From: Al Viro <viro@zeniv.linux.org.uk>
To: David Howells <dhowells@redhat.com>
Cc: netdev@vger.kernel.org, "David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
David Ahern <dsahern@kernel.org>,
Matthew Wilcox <willy@infradead.org>,
Christoph Hellwig <hch@infradead.org>,
Jens Axboe <axboe@kernel.dk>, Jeff Layton <jlayton@kernel.org>,
Christian Brauner <brauner@kernel.org>,
Chuck Lever III <chuck.lever@oracle.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH net-next v6 06/18] net: Add a function to splice pages into an skbuff for MSG_SPLICE_PAGES
Date: Thu, 13 Apr 2023 05:41:23 +0100 [thread overview]
Message-ID: <20230413044123.GB3390869@ZenIV> (raw)
In-Reply-To: <20230411160902.4134381-7-dhowells@redhat.com>
On Tue, Apr 11, 2023 at 05:08:50PM +0100, David Howells wrote:
> Add a function to handle MSG_SPLICE_PAGES being passed internally to
> sendmsg(). Pages are spliced into the given socket buffer if possible and
> copied in if not (ie. they're slab pages or have a zero refcount).
That "ie." would better be "e.g." - that condition is *not* enough for
tell the unsafe ones from the rest.
sendpage_ok() would be better off called "might_be_ok_to_sendpage()".
If it's false, we'd better not grab a reference to the page and expect the
sucker to stay safe until the reference is dropped. However, AFAICS
it might return true on a page that is not safe in that respect.
What rules do you propose for sendpage users? "Pass whatever page reference
you want, it'll do the right thing"? Anything short of that would better
be documented as explicitly as possible...
next prev parent reply other threads:[~2023-04-13 4:41 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-11 16:08 [PATCH net-next v6 00/18] splice, net: Replace sendpage with sendmsg(MSG_SPLICE_PAGES), part 1 David Howells
2023-04-11 16:08 ` [PATCH net-next v6 01/18] net: Declare MSG_SPLICE_PAGES internal sendmsg() flag David Howells
2023-04-13 0:51 ` Al Viro
2023-04-13 4:29 ` Al Viro
2023-04-13 20:39 ` David Howells
2023-04-13 20:49 ` Al Viro
2023-04-13 21:01 ` Al Viro
2023-04-11 16:08 ` [PATCH net-next v6 02/18] mm: Move the page fragment allocator from page_alloc.c into its own file David Howells
2023-04-11 16:08 ` [PATCH net-next v6 03/18] mm: Make the page_frag_cache allocator use multipage folios David Howells
2023-04-11 16:08 ` [PATCH net-next v6 04/18] mm: Make the page_frag_cache allocator use per-cpu David Howells
2023-04-11 16:55 ` Christoph Hellwig
2023-04-12 15:31 ` Christoph Hellwig
2023-04-12 23:12 ` David Howells
2023-04-11 16:08 ` [PATCH net-next v6 05/18] net: Pass max frags into skb_append_pagefrags() David Howells
2023-04-11 16:08 ` [PATCH net-next v6 06/18] net: Add a function to splice pages into an skbuff for MSG_SPLICE_PAGES David Howells
2023-04-13 4:41 ` Al Viro [this message]
2023-04-13 21:26 ` How to determine if a page can be spliced into an skbuff, or if it should be copied/rejected? David Howells
2023-04-11 16:08 ` [PATCH net-next v6 07/18] tcp: Support MSG_SPLICE_PAGES David Howells
2023-04-11 17:09 ` Eric Dumazet
2023-04-11 17:49 ` David Howells
2023-04-11 16:08 ` [PATCH net-next v6 08/18] tcp: Convert do_tcp_sendpages() to use MSG_SPLICE_PAGES David Howells
2023-04-11 16:08 ` [PATCH net-next v6 09/18] tcp_bpf: Inline do_tcp_sendpages as it's now a wrapper around tcp_sendmsg David Howells
2023-04-11 16:08 ` [PATCH net-next v6 10/18] espintcp: Inline do_tcp_sendpages() David Howells
2023-04-11 16:08 ` [PATCH net-next v6 11/18] tls: " David Howells
2023-04-11 16:08 ` [PATCH net-next v6 12/18] siw: " David Howells
2023-04-11 17:22 ` Tom Talpey
2023-04-11 16:08 ` [PATCH net-next v6 13/18] tcp: Fold do_tcp_sendpages() into tcp_sendpage_locked() David Howells
2023-04-11 16:08 ` [PATCH net-next v6 14/18] ip, udp: Support MSG_SPLICE_PAGES David Howells
2023-04-11 16:08 ` [PATCH net-next v6 15/18] ip6, udp6: " David Howells
2023-04-11 16:09 ` [PATCH net-next v6 16/18] udp: Convert udp_sendpage() to use MSG_SPLICE_PAGES David Howells
2023-04-11 16:09 ` [PATCH net-next v6 17/18] ip: Remove ip_append_page() David Howells
2023-04-11 16:09 ` [PATCH net-next v6 18/18] af_unix: Support MSG_SPLICE_PAGES David Howells
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