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Date: Thu, 20 Jun 2024 17:20:26 +0200
From: Christoph Hellwig <hch@lst.de>
To: Matthew Wilcox <willy@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>,
	Kent Overstreet <kent.overstreet@linux.dev>,
	Hongbo Li <lihongbo22@huawei.com>, linux-bcachefs@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org,
	hch@lst.de
Subject: Re: bvec_iter.bi_sector -> loff_t?
Message-ID: <20240620152026.GA25908@lst.de>
References: <20240620132157.888559-1-lihongbo22@huawei.com> <bbf7lnl2d5sxdzqbv3jcn6gxmtnsnscakqmfdf6vj4fcs3nasx@zvjsxfwkavgm> <ZnQ0gdpcplp_-aw7@casper.infradead.org> <pfxno4kzdgk6imw7vt2wvpluybohbf6brka6tlx34lu2zbbuaz@khifgy2v2z5n> <ZnRBkr_7Ah8Hj-i-@casper.infradead.org> <0f74318e-2442-4d7d-b839-2277a40ca196@kernel.dk> <ZnRHi3Cfh_w7ZQa1@casper.infradead.org>
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On Thu, Jun 20, 2024 at 04:15:23PM +0100, Matthew Wilcox wrote:
> > 
> > and have O_DIRECT with a 32-bit memory alignment work just fine, where
> > before it would EINVAL. The sector size memory alignment thing has
> > always been odd and never rooted in anything other than "oh let's just
> > require the whole combination of size/disk offset/alignment to be sector
> > based".
> 
> Oh, cool!  https://man7.org/linux/man-pages/man2/open.2.html
> doesn't know about this yet; is anyone working on updating it?

Just remember that there are two kinds of alignments:

 - the memory alignment, which Jens is talking about
 - the offset/size alignment, which is set by the LBA size

statx (optionally) exposes both in the stx_dio_mem_align and
stx_dio_offset_align fields, which are documented in the statx(2)
man page.  For network file systems like nfs there might be no
alignment requirements at all.