linux-xfs.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Matthew Wilcox <willy@infradead.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: Chris Mason <clm@fb.com>,
	"linux-xfs@vger.kernel.org" <linux-xfs@vger.kernel.org>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"jlayton@kernel.org" <jlayton@kernel.org>,
	"hch@infradead.org" <hch@infradead.org>
Subject: Re: [RFC 0/8] Replacing the readpages a_op
Date: Mon, 13 Jan 2020 14:10:47 -0800	[thread overview]
Message-ID: <20200113221047.GB18216@bombadil.infradead.org> (raw)
In-Reply-To: <910af281-4e2b-3e5d-5533-b5ceafd59665@kernel.dk>

On Mon, Jan 13, 2020 at 03:00:40PM -0700, Jens Axboe wrote:
> On 1/13/20 2:58 PM, Matthew Wilcox wrote:
> > On Mon, Jan 13, 2020 at 06:00:52PM +0000, Chris Mason wrote:
> >> This is true, I didn't explain that part well ;)  Depending on 
> >> compression etc we might end up poking the xarray inside the actual IO 
> >> functions, but the main difference is that btrfs is building a single 
> >> bio.  You're moving the plug so you'll merge into single bio, but I'd 
> >> rather build 2MB bios than merge them.
> > 
> > Why don't we store a bio pointer inside the plug?  You're opencoding that,
> > iomap is opencoding that, and I bet there's a dozen other places where
> > we pass a bio around.  Then blk_finish_plug can submit the bio.
> 
> Plugs aren't necessarily a bio, they can be callbacks too.

I'm thinking something as simple as this:

@@ -1711,6 +1711,7 @@ void blk_start_plug(struct blk_plug *plug)
 
        INIT_LIST_HEAD(&plug->mq_list);
        INIT_LIST_HEAD(&plug->cb_list);
+       plug->bio = NULL;
        plug->rq_count = 0;
        plug->multiple_queues = false;
 
@@ -1786,6 +1787,8 @@ void blk_finish_plug(struct blk_plug *plug)
 {
        if (plug != current->plug)
                return;
+       if (plug->bio)
+               submit_bio(plug->bio);
        blk_flush_plug_list(plug, false);
 
        current->plug = NULL;
@@ -1160,6 +1160,7 @@ extern void blk_set_queue_dying(struct request_queue *);
 struct blk_plug {
        struct list_head mq_list; /* blk-mq requests */
        struct list_head cb_list; /* md requires an unplug callback */
+       struct bio *bio;
        unsigned short rq_count;
        bool multiple_queues;
 };

with accessors to 'get_current_bio()' and 'set_current_bio()'.

  reply	other threads:[~2020-01-13 22:10 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-13 15:37 [RFC 0/8] Replacing the readpages a_op Matthew Wilcox
2020-01-13 15:37 ` [PATCH 1/8] pagevec: Add an iterator Matthew Wilcox
2020-01-13 15:37 ` [PATCH 2/8] mm: Fix the return type of __do_page_cache_readahead Matthew Wilcox
2020-01-13 15:37 ` [PATCH 3/8] mm: Use a pagevec for readahead Matthew Wilcox
2020-01-13 15:37 ` [PATCH 4/8] mm/fs: Add a_ops->readahead Matthew Wilcox
2020-01-13 18:22   ` Daniel Wagner
2020-01-13 19:17     ` Matthew Wilcox
2020-01-13 15:37 ` [PATCH 5/8] iomap,xfs: Convert from readpages to readahead Matthew Wilcox
2020-01-13 15:37 ` [PATCH 6/8] cifs: " Matthew Wilcox
2020-01-13 15:37 ` [PATCH 7/8] mm: Remove add_to_page_cache_locked Matthew Wilcox
2020-01-13 15:37 ` [PATCH 8/8] mm: Unify all add_to_page_cache variants Matthew Wilcox
2020-01-13 16:42 ` [RFC 0/8] Replacing the readpages a_op Chris Mason
2020-01-13 17:40   ` Matthew Wilcox
2020-01-13 18:00     ` Chris Mason
2020-01-13 21:58       ` Matthew Wilcox
2020-01-13 22:00         ` Jens Axboe
2020-01-13 22:10           ` Matthew Wilcox [this message]
2020-01-13 22:14             ` Jens Axboe
2020-01-13 22:27               ` Matthew Wilcox
2020-01-13 22:30                 ` Jens Axboe
2020-01-13 22:34                 ` Chris Mason
2020-01-14  1:01                   ` Matthew Wilcox
2020-01-14  1:07                     ` Chris Mason
2020-01-13 17:54   ` Matthew Wilcox
2020-01-13 22:19     ` Jens Axboe

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200113221047.GB18216@bombadil.infradead.org \
    --to=willy@infradead.org \
    --cc=axboe@kernel.dk \
    --cc=clm@fb.com \
    --cc=hch@infradead.org \
    --cc=jlayton@kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-xfs@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).