UBI: avoid unnecessary division operations

UBI already checks that @min io size is the power of 2 at io_init.
It is save to use bit operations then.

Signed-off-by: Kyungmin Park <[e-mail]>
Signed-off-by: Artem Bityutskiy <[e-mail]>

drivers/mtd/ubi/build.c

···
 	ubi->min_io_size = ubi->mtd->writesize;
 	ubi->hdrs_min_io_size = ubi->mtd->writesize >> ubi->mtd->subpage_sft;
 
-	/* Make sure minimal I/O unit is power of 2 */
+	/*
+	 * Make sure minimal I/O unit is power of 2. Note, there is no
+	 * fundamental reason for this assumption. It is just an optimization
+	 * which allows us to avoid costly division operations.
+	 */
 	if (!is_power_of_2(ubi->min_io_size)) {
 		ubi_err("min. I/O unit (%d) is not power of 2",
 			ubi->min_io_size);
···
 	if (ubi->vid_hdr_offset < UBI_EC_HDR_SIZE ||
 	    ubi->leb_start < ubi->vid_hdr_offset + UBI_VID_HDR_SIZE ||
 	    ubi->leb_start > ubi->peb_size - UBI_VID_HDR_SIZE ||
-	    ubi->leb_start % ubi->min_io_size) {
+	    ubi->leb_start & (ubi->min_io_size - 1)) {
 		ubi_err("bad VID header (%d) or data offsets (%d)",
 			ubi->vid_hdr_offset, ubi->leb_start);
 		return -EINVAL;

drivers/mtd/ubi/cdev.c

···
 	off = do_div(tmp, vol->usable_leb_size);
 	lnum = tmp;
 
-	if (off % ubi->min_io_size) {
+	if (off & (ubi->min_io_size - 1)) {
 		dbg_err("unaligned position");
 		return -EINVAL;
 	}
···
 		count_save = count = vol->used_bytes - *offp;
 
 	/* We can write only in fractions of the minimum I/O unit */
-	if (count % ubi->min_io_size) {
+	if (count & (ubi->min_io_size - 1)) {
 		dbg_err("unaligned write length");
 		return -EINVAL;
 	}
···
 	if (req->alignment > ubi->leb_size)
 		goto bad;
 
-	n = req->alignment % ubi->min_io_size;
+	n = req->alignment & (ubi->min_io_size - 1);
 	if (req->alignment != 1 && n)
 		goto bad;
 

drivers/mtd/ubi/eba.c

···
 		/* If this is the last LEB @len may be unaligned */
 		len = ALIGN(data_size, ubi->min_io_size);
 	else
-		ubi_assert(len % ubi->min_io_size == 0);
+		ubi_assert(!(len & (ubi->min_io_size - 1)));
 
 	vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
 	if (!vid_hdr)

drivers/mtd/ubi/kapi.c

···
 		return -EROFS;
 
 	if (lnum < 0 || lnum >= vol->reserved_pebs || offset < 0 || len < 0 ||
-	    offset + len > vol->usable_leb_size || offset % ubi->min_io_size ||
-	    len % ubi->min_io_size)
+	    offset + len > vol->usable_leb_size ||
+	    offset & (ubi->min_io_size - 1) || len & (ubi->min_io_size - 1))
 		return -EINVAL;
 
 	if (dtype != UBI_LONGTERM && dtype != UBI_SHORTTERM &&
···
 		return -EROFS;
 
 	if (lnum < 0 || lnum >= vol->reserved_pebs || len < 0 ||
-	    len > vol->usable_leb_size || len % ubi->min_io_size)
+	    len > vol->usable_leb_size || len & (ubi->min_io_size - 1))
 		return -EINVAL;
 
 	if (dtype != UBI_LONGTERM && dtype != UBI_SHORTTERM &&

drivers/mtd/ubi/misc.c

···
 {
 	int i;
 
-	ubi_assert(length % ubi->min_io_size == 0);
+	ubi_assert(!(length & (ubi->min_io_size - 1)));
 
 	for (i = length - 1; i >= 0; i--)
 		if (((const uint8_t *)buf)[i] != 0xFF)

drivers/mtd/ubi/vmt.c

···
 		goto fail;
 	}
 
-	n = vol->alignment % ubi->min_io_size;
+	n = vol->alignment & (ubi->min_io_size - 1);
 	if (vol->alignment != 1 && n) {
 		ubi_err("alignment is not multiple of min I/O unit");
 		goto fail;

drivers/mtd/ubi/vtbl.c

···
 			goto bad;
 		}
 
-		n = alignment % ubi->min_io_size;
+		n = alignment & (ubi->min_io_size - 1);
 		if (alignment != 1 && n) {
 			err = 5;
 			goto bad;
···
 		return -EINVAL;
 	}
 
-	if (si->highest_vol_id >= ubi->vtbl_slots + UBI_INT_VOL_COUNT&&
+	if (si->highest_vol_id >= ubi->vtbl_slots + UBI_INT_VOL_COUNT &&
 	    si->highest_vol_id < UBI_INTERNAL_VOL_START) {
 		ubi_err("too large volume ID %d found by scanning",
 			si->highest_vol_id);
 		return -EINVAL;
 	}
-
 
 	for (i = 0; i < ubi->vtbl_slots + UBI_INT_VOL_COUNT; i++) {
 		cond_resched();

drivers/mtd/ubi/wl.c

···
 		int err;
 
 		if (kthread_should_stop())
-			goto out;
+			break;
 
 		if (try_to_freeze())
 			continue;
···
 		cond_resched();
 	}
 
-out:
 	dbg_wl("background thread \"%s\" is killed", ubi->bgt_name);
 	return 0;
 }