dir.c

来自「一个类似windows」· C语言 代码 · 共 1,421 行 · 第 1/4 页

	u8 *name = NULL;
	int rc, err, ir_pos, cur_bmp_pos;
	struct address_space *ia_mapping, *bmp_mapping;
	struct page *bmp_page = NULL, *ia_page = NULL;
	u8 *kaddr, *bmp, *index_end;
	attr_search_context *ctx;

	fpos = filp->f_pos;
	ntfs_debug("Entering for inode 0x%lx, fpos 0x%Lx.",
			vdir->i_ino, fpos);
	rc = err = 0;
	/* Are we at end of dir yet? */
	if (fpos >= vdir->i_size + vol->mft_record_size)
		goto done;
	/* Emulate . and .. for all directories. */
	if (!fpos) {
		ntfs_debug("Calling filldir for . with len 1, fpos 0x0, "
				"inode 0x%lx, DT_DIR.", vdir->i_ino);
		rc = filldir(dirent, ".", 1, fpos, vdir->i_ino, DT_DIR);
		if (rc)
			goto done;
		fpos++;
	}
	if (fpos == 1) {
		ntfs_debug("Calling filldir for .. with len 2, fpos 0x1, "
				"inode 0x%lx, DT_DIR.",
				parent_ino(filp->f_dentry));
		rc = filldir(dirent, "..", 2, fpos,
				parent_ino(filp->f_dentry), DT_DIR);
		if (rc)
			goto done;
		fpos++;
	}
	m = NULL;
	ctx = NULL;
	/*
	 * Allocate a buffer to store the current name being processed
	 * converted to format determined by current NLS.
	 */
	name = (u8*)kmalloc(NTFS_MAX_NAME_LEN * NLS_MAX_CHARSET_SIZE + 1,
			GFP_NOFS);
	if (unlikely(!name)) {
		err = -ENOMEM;
		goto err_out;
	}
	/* Are we jumping straight into the index allocation attribute? */
	if (fpos >= vol->mft_record_size)
		goto skip_index_root;
	/* Get hold of the mft record for the directory. */
	m = map_mft_record(ndir);
	if (unlikely(IS_ERR(m))) {
		err = PTR_ERR(m);
		m = NULL;
		goto err_out;
	}
	ctx = get_attr_search_ctx(ndir, m);
	if (unlikely(!ctx)) {
		err = -ENOMEM;
		goto err_out;
	}
	/* Get the offset into the index root attribute. */
	ir_pos = (s64)fpos;
	/* Find the index root attribute in the mft record. */
	if (unlikely(!lookup_attr(AT_INDEX_ROOT, I30, 4, CASE_SENSITIVE, 0,
			NULL, 0, ctx))) {
		ntfs_error(sb, "Index root attribute missing in directory "
				"inode 0x%lx.", vdir->i_ino);
		goto err_out;
	}
	/* Get to the index root value (it's been verified in read_inode). */
	ir = (INDEX_ROOT*)((u8*)ctx->attr +
			le16_to_cpu(ctx->attr->data.resident.value_offset));
	index_end = (u8*)&ir->index + le32_to_cpu(ir->index.index_length);
	/* The first index entry. */
	ie = (INDEX_ENTRY*)((u8*)&ir->index +
			le32_to_cpu(ir->index.entries_offset));
	/*
	 * Loop until we exceed valid memory (corruption case) or until we
	 * reach the last entry or until filldir tells us it has had enough
	 * or signals an error (both covered by the rc test).
	 */
	for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
		ntfs_debug("In index root, offset 0x%x.", (u8*)ie - (u8*)ir);
		/* Bounds checks. */
		if (unlikely((u8*)ie < (u8*)ctx->mrec || (u8*)ie +
				sizeof(INDEX_ENTRY_HEADER) > index_end ||
				(u8*)ie + le16_to_cpu(ie->key_length) >
				index_end))
			goto err_out;
		/* The last entry cannot contain a name. */
		if (ie->flags & INDEX_ENTRY_END)
			break;
		/* Skip index root entry if continuing previous readdir. */
		if (ir_pos > (u8*)ie - (u8*)ir)
			continue;
		/* Submit the name to the filldir callback. */
		rc = ntfs_filldir(vol, &fpos, ndir, INDEX_TYPE_ROOT, ir, ie,
				name, dirent, filldir);
		if (rc) {
			put_attr_search_ctx(ctx);
			unmap_mft_record(ndir);
			goto abort;
		}
	}
	/*
	 * We are done with the index root and the mft record for that matter.
	 * We need to release it, otherwise we deadlock on ntfs_attr_iget()
	 * and/or ntfs_read_page().
	 */
	put_attr_search_ctx(ctx);
	unmap_mft_record(ndir);
	m = NULL;
	ctx = NULL;
	/* If there is no index allocation attribute we are finished. */
	if (!NInoIndexAllocPresent(ndir))
		goto EOD;
	/* Advance fpos to the beginning of the index allocation. */
	fpos = vol->mft_record_size;
skip_index_root:
	kaddr = NULL;
	prev_ia_pos = -1LL;
	/* Get the offset into the index allocation attribute. */
	ia_pos = (s64)fpos - vol->mft_record_size;
	ia_mapping = vdir->i_mapping;
	bmp_vi = ndir->itype.index.bmp_ino;
	if (unlikely(!bmp_vi)) {
		ntfs_debug("Inode %lu, regetting index bitmap.", vdir->i_ino);
		bmp_vi = ntfs_attr_iget(vdir, AT_BITMAP, I30, 4);
		if (unlikely(IS_ERR(bmp_vi))) {
			ntfs_error(sb, "Failed to get bitmap attribute.");
			err = PTR_ERR(bmp_vi);
			goto err_out;
		}
		ndir->itype.index.bmp_ino = bmp_vi;
	}
	bmp_mapping = bmp_vi->i_mapping;
	/* Get the starting bitmap bit position and sanity check it. */
	bmp_pos = ia_pos >> ndir->itype.index.block_size_bits;
	if (unlikely(bmp_pos >> 3 >= bmp_vi->i_size)) {
		ntfs_error(sb, "Current index allocation position exceeds "
				"index bitmap size.");
		goto err_out;
	}
	/* Get the starting bit position in the current bitmap page. */
	cur_bmp_pos = bmp_pos & ((PAGE_CACHE_SIZE * 8) - 1);
	bmp_pos &= ~(u64)((PAGE_CACHE_SIZE * 8) - 1);
get_next_bmp_page:
	ntfs_debug("Reading bitmap with page index 0x%Lx, bit ofs 0x%Lx",
			(long long)bmp_pos >> (3 + PAGE_CACHE_SHIFT),
			(long long)bmp_pos & ((PAGE_CACHE_SIZE * 8) - 1));
	bmp_page = ntfs_map_page(bmp_mapping,
			bmp_pos >> (3 + PAGE_CACHE_SHIFT));
	if (unlikely(IS_ERR(bmp_page))) {
		ntfs_error(sb, "Reading index bitmap failed.");
		err = PTR_ERR(bmp_page);
		bmp_page = NULL;
		goto err_out;
	}
	bmp = (u8*)page_address(bmp_page);
	/* Find next index block in use. */
	while (!(bmp[cur_bmp_pos >> 3] & (1 << (cur_bmp_pos & 7)))) {
find_next_index_buffer:
		cur_bmp_pos++;
		/*
		 * If we have reached the end of the bitmap page, get the next
		 * page, and put away the old one.
		 */
		if (unlikely((cur_bmp_pos >> 3) >= PAGE_CACHE_SIZE)) {
			ntfs_unmap_page(bmp_page);
			bmp_pos += PAGE_CACHE_SIZE * 8;
			cur_bmp_pos = 0;
			goto get_next_bmp_page;
		}
		/* If we have reached the end of the bitmap, we are done. */
		if (unlikely(((bmp_pos + cur_bmp_pos) >> 3) >= vdir->i_size))
			goto unm_EOD;
		ia_pos = (bmp_pos + cur_bmp_pos) <<
				ndir->itype.index.block_size_bits;
	}
	ntfs_debug("Handling index buffer 0x%Lx.",
			(long long)bmp_pos + cur_bmp_pos);
	/* If the current index buffer is in the same page we reuse the page. */
	if ((prev_ia_pos & PAGE_CACHE_MASK) != (ia_pos & PAGE_CACHE_MASK)) {
		prev_ia_pos = ia_pos;
		if (likely(ia_page != NULL))
			ntfs_unmap_page(ia_page);
		/*
		 * Map the page cache page containing the current ia_pos,
		 * reading it from disk if necessary.
		 */
		ia_page = ntfs_map_page(ia_mapping, ia_pos >> PAGE_CACHE_SHIFT);
		if (unlikely(IS_ERR(ia_page))) {
			ntfs_error(sb, "Reading index allocation data failed.");
			err = PTR_ERR(ia_page);
			ia_page = NULL;
			goto err_out;
		}
		kaddr = (u8*)page_address(ia_page);
	}
	/* Get the current index buffer. */
	ia = (INDEX_ALLOCATION*)(kaddr + (ia_pos & ~PAGE_CACHE_MASK &
			~(s64)(ndir->itype.index.block_size - 1)));
	/* Bounds checks. */
	if (unlikely((u8*)ia < kaddr || (u8*)ia > kaddr + PAGE_CACHE_SIZE)) {
		ntfs_error(sb, "Out of bounds check failed. Corrupt directory "
				"inode 0x%lx or driver bug.", vdir->i_ino);
		goto err_out;
	}
	if (unlikely(sle64_to_cpu(ia->index_block_vcn) != (ia_pos &
			~(s64)(ndir->itype.index.block_size - 1)) >>
			ndir->itype.index.vcn_size_bits)) {
		ntfs_error(sb, "Actual VCN (0x%Lx) of index buffer is "
				"different from expected VCN (0x%Lx). "
				"Directory inode 0x%lx is corrupt or driver "
				"bug. ",
				(long long)sle64_to_cpu(ia->index_block_vcn),
				(long long)ia_pos >>
				ndir->itype.index.vcn_size_bits, vdir->i_ino);
		goto err_out;
	}
	if (unlikely(le32_to_cpu(ia->index.allocated_size) + 0x18 !=
			ndir->itype.index.block_size)) {
		ntfs_error(sb, "Index buffer (VCN 0x%Lx) of directory inode "
				"0x%lx has a size (%u) differing from the "
				"directory specified size (%u). Directory "
				"inode is corrupt or driver bug.",
				(long long)ia_pos >>
				ndir->itype.index.vcn_size_bits, vdir->i_ino,
				le32_to_cpu(ia->index.allocated_size) + 0x18,
				ndir->itype.index.block_size);
		goto err_out;
	}
	index_end = (u8*)ia + ndir->itype.index.block_size;
	if (unlikely(index_end > kaddr + PAGE_CACHE_SIZE)) {
		ntfs_error(sb, "Index buffer (VCN 0x%Lx) of directory inode "
				"0x%lx crosses page boundary. Impossible! "
				"Cannot access! This is probably a bug in the "
				"driver.", (long long)ia_pos >>
				ndir->itype.index.vcn_size_bits, vdir->i_ino);
		goto err_out;
	}
	ia_start = ia_pos & ~(s64)(ndir->itype.index.block_size - 1);
	index_end = (u8*)&ia->index + le32_to_cpu(ia->index.index_length);
	if (unlikely(index_end > (u8*)ia + ndir->itype.index.block_size)) {
		ntfs_error(sb, "Size of index buffer (VCN 0x%Lx) of directory "
				"inode 0x%lx exceeds maximum size.",
				(long long)ia_pos >>
				ndir->itype.index.vcn_size_bits, vdir->i_ino);
		goto err_out;
	}
	/* The first index entry in this index buffer. */
	ie = (INDEX_ENTRY*)((u8*)&ia->index +
			le32_to_cpu(ia->index.entries_offset));
	/*
	 * Loop until we exceed valid memory (corruption case) or until we
	 * reach the last entry or until filldir tells us it has had enough
	 * or signals an error (both covered by the rc test).
	 */
	for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
		ntfs_debug("In index allocation, offset 0x%Lx.",
				(long long)ia_start + ((u8*)ie - (u8*)ia));
		/* Bounds checks. */
		if (unlikely((u8*)ie < (u8*)ia || (u8*)ie +
				sizeof(INDEX_ENTRY_HEADER) > index_end ||
				(u8*)ie + le16_to_cpu(ie->key_length) >
				index_end))
			goto err_out;
		/* The last entry cannot contain a name. */
		if (ie->flags & INDEX_ENTRY_END)
			break;
		/* Skip index block entry if continuing previous readdir. */
		if (ia_pos - ia_start > (u8*)ie - (u8*)ia)
			continue;
		/* Submit the name to the filldir callback. */
		rc = ntfs_filldir(vol, &fpos, ndir, INDEX_TYPE_ALLOCATION, ia,
				ie, name, dirent, filldir);
		if (rc) {
			ntfs_unmap_page(ia_page);
			ntfs_unmap_page(bmp_page);
			goto abort;
		}
	}
	goto find_next_index_buffer;
unm_EOD:
	if (ia_page)
		ntfs_unmap_page(ia_page);
	ntfs_unmap_page(bmp_page);
EOD:
	/* We are finished, set fpos to EOD. */
	fpos = vdir->i_size + vol->mft_record_size;
abort:
	kfree(name);
done:
#ifdef DEBUG
	if (!rc)
		ntfs_debug("EOD, fpos 0x%Lx, returning 0.", fpos);
	else
		ntfs_debug("filldir returned %i, fpos 0x%Lx, returning 0.",
				rc, fpos);
#endif
	filp->f_pos = fpos;
	return 0;
err_out:
	if (bmp_page)
		ntfs_unmap_page(bmp_page);
	if (ia_page)
		ntfs_unmap_page(ia_page);
	if (name)
		kfree(name);
	if (ctx)
		put_attr_search_ctx(ctx);
	if (m)
		unmap_mft_record(ndir);
	if (!err)
		err = -EIO;
	ntfs_debug("Failed. Returning error code %i.", -err);
	filp->f_pos = fpos;
	return err;
}

/**
 * ntfs_dir_open - called when an inode is about to be opened
 * @vi:		inode to be opened
 * @filp:	file structure describing the inode
 *
 * Limit directory size to the page cache limit on architectures where unsigned
 * long is 32-bits. This is the most we can do for now without overflowing the
 * page cache page index. Doing it this way means we don't run into problems
 * because of existing too large directories. It would be better to allow the
 * user to read the accessible part of the directory but I doubt very much
 * anyone is going to hit this check on a 32-bit architecture, so there is no
 * point in adding the extra complexity required to support this.
 *
 * On 64-bit architectures, the check is hopefully optimized away by the
 * compiler.
 */
static int ntfs_dir_open(struct inode *vi, struct file *filp)
{
	if (sizeof(unsigned long) < 8) {
		if (vi->i_size > MAX_LFS_FILESIZE)
			return -EFBIG;
	}
	return 0;
}

struct file_operations ntfs_dir_ops = {
	.llseek		= generic_file_llseek,	/* Seek inside directory. */
	.read		= generic_read_dir,	/* Return -EISDIR. */
	.readdir	= ntfs_readdir,		/* Read directory contents. */
	.open		= ntfs_dir_open,	/* Open directory. */
};