truncate.c

linux 内核源代码

/*
 * truncate.c
 *
 * PURPOSE
 *	Truncate handling routines for the OSTA-UDF(tm) filesystem.
 *
 * COPYRIGHT
 *	This file is distributed under the terms of the GNU General Public
 *	License (GPL). Copies of the GPL can be obtained from:
 *		ftp://prep.ai.mit.edu/pub/gnu/GPL
 *	Each contributing author retains all rights to their own work.
 *
 *  (C) 1999-2004 Ben Fennema
 *  (C) 1999 Stelias Computing Inc
 *
 * HISTORY
 *
 *  02/24/99 blf  Created.
 *
 */

#include "udfdecl.h"
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/udf_fs.h>
#include <linux/buffer_head.h>

#include "udf_i.h"
#include "udf_sb.h"

static void extent_trunc(struct inode *inode, struct extent_position *epos,
			 kernel_lb_addr eloc, int8_t etype, uint32_t elen,
			 uint32_t nelen)
{
	kernel_lb_addr neloc = {};
	int last_block = (elen + inode->i_sb->s_blocksize - 1) >>
		inode->i_sb->s_blocksize_bits;
	int first_block = (nelen + inode->i_sb->s_blocksize - 1) >>
		inode->i_sb->s_blocksize_bits;

	if (nelen) {
		if (etype == (EXT_NOT_RECORDED_ALLOCATED >> 30)) {
			udf_free_blocks(inode->i_sb, inode, eloc, 0,
					last_block);
			etype = (EXT_NOT_RECORDED_NOT_ALLOCATED >> 30);
		} else
			neloc = eloc;
		nelen = (etype << 30) | nelen;
	}

	if (elen != nelen) {
		udf_write_aext(inode, epos, neloc, nelen, 0);
		if (last_block - first_block > 0) {
			if (etype == (EXT_RECORDED_ALLOCATED >> 30))
				mark_inode_dirty(inode);

			if (etype != (EXT_NOT_RECORDED_NOT_ALLOCATED >> 30))
				udf_free_blocks(inode->i_sb, inode, eloc,
						first_block,
						last_block - first_block);
		}
	}
}

/*
 * Truncate the last extent to match i_size. This function assumes
 * that preallocation extent is already truncated.
 */
void udf_truncate_tail_extent(struct inode *inode)
{
	struct extent_position epos = {};
	kernel_lb_addr eloc;
	uint32_t elen, nelen;
	uint64_t lbcount = 0;
	int8_t etype = -1, netype;
	int adsize;

	if (UDF_I_ALLOCTYPE(inode) == ICBTAG_FLAG_AD_IN_ICB ||
	    inode->i_size == UDF_I_LENEXTENTS(inode))
		return;
	/* Are we going to delete the file anyway? */
	if (inode->i_nlink == 0)
		return;

	if (UDF_I_ALLOCTYPE(inode) == ICBTAG_FLAG_AD_SHORT)
		adsize = sizeof(short_ad);
	else if (UDF_I_ALLOCTYPE(inode) == ICBTAG_FLAG_AD_LONG)
		adsize = sizeof(long_ad);
	else
		BUG();

	/* Find the last extent in the file */
	while ((netype = udf_next_aext(inode, &epos, &eloc, &elen, 1)) != -1) {
		etype = netype;
		lbcount += elen;
		if (lbcount > inode->i_size) {
			if (lbcount - inode->i_size >= inode->i_sb->s_blocksize)
				printk(KERN_WARNING
				       "udf_truncate_tail_extent(): Too long "
				       "extent after EOF in inode %u: i_size: "
				       "%Ld lbcount: %Ld extent %u+%u\n",
				       (unsigned)inode->i_ino,
				       (long long)inode->i_size,
				       (long long)lbcount,
				       (unsigned)eloc.logicalBlockNum,
				       (unsigned)elen);
			nelen = elen - (lbcount - inode->i_size);
			epos.offset -= adsize;
			extent_trunc(inode, &epos, eloc, etype, elen, nelen);
			epos.offset += adsize;
			if (udf_next_aext(inode, &epos, &eloc, &elen, 1) != -1)
				printk(KERN_ERR "udf_truncate_tail_extent(): "
				       "Extent after EOF in inode %u.\n",
				       (unsigned)inode->i_ino);
			break;
		}
	}
	/* This inode entry is in-memory only and thus we don't have to mark
	 * the inode dirty */
	UDF_I_LENEXTENTS(inode) = inode->i_size;
	brelse(epos.bh);
}

void udf_discard_prealloc(struct inode *inode)
{
	struct extent_position epos = { NULL, 0, {0, 0} };
	kernel_lb_addr eloc;
	uint32_t elen;
	uint64_t lbcount = 0;
	int8_t etype = -1, netype;
	int adsize;

	if (UDF_I_ALLOCTYPE(inode) == ICBTAG_FLAG_AD_IN_ICB ||
	    inode->i_size == UDF_I_LENEXTENTS(inode))
		return;

	if (UDF_I_ALLOCTYPE(inode) == ICBTAG_FLAG_AD_SHORT)
		adsize = sizeof(short_ad);
	else if (UDF_I_ALLOCTYPE(inode) == ICBTAG_FLAG_AD_LONG)
		adsize = sizeof(long_ad);
	else
		adsize = 0;

	epos.block = UDF_I_LOCATION(inode);

	/* Find the last extent in the file */
	while ((netype = udf_next_aext(inode, &epos, &eloc, &elen, 1)) != -1) {
		etype = netype;
		lbcount += elen;
	}
	if (etype == (EXT_NOT_RECORDED_ALLOCATED >> 30)) {
		epos.offset -= adsize;
		lbcount -= elen;
		extent_trunc(inode, &epos, eloc, etype, elen, 0);
		if (!epos.bh) {
			UDF_I_LENALLOC(inode) =
				epos.offset - udf_file_entry_alloc_offset(inode);
			mark_inode_dirty(inode);
		} else {
			struct allocExtDesc *aed =
				(struct allocExtDesc *)(epos.bh->b_data);
			aed->lengthAllocDescs =
				cpu_to_le32(epos.offset -
					    sizeof(struct allocExtDesc));
			if (!UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_STRICT) ||
			    UDF_SB_UDFREV(inode->i_sb) >= 0x0201)
				udf_update_tag(epos.bh->b_data, epos.offset);
			else
				udf_update_tag(epos.bh->b_data,
					       sizeof(struct allocExtDesc));
			mark_buffer_dirty_inode(epos.bh, inode);
		}
	}
	/* This inode entry is in-memory only and thus we don't have to mark
	 * the inode dirty */
	UDF_I_LENEXTENTS(inode) = lbcount;
	brelse(epos.bh);
}

void udf_truncate_extents(struct inode *inode)
{
	struct extent_position epos;
	kernel_lb_addr eloc, neloc = {};
	uint32_t elen, nelen = 0, indirect_ext_len = 0, lenalloc;
	int8_t etype;
	struct super_block *sb = inode->i_sb;
	sector_t first_block = inode->i_size >> sb->s_blocksize_bits, offset;
	loff_t byte_offset;
	int adsize;

	if (UDF_I_ALLOCTYPE(inode) == ICBTAG_FLAG_AD_SHORT)
		adsize = sizeof(short_ad);
	else if (UDF_I_ALLOCTYPE(inode) == ICBTAG_FLAG_AD_LONG)
		adsize = sizeof(long_ad);
	else
		BUG();

	etype = inode_bmap(inode, first_block, &epos, &eloc, &elen, &offset);
	byte_offset = (offset << sb->s_blocksize_bits) +
		(inode->i_size & (sb->s_blocksize - 1));
	if (etype != -1) {
		epos.offset -= adsize;
		extent_trunc(inode, &epos, eloc, etype, elen, byte_offset);
		epos.offset += adsize;
		if (byte_offset)
			lenalloc = epos.offset;
		else
			lenalloc = epos.offset - adsize;

		if (!epos.bh)
			lenalloc -= udf_file_entry_alloc_offset(inode);
		else
			lenalloc -= sizeof(struct allocExtDesc);

		while ((etype = udf_current_aext(inode, &epos, &eloc, &elen, 0)) != -1) {
			if (etype == (EXT_NEXT_EXTENT_ALLOCDECS >> 30)) {
				udf_write_aext(inode, &epos, neloc, nelen, 0);
				if (indirect_ext_len) {
					/* We managed to free all extents in the
					 * indirect extent - free it too */
					if (!epos.bh)
						BUG();
					udf_free_blocks(sb, inode, epos.block,
							0, indirect_ext_len);
				} else {
					if (!epos.bh) {
						UDF_I_LENALLOC(inode) = lenalloc;
						mark_inode_dirty(inode);
					} else {
						struct allocExtDesc *aed =
							(struct allocExtDesc *)(epos.bh->b_data);
						aed->lengthAllocDescs =
						    cpu_to_le32(lenalloc);
						if (!UDF_QUERY_FLAG(sb, UDF_FLAG_STRICT) ||
						    UDF_SB_UDFREV(sb) >= 0x0201)
							udf_update_tag(epos.bh->b_data,
								       lenalloc +
								       sizeof(struct allocExtDesc));
						else
							udf_update_tag(epos.bh->b_data,
								       sizeof(struct allocExtDesc));
						mark_buffer_dirty_inode(epos.bh, inode);
					}
				}
				brelse(epos.bh);
				epos.offset = sizeof(struct allocExtDesc);
				epos.block = eloc;
				epos.bh = udf_tread(sb, udf_get_lb_pblock(sb, eloc, 0));
				if (elen)
					indirect_ext_len = (elen + sb->s_blocksize -1) >>
						sb->s_blocksize_bits;
				else
					indirect_ext_len = 1;
			} else {
				extent_trunc(inode, &epos, eloc, etype, elen, 0);
				epos.offset += adsize;
			}
		}

		if (indirect_ext_len) {
			if (!epos.bh)
				BUG();
			udf_free_blocks(sb, inode, epos.block, 0,
					indirect_ext_len);
		} else {
			if (!epos.bh) {
				UDF_I_LENALLOC(inode) = lenalloc;
				mark_inode_dirty(inode);
			} else {
				struct allocExtDesc *aed =
				    (struct allocExtDesc *)(epos.bh->b_data);
				aed->lengthAllocDescs = cpu_to_le32(lenalloc);
				if (!UDF_QUERY_FLAG(sb, UDF_FLAG_STRICT) ||
				    UDF_SB_UDFREV(sb) >= 0x0201)
					udf_update_tag(epos.bh->b_data,
						       lenalloc + sizeof(struct allocExtDesc));
				else
					udf_update_tag(epos.bh->b_data,
						       sizeof(struct allocExtDesc));
				mark_buffer_dirty_inode(epos.bh, inode);
			}
		}
	} else if (inode->i_size) {
		if (byte_offset) {
			kernel_long_ad extent;

			/*
			 *  OK, there is not extent covering inode->i_size and
			 *  no extent above inode->i_size => truncate is
			 *  extending the file by 'offset' blocks.
			 */
			if ((!epos.bh &&
			     epos.offset == udf_file_entry_alloc_offset(inode)) ||
			    (epos.bh && epos.offset == sizeof(struct allocExtDesc))) {
				/* File has no extents at all or has empty last
				 * indirect extent! Create a fake extent... */
				extent.extLocation.logicalBlockNum = 0;
				extent.extLocation.partitionReferenceNum = 0;
				extent.extLength = EXT_NOT_RECORDED_NOT_ALLOCATED;
			} else {
				epos.offset -= adsize;
				etype = udf_next_aext(inode, &epos,
						      &extent.extLocation,
						      &extent.extLength, 0);
				extent.extLength |= etype << 30;
			}
			udf_extend_file(inode, &epos, &extent,
					offset + ((inode->i_size & (sb->s_blocksize - 1)) != 0));
		}
	}
	UDF_I_LENEXTENTS(inode) = inode->i_size;

	brelse(epos.bh);
}