From 1eed61e1a9c9fee19938a00674e30cd7c9a64864 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jean-Pierre=20Andr=C3=A9?= <jpandre@users.sourceforge.net>
Date: Tue, 25 May 2010 10:29:34 +0200
Subject: [PATCH] enabled downsizing compressed files

---
 libntfs-3g/attrib.c | 24 +++++++++++++++++-------
 src/lowntfs-3g.c    |  9 +--------
 src/ntfs-3g.c       |  9 +--------
 3 files changed, 19 insertions(+), 23 deletions(-)

diff --git a/libntfs-3g/attrib.c b/libntfs-3g/attrib.c
index eb841fce..48906157 100644
--- a/libntfs-3g/attrib.c
+++ b/libntfs-3g/attrib.c
@@ -5533,8 +5533,19 @@ static int ntfs_non_resident_attr_shrink(ntfs_attr *na, const s64 newsize)
 	}
 
 	/* The first cluster outside the new allocation. */
-	first_free_vcn = (newsize + vol->cluster_size - 1) >>
-			vol->cluster_size_bits;
+	if (na->data_flags & ATTR_COMPRESSION_MASK)
+		/*
+		 * For compressed files we must keep full compressions blocks,
+		 * but currently we do not decompress/recompress the last
+		 * block to truncate the data, so we may leave more allocated
+		 * clusters than really needed.
+		 */
+		first_free_vcn = (((newsize - 1)
+				 | (na->compression_block_size - 1)) + 1)
+				   >> vol->cluster_size_bits;
+	else
+		first_free_vcn = (newsize + vol->cluster_size - 1) >>
+				vol->cluster_size_bits;
 	/*
 	 * Compare the new allocation with the old one and only deallocate
 	 * clusters if there is a change.
@@ -5923,8 +5934,7 @@ int ntfs_attr_truncate(ntfs_attr *na, const s64 newsize)
 			 != const_cpu_to_le16(0);
 	if (compressed
 	   && NAttrNonResident(na)
-	   && (((na->data_flags & ATTR_COMPRESSION_MASK) != ATTR_IS_COMPRESSED)
-		|| (newsize && (newsize < na->data_size)))) {
+	   && ((na->data_flags & ATTR_COMPRESSION_MASK) != ATTR_IS_COMPRESSED)) {
 		errno = EOPNOTSUPP;
 		ntfs_log_perror("Failed to truncate compressed attribute");
 		goto out;
@@ -5932,16 +5942,16 @@ int ntfs_attr_truncate(ntfs_attr *na, const s64 newsize)
 	if (NAttrNonResident(na)) {
 		/*
 		 * For compressed data, the last block must be fully
-		 * allocated, and we do not known the size of compression
+		 * allocated, and we do not know the size of compression
 		 * block until the attribute has been made non-resident.
 		 * Moreover we can only process a single compression
 		 * block at a time (from where we are about to write),
 		 * so we silently do not allocate more.
 		 *
-		 * Note : do not request truncate on compressed files
+		 * Note : do not request upsizing of compressed files
 		 * unless being able to face the consequences !
 		 */
-		if (compressed && newsize)
+		if (compressed && newsize && (newsize > na->data_size))
 			fullsize = (na->initialized_size
 				 | (na->compression_block_size - 1)) + 1;
 		else
diff --git a/src/lowntfs-3g.c b/src/lowntfs-3g.c
index 2cf6e0e5..f89eac92 100644
--- a/src/lowntfs-3g.c
+++ b/src/lowntfs-3g.c
@@ -1554,16 +1554,9 @@ static int ntfs_fuse_trunc(struct SECURITY_CONTEXT *scx, fuse_ino_t ino,
 	}
 #endif
 		/*
-		 * for compressed files, only deleting contents and expanding
-		 * are implemented. Expanding is done by inserting a final
+		 * for compressed files, upsizing is done by inserting a final
 		 * zero, which is optimized as creating a hole when possible. 
 		 */
-	if ((na->data_flags & ATTR_COMPRESSION_MASK)
-	    && size
-	    && (size < na->initialized_size)) {
-		errno = EOPNOTSUPP;
-		goto exit;
-	}
 	oldsize = na->data_size;
 	if ((na->data_flags & ATTR_COMPRESSION_MASK)
 	    && (size > na->initialized_size)) {
diff --git a/src/ntfs-3g.c b/src/ntfs-3g.c
index 50bd80f9..970b0456 100644
--- a/src/ntfs-3g.c
+++ b/src/ntfs-3g.c
@@ -1413,16 +1413,9 @@ static int ntfs_fuse_trunc(const char *org_path, off_t size,
 	}
 #endif
 		/*
-		 * for compressed files, only deleting contents and expanding
-		 * are implemented. Expanding is done by inserting a final
+		 * For compressed files, upsizing is done by inserting a final
 		 * zero, which is optimized as creating a hole when possible. 
 		 */
-	if ((na->data_flags & ATTR_COMPRESSION_MASK)
-	    && size
-	    && (size < na->initialized_size)) {
-		errno = EOPNOTSUPP;
-		goto exit;
-	}
 	oldsize = na->data_size;
 	if ((na->data_flags & ATTR_COMPRESSION_MASK)
 	    && (size > na->initialized_size)) {