += chunk;	/* Bytes read so far. */
		pos += chunk;		/* Position within the file. */
	}

	if (lmfs_rdwt_err() != OK)
		r = lmfs_rdwt_err();	/* Check for disk error. */
	if (lmfs_rdwt_err() == END_OF_FILE)
		r = OK;

	return (r == OK) ? cum_io : r;
}
Exemplo n.º 3
0
/*===========================================================================*
 *				fs_readwrite				     *
 *===========================================================================*/
int fs_readwrite(void)
{
  int r, rw_flag, block_spec;
  int regular;
  cp_grant_id_t gid;
  off_t position, f_size, bytes_left;
  unsigned int off, cum_io, block_size, chunk;
  mode_t mode_word;
  int completed;
  struct inode *rip;
  size_t nrbytes;

  r = OK;
  
  /* Find the inode referred */
  if ((rip = find_inode(fs_dev, (ino_t) fs_m_in.REQ_INODE_NR)) == NULL)
	return(EINVAL);

  mode_word = rip->i_mode & I_TYPE;
  regular = (mode_word == I_REGULAR || mode_word == I_NAMED_PIPE);
  block_spec = (mode_word == I_BLOCK_SPECIAL ? 1 : 0);
  
  /* Determine blocksize */
  if (block_spec) {
	block_size = get_block_size( (dev_t) rip->i_zone[0]);
	f_size = MAX_FILE_POS;
  } else {
  	block_size = rip->i_sp->s_block_size;
  	f_size = rip->i_size;
  }

  /* Get the values from the request message */ 
  rw_flag = (fs_m_in.m_type == REQ_READ ? READING : WRITING);
  gid = (cp_grant_id_t) fs_m_in.REQ_GRANT;
  position = (off_t) fs_m_in.REQ_SEEK_POS_LO;
  nrbytes = (size_t) fs_m_in.REQ_NBYTES;
  
  lmfs_reset_rdwt_err();

  /* If this is file i/o, check we can write */
  if (rw_flag == WRITING && !block_spec) {
  	  if(rip->i_sp->s_rd_only) 
		  return EROFS;

	  /* Check in advance to see if file will grow too big. */
	  if (position > (off_t) (rip->i_sp->s_max_size - nrbytes))
		  return(EFBIG);

	  /* Clear the zone containing present EOF if hole about
	   * to be created.  This is necessary because all unwritten
	   * blocks prior to the EOF must read as zeros.
	   */
	  if(position > f_size) clear_zone(rip, f_size, 0);
  }

  /* If this is block i/o, check we can write */
  if(block_spec && rw_flag == WRITING &&
  	(dev_t) rip->i_zone[0] == superblock.s_dev && superblock.s_rd_only)
		return EROFS;
	      
  cum_io = 0;
  /* Split the transfer into chunks that don't span two blocks. */
  while (nrbytes > 0) {
	  off = ((unsigned int) position) % block_size; /* offset in blk*/
	  chunk = min(nrbytes, block_size - off);

	  if (rw_flag == READING) {
		  bytes_left = f_size - position;
		  if (position >= f_size) break;	/* we are beyond EOF */
		  if (chunk > (unsigned int) bytes_left) chunk = bytes_left;
	  }
	  
	  /* Read or write 'chunk' bytes. */
	  r = rw_chunk(rip, cvul64((unsigned long) position), off, chunk,
	  	       nrbytes, rw_flag, gid, cum_io, block_size, &completed);

	  if (r != OK) break;	/* EOF reached */
	  if (lmfs_rdwt_err() < 0) break;

	  /* Update counters and pointers. */
	  nrbytes -= chunk;	/* bytes yet to be read */
	  cum_io += chunk;	/* bytes read so far */
	  position += (off_t) chunk;	/* position within the file */
  }

  fs_m_out.RES_SEEK_POS_LO = position; /* It might change later and the VFS
					   has to know this value */
  
  /* On write, update file size and access time. */
  if (rw_flag == WRITING) {
	  if (regular || mode_word == I_DIRECTORY) {
		  if (position > f_size) rip->i_size = position;
	  }
  } 

  rip->i_seek = NO_SEEK;

  if (lmfs_rdwt_err() != OK) r = lmfs_rdwt_err();	/* check for disk error */
  if (lmfs_rdwt_err() == END_OF_FILE) r = OK;

  /* even on a ROFS, writing to a device node on it is fine, 
   * just don't update the inode stats for it. And dito for reading.
   */
  if (r == OK && !rip->i_sp->s_rd_only) {
	  if (rw_flag == READING) rip->i_update |= ATIME;
	  if (rw_flag == WRITING) rip->i_update |= CTIME | MTIME;
	  IN_MARKDIRTY(rip);		/* inode is thus now dirty */
  }
  
  fs_m_out.RES_NBYTES = cum_io;
  
  return(r);
}
Exemplo n.º 4
0
/*===========================================================================*
 *				fs_readwrite				     *
 *===========================================================================*/
ssize_t fs_readwrite(ino_t ino_nr, struct fsdriver_data *data, size_t nrbytes,
	off_t position, int call)
{
  int r;
  int regular;
  off_t f_size, bytes_left;
  size_t off, cum_io, block_size, chunk;
  mode_t mode_word;
  int completed;
  struct inode *rip;
  
  r = OK;
  
  /* Find the inode referred */
  if ((rip = find_inode(fs_dev, ino_nr)) == NULL)
	return(EINVAL);

  mode_word = rip->i_mode & I_TYPE;
  regular = (mode_word == I_REGULAR);
  
  /* Determine blocksize */
  block_size = rip->i_sp->s_block_size;
  f_size = rip->i_size;

  lmfs_reset_rdwt_err();

  /* If this is file i/o, check we can write */
  if (call == FSC_WRITE) {
  	  if(rip->i_sp->s_rd_only) 
		  return EROFS;

	  /* Check in advance to see if file will grow too big. */
	  if (position > (off_t) (rip->i_sp->s_max_size - nrbytes))
		  return(EFBIG);

	  /* Clear the zone containing present EOF if hole about
	   * to be created.  This is necessary because all unwritten
	   * blocks prior to the EOF must read as zeros.
	   */
	  if(position > f_size) clear_zone(rip, f_size, 0);
  }

  cum_io = 0;
  /* Split the transfer into chunks that don't span two blocks. */
  while (nrbytes > 0) {
	  off = ((unsigned int) position) % block_size; /* offset in blk*/
	  chunk = block_size - off;
	  if (chunk > nrbytes)
		chunk = nrbytes;

	  if (call == FSC_READ) {
		  bytes_left = f_size - position;
		  if (position >= f_size) break;	/* we are beyond EOF */
		  if (chunk > (unsigned int) bytes_left) chunk = bytes_left;
	  }
	  
	  /* Read or write 'chunk' bytes. */
	  r = rw_chunk(rip, ((u64_t)((unsigned long)position)), off, chunk,
		nrbytes, call, data, cum_io, block_size, &completed);

	  if (r != OK) break;	/* EOF reached */
	  if (lmfs_rdwt_err() < 0) break;

	  /* Update counters and pointers. */
	  nrbytes -= chunk;	/* bytes yet to be read */
	  cum_io += chunk;	/* bytes read so far */
	  position += (off_t) chunk;	/* position within the file */
  }

  /* On write, update file size and access time. */
  if (call == FSC_WRITE) {
	  if (regular || mode_word == I_DIRECTORY) {
		  if (position > f_size) rip->i_size = position;
	  }
  } 

  rip->i_seek = NO_SEEK;

  if (lmfs_rdwt_err() != OK) r = lmfs_rdwt_err(); /* check for disk error */
  if (lmfs_rdwt_err() == END_OF_FILE) r = OK;

  if (r != OK)
	return r;

  /* even on a ROFS, writing to a device node on it is fine, 
   * just don't update the inode stats for it. And dito for reading.
   */
  if (!rip->i_sp->s_rd_only) {
	  if (call == FSC_READ) rip->i_update |= ATIME;
	  if (call == FSC_WRITE) rip->i_update |= CTIME | MTIME;
	  IN_MARKDIRTY(rip);		/* inode is thus now dirty */
  }
  
  return cum_io;
}
Exemplo n.º 5
0
/*===========================================================================*
 *				fs_breadwrite				     *
 *===========================================================================*/
int fs_breadwrite(void)
{
  int r, rw_flag, completed;
  cp_grant_id_t gid;
  u64_t position;
  unsigned int off, cum_io, chunk, block_size;
  size_t nrbytes;
  dev_t target_dev;

  /* Pseudo inode for rw_chunk */
  struct inode rip;
  
  r = OK;

  target_dev = (dev_t) fs_m_in.REQ_DEV2;
  
  /* Get the values from the request message */ 
  rw_flag = (fs_m_in.m_type == REQ_BREAD ? READING : WRITING);
  gid = (cp_grant_id_t) fs_m_in.REQ_GRANT;
  position = make64((unsigned long) fs_m_in.REQ_SEEK_POS_LO,
  		    (unsigned long) fs_m_in.REQ_SEEK_POS_HI);
  nrbytes = (size_t) fs_m_in.REQ_NBYTES;
  
  block_size = get_block_size(target_dev);

  /* Don't block-write to a RO-mounted filesystem. */
  if(superblock.s_dev == target_dev && superblock.s_rd_only)
  	return EROFS;

  rip.i_zone[0] = (zone_t) target_dev;
  rip.i_mode = I_BLOCK_SPECIAL;
  rip.i_size = 0;

  lmfs_reset_rdwt_err();
  
  cum_io = 0;
  /* Split the transfer into chunks that don't span two blocks. */
  while (nrbytes > 0) {
	  off = rem64u(position, block_size);	/* offset in blk*/
	  chunk = min(nrbytes, block_size - off);

	  /* Read or write 'chunk' bytes. */
	  r = rw_chunk(&rip, position, off, chunk, nrbytes, rw_flag, gid,
	  	       cum_io, block_size, &completed);

	  if (r != OK) break;	/* EOF reached */
	  if (lmfs_rdwt_err() < 0) break;

	  /* Update counters and pointers. */
	  nrbytes -= chunk;	        /* bytes yet to be read */
	  cum_io += chunk;	        /* bytes read so far */
	  position = add64ul(position, chunk);	/* position within the file */
  }
  
  fs_m_out.RES_SEEK_POS_LO = ex64lo(position); 
  fs_m_out.RES_SEEK_POS_HI = ex64hi(position); 
  
  if (lmfs_rdwt_err() != OK) r = lmfs_rdwt_err();	/* check for disk error */
  if (lmfs_rdwt_err() == END_OF_FILE) r = OK;

  fs_m_out.RES_NBYTES = cum_io;
  
  return(r);
}