Re: [PATCH v2] block: simplify blksize_bits() implementation

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On 10/29/22 20:25, Dawei Li wrote:
On Sat, Oct 29, 2022 at 08:00:58PM -0700, Bart Van Assche wrote:
On 10/29/22 19:17, Dawei Li wrote:
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 57ed49f20d2e..7b537afe8b38 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1349,12 +1349,7 @@ static inline int blk_rq_aligned(struct request_queue *q, unsigned long addr,
   /* 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 order_base_2((size + SECTOR_SIZE - 1) >> SECTOR_SHIFT) + SECTOR_SHIFT;
   }

Why the rounding ("+ SECTOR_SIZE - 1")? The blksize_bits() argument should
be an argument of two.

Yeah, that's what's supposed to be.
But I thought maybe a "just in case" is more robust?
Should we consider these corner cases(!is_power_of_2())?

I don't think that the Linux kernel supports block sizes that are not a power of two. Hence my request to leave out the rounding code. Keeping that code would be misleading because it would suggest that the blksize_bits() argument can be something else than a power of two.

Thanks,

Bart.




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