Date:   Tue, 31 Jan 2023 05:28:19 +0000
From:   Matthew Wilcox <willy@infradead.org>
To:     Jakub Kicinski <kuba@kernel.org>
Cc:     Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
        Ilya Dryomov <idryomov@gmail.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Minchan Kim <minchan@kernel.org>,
        Sergey Senozhatsky <senozhatsky@chromium.org>,
        Keith Busch <kbusch@kernel.org>,
        Sagi Grimberg <sagi@grimberg.me>,
        Chaitanya Kulkarni <kch@nvidia.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        David Howells <dhowells@redhat.com>,
        Marc Dionne <marc.dionne@auristor.com>,
        Xiubo Li <xiubli@redhat.com>, Steve French <sfrench@samba.org>,
        Trond Myklebust <trond.myklebust@hammerspace.com>,
        Anna Schumaker <anna@kernel.org>,
        Mike Marshall <hubcap@omnibond.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>,
        Chuck Lever <chuck.lever@oracle.com>,
        linux-block@vger.kernel.org, ceph-devel@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        linux-nvme@lists.infradead.org, linux-scsi@vger.kernel.org,
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        netdev@vger.kernel.org, linux-afs@lists.infradead.org,
        linux-cifs@vger.kernel.org, samba-technical@lists.samba.org,
        linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org,
        devel@lists.orangefs.org, io-uring@vger.kernel.org,
        linux-mm@kvack.org
Subject: Re: [PATCH 01/23] block: factor out a bvec_set_page helper
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On Tue, Jan 31, 2023 at 05:00:32AM +0000, Matthew Wilcox wrote:
> On Mon, Jan 30, 2023 at 08:47:58PM -0800, Jakub Kicinski wrote:
> > kinda random thought but since we're touching this area - could we
> > perhaps move the definition of struct bio_vec and trivial helpers 
> > like this into a new header? bvec.h pulls in mm.h which is a right
> > behemoth :S
> 
> I bet we can drop mm.h now.  It was originally added for nth_page()
> in 3d75ca0adef4 but those were all removed by b8753433fc61.
> 
> A quick smoke test on my default testing config doesn't find any
> problems.  Let me send a patch and see if the build bots complain.

Disappointingly, it doesn't really change anything.  1134 files
depend on mm.h both before and after [1].  Looks like it's due to
arch/x86/include/asm/cacheflush.h pulling in linux/mm.h, judging by the
contents of .build_test_kernel-x86_64/net/ipv6/.inet6_hashtables.o.cmd.
But *lots* of header files pull in mm.h, including scatterlist.h,
vt_kern.h, net.h, nfs_fs.h, sunrpc/svc.h and security.h.

I suppose it may cut down on include loops to drop it here, so I'm
still in favour of the patch I posted, but this illustrates how
deeply entangled our headers still are.

[1] find .build_test_kernel-x86_64/ -name '.*.cmd' |xargs grep 'include/linux/mm.h' |wc -l