UBI: avoid unnecessary division operations
Linux-MTD Mailing List
linux-mtd at lists.infradead.org
Fri Jul 25 10:59:03 EDT 2008
Gitweb: http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=cadb40ccc16a26a738f1cbc963e35b21edd93e79
Commit: cadb40ccc16a26a738f1cbc963e35b21edd93e79
Parent: a0fd1efd488092951f310fdb777b8a540cf84dcb
Author: Kyungmin Park <kyungmin.park at samsung.com>
AuthorDate: Thu May 22 10:32:18 2008 +0900
Committer: Artem Bityutskiy <Artem.Bityutskiy at nokia.com>
CommitDate: Thu Jul 24 13:32:54 2008 +0300
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 at samsung.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy at nokia.com>
---
drivers/mtd/ubi/build.c | 8 ++++++--
drivers/mtd/ubi/cdev.c | 6 +++---
drivers/mtd/ubi/eba.c | 2 +-
drivers/mtd/ubi/kapi.c | 6 +++---
drivers/mtd/ubi/misc.c | 2 +-
drivers/mtd/ubi/vmt.c | 2 +-
drivers/mtd/ubi/vtbl.c | 5 ++---
drivers/mtd/ubi/wl.c | 3 +--
8 files changed, 18 insertions(+), 16 deletions(-)
diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 961416a..ff4425d 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 89193ba..0cdaf9f 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 7ce91ca..37d7784 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 a70d588..5150883 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 93e0528..22ad314 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 5be58d8..7402025 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 42a7815..d9af11a 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 a471a49..cc8fe29 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;
}
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