NTFS: Fixup handling of sparse, compressed, and encrypted attributes in

fs/ntfs/aops.c::ntfs_writepage().

Signed-off-by: Anton Altaparmakov <aia21@cantab.net>

fs/ntfs/ChangeLog

@@ -79,6 +79,8 @@ ToDo/Notes:
 	  fs/ntfs/inode.c::ntfs_read_locked_{,attr_,index_}inode().
 	- Make ntfs_write_block() not instantiate sparse blocks if they contain
 	  only zeroes.
+	- Fixup handling of sparse, compressed, and encrypted attributes in
+	  fs/ntfs/aops.c::ntfs_writepage().
 
 2.1.23 - Implement extension of resident files and make writing safe as well as
 	 many bug fixes, cleanups, and enhancements...

fs/ntfs/aops.c

@@ -1301,38 +1301,42 @@ retry_writepage:
 		ntfs_debug("Write outside i_size - truncated?");
 		return 0;
 	}
-	/* NInoNonResident() == NInoIndexAllocPresent() */
-	if (NInoNonResident(ni)) {
 	/*
-		 * Only unnamed $DATA attributes can be compressed, encrypted,
+	 * Only $DATA attributes can be encrypted and only unnamed $DATA
-		 * and/or sparse.
+	 * attributes can be compressed.  Index root can have the flags set but
+	 * this means to create compressed/encrypted files, not that the
+	 * attribute is compressed/encrypted.
 	 */
-		if (ni->type == AT_DATA && !ni->name_len) {
+	if (ni->type != AT_INDEX_ROOT) {
 		/* If file is encrypted, deny access, just like NT4. */
 		if (NInoEncrypted(ni)) {
 			unlock_page(page);
+			BUG_ON(ni->type != AT_DATA);
 			ntfs_debug("Denying write access to encrypted "
 					"file.");
 			return -EACCES;
 		}
 		/* Compressed data streams are handled in compress.c. */
-			if (NInoCompressed(ni)) {
+		if (NInoNonResident(ni) && NInoCompressed(ni)) {
-				// TODO: Implement and replace this check with
+			BUG_ON(ni->type != AT_DATA);
+			BUG_ON(ni->name_len);
+			// TODO: Implement and replace this with
 			// return ntfs_write_compressed_block(page);
 			unlock_page(page);
-				ntfs_error(vi->i_sb, "Writing to compressed "
+			ntfs_error(vi->i_sb, "Writing to compressed files is "
-						"files is not supported yet. "
+					"not supported yet.  Sorry.");
-						"Sorry.");
 			return -EOPNOTSUPP;
 		}
 		// TODO: Implement and remove this check.
-			if (NInoSparse(ni)) {
+		if (NInoNonResident(ni) && NInoSparse(ni)) {
 			unlock_page(page);
-				ntfs_error(vi->i_sb, "Writing to sparse files "
+			ntfs_error(vi->i_sb, "Writing to sparse files is not "
-						"is not supported yet. Sorry.");
+					"supported yet.  Sorry.");
 			return -EOPNOTSUPP;
 		}
 	}
+	/* NInoNonResident() == NInoIndexAllocPresent() */
+	if (NInoNonResident(ni)) {
 		/* We have to zero every time due to mmap-at-end-of-file. */
 		if (page->index >= (i_size >> PAGE_CACHE_SHIFT)) {
 			/* The page straddles i_size. */
@@ -1345,14 +1349,16 @@ retry_writepage:
 		/* Handle mst protected attributes. */
 		if (NInoMstProtected(ni))
 			return ntfs_write_mst_block(page, wbc);
-		/* Normal data stream. */
+		/* Normal, non-resident data stream. */
 		return ntfs_write_block(page, wbc);
 	}
 	/*
-	 * Attribute is resident, implying it is not compressed, encrypted,
+	 * Attribute is resident, implying it is not compressed, encrypted, or
-	 * sparse, or mst protected.  This also means the attribute is smaller
+	 * mst protected.  This also means the attribute is smaller than an mft
-	 * than an mft record and hence smaller than a page, so can simply
+	 * record and hence smaller than a page, so can simply return error on
-	 * return error on any pages with index above 0.
+	 * any pages with index above 0.  Note the attribute can actually be
+	 * marked compressed but if it is resident the actual data is not
+	 * compressed so we are ok to ignore the compressed flag here.
 	 */
 	BUG_ON(page_has_buffers(page));
 	BUG_ON(!PageUptodate(page));
@@ -1401,30 +1407,14 @@ retry_writepage:
 	BUG_ON(PageWriteback(page));
 	set_page_writeback(page);
 	unlock_page(page);
-
 	/*
-	 * Here, we don't need to zero the out of bounds area everytime because
+	 * Here, we do not need to zero the out of bounds area everytime
-	 * the below memcpy() already takes care of the mmap-at-end-of-file
+	 * because the below memcpy() already takes care of the
-	 * requirements. If the file is converted to a non-resident one, then
+	 * mmap-at-end-of-file requirements.  If the file is converted to a
-	 * the code path use is switched to the non-resident one where the
+	 * non-resident one, then the code path use is switched to the
-	 * zeroing happens on each ntfs_writepage() invocation.
+	 * non-resident one where the zeroing happens on each ntfs_writepage()
-	 *
+	 * invocation.
-	 * The above also applies nicely when i_size is decreased.
-	 *
-	 * When i_size is increased, the memory between the old and new i_size
-	 * _must_ be zeroed (or overwritten with new data). Otherwise we will
-	 * expose data to userspace/disk which should never have been exposed.
-	 *
-	 * FIXME: Ensure that i_size increases do the zeroing/overwriting and
-	 * if we cannot guarantee that, then enable the zeroing below.  If the
-	 * zeroing below is enabled, we MUST move the unlock_page() from above
-	 * to after the kunmap_atomic(), i.e. just before the
-	 * end_page_writeback().
-	 * UPDATE: ntfs_prepare/commit_write() do the zeroing on i_size
-	 * increases for resident attributes so those are ok.
-	 * TODO: ntfs_truncate(), others?
 	 */
-
 	attr_len = le32_to_cpu(ctx->attr->data.resident.value_length);
 	i_size = i_size_read(vi);
 	if (unlikely(attr_len > i_size)) {