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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pWfop-000DxZ-R5; Mon, 27 Feb 2023 15:53:39 +0000 Date: Mon, 27 Feb 2023 15:53:39 +0000 From: Matthew Wilcox To: David Howells Cc: Jens Axboe , Miklos Szeredi , Amit Shah , linux-fsdevel@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC][PATCH v2] splice: Prevent gifting of multipage folios Message-ID: References: <2740801.1677513063@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2740801.1677513063@warthog.procyon.org.uk> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 56ACE12000A X-Stat-Signature: jocz76tzjrp3sqgnixtc439zscp9iof1 X-HE-Tag: 1677513230-984827 X-HE-Meta: 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 BFIOi32/ BKWp3E7OqNhOLTmcPa1pBugDPvONt5X/FNEeo0tqaudD+VkBFuHs8jLJfzjHWbjejEdr4jHsvl02yjRnjNHeK3uGLklTPowzZRumUrCQ7qL/gzQT/N0NP+N+kyYRVUAC2Q4yzhD1K4ewMeG9pcZYfLCsoGKjGOOe15Cf0j6pvLJ3ljjpdOtBmLRW+JRZnH21pb3Evxj4kbb+l/fOsHZ84RVROl/VXqePFuI6mexY1JbzEY+zKsWDWYpZAo0t8YInJ8I9zfS/GdnA0+8shLHyo8Nidan72df7N3JE9s6xIlfeRlRDaiXziC678S2xI8I0m3JLTnDU5WhoKuqZUe6s0Pc418Fou3wt6PloAUBQDsMmTgCu+nU+3rQuHBrNiwTLZCAA9P5yEDhowG1GPNgahOsH50u143K9VN0OL X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Feb 27, 2023 at 03:51:03PM +0000, David Howells wrote: > > Don't let parts of compound pages/multipage folios be gifted by (vm)splice > into a pipe as the other end may only be expecting single-page gifts (fuse > and virtio console for example). > > replace_page_cache_folio(), for example, will do the wrong thing if it > tries to replace a single paged folio with a multipage folio. > > Try to avoid this by making add_to_pipe() remove the gift flag on multipage > folios. > > Fixes: 7afa6fd037e5 ("[PATCH] vmsplice: allow user to pass in gift pages") > Signed-off-by: David Howells > cc: Matthew Wilcox Reviewed-by: Matthew Wilcox (Oracle) Cc: stable@vger.kernel.org > cc: Jens Axboe > cc: Miklos Szeredi > cc: Amit Shah > cc: linux-fsdevel@vger.kernel.org > cc: virtualization@lists.linux-foundation.org > cc: linux-mm@kvack.org > --- > fs/splice.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/fs/splice.c b/fs/splice.c > index 2e76dbb81a8f..8bbd7794d9f0 100644 > --- a/fs/splice.c > +++ b/fs/splice.c > @@ -240,6 +240,8 @@ ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct pipe_buffer *buf) > } else if (pipe_full(head, tail, pipe->max_usage)) { > ret = -EAGAIN; > } else { > + if (PageCompound(buf->page)) > + buf->flags &= ~PIPE_BUF_FLAG_GIFT; > pipe->bufs[head & mask] = *buf; > pipe->head = head + 1; > return buf->len; >