attrib.c

来自「一个类似windows」· C语言 代码 · 共 1,722 行 · 第 1/4 页

	/* Space required: @dst size + @src size + one new hole. */
	dst = ntfs_rl_realloc(dst, dsize, dsize + ssize + 1);
	if (IS_ERR(dst))
		return dst;
	/*
	 * We are guaranteed to succeed from here so can start modifying the
	 * original run lists.
	 */

	/* Move the tail of @dst out of the way, then copy in @src. */
	ntfs_rl_mm(dst, loc + 1 + ssize, loc, dsize - loc);
	ntfs_rl_mc(dst, loc + 1, src, 0, ssize);

	/* Adjust the size of the holes either size of @src. */
	dst[loc].length         = dst[loc+1].vcn       - dst[loc].vcn;
	dst[loc+ssize+1].vcn    = dst[loc+ssize].vcn   + dst[loc+ssize].length;
	dst[loc+ssize+1].length = dst[loc+ssize+2].vcn - dst[loc+ssize+1].vcn;

	return dst;
}

/**
 * ntfs_merge_run_lists - merge two run_lists into one
 * @drl:	original run list to be worked on
 * @srl:	new run list to be merged into @drl
 *
 * First we sanity check the two run lists @srl and @drl to make sure that they
 * are sensible and can be merged. The run list @srl must be either after the
 * run list @drl or completely within a hole (or unmapped region) in @drl.
 *
 * It is up to the caller to serialize access to the run lists @drl and @srl.
 *
 * Merging of run lists is necessary in two cases:
 *   1. When attribute lists are used and a further extent is being mapped.
 *   2. When new clusters are allocated to fill a hole or extend a file.
 *
 * There are four possible ways @srl can be merged. It can:
 *	- be inserted at the beginning of a hole,
 *	- split the hole in two and be inserted between the two fragments,
 *	- be appended at the end of a hole, or it can
 *	- replace the whole hole.
 * It can also be appended to the end of the run list, which is just a variant
 * of the insert case.
 *
 * On success, return a pointer to the new, combined, run list. Note, both
 * run lists @drl and @srl are deallocated before returning so you cannot use
 * the pointers for anything any more. (Strictly speaking the returned run list
 * may be the same as @dst but this is irrelevant.)
 *
 * On error, return -errno. Both run lists are left unmodified. The following
 * error codes are defined:
 *	-ENOMEM	- Not enough memory to allocate run list array.
 *	-EINVAL	- Invalid parameters were passed in.
 *	-ERANGE	- The run lists overlap and cannot be merged.
 */
run_list_element *ntfs_merge_run_lists(run_list_element *drl,
		run_list_element *srl)
{
	int di, si;		/* Current index into @[ds]rl. */
	int sstart;		/* First index with lcn > LCN_RL_NOT_MAPPED. */
	int dins;		/* Index into @drl at which to insert @srl. */
	int dend, send;		/* Last index into @[ds]rl. */
	int dfinal, sfinal;	/* The last index into @[ds]rl with
				   lcn >= LCN_HOLE. */
	int marker = 0;
	VCN marker_vcn = 0;

#ifdef DEBUG
	ntfs_debug("dst:");
	ntfs_debug_dump_runlist(drl);
	ntfs_debug("src:");
	ntfs_debug_dump_runlist(srl);
#endif

 	/* Check for silly calling... */
	if (unlikely(!srl))
		return drl;
	if (unlikely(IS_ERR(srl) || IS_ERR(drl)))
		return ERR_PTR(-EINVAL);

	/* Check for the case where the first mapping is being done now. */
	if (unlikely(!drl)) {
		drl = srl;
		/* Complete the source run list if necessary. */
		if (unlikely(drl[0].vcn)) {
			/* Scan to the end of the source run list. */
			for (dend = 0; likely(drl[dend].length); dend++)
				;
			drl = ntfs_rl_realloc(drl, dend, dend + 1);
			if (IS_ERR(drl))
				return drl;
			/* Insert start element at the front of the run list. */
			ntfs_rl_mm(drl, 1, 0, dend);
			drl[0].vcn = 0;
			drl[0].lcn = LCN_RL_NOT_MAPPED;
			drl[0].length = drl[1].vcn;
		}
		goto finished;
	}

	si = di = 0;

	/* Skip any unmapped start element(s) in the source run_list. */
	while (srl[si].length && srl[si].lcn < (LCN)LCN_HOLE)
		si++;

	/* Can't have an entirely unmapped source run list. */
	BUG_ON(!srl[si].length);

	/* Record the starting points. */
	sstart = si;

	/*
	 * Skip forward in @drl until we reach the position where @srl needs to
	 * be inserted. If we reach the end of @drl, @srl just needs to be
	 * appended to @drl.
	 */
	for (; drl[di].length; di++) {
		if (drl[di].vcn + drl[di].length > srl[sstart].vcn)
			break;
	}
	dins = di;

	/* Sanity check for illegal overlaps. */
	if ((drl[di].vcn == srl[si].vcn) && (drl[di].lcn >= 0) &&
			(srl[si].lcn >= 0)) {
		ntfs_error(NULL, "Run lists overlap. Cannot merge!");
		return ERR_PTR(-ERANGE);
	}

	/* Scan to the end of both run lists in order to know their sizes. */
	for (send = si; srl[send].length; send++)
		;
	for (dend = di; drl[dend].length; dend++)
		;

	if (srl[send].lcn == (LCN)LCN_ENOENT)
		marker_vcn = srl[marker = send].vcn;

	/* Scan to the last element with lcn >= LCN_HOLE. */
	for (sfinal = send; sfinal >= 0 && srl[sfinal].lcn < LCN_HOLE; sfinal--)
		;
	for (dfinal = dend; dfinal >= 0 && drl[dfinal].lcn < LCN_HOLE; dfinal--)
		;

	{
	BOOL start;
	BOOL finish;
	int ds = dend + 1;		/* Number of elements in drl & srl */
	int ss = sfinal - sstart + 1;

	start  = ((drl[dins].lcn <  LCN_RL_NOT_MAPPED) ||    /* End of file   */
		  (drl[dins].vcn == srl[sstart].vcn));	     /* Start of hole */
	finish = ((drl[dins].lcn >= LCN_RL_NOT_MAPPED) &&    /* End of file   */
		 ((drl[dins].vcn + drl[dins].length) <=      /* End of hole   */
		  (srl[send - 1].vcn + srl[send - 1].length)));

	/* Or we'll lose an end marker */
	if (start && finish && (drl[dins].length == 0))
		ss++;
	if (marker && (drl[dins].vcn + drl[dins].length > srl[send - 1].vcn))
		finish = FALSE;
#if 0
	ntfs_debug("dfinal = %i, dend = %i", dfinal, dend);
	ntfs_debug("sstart = %i, sfinal = %i, send = %i", sstart, sfinal, send);
	ntfs_debug("start = %i, finish = %i", start, finish);
	ntfs_debug("ds = %i, ss = %i, dins = %i", ds, ss, dins);
#endif
	if (start) {
		if (finish)
			drl = ntfs_rl_replace(drl, ds, srl + sstart, ss, dins);
		else
			drl = ntfs_rl_insert(drl, ds, srl + sstart, ss, dins);
	} else {
		if (finish)
			drl = ntfs_rl_append(drl, ds, srl + sstart, ss, dins);
		else
			drl = ntfs_rl_split(drl, ds, srl + sstart, ss, dins);
	}
	if (IS_ERR(drl)) {
		ntfs_error(NULL, "Merge failed.");
		return drl;
	}
	ntfs_free(srl);
	if (marker) {
		ntfs_debug("Triggering marker code.");
		for (ds = dend; drl[ds].length; ds++)
			;
		/* We only need to care if @srl ended after @drl. */
		if (drl[ds].vcn <= marker_vcn) {
			int slots = 0;

			if (drl[ds].vcn == marker_vcn) {
				ntfs_debug("Old marker = 0x%Lx, replacing with "
						"LCN_ENOENT.\n",
						(unsigned long long)
						drl[ds].lcn);
				drl[ds].lcn = (LCN)LCN_ENOENT;
				goto finished;
			}
			/*
			 * We need to create an unmapped run list element in
			 * @drl or extend an existing one before adding the
			 * ENOENT terminator.
			 */
			if (drl[ds].lcn == (LCN)LCN_ENOENT) {
				ds--;
				slots = 1;
			}
			if (drl[ds].lcn != (LCN)LCN_RL_NOT_MAPPED) {
				/* Add an unmapped run list element. */
				if (!slots) {
					/* FIXME/TODO: We need to have the
					 * extra memory already! (AIA) */
					drl = ntfs_rl_realloc(drl, ds, ds + 2);
					if (!drl)
						goto critical_error;
					slots = 2;
				}
				ds++;
				/* Need to set vcn if it isn't set already. */
				if (slots != 1)
					drl[ds].vcn = drl[ds - 1].vcn +
							drl[ds - 1].length;
				drl[ds].lcn = (LCN)LCN_RL_NOT_MAPPED;
				/* We now used up a slot. */
				slots--;
			}
			drl[ds].length = marker_vcn - drl[ds].vcn;
			/* Finally add the ENOENT terminator. */
			ds++;
			if (!slots) {
				/* FIXME/TODO: We need to have the extra
				 * memory already! (AIA) */
				drl = ntfs_rl_realloc(drl, ds, ds + 1);
				if (!drl)
					goto critical_error;
			}
			drl[ds].vcn = marker_vcn;
			drl[ds].lcn = (LCN)LCN_ENOENT;
			drl[ds].length = (s64)0;
		}
	}
	}

finished:
	/* The merge was completed successfully. */
	ntfs_debug("Merged run list:");
	ntfs_debug_dump_runlist(drl);
	return drl;

critical_error:
	/* Critical error! We cannot afford to fail here. */
	ntfs_error(NULL, "Critical error! Not enough memory.");
	panic("NTFS: Cannot continue.");
}

/**
 * decompress_mapping_pairs - convert mapping pairs array to run list
 * @vol:	ntfs volume on which the attribute resides
 * @attr:	attribute record whose mapping pairs array to decompress
 * @old_rl:	optional run list in which to insert @attr's run list
 *
 * It is up to the caller to serialize access to the run list @old_rl.
 *
 * Decompress the attribute @attr's mapping pairs array into a run list. On
 * success, return the decompressed run list.
 *
 * If @old_rl is not NULL, decompressed run list is inserted into the
 * appropriate place in @old_rl and the resultant, combined run list is
 * returned. The original @old_rl is deallocated.
 *
 * On error, return -errno. @old_rl is left unmodified in that case.
 *
 * The following error codes are defined:
 *	-ENOMEM	- Not enough memory to allocate run list array.
 * 	-EIO	- Corrupt run list.
 * 	-EINVAL	- Invalid parameters were passed in.
 * 	-ERANGE	- The two run lists overlap.
 *
 * FIXME: For now we take the conceptionally simplest approach of creating the
 * new run list disregarding the already existing one and then splicing the
 * two into one, if that is possible (we check for overlap and discard the new
 * run list if overlap present before returning ERR_PTR(-ERANGE)).
 */
run_list_element *decompress_mapping_pairs(const ntfs_volume *vol,
		const ATTR_RECORD *attr, run_list_element *old_rl)
{
	VCN vcn;		/* Current vcn. */
	LCN lcn; 		/* Current lcn. */
	s64 deltaxcn;		/* Change in [vl]cn. */
	run_list_element *rl;	/* The output run list. */
	u8 *buf;		/* Current position in mapping pairs array. */
	u8 *attr_end;		/* End of attribute. */
	int rlsize;		/* Size of run list buffer. */
	u16 rlpos;		/* Current run list position in units of
				   run_list_elements. */
	u8 b;			/* Current byte offset in buf. */

#ifdef DEBUG
	/* Make sure attr exists and is non-resident. */
	if (!attr || !attr->non_resident || sle64_to_cpu(
			attr->data.non_resident.lowest_vcn) < (VCN)0) {
		ntfs_error(vol->sb, "Invalid arguments.");
		return ERR_PTR(-EINVAL);
	}
#endif
	/* Start at vcn = lowest_vcn and lcn 0. */
	vcn = sle64_to_cpu(attr->data.non_resident.lowest_vcn);
	lcn = 0;
	/* Get start of the mapping pairs array. */
	buf = (u8*)attr + le16_to_cpu(
			attr->data.non_resident.mapping_pairs_offset);
	attr_end = (u8*)attr + le32_to_cpu(attr->length);
	if (unlikely(buf < (u8*)attr || buf > attr_end)) {
		ntfs_error(vol->sb, "Corrupt attribute.");
		return ERR_PTR(-EIO);
	}
	/* Current position in run list array. */
	rlpos = 0;
	/* Allocate first page and set current run list size to one page. */
	rl = ntfs_malloc_nofs(rlsize = PAGE_SIZE);
	if (unlikely(!rl))
		return ERR_PTR(-ENOMEM);
	/* Insert unmapped starting element if necessary. */
	if (vcn) {
		rl->vcn = (VCN)0;
		rl->lcn = (LCN)LCN_RL_NOT_MAPPED;
		rl->length = vcn;
		rlpos++;
	}
	while (buf < attr_end && *buf) {
		/*
		 * Allocate more memory if needed, including space for the
		 * not-mapped and terminator elements. ntfs_malloc_nofs()
		 * operates on whole pages only.
		 */
		if (((rlpos + 3) * sizeof(*old_rl)) > rlsize) {
			run_list_element *rl2;

			rl2 = ntfs_malloc_nofs(rlsize + (int)PAGE_SIZE);
			if (unlikely(!rl2)) {
				ntfs_free(rl);
				return ERR_PTR(-ENOMEM);
			}
			memcpy(rl2, rl, rlsize);
			ntfs_free(rl);
			rl = rl2;
			rlsize += PAGE_SIZE;
		}
		/* Enter the current vcn into the current run_list element. */
		rl[rlpos].vcn = vcn;
		/*
		 * Get the change in vcn, i.e. the run length in clusters.
		 * Doing it this way ensures that we signextend negative values.
		 * A negative run length doesn't make any sense, but hey, I
		 * didn't make up the NTFS specs and Windows NT4 treats the run
		 * length as a signed value so that's how it is...
		 */
		b = *buf & 0xf;
		if (b) {
			if (unlikely(buf + b > attr_end))
				goto io_error;
			for (deltaxcn = (s8)buf[b--]; b; b--)
				deltaxcn = (deltaxcn << 8) + buf[b];
		} else { /* The length entry is compulsory. */
			ntfs_error(vol->sb, "Missing length entry in mapping "
					"pairs array.");
			deltaxcn = (s64)-1;
		}
		/*
		 * Assume a negative length to indicate data corruption and
		 * hence clean-up and return NULL.
		 */
		if (unlikely(deltaxcn < 0)) {
			ntfs_error(vol->sb, "Invalid length in mapping pairs "
					"array.");
			goto err_out;
		}
		/*
		 * Enter the current run length into the current run list
		 * element.
		 */
		rl[rlpos].length = deltaxcn;
		/* Increment the current vcn by the current run length. */
		vcn += deltaxcn;
		/*
		 * There might be no lcn change at all, as is the case for
		 * sparse clusters on NTFS 3.0+, in which case we set the lcn
		 * to LCN_HOLE.
		 */
		if (!(*buf & 0xf0))
			rl[rlpos].lcn = (LCN)LCN_HOLE;
		else {
			/* Get the lcn change which really can be negative. */
			u8 b2 = *buf & 0xf;
			b = b2 + ((*buf >> 4) & 0xf);
			if (buf + b > attr_end)
				goto io_error;
			for (deltaxcn = (s8)buf[b--]; b > b2; b--)
				deltaxcn = (deltaxcn << 8) + buf[b];
			/* Change the current lcn to its new value. */
			lcn += deltaxcn;
#ifdef DEBUG
			/*
			 * On NTFS 1.2-, apparently can have lcn == -1 to
			 * indicate a hole. But we haven't verified ourselves
			 * whether it is really the lcn or the deltaxcn that is
			 * -1. So if either is found give us a message so we
			 * can investigate it further!
			 */
			if (vol->major_ver < 3) {
				if (unlikely(deltaxcn == (LCN)-1))
					ntfs_error(vol->sb, "lcn delta == -1");
				if (unlikely(lcn == (LCN)-1))
					ntfs_error(vol->sb, "lcn == -1");
			}
#endif
			/* Check lcn is not below -1. */
			if (unlikely(lcn < (LCN)-1)) {
				ntfs_error(vol->sb, "Invalid LCN < -1 in "
						"mapping pairs array.");
				goto err_out;
			}
			/* Enter the current lcn into the run_list element. */
			rl[rlpos].lcn = lcn;
		}
		/* Get to the next run_list element. */
		rlpos++;
		/* Increment the buffer position to the next mapping pair. */