[PATCH 2/37] Re: [2.6-BK-URL] NTFS: 2.1.21 - Big update with race/bugfixes

[Anton Altaparmakov]

This is patch 2/37 in the series.  It contains the following ChangeSet:

<aia21@xxxxxxxxxx> (04/09/30 1.2000.1.1)
   NTFS: Splitt runlist related functions off from attrib.[hc] to runlist.[hc].
   
   Signed-off-by: Anton Altaparmakov <aia21@xxxxxxxxxx>

Best regards,

	Anton
-- 
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK
Linux NTFS maintainer / IRC: #ntfs on irc.freenode.net
WWW: http://linux-ntfs.sf.net/, http://www-stu.christs.cam.ac.uk/~aia21/

===================================================================

diff -Nru a/fs/ntfs/ChangeLog b/fs/ntfs/ChangeLog
--- a/fs/ntfs/ChangeLog	2004-10-19 10:13:11 +01:00
+++ b/fs/ntfs/ChangeLog	2004-10-19 10:13:11 +01:00
@@ -25,6 +25,7 @@
 
 	- Implement extent mft record deallocation
 	  fs/ntfs/mft.c::ntfs_extent_mft_record_free().
+	- Splitt runlist related functions off from attrib.[hc] to runlist.[hc].
 
 2.1.19 - Many cleanups, improvements, and a minor bug fix.
 
diff -Nru a/fs/ntfs/Makefile b/fs/ntfs/Makefile
--- a/fs/ntfs/Makefile	2004-10-19 10:13:11 +01:00
+++ b/fs/ntfs/Makefile	2004-10-19 10:13:11 +01:00
@@ -3,8 +3,8 @@
 obj-$(CONFIG_NTFS_FS) += ntfs.o
 
 ntfs-objs := aops.o attrib.o collate.o compress.o debug.o dir.o file.o \
-	     index.o inode.o mft.o mst.o namei.o super.o sysctl.o unistr.o \
-	     upcase.o
+	     index.o inode.o mft.o mst.o namei.o runlist.o super.o sysctl.o \
+	     unistr.o upcase.o
 
 EXTRA_CFLAGS = -DNTFS_VERSION=\"2.1.20-WIP\"
 
diff -Nru a/fs/ntfs/attrib.c b/fs/ntfs/attrib.c
--- a/fs/ntfs/attrib.c	2004-10-19 10:13:11 +01:00
+++ b/fs/ntfs/attrib.c	2004-10-19 10:13:11 +01:00
@@ -1,5 +1,5 @@
 /**
- * attrib.c - NTFS attribute operations. Part of the Linux-NTFS project.
+ * attrib.c - NTFS attribute operations.  Part of the Linux-NTFS project.
  *
  * Copyright (c) 2001-2004 Anton Altaparmakov
  * Copyright (c) 2002 Richard Russon
@@ -22,914 +22,7 @@
 
 #include <linux/buffer_head.h>
 #include "ntfs.h"
-#include "dir.h"
-
-/* Temporary helper functions -- might become macros */
-
-/**
- * ntfs_rl_mm - runlist memmove
- *
- * It is up to the caller to serialize access to the runlist @base.
- */
-static inline void ntfs_rl_mm(runlist_element *base, int dst, int src,
-		int size)
-{
-	if (likely((dst != src) && (size > 0)))
-		memmove(base + dst, base + src, size * sizeof (*base));
-}
-
-/**
- * ntfs_rl_mc - runlist memory copy
- *
- * It is up to the caller to serialize access to the runlists @dstbase and
- * @srcbase.
- */
-static inline void ntfs_rl_mc(runlist_element *dstbase, int dst,
-		runlist_element *srcbase, int src, int size)
-{
-	if (likely(size > 0))
-		memcpy(dstbase + dst, srcbase + src, size * sizeof(*dstbase));
-}
-
-/**
- * ntfs_rl_realloc - Reallocate memory for runlists
- * @rl:		original runlist
- * @old_size:	number of runlist elements in the original runlist @rl
- * @new_size:	number of runlist elements we need space for
- *
- * As the runlists grow, more memory will be required.  To prevent the
- * kernel having to allocate and reallocate large numbers of small bits of
- * memory, this function returns and entire page of memory.
- *
- * It is up to the caller to serialize access to the runlist @rl.
- *
- * N.B.  If the new allocation doesn't require a different number of pages in
- *       memory, the function will return the original pointer.
- *
- * On success, return a pointer to the newly allocated, or recycled, memory.
- * On error, return -errno. The following error codes are defined:
- *	-ENOMEM	- Not enough memory to allocate runlist array.
- *	-EINVAL	- Invalid parameters were passed in.
- */
-static inline runlist_element *ntfs_rl_realloc(runlist_element *rl,
-		int old_size, int new_size)
-{
-	runlist_element *new_rl;
-
-	old_size = PAGE_ALIGN(old_size * sizeof(*rl));
-	new_size = PAGE_ALIGN(new_size * sizeof(*rl));
-	if (old_size == new_size)
-		return rl;
-
-	new_rl = ntfs_malloc_nofs(new_size);
-	if (unlikely(!new_rl))
-		return ERR_PTR(-ENOMEM);
-
-	if (likely(rl != NULL)) {
-		if (unlikely(old_size > new_size))
-			old_size = new_size;
-		memcpy(new_rl, rl, old_size);
-		ntfs_free(rl);
-	}
-	return new_rl;
-}
-
-/**
- * ntfs_are_rl_mergeable - test if two runlists can be joined together
- * @dst:	original runlist
- * @src:	new runlist to test for mergeability with @dst
- *
- * Test if two runlists can be joined together. For this, their VCNs and LCNs
- * must be adjacent.
- *
- * It is up to the caller to serialize access to the runlists @dst and @src.
- *
- * Return: TRUE   Success, the runlists can be merged.
- *	   FALSE  Failure, the runlists cannot be merged.
- */
-static inline BOOL ntfs_are_rl_mergeable(runlist_element *dst,
-		runlist_element *src)
-{
-	BUG_ON(!dst);
-	BUG_ON(!src);
-
-	if ((dst->lcn < 0) || (src->lcn < 0))     /* Are we merging holes? */
-		return FALSE;
-	if ((dst->lcn + dst->length) != src->lcn) /* Are the runs contiguous? */
-		return FALSE;
-	if ((dst->vcn + dst->length) != src->vcn) /* Are the runs misaligned? */
-		return FALSE;
-
-	return TRUE;
-}
-
-/**
- * __ntfs_rl_merge - merge two runlists without testing if they can be merged
- * @dst:	original, destination runlist
- * @src:	new runlist to merge with @dst
- *
- * Merge the two runlists, writing into the destination runlist @dst. The
- * caller must make sure the runlists can be merged or this will corrupt the
- * destination runlist.
- *
- * It is up to the caller to serialize access to the runlists @dst and @src.
- */
-static inline void __ntfs_rl_merge(runlist_element *dst, runlist_element *src)
-{
-	dst->length += src->length;
-}
-
-/**
- * ntfs_rl_merge - test if two runlists can be joined together and merge them
- * @dst:	original, destination runlist
- * @src:	new runlist to merge with @dst
- *
- * Test if two runlists can be joined together. For this, their VCNs and LCNs
- * must be adjacent. If they can be merged, perform the merge, writing into
- * the destination runlist @dst.
- *
- * It is up to the caller to serialize access to the runlists @dst and @src.
- *
- * Return: TRUE   Success, the runlists have been merged.
- *	   FALSE  Failure, the runlists cannot be merged and have not been
- *		  modified.
- */
-static inline BOOL ntfs_rl_merge(runlist_element *dst, runlist_element *src)
-{
-	BOOL merge = ntfs_are_rl_mergeable(dst, src);
-
-	if (merge)
-		__ntfs_rl_merge(dst, src);
-	return merge;
-}
-
-/**
- * ntfs_rl_append - append a runlist after a given element
- * @dst:	original runlist to be worked on
- * @dsize:	number of elements in @dst (including end marker)
- * @src:	runlist to be inserted into @dst
- * @ssize:	number of elements in @src (excluding end marker)
- * @loc:	append the new runlist @src after this element in @dst
- *
- * Append the runlist @src after element @loc in @dst.  Merge the right end of
- * the new runlist, if necessary. Adjust the size of the hole before the
- * appended runlist.
- *
- * It is up to the caller to serialize access to the runlists @dst and @src.
- *
- * On success, return a pointer to the new, combined, runlist. Note, both
- * runlists @dst and @src are deallocated before returning so you cannot use
- * the pointers for anything any more. (Strictly speaking the returned runlist
- * may be the same as @dst but this is irrelevant.)
- *
- * On error, return -errno. Both runlists are left unmodified. The following
- * error codes are defined:
- *	-ENOMEM	- Not enough memory to allocate runlist array.
- *	-EINVAL	- Invalid parameters were passed in.
- */
-static inline runlist_element *ntfs_rl_append(runlist_element *dst,
-		int dsize, runlist_element *src, int ssize, int loc)
-{
-	BOOL right;
-	int magic;
-
-	BUG_ON(!dst);
-	BUG_ON(!src);
-
-	/* First, check if the right hand end needs merging. */
-	right = ntfs_are_rl_mergeable(src + ssize - 1, dst + loc + 1);
-
-	/* Space required: @dst size + @src size, less one if we merged. */
-	dst = ntfs_rl_realloc(dst, dsize, dsize + ssize - right);
-	if (IS_ERR(dst))
-		return dst;
-	/*
-	 * We are guaranteed to succeed from here so can start modifying the
-	 * original runlists.
-	 */
-
-	/* First, merge the right hand end, if necessary. */
-	if (right)
-		__ntfs_rl_merge(src + ssize - 1, dst + loc + 1);
-
-	magic = loc + ssize;
-
-	/* Move the tail of @dst out of the way, then copy in @src. */
-	ntfs_rl_mm(dst, magic + 1, loc + 1 + right, dsize - loc - 1 - right);
-	ntfs_rl_mc(dst, loc + 1, src, 0, ssize);
-
-	/* Adjust the size of the preceding hole. */
-	dst[loc].length = dst[loc + 1].vcn - dst[loc].vcn;
-
-	/* We may have changed the length of the file, so fix the end marker */
-	if (dst[magic + 1].lcn == LCN_ENOENT)
-		dst[magic + 1].vcn = dst[magic].vcn + dst[magic].length;
-
-	return dst;
-}
-
-/**
- * ntfs_rl_insert - insert a runlist into another
- * @dst:	original runlist to be worked on
- * @dsize:	number of elements in @dst (including end marker)
- * @src:	new runlist to be inserted
- * @ssize:	number of elements in @src (excluding end marker)
- * @loc:	insert the new runlist @src before this element in @dst
- *
- * Insert the runlist @src before element @loc in the runlist @dst. Merge the
- * left end of the new runlist, if necessary. Adjust the size of the hole
- * after the inserted runlist.
- *
- * It is up to the caller to serialize access to the runlists @dst and @src.
- *
- * On success, return a pointer to the new, combined, runlist. Note, both
- * runlists @dst and @src are deallocated before returning so you cannot use
- * the pointers for anything any more. (Strictly speaking the returned runlist
- * may be the same as @dst but this is irrelevant.)
- *
- * On error, return -errno. Both runlists are left unmodified. The following
- * error codes are defined:
- *	-ENOMEM	- Not enough memory to allocate runlist array.
- *	-EINVAL	- Invalid parameters were passed in.
- */
-static inline runlist_element *ntfs_rl_insert(runlist_element *dst,
-		int dsize, runlist_element *src, int ssize, int loc)
-{
-	BOOL left = FALSE;
-	BOOL disc = FALSE;	/* Discontinuity */
-	BOOL hole = FALSE;	/* Following a hole */
-	int magic;
-
-	BUG_ON(!dst);
-	BUG_ON(!src);
-
-	/* disc => Discontinuity between the end of @dst and the start of @src.
-	 *	   This means we might need to insert a hole.
-	 * hole => @dst ends with a hole or an unmapped region which we can
-	 *	   extend to match the discontinuity. */
-	if (loc == 0)
-		disc = (src[0].vcn > 0);
-	else {
-		s64 merged_length;
-
-		left = ntfs_are_rl_mergeable(dst + loc - 1, src);
-
-		merged_length = dst[loc - 1].length;
-		if (left)
-			merged_length += src->length;
-
-		disc = (src[0].vcn > dst[loc - 1].vcn + merged_length);
-		if (disc)
-			hole = (dst[loc - 1].lcn == LCN_HOLE);
-	}
-
-	/* Space required: @dst size + @src size, less one if we merged, plus
-	 * one if there was a discontinuity, less one for a trailing hole. */
-	dst = ntfs_rl_realloc(dst, dsize, dsize + ssize - left + disc - hole);
-	if (IS_ERR(dst))
-		return dst;
-	/*
-	 * We are guaranteed to succeed from here so can start modifying the
-	 * original runlist.
-	 */
-
-	if (left)
-		__ntfs_rl_merge(dst + loc - 1, src);
-
-	magic = loc + ssize - left + disc - hole;
-
-	/* Move the tail of @dst out of the way, then copy in @src. */
-	ntfs_rl_mm(dst, magic, loc, dsize - loc);
-	ntfs_rl_mc(dst, loc + disc - hole, src, left, ssize - left);
-
-	/* Adjust the VCN of the last run ... */
-	if (dst[magic].lcn <= LCN_HOLE)
-		dst[magic].vcn = dst[magic - 1].vcn + dst[magic - 1].length;
-	/* ... and the length. */
-	if (dst[magic].lcn == LCN_HOLE || dst[magic].lcn == LCN_RL_NOT_MAPPED)
-		dst[magic].length = dst[magic + 1].vcn - dst[magic].vcn;
-
-	/* Writing beyond the end of the file and there's a discontinuity. */
-	if (disc) {
-		if (hole)
-			dst[loc - 1].length = dst[loc].vcn - dst[loc - 1].vcn;
-		else {
-			if (loc > 0) {
-				dst[loc].vcn = dst[loc - 1].vcn +
-						dst[loc - 1].length;
-				dst[loc].length = dst[loc + 1].vcn -
-						dst[loc].vcn;
-			} else {
-				dst[loc].vcn = 0;
-				dst[loc].length = dst[loc + 1].vcn;
-			}
-			dst[loc].lcn = LCN_RL_NOT_MAPPED;
-		}
-
-		magic += hole;
-
-		if (dst[magic].lcn == LCN_ENOENT)
-			dst[magic].vcn = dst[magic - 1].vcn +
-					dst[magic - 1].length;
-	}
-	return dst;
-}
-
-/**
- * ntfs_rl_replace - overwrite a runlist element with another runlist
- * @dst:	original runlist to be worked on
- * @dsize:	number of elements in @dst (including end marker)
- * @src:	new runlist to be inserted
- * @ssize:	number of elements in @src (excluding end marker)
- * @loc:	index in runlist @dst to overwrite with @src
- *
- * Replace the runlist element @dst at @loc with @src. Merge the left and
- * right ends of the inserted runlist, if necessary.
- *
- * It is up to the caller to serialize access to the runlists @dst and @src.
- *
- * On success, return a pointer to the new, combined, runlist. Note, both
- * runlists @dst and @src are deallocated before returning so you cannot use
- * the pointers for anything any more. (Strictly speaking the returned runlist
- * may be the same as @dst but this is irrelevant.)
- *
- * On error, return -errno. Both runlists are left unmodified. The following
- * error codes are defined:
- *	-ENOMEM	- Not enough memory to allocate runlist array.
- *	-EINVAL	- Invalid parameters were passed in.
- */
-static inline runlist_element *ntfs_rl_replace(runlist_element *dst,
-		int dsize, runlist_element *src, int ssize, int loc)
-{
-	BOOL left = FALSE;
-	BOOL right;
-	int magic;
-
-	BUG_ON(!dst);
-	BUG_ON(!src);
-
-	/* First, merge the left and right ends, if necessary. */
-	right = ntfs_are_rl_mergeable(src + ssize - 1, dst + loc + 1);
-	if (loc > 0)
-		left = ntfs_are_rl_mergeable(dst + loc - 1, src);
-
-	/* Allocate some space. We'll need less if the left, right, or both
-	 * ends were merged. */
-	dst = ntfs_rl_realloc(dst, dsize, dsize + ssize - left - right);
-	if (IS_ERR(dst))
-		return dst;
-	/*
-	 * We are guaranteed to succeed from here so can start modifying the
-	 * original runlists.
-	 */
-	if (right)
-		__ntfs_rl_merge(src + ssize - 1, dst + loc + 1);
-	if (left)
-		__ntfs_rl_merge(dst + loc - 1, src);
-
-	/* FIXME: What does this mean? (AIA) */
-	magic = loc + ssize - left;
-
-	/* Move the tail of @dst out of the way, then copy in @src. */
-	ntfs_rl_mm(dst, magic, loc + right + 1, dsize - loc - right - 1);
-	ntfs_rl_mc(dst, loc, src, left, ssize - left);
-
-	/* We may have changed the length of the file, so fix the end marker */
-	if (dst[magic].lcn == LCN_ENOENT)
-		dst[magic].vcn = dst[magic - 1].vcn + dst[magic - 1].length;
-	return dst;
-}
-
-/**
- * ntfs_rl_split - insert a runlist into the centre of a hole
- * @dst:	original runlist to be worked on
- * @dsize:	number of elements in @dst (including end marker)
- * @src:	new runlist to be inserted
- * @ssize:	number of elements in @src (excluding end marker)
- * @loc:	index in runlist @dst at which to split and insert @src
- *
- * Split the runlist @dst at @loc into two and insert @new in between the two
- * fragments. No merging of runlists is necessary. Adjust the size of the
- * holes either side.
- *
- * It is up to the caller to serialize access to the runlists @dst and @src.
- *
- * On success, return a pointer to the new, combined, runlist. Note, both
- * runlists @dst and @src are deallocated before returning so you cannot use
- * the pointers for anything any more. (Strictly speaking the returned runlist
- * may be the same as @dst but this is irrelevant.)
- *
- * On error, return -errno. Both runlists are left unmodified. The following
- * error codes are defined:
- *	-ENOMEM	- Not enough memory to allocate runlist array.
- *	-EINVAL	- Invalid parameters were passed in.
- */
-static inline runlist_element *ntfs_rl_split(runlist_element *dst, int dsize,
-		runlist_element *src, int ssize, int loc)
-{
-	BUG_ON(!dst);
-	BUG_ON(!src);
-
-	/* 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 runlists.
-	 */
-
-	/* 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_runlists - merge two runlists into one
- * @drl:	original runlist to be worked on
- * @srl:	new runlist to be merged into @drl
- *
- * First we sanity check the two runlists @srl and @drl to make sure that they
- * are sensible and can be merged. The runlist @srl must be either after the
- * runlist @drl or completely within a hole (or unmapped region) in @drl.
- *
- * It is up to the caller to serialize access to the runlists @drl and @srl.
- *
- * Merging of runlists 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 runlist, which is just a variant
- * of the insert case.
- *
- * On success, return a pointer to the new, combined, runlist. Note, both
- * runlists @drl and @srl are deallocated before returning so you cannot use
- * the pointers for anything any more. (Strictly speaking the returned runlist
- * may be the same as @dst but this is irrelevant.)
- *
- * On error, return -errno. Both runlists are left unmodified. The following
- * error codes are defined:
- *	-ENOMEM	- Not enough memory to allocate runlist array.
- *	-EINVAL	- Invalid parameters were passed in.
- *	-ERANGE	- The runlists overlap and cannot be merged.
- */
-runlist_element *ntfs_merge_runlists(runlist_element *drl,
-		runlist_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 (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 runlist if necessary. */
-		if (unlikely(drl[0].vcn)) {
-			/* Scan to the end of the source runlist. */
-			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 runlist. */
-			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 runlist. */
-	while (srl[si].length && srl[si].lcn < (LCN)LCN_HOLE)
-		si++;
-
-	/* Can't have an entirely unmapped source runlist. */
-	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 runlists 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%llx, replacing "
-						"with LCN_ENOENT.",
-						(unsigned long long)
-						drl[ds].lcn);
-				drl[ds].lcn = (LCN)LCN_ENOENT;
-				goto finished;
-			}
-			/*
-			 * We need to create an unmapped runlist 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 runlist 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 runlist:");
-	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 runlist
- * @vol:	ntfs volume on which the attribute resides
- * @attr:	attribute record whose mapping pairs array to decompress
- * @old_rl:	optional runlist in which to insert @attr's runlist
- *
- * It is up to the caller to serialize access to the runlist @old_rl.
- *
- * Decompress the attribute @attr's mapping pairs array into a runlist. On
- * success, return the decompressed runlist.
- *
- * If @old_rl is not NULL, decompressed runlist is inserted into the
- * appropriate place in @old_rl and the resultant, combined runlist 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 runlist array.
- *	-EIO	- Corrupt runlist.
- *	-EINVAL	- Invalid parameters were passed in.
- *	-ERANGE	- The two runlists overlap.
- *
- * FIXME: For now we take the conceptionally simplest approach of creating the
- * new runlist disregarding the already existing one and then splicing the
- * two into one, if that is possible (we check for overlap and discard the new
- * runlist if overlap present before returning ERR_PTR(-ERANGE)).
- */
-runlist_element *decompress_mapping_pairs(const ntfs_volume *vol,
-		const ATTR_RECORD *attr, runlist_element *old_rl)
-{
-	VCN vcn;		/* Current vcn. */
-	LCN lcn;		/* Current lcn. */
-	s64 deltaxcn;		/* Change in [vl]cn. */
-	runlist_element *rl;	/* The output runlist. */
-	u8 *buf;		/* Current position in mapping pairs array. */
-	u8 *attr_end;		/* End of attribute. */
-	int rlsize;		/* Size of runlist buffer. */
-	u16 rlpos;		/* Current runlist position in units of
-				   runlist_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 runlist array. */
-	rlpos = 0;
-	/* Allocate first page and set current runlist 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) {
-			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);
-}
+//#include "dir.h"
 
 /**
  * ntfs_map_runlist - map (a part of) a runlist of an ntfs inode
@@ -993,63 +86,6 @@
 }
 
 /**
- * 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
@@ -1861,6 +897,11 @@
 		/* Sanity checks are performed elsewhere. */
 		ctx->attr = (ATTR_RECORD*)((u8*)ctx->mrec +
 				le16_to_cpu(ctx->mrec->attrs_offset));
+		/*
+		 * This needs resetting due to ntfs_external_attr_find() which
+		 * can leave it set despite having zeroed ctx->base_ntfs_ino.
+		 */
+		ctx->al_entry = NULL;
 		return;
 	} /* Attribute list. */
 	if (ctx->ntfs_ino != ctx->base_ntfs_ino)
diff -Nru a/fs/ntfs/attrib.h b/fs/ntfs/attrib.h
--- a/fs/ntfs/attrib.h	2004-10-19 10:13:11 +01:00
+++ b/fs/ntfs/attrib.h	2004-10-19 10:13:11 +01:00
@@ -24,23 +24,11 @@
 #ifndef _LINUX_NTFS_ATTRIB_H
 #define _LINUX_NTFS_ATTRIB_H
 
-#include <linux/fs.h>
-
 #include "endian.h"
 #include "types.h"
 #include "layout.h"
-
-static inline void init_runlist(runlist *rl)
-{
-	rl->rl = NULL;
-	init_rwsem(&rl->lock);
-}
-
-typedef enum {
-	LCN_HOLE		= -1,	/* Keep this as highest value or die! */
-	LCN_RL_NOT_MAPPED	= -2,
-	LCN_ENOENT		= -3,
-} LCN_SPECIAL_VALUES;
+#include "inode.h"
+#include "runlist.h"
 
 /**
  * ntfs_attr_search_ctx - used in attribute search functions
@@ -71,12 +59,7 @@
 	ATTR_RECORD *base_attr;
 } ntfs_attr_search_ctx;
 
-extern runlist_element *decompress_mapping_pairs(const ntfs_volume *vol,
-		const ATTR_RECORD *attr, runlist_element *old_rl);
-
 extern int ntfs_map_runlist(ntfs_inode *ni, VCN vcn);
-
-extern LCN ntfs_vcn_to_lcn(const runlist_element *rl, const VCN vcn);
 
 extern runlist_element *ntfs_find_vcn(ntfs_inode *ni, const VCN vcn,
 		const BOOL need_write);
diff -Nru a/fs/ntfs/runlist.c b/fs/ntfs/runlist.c
--- /dev/null	Wed Dec 31 16:00:00 196900
+++ b/fs/ntfs/runlist.c	2004-10-19 10:13:11 +01:00
@@ -0,0 +1,986 @@
+/**
+ * runlist.c - NTFS runlist handling code.  Part of the Linux-NTFS project.
+ *
+ * Copyright (c) 2001-2004 Anton Altaparmakov
+ * Copyright (c) 2002 Richard Russon
+ *
+ * This program/include file is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as published
+ * by the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program/include file is distributed in the hope that it will be
+ * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program (in the main directory of the Linux-NTFS
+ * distribution in the file COPYING); if not, write to the Free Software
+ * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include "ntfs.h"
+#include "dir.h"
+
+/**
+ * ntfs_rl_mm - runlist memmove
+ *
+ * It is up to the caller to serialize access to the runlist @base.
+ */
+static inline void ntfs_rl_mm(runlist_element *base, int dst, int src,
+		int size)
+{
+	if (likely((dst != src) && (size > 0)))
+		memmove(base + dst, base + src, size * sizeof (*base));
+}
+
+/**
+ * ntfs_rl_mc - runlist memory copy
+ *
+ * It is up to the caller to serialize access to the runlists @dstbase and
+ * @srcbase.
+ */
+static inline void ntfs_rl_mc(runlist_element *dstbase, int dst,
+		runlist_element *srcbase, int src, int size)
+{
+	if (likely(size > 0))
+		memcpy(dstbase + dst, srcbase + src, size * sizeof(*dstbase));
+}
+
+/**
+ * ntfs_rl_realloc - Reallocate memory for runlists
+ * @rl:		original runlist
+ * @old_size:	number of runlist elements in the original runlist @rl
+ * @new_size:	number of runlist elements we need space for
+ *
+ * As the runlists grow, more memory will be required.  To prevent the
+ * kernel having to allocate and reallocate large numbers of small bits of
+ * memory, this function returns and entire page of memory.
+ *
+ * It is up to the caller to serialize access to the runlist @rl.
+ *
+ * N.B.  If the new allocation doesn't require a different number of pages in
+ *       memory, the function will return the original pointer.
+ *
+ * On success, return a pointer to the newly allocated, or recycled, memory.
+ * On error, return -errno. The following error codes are defined:
+ *	-ENOMEM	- Not enough memory to allocate runlist array.
+ *	-EINVAL	- Invalid parameters were passed in.
+ */
+static inline runlist_element *ntfs_rl_realloc(runlist_element *rl,
+		int old_size, int new_size)
+{
+	runlist_element *new_rl;
+
+	old_size = PAGE_ALIGN(old_size * sizeof(*rl));
+	new_size = PAGE_ALIGN(new_size * sizeof(*rl));
+	if (old_size == new_size)
+		return rl;
+
+	new_rl = ntfs_malloc_nofs(new_size);
+	if (unlikely(!new_rl))
+		return ERR_PTR(-ENOMEM);
+
+	if (likely(rl != NULL)) {
+		if (unlikely(old_size > new_size))
+			old_size = new_size;
+		memcpy(new_rl, rl, old_size);
+		ntfs_free(rl);
+	}
+	return new_rl;
+}
+
+/**
+ * ntfs_are_rl_mergeable - test if two runlists can be joined together
+ * @dst:	original runlist
+ * @src:	new runlist to test for mergeability with @dst
+ *
+ * Test if two runlists can be joined together. For this, their VCNs and LCNs
+ * must be adjacent.
+ *
+ * It is up to the caller to serialize access to the runlists @dst and @src.
+ *
+ * Return: TRUE   Success, the runlists can be merged.
+ *	   FALSE  Failure, the runlists cannot be merged.
+ */
+static inline BOOL ntfs_are_rl_mergeable(runlist_element *dst,
+		runlist_element *src)
+{
+	BUG_ON(!dst);
+	BUG_ON(!src);
+
+	if ((dst->lcn < 0) || (src->lcn < 0))     /* Are we merging holes? */
+		return FALSE;
+	if ((dst->lcn + dst->length) != src->lcn) /* Are the runs contiguous? */
+		return FALSE;
+	if ((dst->vcn + dst->length) != src->vcn) /* Are the runs misaligned? */
+		return FALSE;
+
+	return TRUE;
+}
+
+/**
+ * __ntfs_rl_merge - merge two runlists without testing if they can be merged
+ * @dst:	original, destination runlist
+ * @src:	new runlist to merge with @dst
+ *
+ * Merge the two runlists, writing into the destination runlist @dst. The
+ * caller must make sure the runlists can be merged or this will corrupt the
+ * destination runlist.
+ *
+ * It is up to the caller to serialize access to the runlists @dst and @src.
+ */
+static inline void __ntfs_rl_merge(runlist_element *dst, runlist_element *src)
+{
+	dst->length += src->length;
+}
+
+/**
+ * ntfs_rl_merge - test if two runlists can be joined together and merge them
+ * @dst:	original, destination runlist
+ * @src:	new runlist to merge with @dst
+ *
+ * Test if two runlists can be joined together. For this, their VCNs and LCNs
+ * must be adjacent. If they can be merged, perform the merge, writing into
+ * the destination runlist @dst.
+ *
+ * It is up to the caller to serialize access to the runlists @dst and @src.
+ *
+ * Return: TRUE   Success, the runlists have been merged.
+ *	   FALSE  Failure, the runlists cannot be merged and have not been
+ *		  modified.
+ */
+static inline BOOL ntfs_rl_merge(runlist_element *dst, runlist_element *src)
+{
+	BOOL merge = ntfs_are_rl_mergeable(dst, src);
+
+	if (merge)
+		__ntfs_rl_merge(dst, src);
+	return merge;
+}
+
+/**
+ * ntfs_rl_append - append a runlist after a given element
+ * @dst:	original runlist to be worked on
+ * @dsize:	number of elements in @dst (including end marker)
+ * @src:	runlist to be inserted into @dst
+ * @ssize:	number of elements in @src (excluding end marker)
+ * @loc:	append the new runlist @src after this element in @dst
+ *
+ * Append the runlist @src after element @loc in @dst.  Merge the right end of
+ * the new runlist, if necessary. Adjust the size of the hole before the
+ * appended runlist.
+ *
+ * It is up to the caller to serialize access to the runlists @dst and @src.
+ *
+ * On success, return a pointer to the new, combined, runlist. Note, both
+ * runlists @dst and @src are deallocated before returning so you cannot use
+ * the pointers for anything any more. (Strictly speaking the returned runlist
+ * may be the same as @dst but this is irrelevant.)
+ *
+ * On error, return -errno. Both runlists are left unmodified. The following
+ * error codes are defined:
+ *	-ENOMEM	- Not enough memory to allocate runlist array.
+ *	-EINVAL	- Invalid parameters were passed in.
+ */
+static inline runlist_element *ntfs_rl_append(runlist_element *dst,
+		int dsize, runlist_element *src, int ssize, int loc)
+{
+	BOOL right;
+	int magic;
+
+	BUG_ON(!dst);
+	BUG_ON(!src);
+
+	/* First, check if the right hand end needs merging. */
+	right = ntfs_are_rl_mergeable(src + ssize - 1, dst + loc + 1);
+
+	/* Space required: @dst size + @src size, less one if we merged. */
+	dst = ntfs_rl_realloc(dst, dsize, dsize + ssize - right);
+	if (IS_ERR(dst))
+		return dst;
+	/*
+	 * We are guaranteed to succeed from here so can start modifying the
+	 * original runlists.
+	 */
+
+	/* First, merge the right hand end, if necessary. */
+	if (right)
+		__ntfs_rl_merge(src + ssize - 1, dst + loc + 1);
+
+	magic = loc + ssize;
+
+	/* Move the tail of @dst out of the way, then copy in @src. */
+	ntfs_rl_mm(dst, magic + 1, loc + 1 + right, dsize - loc - 1 - right);
+	ntfs_rl_mc(dst, loc + 1, src, 0, ssize);
+
+	/* Adjust the size of the preceding hole. */
+	dst[loc].length = dst[loc + 1].vcn - dst[loc].vcn;
+
+	/* We may have changed the length of the file, so fix the end marker */
+	if (dst[magic + 1].lcn == LCN_ENOENT)
+		dst[magic + 1].vcn = dst[magic].vcn + dst[magic].length;
+
+	return dst;
+}
+
+/**
+ * ntfs_rl_insert - insert a runlist into another
+ * @dst:	original runlist to be worked on
+ * @dsize:	number of elements in @dst (including end marker)
+ * @src:	new runlist to be inserted
+ * @ssize:	number of elements in @src (excluding end marker)
+ * @loc:	insert the new runlist @src before this element in @dst
+ *
+ * Insert the runlist @src before element @loc in the runlist @dst. Merge the
+ * left end of the new runlist, if necessary. Adjust the size of the hole
+ * after the inserted runlist.
+ *
+ * It is up to the caller to serialize access to the runlists @dst and @src.
+ *
+ * On success, return a pointer to the new, combined, runlist. Note, both
+ * runlists @dst and @src are deallocated before returning so you cannot use
+ * the pointers for anything any more. (Strictly speaking the returned runlist
+ * may be the same as @dst but this is irrelevant.)
+ *
+ * On error, return -errno. Both runlists are left unmodified. The following
+ * error codes are defined:
+ *	-ENOMEM	- Not enough memory to allocate runlist array.
+ *	-EINVAL	- Invalid parameters were passed in.
+ */
+static inline runlist_element *ntfs_rl_insert(runlist_element *dst,
+		int dsize, runlist_element *src, int ssize, int loc)
+{
+	BOOL left = FALSE;
+	BOOL disc = FALSE;	/* Discontinuity */
+	BOOL hole = FALSE;	/* Following a hole */
+	int magic;
+
+	BUG_ON(!dst);
+	BUG_ON(!src);
+
+	/* disc => Discontinuity between the end of @dst and the start of @src.
+	 *	   This means we might need to insert a hole.
+	 * hole => @dst ends with a hole or an unmapped region which we can
+	 *	   extend to match the discontinuity. */
+	if (loc == 0)
+		disc = (src[0].vcn > 0);
+	else {
+		s64 merged_length;
+
+		left = ntfs_are_rl_mergeable(dst + loc - 1, src);
+
+		merged_length = dst[loc - 1].length;
+		if (left)
+			merged_length += src->length;
+
+		disc = (src[0].vcn > dst[loc - 1].vcn + merged_length);
+		if (disc)
+			hole = (dst[loc - 1].lcn == LCN_HOLE);
+	}
+
+	/* Space required: @dst size + @src size, less one if we merged, plus
+	 * one if there was a discontinuity, less one for a trailing hole. */
+	dst = ntfs_rl_realloc(dst, dsize, dsize + ssize - left + disc - hole);
+	if (IS_ERR(dst))
+		return dst;
+	/*
+	 * We are guaranteed to succeed from here so can start modifying the
+	 * original runlist.
+	 */
+
+	if (left)
+		__ntfs_rl_merge(dst + loc - 1, src);
+
+	magic = loc + ssize - left + disc - hole;
+
+	/* Move the tail of @dst out of the way, then copy in @src. */
+	ntfs_rl_mm(dst, magic, loc, dsize - loc);
+	ntfs_rl_mc(dst, loc + disc - hole, src, left, ssize - left);
+
+	/* Adjust the VCN of the last run ... */
+	if (dst[magic].lcn <= LCN_HOLE)
+		dst[magic].vcn = dst[magic - 1].vcn + dst[magic - 1].length;
+	/* ... and the length. */
+	if (dst[magic].lcn == LCN_HOLE || dst[magic].lcn == LCN_RL_NOT_MAPPED)
+		dst[magic].length = dst[magic + 1].vcn - dst[magic].vcn;
+
+	/* Writing beyond the end of the file and there's a discontinuity. */
+	if (disc) {
+		if (hole)
+			dst[loc - 1].length = dst[loc].vcn - dst[loc - 1].vcn;
+		else {
+			if (loc > 0) {
+				dst[loc].vcn = dst[loc - 1].vcn +
+						dst[loc - 1].length;
+				dst[loc].length = dst[loc + 1].vcn -
+						dst[loc].vcn;
+			} else {
+				dst[loc].vcn = 0;
+				dst[loc].length = dst[loc + 1].vcn;
+			}
+			dst[loc].lcn = LCN_RL_NOT_MAPPED;
+		}
+
+		magic += hole;
+
+		if (dst[magic].lcn == LCN_ENOENT)
+			dst[magic].vcn = dst[magic - 1].vcn +
+					dst[magic - 1].length;
+	}
+	return dst;
+}
+
+/**
+ * ntfs_rl_replace - overwrite a runlist element with another runlist
+ * @dst:	original runlist to be worked on
+ * @dsize:	number of elements in @dst (including end marker)
+ * @src:	new runlist to be inserted
+ * @ssize:	number of elements in @src (excluding end marker)
+ * @loc:	index in runlist @dst to overwrite with @src
+ *
+ * Replace the runlist element @dst at @loc with @src. Merge the left and
+ * right ends of the inserted runlist, if necessary.
+ *
+ * It is up to the caller to serialize access to the runlists @dst and @src.
+ *
+ * On success, return a pointer to the new, combined, runlist. Note, both
+ * runlists @dst and @src are deallocated before returning so you cannot use
+ * the pointers for anything any more. (Strictly speaking the returned runlist
+ * may be the same as @dst but this is irrelevant.)
+ *
+ * On error, return -errno. Both runlists are left unmodified. The following
+ * error codes are defined:
+ *	-ENOMEM	- Not enough memory to allocate runlist array.
+ *	-EINVAL	- Invalid parameters were passed in.
+ */
+static inline runlist_element *ntfs_rl_replace(runlist_element *dst,
+		int dsize, runlist_element *src, int ssize, int loc)
+{
+	BOOL left = FALSE;
+	BOOL right;
+	int magic;
+
+	BUG_ON(!dst);
+	BUG_ON(!src);
+
+	/* First, merge the left and right ends, if necessary. */
+	right = ntfs_are_rl_mergeable(src + ssize - 1, dst + loc + 1);
+	if (loc > 0)
+		left = ntfs_are_rl_mergeable(dst + loc - 1, src);
+
+	/* Allocate some space. We'll need less if the left, right, or both
+	 * ends were merged. */
+	dst = ntfs_rl_realloc(dst, dsize, dsize + ssize - left - right);
+	if (IS_ERR(dst))
+		return dst;
+	/*
+	 * We are guaranteed to succeed from here so can start modifying the
+	 * original runlists.
+	 */
+	if (right)
+		__ntfs_rl_merge(src + ssize - 1, dst + loc + 1);
+	if (left)
+		__ntfs_rl_merge(dst + loc - 1, src);
+
+	/* FIXME: What does this mean? (AIA) */
+	magic = loc + ssize - left;
+
+	/* Move the tail of @dst out of the way, then copy in @src. */
+	ntfs_rl_mm(dst, magic, loc + right + 1, dsize - loc - right - 1);
+	ntfs_rl_mc(dst, loc, src, left, ssize - left);
+
+	/* We may have changed the length of the file, so fix the end marker */
+	if (dst[magic].lcn == LCN_ENOENT)
+		dst[magic].vcn = dst[magic - 1].vcn + dst[magic - 1].length;
+	return dst;
+}
+
+/**
+ * ntfs_rl_split - insert a runlist into the centre of a hole
+ * @dst:	original runlist to be worked on
+ * @dsize:	number of elements in @dst (including end marker)
+ * @src:	new runlist to be inserted
+ * @ssize:	number of elements in @src (excluding end marker)
+ * @loc:	index in runlist @dst at which to split and insert @src
+ *
+ * Split the runlist @dst at @loc into two and insert @new in between the two
+ * fragments. No merging of runlists is necessary. Adjust the size of the
+ * holes either side.
+ *
+ * It is up to the caller to serialize access to the runlists @dst and @src.
+ *
+ * On success, return a pointer to the new, combined, runlist. Note, both
+ * runlists @dst and @src are deallocated before returning so you cannot use
+ * the pointers for anything any more. (Strictly speaking the returned runlist
+ * may be the same as @dst but this is irrelevant.)
+ *
+ * On error, return -errno. Both runlists are left unmodified. The following
+ * error codes are defined:
+ *	-ENOMEM	- Not enough memory to allocate runlist array.
+ *	-EINVAL	- Invalid parameters were passed in.
+ */
+static inline runlist_element *ntfs_rl_split(runlist_element *dst, int dsize,
+		runlist_element *src, int ssize, int loc)
+{
+	BUG_ON(!dst);
+	BUG_ON(!src);
+
+	/* 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 runlists.
+	 */
+
+	/* 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_runlists - merge two runlists into one
+ * @drl:	original runlist to be worked on
+ * @srl:	new runlist to be merged into @drl
+ *
+ * First we sanity check the two runlists @srl and @drl to make sure that they
+ * are sensible and can be merged. The runlist @srl must be either after the
+ * runlist @drl or completely within a hole (or unmapped region) in @drl.
+ *
+ * It is up to the caller to serialize access to the runlists @drl and @srl.
+ *
+ * Merging of runlists 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 runlist, which is just a variant
+ * of the insert case.
+ *
+ * On success, return a pointer to the new, combined, runlist. Note, both
+ * runlists @drl and @srl are deallocated before returning so you cannot use
+ * the pointers for anything any more. (Strictly speaking the returned runlist
+ * may be the same as @dst but this is irrelevant.)
+ *
+ * On error, return -errno. Both runlists are left unmodified. The following
+ * error codes are defined:
+ *	-ENOMEM	- Not enough memory to allocate runlist array.
+ *	-EINVAL	- Invalid parameters were passed in.
+ *	-ERANGE	- The runlists overlap and cannot be merged.
+ */
+runlist_element *ntfs_merge_runlists(runlist_element *drl,
+		runlist_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 (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 runlist if necessary. */
+		if (unlikely(drl[0].vcn)) {
+			/* Scan to the end of the source runlist. */
+			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 runlist. */
+			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 runlist. */
+	while (srl[si].length && srl[si].lcn < (LCN)LCN_HOLE)
+		si++;
+
+	/* Can't have an entirely unmapped source runlist. */
+	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 runlists 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%llx, replacing "
+						"with LCN_ENOENT.",
+						(unsigned long long)
+						drl[ds].lcn);
+				drl[ds].lcn = (LCN)LCN_ENOENT;
+				goto finished;
+			}
+			/*
+			 * We need to create an unmapped runlist 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 runlist 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 runlist:");
+	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 runlist
+ * @vol:	ntfs volume on which the attribute resides
+ * @attr:	attribute record whose mapping pairs array to decompress
+ * @old_rl:	optional runlist in which to insert @attr's runlist
+ *
+ * It is up to the caller to serialize access to the runlist @old_rl.
+ *
+ * Decompress the attribute @attr's mapping pairs array into a runlist. On
+ * success, return the decompressed runlist.
+ *
+ * If @old_rl is not NULL, decompressed runlist is inserted into the
+ * appropriate place in @old_rl and the resultant, combined runlist 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 runlist array.
+ *	-EIO	- Corrupt runlist.
+ *	-EINVAL	- Invalid parameters were passed in.
+ *	-ERANGE	- The two runlists overlap.
+ *
+ * FIXME: For now we take the conceptionally simplest approach of creating the
+ * new runlist disregarding the already existing one and then splicing the
+ * two into one, if that is possible (we check for overlap and discard the new
+ * runlist if overlap present before returning ERR_PTR(-ERANGE)).
+ */
+runlist_element *decompress_mapping_pairs(const ntfs_volume *vol,
+		const ATTR_RECORD *attr, runlist_element *old_rl)
+{
+	VCN vcn;		/* Current vcn. */
+	LCN lcn;		/* Current lcn. */
+	s64 deltaxcn;		/* Change in [vl]cn. */
+	runlist_element *rl;	/* The output runlist. */
+	u8 *buf;		/* Current position in mapping pairs array. */
+	u8 *attr_end;		/* End of attribute. */
+	int rlsize;		/* Size of runlist buffer. */
+	u16 rlpos;		/* Current runlist position in units of
+				   runlist_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 runlist array. */
+	rlpos = 0;
+	/* Allocate first page and set current runlist 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) {
+			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_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;
+}
diff -Nru a/fs/ntfs/runlist.h b/fs/ntfs/runlist.h
--- /dev/null	Wed Dec 31 16:00:00 196900
+++ b/fs/ntfs/runlist.h	2004-10-19 10:13:11 +01:00
@@ -0,0 +1,48 @@
+/*
+ * runlist.h - Defines for runlist handling in NTFS Linux kernel driver.
+ *	       Part of the Linux-NTFS project.
+ *
+ * Copyright (c) 2001-2004 Anton Altaparmakov
+ * Copyright (c) 2002 Richard Russon
+ *
+ * This program/include file is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as published
+ * by the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program/include file is distributed in the hope that it will be
+ * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program (in the main directory of the Linux-NTFS
+ * distribution in the file COPYING); if not, write to the Free Software
+ * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#ifndef _LINUX_NTFS_RUNLIST_H
+#define _LINUX_NTFS_RUNLIST_H
+
+#include "types.h"
+#include "layout.h"
+#include "volume.h"
+
+static inline void init_runlist(runlist *rl)
+{
+	rl->rl = NULL;
+	init_rwsem(&rl->lock);
+}
+
+typedef enum {
+	LCN_HOLE		= -1,	/* Keep this as highest value or die! */
+	LCN_RL_NOT_MAPPED	= -2,
+	LCN_ENOENT		= -3,
+} LCN_SPECIAL_VALUES;
+
+extern runlist_element *decompress_mapping_pairs(const ntfs_volume *vol,
+		const ATTR_RECORD *attr, runlist_element *old_rl);
+
+extern LCN ntfs_vcn_to_lcn(const runlist_element *rl, const VCN vcn);
+
+#endif /* _LINUX_NTFS_RUNLIST_H */
-
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