attrib.c

来自「Linux Kernel 2.6.9 for OMAP1710」· C语言 代码 · 共 1,911 行 · 第 1/5 页

		 * not-mapped and terminator elements. ntfs_malloc_nofs()
		 * operates on whole pages only.
		 */
		if (((rlpos + 3) * sizeof(*old_rl)) > rlsize) {
			runlist_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 runlist 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 runlist
		 * 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 runlist element. */
			rl[rlpos].lcn = lcn;
		}
		/* Get to the next runlist element. */
		rlpos++;
		/* Increment the buffer position to the next mapping pair. */
		buf += (*buf & 0xf) + ((*buf >> 4) & 0xf) + 1;
	}
	if (unlikely(buf >= attr_end))
		goto io_error;
	/*
	 * If there is a highest_vcn specified, it must be equal to the final
	 * vcn in the runlist - 1, or something has gone badly wrong.
	 */
	deltaxcn = sle64_to_cpu(attr->data.non_resident.highest_vcn);
	if (unlikely(deltaxcn && vcn - 1 != deltaxcn)) {
mpa_err:
		ntfs_error(vol->sb, "Corrupt mapping pairs array in "
				"non-resident attribute.");
		goto err_out;
	}
	/* Setup not mapped runlist element if this is the base extent. */
	if (!attr->data.non_resident.lowest_vcn) {
		VCN max_cluster;

		max_cluster = (sle64_to_cpu(
				attr->data.non_resident.allocated_size) +
				vol->cluster_size - 1) >>
				vol->cluster_size_bits;
		/*
		 * If there is a difference between the highest_vcn and the
		 * highest cluster, the runlist is either corrupt or, more
		 * likely, there are more extents following this one.
		 */
		if (deltaxcn < --max_cluster) {
			ntfs_debug("More extents to follow; deltaxcn = 0x%llx, "
					"max_cluster = 0x%llx",
					(unsigned long long)deltaxcn,
					(unsigned long long)max_cluster);
			rl[rlpos].vcn = vcn;
			vcn += rl[rlpos].length = max_cluster - deltaxcn;
			rl[rlpos].lcn = (LCN)LCN_RL_NOT_MAPPED;
			rlpos++;
		} else if (unlikely(deltaxcn > max_cluster)) {
			ntfs_error(vol->sb, "Corrupt attribute. deltaxcn = "
					"0x%llx, max_cluster = 0x%llx",
					(unsigned long long)deltaxcn,
					(unsigned long long)max_cluster);
			goto mpa_err;
		}
		rl[rlpos].lcn = (LCN)LCN_ENOENT;
	} else /* Not the base extent. There may be more extents to follow. */
		rl[rlpos].lcn = (LCN)LCN_RL_NOT_MAPPED;

	/* Setup terminating runlist element. */
	rl[rlpos].vcn = vcn;
	rl[rlpos].length = (s64)0;
	/* If no existing runlist was specified, we are done. */
	if (!old_rl) {
		ntfs_debug("Mapping pairs array successfully decompressed:");
		ntfs_debug_dump_runlist(rl);
		return rl;
	}
	/* Now combine the new and old runlists checking for overlaps. */
	old_rl = ntfs_merge_runlists(old_rl, rl);
	if (likely(!IS_ERR(old_rl)))
		return old_rl;
	ntfs_free(rl);
	ntfs_error(vol->sb, "Failed to merge runlists.");
	return old_rl;
io_error:
	ntfs_error(vol->sb, "Corrupt attribute.");
err_out:
	ntfs_free(rl);
	return ERR_PTR(-EIO);
}

/**
 * ntfs_map_runlist - map (a part of) a runlist of an ntfs inode
 * @ni:		ntfs inode for which to map (part of) a runlist
 * @vcn:	map runlist part containing this vcn
 *
 * Map the part of a runlist containing the @vcn of the ntfs inode @ni.
 *
 * Return 0 on success and -errno on error.
 *
 * Locking: - The runlist must be unlocked on entry and is unlocked on return.
 *	    - This function takes the lock for writing and modifies the runlist.
 */
int ntfs_map_runlist(ntfs_inode *ni, VCN vcn)
{
	ntfs_inode *base_ni;
	ntfs_attr_search_ctx *ctx;
	MFT_RECORD *mrec;
	int err = 0;

	ntfs_debug("Mapping runlist part containing vcn 0x%llx.",
			(unsigned long long)vcn);

	if (!NInoAttr(ni))
		base_ni = ni;
	else
		base_ni = ni->ext.base_ntfs_ino;

	mrec = map_mft_record(base_ni);
	if (IS_ERR(mrec))
		return PTR_ERR(mrec);
	ctx = ntfs_attr_get_search_ctx(base_ni, mrec);
	if (unlikely(!ctx)) {
		err = -ENOMEM;
		goto err_out;
	}
	err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
			CASE_SENSITIVE, vcn, NULL, 0, ctx);
	if (unlikely(err))
		goto put_err_out;

	down_write(&ni->runlist.lock);
	/* Make sure someone else didn't do the work while we were sleeping. */
	if (likely(ntfs_vcn_to_lcn(ni->runlist.rl, vcn) <= LCN_RL_NOT_MAPPED)) {
		runlist_element *rl;

		rl = decompress_mapping_pairs(ni->vol, ctx->attr,
				ni->runlist.rl);
		if (IS_ERR(rl))
			err = PTR_ERR(rl);
		else
			ni->runlist.rl = rl;
	}
	up_write(&ni->runlist.lock);

put_err_out:
	ntfs_attr_put_search_ctx(ctx);
err_out:
	unmap_mft_record(base_ni);
	return err;
}

/**
 * ntfs_vcn_to_lcn - convert a vcn into a lcn given a runlist
 * @rl:		runlist to use for conversion
 * @vcn:	vcn to convert
 *
 * Convert the virtual cluster number @vcn of an attribute into a logical
 * cluster number (lcn) of a device using the runlist @rl to map vcns to their
 * corresponding lcns.
 *
 * It is up to the caller to serialize access to the runlist @rl.
 *
 * Since lcns must be >= 0, we use negative return values with special meaning:
 *
 * Return value			Meaning / Description
 * ==================================================
 *  -1 = LCN_HOLE		Hole / not allocated on disk.
 *  -2 = LCN_RL_NOT_MAPPED	This is part of the runlist which has not been
 *				inserted into the runlist yet.
 *  -3 = LCN_ENOENT		There is no such vcn in the attribute.
 *
 * Locking: - The caller must have locked the runlist (for reading or writing).
 *	    - This function does not touch the lock.
 */
LCN ntfs_vcn_to_lcn(const runlist_element *rl, const VCN vcn)
{
	int i;

	BUG_ON(vcn < 0);
	/*
	 * If rl is NULL, assume that we have found an unmapped runlist. The
	 * caller can then attempt to map it and fail appropriately if
	 * necessary.
	 */
	if (unlikely(!rl))
		return (LCN)LCN_RL_NOT_MAPPED;

	/* Catch out of lower bounds vcn. */
	if (unlikely(vcn < rl[0].vcn))
		return (LCN)LCN_ENOENT;

	for (i = 0; likely(rl[i].length); i++) {
		if (unlikely(vcn < rl[i+1].vcn)) {
			if (likely(rl[i].lcn >= (LCN)0))
				return rl[i].lcn + (vcn - rl[i].vcn);
			return rl[i].lcn;
		}
	}
	/*
	 * The terminator element is setup to the correct value, i.e. one of
	 * LCN_HOLE, LCN_RL_NOT_MAPPED, or LCN_ENOENT.
	 */
	if (likely(rl[i].lcn < (LCN)0))
		return rl[i].lcn;
	/* Just in case... We could replace this with BUG() some day. */
	return (LCN)LCN_ENOENT;
}

/**
 * ntfs_find_vcn - find a vcn in the runlist described by an ntfs inode
 * @ni:		ntfs inode describing the runlist to search
 * @vcn:	vcn to find
 * @need_write:	if false, lock for reading and if true, lock for writing
 *
 * Find the virtual cluster number @vcn in the runlist described by the ntfs
 * inode @ni and return the address of the runlist element containing the @vcn.
 * The runlist is left locked and the caller has to unlock it.  If @need_write
 * is true, the runlist is locked for writing and if @need_write is false, the
 * runlist is locked for reading.  In the error case, the runlist is not left
 * locked.
 *
 * Note you need to distinguish between the lcn of the returned runlist element
 * being >= 0 and LCN_HOLE.  In the later case you have to return zeroes on
 * read and allocate clusters on write.
 *
 * Return the runlist element containing the @vcn on success and
 * ERR_PTR(-errno) on error.  You need to test the return value with IS_ERR()
 * to decide if the return is success or failure and PTR_ERR() to get to the
 * error code if IS_ERR() is true.
 *
 * The possible error return codes are:
 *	-ENOENT - No such vcn in the runlist, i.e. @vcn is out of bounds.
 *	-ENOMEM - Not enough memory to map runlist.
 *	-EIO	- Critical error (runlist/file is corrupt, i/o error, etc).
 *
 * Locking: - The runlist must be unlocked on entry.
 *	    - On failing return, the runlist is unlocked.
 *	    - On successful return, the runlist is locked.  If @need_write us
 *	      true, it is locked for writing.  Otherwise is is locked for
 *	      reading.
 */
runlist_element *ntfs_find_vcn(ntfs_inode *ni, const VCN vcn,
		const BOOL need_write)
{
	runlist_element *rl;
	int err = 0;
	BOOL is_retry = FALSE;

	ntfs_debug("Entering for i_ino 0x%lx, vcn 0x%llx, lock for %sing.",
			ni->mft_no, (unsigned long long)vcn,
			!need_write ? "read" : "writ");
	BUG_ON(!ni);
	BUG_ON(!NInoNonResident(ni));
	BUG_ON(vcn < 0);
lock_retry_remap:
	if (!need_write)
		down_read(&ni->runlist.lock);
	else
		down_write(&ni->runlist.lock);
	rl = ni->runlist.rl;
	if (likely(rl && vcn >= rl[0].vcn)) {
		while (likely(rl->length)) {
			if (likely(vcn < rl[1].vcn)) {
				if (likely(rl->lcn >= (LCN)LCN_HOLE)) {
					ntfs_debug("Done.");
					return rl;
				}
				break;
			}
			rl++;
		}
		if (likely(rl->lcn != (LCN)LCN_RL_NOT_MAPPED)) {
			if (likely(rl->lcn == (LCN)LCN_ENOENT))
				err = -ENOENT;
			else
				err = -EIO;
		}
	}
	if (!need_write)
		up_read(&ni->runlist.lock);
	else
		up_write(&ni->runlist.lock);
	if (!err && !is_retry) {
		/*
		 * The @vcn is in an unmapped region, map the runlist and
		 * retry.
		 */
		err = ntfs_map_runlist(ni, vcn);
		if (likely(!err)) {
			is_retry = TRUE;
			goto lock_retry_remap;
		}
		/*
		 * -EINVAL and -ENOENT coming from a failed mapping attempt are
		 * equivalent to i/o errors for us as they should not happen in
		 * our code paths.
		 */
		if (err == -EINVAL || err == -ENOENT)
			err = -EIO;
	} else if (!err)
		err = -EIO;
	ntfs_error(ni->vol->sb, "Failed with error code %i.", err);
	return ERR_PTR(err);
}

/**