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Date:   Mon, 2 Nov 2020 16:18:17 +0100
From:   David Sterba <dsterba@suse.cz>
To:     Qu Wenruo <quwenruo.btrfs@gmx.com>
Cc:     David Sterba <dsterba@suse.com>, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 03/10] btrfs: replace s_blocksize_bits with
 fs_info::sectorsize_bits
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On Mon, Nov 02, 2020 at 10:23:43PM +0800, Qu Wenruo wrote:
> 
> 
> On 2020/10/29 下午10:27, David Sterba wrote:
> > The value of super_block::s_blocksize_bits is the same as
> > fs_info::sectorsize_bits, but we don't need to do the extra dereferences
> > in many functions and storing the bits as u32 (in fs_info) generates
> > shorter assembly.
> > 
> > Signed-off-by: David Sterba <dsterba@suse.com>
> 
> This patch is great.
> 
> I was just going to kill all "inode->i_sb->s_blocksize_bits" for subpage.
> 
> Although for subpage case, we may populate sb->s_blocksize_bits to
> PAGE_SHIFT, as current subpage doesn't support real subpage write at all.
> Thus we want everything from DIO alignement to reflink alignment to
> still be PAGE_SIZE.

Yeah the different alignment constraints with subpage will be
interesting.