From: Christoph Hellwig <hch@lst.de>
To: Jan Kara <jack@suse.cz>, David Howells <dhowells@redhat.com>,
David Hildenbrand <david@redhat.com>,
Peter Xu <peterx@redhat.com>
Cc: Lei Huang <lei.huang@linux.intel.com>,
miklos@szeredi.hu, Xiubo Li <xiubli@redhat.com>,
Ilya Dryomov <idryomov@gmail.com>,
Jeff Layton <jlayton@kernel.org>,
Trond Myklebust <trond.myklebust@hammerspace.com>,
Anna Schumaker <anna@kernel.org>,
Latchesar Ionkov <lucho@ionkov.net>,
Dominique Martinet <asmadeus@codewreck.org>,
Christian Schoenebeck <linux_oss@crudebyte.com>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
John Fastabend <john.fastabend@gmail.com>,
Jakub Sitnicki <jakub@cloudflare.com>,
Boris Pismenny <borisp@nvidia.com>,
linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
ceph-devel@vger.kernel.org, linux-mm@kvack.org,
v9fs@lists.linux.dev, netdev@vger.kernel.org
Subject: getting rid of the last memory modifitions through gup(FOLL_GET)
Date: Tue, 5 Sep 2023 16:16:04 +0200 [thread overview]
Message-ID: <20230905141604.GA27370@lst.de> (raw)
Hi all,
we've made some nice progress on converting code that modifies user
memory to the pin_user_pages interface, especially though the work
from David Howells on iov_iter_extract_pages. This thread tries to
coordinate on how to finish off this work.
The obvious next step is the remaining users of iov_iter_get_pages2
and iov_iter_get_pages_alloc2. We have three file system direct I/O
users of those left: ceph, fuse and nfs. Lei Huang has sent patches
to convert fuse to iov_iter_extract_pages which I'd love to see merged,
and we'd need equivalent work for ceph and nfs.
The non-file system uses are in the vmsplice code, which only reads
from the pages (but would still benefit from an iov_iter_extract_pages
conversion), and in net. Out of the users in net, all but the 9p code
appear to be for reads from memory, so they don't pin even if a
conversion would be nice to retire iov_iter_get_pages* APIs.
After that we might have to do an audit of the raw get_user_pages APIs,
but there probably aren't many that modify file backed memory.
I'm also wondering what a good debug aid would be for detecting
writes to file backed memory without a previous reservation, but
everything either involves a page flag or file system code. But if
someone has an idea I'm all ear as something mechanical to catch these
uses would be quite helpful.
next reply other threads:[~2023-09-05 16:35 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-05 14:16 Christoph Hellwig [this message]
2023-09-06 9:42 ` getting rid of the last memory modifitions through gup(FOLL_GET) David Hildenbrand
2023-09-08 8:15 ` Christoph Hellwig
2023-09-08 16:48 ` David Hildenbrand
2023-09-09 11:18 ` Christoph Hellwig
2023-09-08 8:41 ` David Howells
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