[PATCH] device-mapper log bitset: fix endian

Clean up the code responsible for the on-disk mirror logs by using the
set_le_bit test_le_bit functions of ext2. That makes the BE machines keep the
bitmap internally in LE order - it does mean you can't use any other type of
operations on the bitmap words but that looks to be OK in this instance. The
efficiency tradeoff is very minimal as you would expect for something that
ext2 uses.

This allows us to remove bits_to_core(), bits_to_disk() and log->disk_bits.

Also increment the mirror log disk version transparently to avoid sharing with
older kernels that suffered from the 64-bit BE bug.

Signed-off-by: Patrick Caulfield <[e-mail]>
Signed-off-by: Alasdair G Kergon <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/md/dm-log.c

···
 /*
  * The on-disk version of the metadata.
  */
-#define MIRROR_DISK_VERSION 1
+#define MIRROR_DISK_VERSION 2
 #define LOG_OFFSET 2
 
 struct log_header {
···
 	struct log_header *disk_header;
 
 	struct io_region bits_location;
-	uint32_t *disk_bits;
 };
 
 /*
···
  */
 static  inline int log_test_bit(uint32_t *bs, unsigned bit)
 {
-	return test_bit(bit, (unsigned long *) bs) ? 1 : 0;
+	return ext2_test_bit(bit, (unsigned long *) bs) ? 1 : 0;
 }
 
 static inline void log_set_bit(struct log_c *l,
 			       uint32_t *bs, unsigned bit)
 {
-	set_bit(bit, (unsigned long *) bs);
+	ext2_set_bit(bit, (unsigned long *) bs);
 	l->touched = 1;
 }
 
 static inline void log_clear_bit(struct log_c *l,
 				 uint32_t *bs, unsigned bit)
 {
-	clear_bit(bit, (unsigned long *) bs);
+	ext2_clear_bit(bit, (unsigned long *) bs);
 	l->touched = 1;
 }
 
···
 		log->header.nr_regions = 0;
 	}
 
+#ifdef __LITTLE_ENDIAN
+	if (log->header.version == 1)
+		log->header.version = 2;
+#endif
+
 	if (log->header.version != MIRROR_DISK_VERSION) {
 		DMWARN("incompatible disk log version");
 		return -EINVAL;
···
 /*----------------------------------------------------------------
  * Bits IO
  *--------------------------------------------------------------*/
-static inline void bits_to_core(uint32_t *core, uint32_t *disk, unsigned count)
-{
-	unsigned i;
-
-	for (i = 0; i < count; i++)
-		core[i] = le32_to_cpu(disk[i]);
-}
-
-static inline void bits_to_disk(uint32_t *core, uint32_t *disk, unsigned count)
-{
-	unsigned i;
-
-	/* copy across the clean/dirty bitset */
-	for (i = 0; i < count; i++)
-		disk[i] = cpu_to_le32(core[i]);
-}
-
 static int read_bits(struct log_c *log)
 {
 	int r;
 	unsigned long ebits;
 
 	r = dm_io_sync_vm(1, &log->bits_location, READ,
-			  log->disk_bits, &ebits);
+			  log->clean_bits, &ebits);
 	if (r)
 		return r;
 
-	bits_to_core(log->clean_bits, log->disk_bits,
-		     log->bitset_uint32_count);
 	return 0;
 }
 
 static int write_bits(struct log_c *log)
 {
 	unsigned long ebits;
-	bits_to_disk(log->clean_bits, log->disk_bits,
-		     log->bitset_uint32_count);
 	return dm_io_sync_vm(1, &log->bits_location, WRITE,
-			     log->disk_bits, &ebits);
+			     log->clean_bits, &ebits);
 }
 
 /*----------------------------------------------------------------
···
 	size = dm_round_up(lc->bitset_uint32_count * sizeof(uint32_t),
 			   1 << SECTOR_SHIFT);
 	lc->bits_location.count = size >> SECTOR_SHIFT;
-	lc->disk_bits = vmalloc(size);
-	if (!lc->disk_bits) {
-		vfree(lc->disk_header);
-		goto bad;
-	}
 	return 0;
 
  bad:
···
 	struct log_c *lc = (struct log_c *) log->context;
 	dm_put_device(lc->ti, lc->log_dev);
 	vfree(lc->disk_header);
-	vfree(lc->disk_bits);
 	core_dtr(log);
 }