From: John Hubbard <jhubbard@nvidia.com>
To: Christoph Hellwig <hch@infradead.org>, <john.hubbard@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Anna Schumaker <anna.schumaker@netapp.com>,
"David S . Miller" <davem@davemloft.net>,
Dominique Martinet <asmadeus@codewreck.org>,
Eric Van Hensbergen <ericvh@gmail.com>,
Jason Gunthorpe <jgg@ziepe.ca>, Jason Wang <jasowang@redhat.com>,
Jens Axboe <axboe@kernel.dk>, Latchesar Ionkov <lucho@ionkov.net>,
"Michael S . Tsirkin" <mst@redhat.com>,
Miklos Szeredi <miklos@szeredi.hu>,
Trond Myklebust <trond.myklebust@hammerspace.com>,
Christoph Hellwig <hch@lst.de>,
Matthew Wilcox <willy@infradead.org>, <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>, <ceph-devel@vger.kernel.org>,
<kvm@vger.kernel.org>, <linux-block@vger.kernel.org>,
<linux-cifs@vger.kernel.org>, <linux-fsdevel@vger.kernel.org>,
<linux-nfs@vger.kernel.org>, <linux-rdma@vger.kernel.org>,
<netdev@vger.kernel.org>, <samba-technical@lists.samba.org>,
<v9fs-developer@lists.sourceforge.net>,
<virtualization@lists.linux-foundation.org>
Subject: Re: [PATCH 00/12] block/bio, fs: convert put_page() to put_user_page*()
Date: Mon, 5 Aug 2019 15:54:35 -0700 [thread overview]
Message-ID: <c35aa2bf-c830-9e57-78ca-9ce6fb6cb53b@nvidia.com> (raw)
In-Reply-To: <20190724061750.GA19397@infradead.org>
On 7/23/19 11:17 PM, Christoph Hellwig wrote:
> On Tue, Jul 23, 2019 at 09:25:06PM -0700, john.hubbard@gmail.com wrote:
>> * Store, in the iov_iter, a "came from gup (get_user_pages)" parameter.
>> Then, use the new iov_iter_get_pages_use_gup() to retrieve it when
>> it is time to release the pages. That allows choosing between put_page()
>> and put_user_page*().
>>
>> * Pass in one more piece of information to bio_release_pages: a "from_gup"
>> parameter. Similar use as above.
>>
>> * Change the block layer, and several file systems, to use
>> put_user_page*().
>
> I think we can do this in a simple and better way. We have 5 ITER_*
> types. Of those ITER_DISCARD as the name suggests never uses pages, so
> we can skip handling it. ITER_PIPE is rejected іn the direct I/O path,
> which leaves us with three.
>
Hi Christoph,
Are you working on anything like this? Or on the put_user_bvec() idea?
Please let me know, otherwise I'll go in and implement something here.
thanks,
--
John Hubbard
NVIDIA
> Out of those ITER_BVEC needs a user page reference, so we want to call
> put_user_page* on it. ITER_BVEC always already has page reference,
> which means in the block direct I/O path path we alread don't take
> a page reference. We should extent that handling to all other calls
> of iov_iter_get_pages / iov_iter_get_pages_alloc. I think we should
> just reject ITER_KVEC for direct I/O as well as we have no users and
> it is rather pointless. Alternatively if we see a use for it the
> callers should always have a life page reference anyway (or might
> be on kmalloc memory), so we really should not take a reference either.
>
> In other words: the only time we should ever have to put a page in
> this patch is when they are user pages. We'll need to clean up
> various bits of code for that, but that can be done gradually before
> even getting to the actual put_user_pages conversion.
>
next prev parent reply other threads:[~2019-08-05 22:54 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-24 4:25 [PATCH 00/12] block/bio, fs: convert put_page() to put_user_page*() john.hubbard
2019-07-24 4:25 ` [PATCH 01/12] mm/gup: add make_dirty arg to put_user_pages_dirty_lock() john.hubbard
2019-07-24 4:25 ` [PATCH 02/12] iov_iter: add helper to test if an iter would use GUP v2 john.hubbard
2019-07-24 4:25 ` [PATCH 03/12] block: bio_release_pages: use flags arg instead of bool john.hubbard
2019-07-24 5:30 ` Christoph Hellwig
2019-07-29 20:57 ` Jerome Glisse
2019-07-30 10:25 ` Christoph Hellwig
2019-07-30 15:57 ` Jerome Glisse
2019-08-01 8:20 ` Christoph Hellwig
2019-07-24 4:25 ` [PATCH 04/12] block: bio_release_pages: convert put_page() to put_user_page*() john.hubbard
2019-07-24 4:25 ` [PATCH 05/12] block_dev: " john.hubbard
2019-07-24 4:25 ` [PATCH 06/12] fs/nfs: " john.hubbard
2019-07-24 4:25 ` [PATCH 07/12] vhost-scsi: " john.hubbard
2019-07-24 4:34 ` John Hubbard
2019-07-24 8:07 ` Michael S. Tsirkin
2019-07-24 4:25 ` [PATCH 08/12] fs/cifs: " john.hubbard
2019-07-24 4:25 ` [PATCH 09/12] fs/fuse: " john.hubbard
2019-07-24 4:25 ` [PATCH 10/12] fs/ceph: " john.hubbard
2019-07-24 4:25 ` [PATCH 11/12] 9p/net: " john.hubbard
2019-07-24 4:25 ` [PATCH 12/12] fs/ceph: fix a build warning: returning a value from void function john.hubbard
2019-07-24 6:17 ` [PATCH 00/12] block/bio, fs: convert put_page() to put_user_page*() Christoph Hellwig
2019-07-24 23:23 ` John Hubbard
2019-08-05 22:54 ` John Hubbard [this message]
2019-08-07 6:34 ` Christoph Hellwig
2019-08-07 6:38 ` John Hubbard
2019-07-25 0:41 ` Bob Liu
2019-07-26 1:24 ` John Hubbard
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