linux-kernel - Re: [git pull] work.misc

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Message-ID: <20210502175946.GY1847222@casper.infradead.org>
Date:   Sun, 2 May 2021 18:59:46 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [git pull] work.misc

On Sun, May 02, 2021 at 09:26:26AM -0700, Linus Torvalds wrote:
> On Sat, May 1, 2021 at 6:30 PM Al Viro <viro@...iv.linux.org.uk> wrote:
> >
> > Mikulas Patocka (1):
> >       buffer: a small optimization in grow_buffers
> 
> Side note: if that optimization actually matters (which I doubt), we
> could just make getblk and friends take s_blocksize_bits instead of
> the block size. And avoid the whole "find first bit" thing.
> 
> As it is, we end up doing odd and broken things if anybody were to
> ever use a non-power-of-2 blocksize (we check that it's a multiple of
> the hw blocksize, we check that it's between 512 and PAGE_SIZE, but we
> don't seem to check that it's a power-of-2).

I think we have checks that the hw blocksize is a power-of-two (maybe
just in SCSI?  see sd_read_capacity())

I don't see much demand in the storage industry for non-power-of-two
sizes; I was once asked about a 12kB sector size at Intel, but when I
said "no", they didn't seem surprised.  I see interest in going smaller
(cacheline sized) for pmem and I see interest in going larger (16kB
sector sizes) for NAND.