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Kaitao Cheng

2020-May-29 14:11 UTC

[Ocfs2-devel] [PATCH v2] blkdev: Replace blksize_bits() with ilog2()

There is a function named ilog2() exist which can replace blksize.
The generated code will be shorter and more efficient on some
architecture, such as arm64. And ilog2() can be optimized according
to different architecture.

Signed-off-by: Kaitao Cheng <pilgrimtao at gmail.com>
---
changes in v2:
	Remove all blksize_bits

 drivers/nvme/target/io-cmd-bdev.c            |  2 +-
 drivers/s390/block/dasd_ioctl.c              |  2 +-
 drivers/usb/gadget/function/storage_common.c |  2 +-
 fs/block_dev.c                               |  6 +++---
 fs/btrfs/disk-io.c                           |  4 ++--
 fs/buffer.c                                  |  2 +-
 fs/direct-io.c                               |  2 +-
 fs/f2fs/data.c                               |  2 +-
 fs/iomap/direct-io.c                         |  2 +-
 fs/ocfs2/super.c                             |  2 +-
 fs/romfs/super.c                             |  2 +-
 include/linux/blkdev.h                       | 11 -----------
 12 files changed, 14 insertions(+), 25 deletions(-)

diff --git a/drivers/nvme/target/io-cmd-bdev.c
b/drivers/nvme/target/io-cmd-bdev.c
index bcf979eb8e83..58bd947e232e 100644
--- a/drivers/nvme/target/io-cmd-bdev.c
+++ b/drivers/nvme/target/io-cmd-bdev.c
@@ -63,7 +63,7 @@ int nvmet_bdev_ns_enable(struct nvmet_ns *ns)
 		return ret;
 	}
 	ns->size = i_size_read(ns->bdev->bd_inode);
-	ns->blksize_shift = blksize_bits(bdev_logical_block_size(ns->bdev));
+	ns->blksize_shift = ilog2(bdev_logical_block_size(ns->bdev));
 	return 0;
 }
 
diff --git a/drivers/s390/block/dasd_ioctl.c b/drivers/s390/block/dasd_ioctl.c
index 777734d1b4e5..55adb134451b 100644
--- a/drivers/s390/block/dasd_ioctl.c
+++ b/drivers/s390/block/dasd_ioctl.c
@@ -228,7 +228,7 @@ dasd_format(struct dasd_block *block, struct format_data_t
*fdata)
 	 */
 	if (fdata->start_unit == 0) {
 		struct block_device *bdev = bdget_disk(block->gdp, 0);
-		bdev->bd_inode->i_blkbits = blksize_bits(fdata->blksize);
+		bdev->bd_inode->i_blkbits = ilog2(fdata->blksize);
 		bdput(bdev);
 	}
 
diff --git a/drivers/usb/gadget/function/storage_common.c
b/drivers/usb/gadget/function/storage_common.c
index f7e6c42558eb..eada3e801dd7 100644
--- a/drivers/usb/gadget/function/storage_common.c
+++ b/drivers/usb/gadget/function/storage_common.c
@@ -233,7 +233,7 @@ int fsg_lun_open(struct fsg_lun *curlun, const char
*filename)
 		blkbits = 11;
 	} else if (inode->i_bdev) {
 		blksize = bdev_logical_block_size(inode->i_bdev);
-		blkbits = blksize_bits(blksize);
+		blkbits = ilog2(blksize);
 	} else {
 		blksize = 512;
 		blkbits = 9;
diff --git a/fs/block_dev.c b/fs/block_dev.c
index a333a648244e..d18496dfc6e7 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -115,7 +115,7 @@ static void set_init_blocksize(struct block_device *bdev)
 		bsize <<= 1;
 	}
 	bdev->bd_block_size = bsize;
-	bdev->bd_inode->i_blkbits = blksize_bits(bsize);
+	bdev->bd_inode->i_blkbits = ilog2(bsize);
 }
 
 int set_blocksize(struct block_device *bdev, int size)
@@ -132,7 +132,7 @@ int set_blocksize(struct block_device *bdev, int size)
 	if (bdev->bd_block_size != size) {
 		sync_blockdev(bdev);
 		bdev->bd_block_size = size;
-		bdev->bd_inode->i_blkbits = blksize_bits(size);
+		bdev->bd_inode->i_blkbits = ilog2(size);
 		kill_bdev(bdev);
 	}
 	return 0;
@@ -147,7 +147,7 @@ int sb_set_blocksize(struct super_block *sb, int size)
 	/* If we get here, we know size is power of two
 	 * and it's value is between 512 and PAGE_SIZE */
 	sb->s_blocksize = size;
-	sb->s_blocksize_bits = blksize_bits(size);
+	sb->s_blocksize_bits = ilog2(size);
 	return sb->s_blocksize;
 }
 
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 7c6f0bbb54a5..711b9fc31c94 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2765,7 +2765,7 @@ static int init_mount_fs_info(struct btrfs_fs_info
*fs_info, struct super_block
 
 	fs_info->sb = sb;
 	sb->s_blocksize = BTRFS_BDEV_BLOCKSIZE;
-	sb->s_blocksize_bits = blksize_bits(BTRFS_BDEV_BLOCKSIZE);
+	sb->s_blocksize_bits = ilog2(BTRFS_BDEV_BLOCKSIZE);
 
 	ret = percpu_counter_init(&fs_info->dio_bytes, 0, GFP_KERNEL);
 	if (ret)
@@ -3059,7 +3059,7 @@ int __cold open_ctree(struct super_block *sb, struct
btrfs_fs_devices *fs_device
 	sb->s_bdi->ra_pages = max(sb->s_bdi->ra_pages, SZ_4M / PAGE_SIZE);
 
 	sb->s_blocksize = sectorsize;
-	sb->s_blocksize_bits = blksize_bits(sectorsize);
+	sb->s_blocksize_bits = ilog2(sectorsize);
 	memcpy(&sb->s_uuid, fs_info->fs_devices->fsid, BTRFS_FSID_SIZE);
 
 	mutex_lock(&fs_info->chunk_mutex);
diff --git a/fs/buffer.c b/fs/buffer.c
index fc8831c392d7..fa92e0afe349 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -907,7 +907,7 @@ static sector_t blkdev_max_block(struct block_device *bdev,
unsigned int size)
 	loff_t sz = i_size_read(bdev->bd_inode);
 
 	if (sz) {
-		unsigned int sizebits = blksize_bits(size);
+		unsigned int sizebits = ilog2(size);
 		retval = (sz >> sizebits);
 	}
 	return retval;
diff --git a/fs/direct-io.c b/fs/direct-io.c
index 1543b5af400e..7ea2cd3effcc 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -1148,7 +1148,7 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode
*inode,
 
 	if (align & blocksize_mask) {
 		if (bdev)
-			blkbits = blksize_bits(bdev_logical_block_size(bdev));
+			blkbits = ilog2(bdev_logical_block_size(bdev));
 		blocksize_mask = (1 << blkbits) - 1;
 		if (align & blocksize_mask)
 			goto out;
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index cb05f71cf850..b896da27942a 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -3458,7 +3458,7 @@ static int check_direct_IO(struct inode *inode, struct
iov_iter *iter,
 
 	if (align & blocksize_mask) {
 		if (bdev)
-			blkbits = blksize_bits(bdev_logical_block_size(bdev));
+			blkbits = ilog2(bdev_logical_block_size(bdev));
 		blocksize_mask = (1 << blkbits) - 1;
 		if (align & blocksize_mask)
 			return -EINVAL;
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index ec7b78e6feca..2a807657d544 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -203,7 +203,7 @@ static loff_t
 iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
 		struct iomap_dio *dio, struct iomap *iomap)
 {
-	unsigned int blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev));
+	unsigned int blkbits = ilog2(bdev_logical_block_size(iomap->bdev));
 	unsigned int fs_block_size = i_blocksize(inode), pad;
 	unsigned int align = iov_iter_alignment(dio->submit.iter);
 	struct bio *bio;
diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
index 71ea9ce71a6b..9b5622881d34 100644
--- a/fs/ocfs2/super.c
+++ b/fs/ocfs2/super.c
@@ -2054,7 +2054,7 @@ static int ocfs2_initialize_super(struct super_block *sb,
 	osb->osb_dx_seed[3] = le32_to_cpu(di->id2.i_super.s_uuid_hash);
 
 	osb->sb = sb;
-	osb->s_sectsize_bits = blksize_bits(sector_size);
+	osb->s_sectsize_bits = ilog2(sector_size);
 	BUG_ON(!osb->s_sectsize_bits);
 
 	spin_lock_init(&osb->dc_task_lock);
diff --git a/fs/romfs/super.c b/fs/romfs/super.c
index e582d001f792..4f6963570739 100644
--- a/fs/romfs/super.c
+++ b/fs/romfs/super.c
@@ -470,7 +470,7 @@ static int romfs_fill_super(struct super_block *sb, struct
fs_context *fc)
 		sb_set_blocksize(sb, ROMBSIZE);
 	} else {
 		sb->s_blocksize = ROMBSIZE;
-		sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
+		sb->s_blocksize_bits = ilog2(ROMBSIZE);
 	}
 #endif
 
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 7d10f4e63232..16038b609c14 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1502,17 +1502,6 @@ static inline int blk_rq_aligned(struct request_queue *q,
unsigned long addr,
 	return !(addr & alignment) && !(len & alignment);
 }
 
-/* assumes size > 256 */
-static inline unsigned int blksize_bits(unsigned int size)
-{
-	unsigned int bits = 8;
-	do {
-		bits++;
-		size >>= 1;
-	} while (size > 256);
-	return bits;
-}
-
 static inline unsigned int block_size(struct block_device *bdev)
 {
 	return bdev->bd_block_size;
-- 
2.20.1

Jens Axboe

2020-May-29 14:13 UTC

head link

[Ocfs2-devel] [PATCH v2] blkdev: Replace blksize_bits() with ilog2()

On 5/29/20 8:11 AM, Kaitao Cheng wrote:> There is a function named ilog2() exist which can replace blksize.
> The generated code will be shorter and more efficient on some
> architecture, such as arm64. And ilog2() can be optimized according
> to different architecture.
When you posted this last time, I said:

"I like the simplification, but do you have any results to back up
 that claim? Is the generated code shorter? Runs faster?"

which you handily ignored, yet sending out a new version. I'm not
going to apply this without justification, your commit message is
handwavy at best.

-- 
Jens Axboe

Christoph Hellwig

2020-May-29 14:15 UTC

head link

[Ocfs2-devel] [PATCH v2] blkdev: Replace blksize_bits() with ilog2()

>  	ns->size = i_size_read(ns->bdev->bd_inode);
> -	ns->blksize_shift =
blksize_bits(bdev_logical_block_size(ns->bdev));
> +	ns->blksize_shift = ilog2(bdev_logical_block_size(ns->bdev));
This should just be:

	ns->blksize_shift = ns->bdev->bd_inode->i_blkbits;
> diff --git a/drivers/s390/block/dasd_ioctl.c
b/drivers/s390/block/dasd_ioctl.c
> index 777734d1b4e5..55adb134451b 100644
> --- a/drivers/s390/block/dasd_ioctl.c
> +++ b/drivers/s390/block/dasd_ioctl.c
> @@ -228,7 +228,7 @@ dasd_format(struct dasd_block *block, struct
format_data_t *fdata)
>  	 */
>  	if (fdata->start_unit == 0) {
>  		struct block_device *bdev = bdget_disk(block->gdp, 0);
> -		bdev->bd_inode->i_blkbits = blksize_bits(fdata->blksize);
> +		bdev->bd_inode->i_blkbits = ilog2(fdata->blksize);
This also needs to set bdev->bd_block_size, so this probably warrants
a separate fix that be backported.  It might be nice to split out
a helper that sets bd_block_size and bd_inode->i_blkbits together
so that such a use is more obvious.
>  	} else if (inode->i_bdev) {
>  		blksize = bdev_logical_block_size(inode->i_bdev);
> -		blkbits = blksize_bits(blksize);
> +		blkbits = ilog2(blksize);
This can just use inode->i_bdev->bd_inode->i_blkbits.
> diff --git a/fs/buffer.c b/fs/buffer.c
> index fc8831c392d7..fa92e0afe349 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -907,7 +907,7 @@ static sector_t blkdev_max_block(struct block_device
*bdev, unsigned int size)
>  	loff_t sz = i_size_read(bdev->bd_inode);
>  
>  	if (sz) {
> -		unsigned int sizebits = blksize_bits(size);
> +		unsigned int sizebits = ilog2(size);
bdev->bd_inode->i_blkbits.
> diff --git a/fs/direct-io.c b/fs/direct-io.c
> index 1543b5af400e..7ea2cd3effcc 100644
> --- a/fs/direct-io.c
> +++ b/fs/direct-io.c
> @@ -1148,7 +1148,7 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct
inode *inode,
>  
>  	if (align & blocksize_mask) {
>  		if (bdev)
> -			blkbits = blksize_bits(bdev_logical_block_size(bdev));
> +			blkbits = ilog2(bdev_logical_block_size(bdev));
bdev->bd_inode->i_blkbits.
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index cb05f71cf850..b896da27942a 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -3458,7 +3458,7 @@ static int check_direct_IO(struct inode *inode,
struct iov_iter *iter,
>  
>  	if (align & blocksize_mask) {
>  		if (bdev)
> -			blkbits = blksize_bits(bdev_logical_block_size(bdev));
> +			blkbits = ilog2(bdev_logical_block_size(bdev));
bdev->bd_inode->i_blkbits.
>  		blocksize_mask = (1 << blkbits) - 1;
>  		if (align & blocksize_mask)
>  			return -EINVAL;
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index ec7b78e6feca..2a807657d544 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -203,7 +203,7 @@ static loff_t
>  iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length,
>  		struct iomap_dio *dio, struct iomap *iomap)
>  {
> -	unsigned int blkbits =
blksize_bits(bdev_logical_block_size(iomap->bdev));
> +	unsigned int blkbits = ilog2(bdev_logical_block_size(iomap->bdev));
iomap->bdev->bd_inode->i_blkbits.

Matthew Wilcox

2020-May-29 20:27 UTC

head link

[Ocfs2-devel] [PATCH v2] blkdev: Replace blksize_bits() with ilog2()

On Fri, May 29, 2020 at 10:11:00PM +0800, Kaitao Cheng
wrote:> There is a function named ilog2() exist which can replace blksize.
> The generated code will be shorter and more efficient on some
> architecture, such as arm64. And ilog2() can be optimized according
> to different architecture.
We'd get the same benefit from a smaller patch with just:

--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1502,15 +1502,9 @@ static inline int blk_rq_aligned(struct request_queue *q,
unsigned long addr,
 	return !(addr & alignment) && !(len & alignment);
 }
 
-/* assumes size > 256 */
 static inline unsigned int blksize_bits(unsigned int size)
 {
-	unsigned int bits = 8;
-	do {
-		bits++;
-		size >>= 1;
-	} while (size > 256);
-	return bits;
+	return ilog2(size);
 }
 
 static inline unsigned int block_size(struct block_device *bdev)

Tao pilgrim

2020-Jun-01 07:22 UTC

head link

[Ocfs2-devel] [PATCH v2] blkdev: Replace blksize_bits() with ilog2()

On Fri, May 29, 2020 at 10:13 PM Jens Axboe <axboe at kernel.dk>
wrote:>
> On 5/29/20 8:11 AM, Kaitao Cheng wrote:
> > There is a function named ilog2() exist which can replace blksize.
> > The generated code will be shorter and more efficient on some
> > architecture, such as arm64. And ilog2() can be optimized according
> > to different architecture.
>
> When you posted this last time, I said:
>
> "I like the simplification, but do you have any results to back up
>  that claim? Is the generated code shorter? Runs faster?"
>
Hi  Jens Axboe:

I did a test on ARM64.
unsigned int ckt_blksize(int size)
{
   return blksize_bits(size);
}
unsigned int ckt_ilog2(int size)
{
    return ilog2(size);
}

When I compiled it into assembly code, I got the following result,

0000000000000088 <ckt_blksize>:
      88: 2a0003e8 mov w8, w0
      8c: 321d03e0 orr w0, wzr, #0x8
      90: 11000400 add w0, w0, #0x1
      94: 7108051f cmp w8, #0x201
      98: 53017d08 lsr w8, w8, #1
      9c: 54ffffa8 b.hi 90 <ckt_blksize+0x8>
      a0: d65f03c0 ret
      a4: d503201f nop

00000000000000a8 <ckt_ilog2>:
      a8: 320013e8 orr w8, wzr, #0x1f
      ac: 5ac01009 clz w9, w0
      b0: 4b090108 sub w8, w8, w9
      b4: 7100001f cmp w0, #0x0
      b8: 5a9f1100 csinv w0, w8, wzr, ne
      bc: d65f03c0 ret

The generated code of ilog2  is shorter , and  runs faster

> which you handily ignored, yet sending out a new version. I'm not
> going to apply this without justification, your commit message is
> handwavy at best.
>
Do I need to write the test content into commit message?



-- 
Yours,
Kaitao Cheng

Ocfs2 devel - May 2020 - [PATCH v2] blkdev: Replace blksize_bits() with ilog2()

[Ocfs2-devel] [PATCH v2] blkdev: Replace blksize_bits() with ilog2()

[Ocfs2-devel] [PATCH v2] blkdev: Replace blksize_bits() with ilog2()

[Ocfs2-devel] [PATCH v2] blkdev: Replace blksize_bits() with ilog2()

[Ocfs2-devel] [PATCH v2] blkdev: Replace blksize_bits() with ilog2()

[Ocfs2-devel] [PATCH v2] blkdev: Replace blksize_bits() with ilog2()