From: Logan Gunthorpe <logang@deltatee.com>
To: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>, Christoph Hellwig <hch@lst.de>,
John Hubbard <jhubbard@nvidia.com>,
Matthew Wilcox <willy@infradead.org>,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
Christoph Hellwig <hch@infradead.org>,
Jeff Layton <jlayton@kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 2/4] iov_iter: Add a function to extract a page list from an iterator
Date: Tue, 6 Dec 2022 11:40:32 -0700 [thread overview]
Message-ID: <8420a781-6ac2-e976-cc43-a04d59d2d043@deltatee.com> (raw)
In-Reply-To: <1251303.1670351737@warthog.procyon.org.uk>
On 2022-12-06 11:35, David Howells wrote:
> Logan Gunthorpe <logang@deltatee.com> wrote:
>
>> If this is going to be a general replacement for iov_iter_get_pages()
>> it's going to need to pass through gup_flags. My recent patchset added
>> versions with these and I think it should be in during the next merge
>> cycle. [1]
>
> Cool. Note that the current iov_iter_get_pages2() is broken, which is why Al
> wanted a replacement. It should not be taking a ref on the pages in an
> XARRAY, BVEC or PIPE - and it should be pinning rather than getting a ref on
> pages in IOVEC or UBUF if the buffer is being read into. I'm guessing that
> your changes move the latter decision to the caller?
My changes maintained the status quo in terms of brokenness. They simply
added the gup_flags so I could pass a P2PDMA flag in a couple specific
cases. I have no objections to the other changes and vaguely look ok to
me, but having not seen patches to convert the users I care about, I
thought I'd point out that the P2PDMA use case will need to be supported
somehow.
Logan
next prev parent reply other threads:[~2022-12-06 18:40 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-02 9:43 [PATCH v3 0/4] iov_iter: Add extraction helpers David Howells
2022-12-02 9:43 ` [PATCH v3 1/4] mm: Move FOLL_* defs to mm_types.h David Howells
2022-12-02 9:43 ` [PATCH v3 2/4] iov_iter: Add a function to extract a page list from an iterator David Howells
2022-12-06 16:43 ` Logan Gunthorpe
2022-12-06 18:35 ` David Howells
2022-12-06 18:40 ` Logan Gunthorpe [this message]
2022-12-02 9:43 ` [PATCH v3 3/4] netfs: Add a function to extract a UBUF or IOVEC into a BVEC iterator David Howells
2022-12-02 9:43 ` [PATCH v3 4/4] netfs: Add a function to extract an iterator into a scatterlist David Howells
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