inode.c

linux 内核源代码

	/* do not read the direct item */
	_get_block_create_0(inode, block, bh_result, 0);
	reiserfs_write_unlock(inode->i_sb);
	return 0;
}

/* special version of get_block that is only used by grab_tail_page right
** now.  It is sent to block_prepare_write, and when you try to get a
** block past the end of the file (or a block from a hole) it returns
** -ENOENT instead of a valid buffer.  block_prepare_write expects to
** be able to do i/o on the buffers returned, unless an error value
** is also returned.
** 
** So, this allows block_prepare_write to be used for reading a single block
** in a page.  Where it does not produce a valid page for holes, or past the
** end of the file.  This turns out to be exactly what we need for reading
** tails for conversion.
**
** The point of the wrapper is forcing a certain value for create, even
** though the VFS layer is calling this function with create==1.  If you 
** don't want to send create == GET_BLOCK_NO_HOLE to reiserfs_get_block, 
** don't use this function.
*/
static int reiserfs_get_block_create_0(struct inode *inode, sector_t block,
				       struct buffer_head *bh_result,
				       int create)
{
	return reiserfs_get_block(inode, block, bh_result, GET_BLOCK_NO_HOLE);
}

/* This is special helper for reiserfs_get_block in case we are executing
   direct_IO request. */
static int reiserfs_get_blocks_direct_io(struct inode *inode,
					 sector_t iblock,
					 struct buffer_head *bh_result,
					 int create)
{
	int ret;

	bh_result->b_page = NULL;

	/* We set the b_size before reiserfs_get_block call since it is
	   referenced in convert_tail_for_hole() that may be called from
	   reiserfs_get_block() */
	bh_result->b_size = (1 << inode->i_blkbits);

	ret = reiserfs_get_block(inode, iblock, bh_result,
				 create | GET_BLOCK_NO_DANGLE);
	if (ret)
		goto out;

	/* don't allow direct io onto tail pages */
	if (buffer_mapped(bh_result) && bh_result->b_blocknr == 0) {
		/* make sure future calls to the direct io funcs for this offset
		 ** in the file fail by unmapping the buffer
		 */
		clear_buffer_mapped(bh_result);
		ret = -EINVAL;
	}
	/* Possible unpacked tail. Flush the data before pages have
	   disappeared */
	if (REISERFS_I(inode)->i_flags & i_pack_on_close_mask) {
		int err;
		lock_kernel();
		err = reiserfs_commit_for_inode(inode);
		REISERFS_I(inode)->i_flags &= ~i_pack_on_close_mask;
		unlock_kernel();
		if (err < 0)
			ret = err;
	}
      out:
	return ret;
}

/*
** helper function for when reiserfs_get_block is called for a hole
** but the file tail is still in a direct item
** bh_result is the buffer head for the hole
** tail_offset is the offset of the start of the tail in the file
**
** This calls prepare_write, which will start a new transaction
** you should not be in a transaction, or have any paths held when you
** call this.
*/
static int convert_tail_for_hole(struct inode *inode,
				 struct buffer_head *bh_result,
				 loff_t tail_offset)
{
	unsigned long index;
	unsigned long tail_end;
	unsigned long tail_start;
	struct page *tail_page;
	struct page *hole_page = bh_result->b_page;
	int retval = 0;

	if ((tail_offset & (bh_result->b_size - 1)) != 1)
		return -EIO;

	/* always try to read until the end of the block */
	tail_start = tail_offset & (PAGE_CACHE_SIZE - 1);
	tail_end = (tail_start | (bh_result->b_size - 1)) + 1;

	index = tail_offset >> PAGE_CACHE_SHIFT;
	/* hole_page can be zero in case of direct_io, we are sure
	   that we cannot get here if we write with O_DIRECT into
	   tail page */
	if (!hole_page || index != hole_page->index) {
		tail_page = grab_cache_page(inode->i_mapping, index);
		retval = -ENOMEM;
		if (!tail_page) {
			goto out;
		}
	} else {
		tail_page = hole_page;
	}

	/* we don't have to make sure the conversion did not happen while
	 ** we were locking the page because anyone that could convert
	 ** must first take i_mutex.
	 **
	 ** We must fix the tail page for writing because it might have buffers
	 ** that are mapped, but have a block number of 0.  This indicates tail
	 ** data that has been read directly into the page, and block_prepare_write
	 ** won't trigger a get_block in this case.
	 */
	fix_tail_page_for_writing(tail_page);
	retval = reiserfs_prepare_write(NULL, tail_page, tail_start, tail_end);
	if (retval)
		goto unlock;

	/* tail conversion might change the data in the page */
	flush_dcache_page(tail_page);

	retval = reiserfs_commit_write(NULL, tail_page, tail_start, tail_end);

      unlock:
	if (tail_page != hole_page) {
		unlock_page(tail_page);
		page_cache_release(tail_page);
	}
      out:
	return retval;
}

static inline int _allocate_block(struct reiserfs_transaction_handle *th,
				  sector_t block,
				  struct inode *inode,
				  b_blocknr_t * allocated_block_nr,
				  struct treepath *path, int flags)
{
	BUG_ON(!th->t_trans_id);

#ifdef REISERFS_PREALLOCATE
	if (!(flags & GET_BLOCK_NO_IMUX)) {
		return reiserfs_new_unf_blocknrs2(th, inode, allocated_block_nr,
						  path, block);
	}
#endif
	return reiserfs_new_unf_blocknrs(th, inode, allocated_block_nr, path,
					 block);
}

int reiserfs_get_block(struct inode *inode, sector_t block,
		       struct buffer_head *bh_result, int create)
{
	int repeat, retval = 0;
	b_blocknr_t allocated_block_nr = 0;	// b_blocknr_t is (unsigned) 32 bit int
	INITIALIZE_PATH(path);
	int pos_in_item;
	struct cpu_key key;
	struct buffer_head *bh, *unbh = NULL;
	struct item_head *ih, tmp_ih;
	__le32 *item;
	int done;
	int fs_gen;
	struct reiserfs_transaction_handle *th = NULL;
	/* space reserved in transaction batch: 
	   . 3 balancings in direct->indirect conversion
	   . 1 block involved into reiserfs_update_sd()
	   XXX in practically impossible worst case direct2indirect()
	   can incur (much) more than 3 balancings.
	   quota update for user, group */
	int jbegin_count =
	    JOURNAL_PER_BALANCE_CNT * 3 + 1 +
	    2 * REISERFS_QUOTA_TRANS_BLOCKS(inode->i_sb);
	int version;
	int dangle = 1;
	loff_t new_offset =
	    (((loff_t) block) << inode->i_sb->s_blocksize_bits) + 1;

	/* bad.... */
	reiserfs_write_lock(inode->i_sb);
	version = get_inode_item_key_version(inode);

	if (!file_capable(inode, block)) {
		reiserfs_write_unlock(inode->i_sb);
		return -EFBIG;
	}

	/* if !create, we aren't changing the FS, so we don't need to
	 ** log anything, so we don't need to start a transaction
	 */
	if (!(create & GET_BLOCK_CREATE)) {
		int ret;
		/* find number of block-th logical block of the file */
		ret = _get_block_create_0(inode, block, bh_result,
					  create | GET_BLOCK_READ_DIRECT);
		reiserfs_write_unlock(inode->i_sb);
		return ret;
	}
	/*
	 * if we're already in a transaction, make sure to close
	 * any new transactions we start in this func
	 */
	if ((create & GET_BLOCK_NO_DANGLE) ||
	    reiserfs_transaction_running(inode->i_sb))
		dangle = 0;

	/* If file is of such a size, that it might have a tail and tails are enabled
	 ** we should mark it as possibly needing tail packing on close
	 */
	if ((have_large_tails(inode->i_sb)
	     && inode->i_size < i_block_size(inode) * 4)
	    || (have_small_tails(inode->i_sb)
		&& inode->i_size < i_block_size(inode)))
		REISERFS_I(inode)->i_flags |= i_pack_on_close_mask;

	/* set the key of the first byte in the 'block'-th block of file */
	make_cpu_key(&key, inode, new_offset, TYPE_ANY, 3 /*key length */ );
	if ((new_offset + inode->i_sb->s_blocksize - 1) > inode->i_size) {
	      start_trans:
		th = reiserfs_persistent_transaction(inode->i_sb, jbegin_count);
		if (!th) {
			retval = -ENOMEM;
			goto failure;
		}
		reiserfs_update_inode_transaction(inode);
	}
      research:

	retval = search_for_position_by_key(inode->i_sb, &key, &path);
	if (retval == IO_ERROR) {
		retval = -EIO;
		goto failure;
	}

	bh = get_last_bh(&path);
	ih = get_ih(&path);
	item = get_item(&path);
	pos_in_item = path.pos_in_item;

	fs_gen = get_generation(inode->i_sb);
	copy_item_head(&tmp_ih, ih);

	if (allocation_needed
	    (retval, allocated_block_nr, ih, item, pos_in_item)) {
		/* we have to allocate block for the unformatted node */
		if (!th) {
			pathrelse(&path);
			goto start_trans;
		}

		repeat =
		    _allocate_block(th, block, inode, &allocated_block_nr,
				    &path, create);

		if (repeat == NO_DISK_SPACE || repeat == QUOTA_EXCEEDED) {
			/* restart the transaction to give the journal a chance to free
			 ** some blocks.  releases the path, so we have to go back to
			 ** research if we succeed on the second try
			 */
			SB_JOURNAL(inode->i_sb)->j_next_async_flush = 1;
			retval = restart_transaction(th, inode, &path);
			if (retval)
				goto failure;
			repeat =
			    _allocate_block(th, block, inode,
					    &allocated_block_nr, NULL, create);

			if (repeat != NO_DISK_SPACE && repeat != QUOTA_EXCEEDED) {
				goto research;
			}
			if (repeat == QUOTA_EXCEEDED)
				retval = -EDQUOT;
			else
				retval = -ENOSPC;
			goto failure;
		}

		if (fs_changed(fs_gen, inode->i_sb)
		    && item_moved(&tmp_ih, &path)) {
			goto research;
		}
	}

	if (indirect_item_found(retval, ih)) {
		b_blocknr_t unfm_ptr;
		/* 'block'-th block is in the file already (there is
		   corresponding cell in some indirect item). But it may be
		   zero unformatted node pointer (hole) */
		unfm_ptr = get_block_num(item, pos_in_item);
		if (unfm_ptr == 0) {
			/* use allocated block to plug the hole */
			reiserfs_prepare_for_journal(inode->i_sb, bh, 1);
			if (fs_changed(fs_gen, inode->i_sb)
			    && item_moved(&tmp_ih, &path)) {
				reiserfs_restore_prepared_buffer(inode->i_sb,
								 bh);
				goto research;
			}
			set_buffer_new(bh_result);
			if (buffer_dirty(bh_result)
			    && reiserfs_data_ordered(inode->i_sb))
				reiserfs_add_ordered_list(inode, bh_result);
			put_block_num(item, pos_in_item, allocated_block_nr);
			unfm_ptr = allocated_block_nr;
			journal_mark_dirty(th, inode->i_sb, bh);
			reiserfs_update_sd(th, inode);
		}
		set_block_dev_mapped(bh_result, unfm_ptr, inode);
		pathrelse(&path);
		retval = 0;
		if (!dangle && th)
			retval = reiserfs_end_persistent_transaction(th);

		reiserfs_write_unlock(inode->i_sb);

		/* the item was found, so new blocks were not added to the file
		 ** there is no need to make sure the inode is updated with this 
		 ** transaction
		 */
		return retval;
	}

	if (!th) {
		pathrelse(&path);
		goto start_trans;
	}

	/* desired position is not found or is in the direct item. We have
	   to append file with holes up to 'block'-th block converting
	   direct items to indirect one if necessary */
	done = 0;
	do {
		if (is_statdata_le_ih(ih)) {
			__le32 unp = 0;
			struct cpu_key tmp_key;

			/* indirect item has to be inserted */
			make_le_item_head(&tmp_ih, &key, version, 1,
					  TYPE_INDIRECT, UNFM_P_SIZE,
					  0 /* free_space */ );

			if (cpu_key_k_offset(&key) == 1) {
				/* we are going to add 'block'-th block to the file. Use
				   allocated block for that */
				unp = cpu_to_le32(allocated_block_nr);
				set_block_dev_mapped(bh_result,
						     allocated_block_nr, inode);
				set_buffer_new(bh_result);
				done = 1;
			}
			tmp_key = key;	// ;)
			set_cpu_key_k_offset(&tmp_key, 1);
			PATH_LAST_POSITION(&path)++;

			retval =
			    reiserfs_insert_item(th, &path, &tmp_key, &tmp_ih,
						 inode, (char *)&unp);
			if (retval) {
				reiserfs_free_block(th, inode,
						    allocated_block_nr, 1);
				goto failure;	// retval == -ENOSPC, -EDQUOT or -EIO or -EEXIST
			}
			//mark_tail_converted (inode);
		} else if (is_direct_le_ih(ih)) {
			/* direct item has to be converted */
			loff_t tail_offset;

			tail_offset =
			    ((le_ih_k_offset(ih) -
			      1) & ~(inode->i_sb->s_blocksize - 1)) + 1;
			if (tail_offset == cpu_key_k_offset(&key)) {
				/* direct item we just found fits into block we have
				   to map. Convert it into unformatted node: use
				   bh_result for the conversion */
				set_block_dev_mapped(bh_result,
						     allocated_block_nr, inode);
				unbh = bh_result;
				done = 1;
			} else {
				/* we have to padd file tail stored in direct item(s)
				   up to block size and convert it to unformatted
				   node. FIXME: this should also get into page cache */

				pathrelse(&path);
				/*
				 * ugly, but we can only end the transaction if
				 * we aren't nested
				 */
				BUG_ON(!th->t_refcount);
				if (th->t_refcount == 1) {
					retval =
					    reiserfs_end_persistent_transaction
					    (th);
					th = NULL;
					if (retval)
						goto failure;
				}

				retval =
				    convert_tail_for_hole(inode, bh_result,
							  tail_offset);
				if (retval) {
					if (retval != -ENOSPC)
						reiserfs_warning(inode->i_sb,
								 "clm-6004: convert tail failed inode %lu, error %d",
								 inode->i_ino,
								 retval);
					if (allocated_block_nr) {
						/* the bitmap, the super, and the stat data == 3 */
						if (!th)
							th = reiserfs_persistent_transaction(inode->i_sb, 3);
						if (th)
							reiserfs_free_block(th,
									    inode,