netdev - Re: [PATCH 01/23] block: factor out a bvec_set

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Message-ID: <2bab7050-dec7-3af8-b643-31b414b8c4b4@acm.org>
Date:   Mon, 30 Jan 2023 09:09:23 -0800
From:   Bart Van Assche <bvanassche@....org>
To:     Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>
Cc:     Ilya Dryomov <idryomov@...il.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Minchan Kim <minchan@...nel.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Keith Busch <kbusch@...nel.org>,
        Sagi Grimberg <sagi@...mberg.me>,
        Chaitanya Kulkarni <kch@...dia.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        David Howells <dhowells@...hat.com>,
        Marc Dionne <marc.dionne@...istor.com>,
        Xiubo Li <xiubli@...hat.com>, Steve French <sfrench@...ba.org>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna@...nel.org>,
        Mike Marshall <hubcap@...ibond.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Chuck Lever <chuck.lever@...cle.com>,
        linux-block@...r.kernel.org, ceph-devel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-nvme@...ts.infradead.org, linux-scsi@...r.kernel.org,
        target-devel@...r.kernel.org, kvm@...r.kernel.org,
        netdev@...r.kernel.org, linux-afs@...ts.infradead.org,
        linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org,
        linux-fsdevel@...r.kernel.org, linux-nfs@...r.kernel.org,
        devel@...ts.orangefs.org, io-uring@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH 01/23] block: factor out a bvec_set_page helper

On 1/30/23 01:21, Christoph Hellwig wrote:
> Add a helper to initialize a bvec based of a page pointer.  This will help
> removing various open code bvec initializations.

Why do you want to remove the open-coded bvec initializations? What is 
wrong with open-coding bvec initialization? This patch series modifies a 
lot of code but does not improve code readability. Anyone who encounters 
code that uses the new function bvec_set_page() has to look up the 
definition of that function to figure out what it does.

> -	iv = bip->bip_vec + bip->bip_vcnt;
> -
>   	if (bip->bip_vcnt &&
>   	    bvec_gap_to_prev(&bdev_get_queue(bio->bi_bdev)->limits,
>   			     &bip->bip_vec[bip->bip_vcnt - 1], offset))
>   		return 0;
>   
> -	iv->bv_page = page;
> -	iv->bv_len = len;
> -	iv->bv_offset = offset;
> +	bvec_set_page(&bip->bip_vec[bip->bip_vcnt], page, len, offset);
>   	bip->bip_vcnt++;

Has it been considered to use structure assignment instead of 
introducing bvec_set_page(), e.g. as follows?

bip->bip_vec[bip->bip_vcnt] = (struct bio_vec) {
       .bv_page = page, .bv_len = len, .bv_offset = offset };

Thanks,

Bart.