libsquashfs: remove the default block writer alignment feature

The idea of the block align feature was to allow micro-managing that
some files are forcefully aligned to 1k/4k ("device block") boundaries,
hoping to improve access time at the cost of data density. The feature
was not exposed in the tools for a long time and eventuall added to the
sort file. Measurement and experimentation showed, that it in fact
worsened the read performance on a test system with an old micro SD
card as the bottle neck.

The feature is removed, and if needed, can be brought back simply by
wrapping/sub-classing the default block writer, if need be..

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 4 insertions, 12 deletions

diff --git a/include/sqfs/block.h b/include/sqfs/block.h
index 30f181c..639fb68 100644
--- a/include/sqfs/block.h
+++ b/include/sqfs/block.h
@@ -72,12 +72,9 @@ typedef enum {
 	SQFS_BLK_DONT_COMPRESS = 0x0001,
 
 	/**
-	 * @brief Align the block on disk to device block size.
-	 *
-	 * If set, the @ref sqfs_block_processor_t will add padding before the
-	 * first block of the affected file and after the last block.
+	 * @brief Don't compute block data checksums.
 	 */
-	SQFS_BLK_ALIGN = 0x0002,
+	SQFS_BLK_DONT_HASH = 0x0002,
 
 	/**
 	 * @brief Don't add the tail end of a file to a fragment block.
@@ -105,11 +102,6 @@ typedef enum {
 	SQFS_BLK_IGNORE_SPARSE = 0x0010,
 
 	/**
-	 * @brief Don't compute block data checksums.
-	 */
-	SQFS_BLK_DONT_HASH = 0x0020,
-
-	/**
 	 * @brief Set by the @ref sqfs_block_processor_t if it determines a
 	 *        block of a file to be sparse, i.e. only zero bytes.
 	 */
@@ -148,9 +140,9 @@ typedef enum {
 	/**
 	 * @brief The combination of all flags that are user settable.
 	 */
-	SQFS_BLK_USER_SETTABLE_FLAGS = 0x003F,
+	SQFS_BLK_USER_SETTABLE_FLAGS = 0x001F,
 
-	SQFS_BLK_FLAGS_ALL = 0xFC3F,
+	SQFS_BLK_FLAGS_ALL = 0xFC1F,
 } SQFS_BLK_FLAGS;
 
 #endif /* SQFS_BLOCK_H */