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 <kyungmin.park@samsung.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

8 files changed, 18 insertions, 16 deletions

diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 961416ac0616..ff4425de1527 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -530,7 +530,11 @@ static int io_init(struct ubi_device *ubi)
         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);
@@ -581,7 +585,7 @@ static int io_init(struct ubi_device *ubi)
         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;
diff --git a/drivers/mtd/ubi/cdev.c b/drivers/mtd/ubi/cdev.c
index 89193ba9451e..0cdaf9fba7b0 100644
--- a/drivers/mtd/ubi/cdev.c
+++ b/drivers/mtd/ubi/cdev.c
@@ -295,7 +295,7 @@ static ssize_t vol_cdev_direct_write(struct file *file, const char __user *buf,
         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;
         }
@@ -304,7 +304,7 @@ static ssize_t vol_cdev_direct_write(struct file *file, const char __user *buf,
                 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;
         }
@@ -564,7 +564,7 @@ static int verify_mkvol_req(const struct ubi_device *ubi,
         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;
 
diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
index 7ce91ca742b1..37d778447943 100644
--- a/drivers/mtd/ubi/eba.c
+++ b/drivers/mtd/ubi/eba.c
@@ -752,7 +752,7 @@ int ubi_eba_write_leb_st(struct ubi_device *ubi, struct ubi_volume *vol,
                 /* 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)
diff --git a/drivers/mtd/ubi/kapi.c b/drivers/mtd/ubi/kapi.c
index a70d58823f8d..51508832566d 100644
--- a/drivers/mtd/ubi/kapi.c
+++ b/drivers/mtd/ubi/kapi.c
@@ -397,8 +397,8 @@ int ubi_leb_write(struct ubi_volume_desc *desc, int lnum, const void *buf,
                 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 &&
@@ -447,7 +447,7 @@ int ubi_leb_change(struct ubi_volume_desc *desc, int lnum, const void *buf,
                 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 &&
diff --git a/drivers/mtd/ubi/misc.c b/drivers/mtd/ubi/misc.c
index 93e052812012..22ad31402945 100644
--- a/drivers/mtd/ubi/misc.c
+++ b/drivers/mtd/ubi/misc.c
@@ -37,7 +37,7 @@ int ubi_calc_data_len(const struct ubi_device *ubi, const void *buf,
 {
         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)
diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
index 5be58d85c639..7402025ded94 100644
--- a/drivers/mtd/ubi/vmt.c
+++ b/drivers/mtd/ubi/vmt.c
@@ -727,7 +727,7 @@ static void paranoid_check_volume(struct ubi_device *ubi, int vol_id)
                 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;
diff --git a/drivers/mtd/ubi/vtbl.c b/drivers/mtd/ubi/vtbl.c
index 42a7815086b7..d9af11a8682b 100644
--- a/drivers/mtd/ubi/vtbl.c
+++ b/drivers/mtd/ubi/vtbl.c
@@ -170,7 +170,7 @@ static int vtbl_check(const struct ubi_device *ubi,
                         goto bad;
                 }
 
-                n = alignment % ubi->min_io_size;
+                n = alignment & (ubi->min_io_size - 1);
                 if (alignment != 1 && n) {
                         err = 5;
                         goto bad;
@@ -684,14 +684,13 @@ static int check_scanning_info(const struct ubi_device *ubi,
                 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();
 
diff --git a/drivers/mtd/ubi/wl.c b/drivers/mtd/ubi/wl.c
index a471a491f0ab..cc8fe2934d2b 100644
--- a/drivers/mtd/ubi/wl.c
+++ b/drivers/mtd/ubi/wl.c
@@ -1368,7 +1368,7 @@ int ubi_thread(void *u)
                 int err;
 
                 if (kthread_should_stop())
-                        goto out;
+                        break;
 
                 if (try_to_freeze())
                         continue;
@@ -1403,7 +1403,6 @@ int ubi_thread(void *u)
                 cond_resched();
         }
 
-out:
         dbg_wl("background thread \"%s\" is killed", ubi->bgt_name);
         return 0;
 }