From: Christoph Hellwig <hch@lst.de>
To: Matthew Wilcox <willy@infradead.org>
Cc: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>,
linux-block@vger.kernel.org, linux-scsi@vger.kernel.org,
target-devel@vger.kernel.org, linux-btrfs@vger.kernel.org,
axboe@kernel.dk, mb@lightnvm.io, martin.petersen@oracle.com,
clm@fb.com, josef@toxicpanda.com, dsterba@suse.com,
johannes.thumshirn@wdc.com, ming.lei@redhat.com, osandov@fb.com,
jefflexu@linux.alibaba.com, hch@lst.de
Subject: Re: [RFC PATCH 0/8] block: fix bio_add_XXX_page() return type
Date: Mon, 24 May 2021 09:35:27 +0200 [thread overview]
Message-ID: <20210524073527.GA24302@lst.de> (raw)
In-Reply-To: <YKeZ5dtxt3gsImsd@casper.infradead.org>
On Fri, May 21, 2021 at 12:30:45PM +0100, Matthew Wilcox wrote:
> On Wed, May 19, 2021 at 11:22:47PM -0700, Chaitanya Kulkarni wrote:
> > The helper functions bio_add_XXX_page() returns the length which is
> > unsigned int but the return type of those functions is defined
> > as int instead of unsigned int.
>
> I've been thinking about this for a few weeks as part of the folio
> patches:
>
> https://lore.kernel.org/linux-fsdevel/20210505150628.111735-72-willy@infradead.org/
>
> - len and off are measured in bytes
> - neither are permitted to be negative
> - for efficiency we only permit them to be up to 4GB
>
> I therefore believe the correct type for these parameters to be size_t,
> and we should range-check them if they're too large. they should
> actually always fit within the page that they're associated with, but
> people do allocate non-compound pages and i'm not trying to break that
> today.
>
> using size_t makes it clear that these are byte counts, not (eg) sector
> counts. i do think it's good to make the return value unsigned so we
> don't have people expecting a negative errno on failure.
I think the right type is bool. We always return either 0 or the full
length we tried to add. Instead of optimizing for a partial add (which
only makes sense for bio_add_hw_page anyway), I'd rather make the
interface as simple as possible.
next prev parent reply other threads:[~2021-05-24 7:35 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-20 6:22 [RFC PATCH 0/8] block: fix bio_add_XXX_page() return type Chaitanya Kulkarni
2021-05-20 6:22 ` [RFC PATCH 1/8] block: fix return type of bio_add_hw_page() Chaitanya Kulkarni
2021-05-20 6:22 ` [RFC PATCH 2/8] block: fix return type of bio_add_pc_page() Chaitanya Kulkarni
2021-05-20 6:22 ` [RFC PATCH 3/8] block: fix return type of bio_add_zone_append_page Chaitanya Kulkarni
2021-05-20 6:22 ` [RFC PATCH 4/8] block: fix return type of bio_add_page() Chaitanya Kulkarni
2021-05-20 6:22 ` [RFC PATCH 5/8] lightnvm: fix variable type pblk-core Chaitanya Kulkarni
2021-05-20 6:22 ` [RFC PATCH 6/8] pscsi: fix variable type pscsi_map_sg Chaitanya Kulkarni
2021-05-20 6:22 ` [RFC PATCH 7/8] btrfs: fix variable type in btrfs_bio_add_page Chaitanya Kulkarni
2021-05-20 6:22 ` [RFC PATCH 8/8] block: fix variable type for zero pages Chaitanya Kulkarni
2021-05-21 10:25 ` [RFC PATCH 0/8] block: fix bio_add_XXX_page() return type Johannes Thumshirn
2021-05-21 21:37 ` Chaitanya Kulkarni
2021-05-21 22:37 ` Omar Sandoval
2021-05-21 23:25 ` Chaitanya Kulkarni
2021-05-21 11:30 ` Matthew Wilcox
2021-05-21 21:51 ` Chaitanya Kulkarni
2021-05-24 7:35 ` Christoph Hellwig [this message]
2021-05-24 13:29 ` Matthew Wilcox
2021-05-26 2:55 ` Chaitanya Kulkarni
2021-05-27 11:43 ` Christoph Hellwig
2021-05-27 17:43 ` Chaitanya Kulkarni
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