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From: Christoph Hellwig <hch@lst.de>
To: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@lst.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Miquel Raynal <miquel.raynal@bootlin.com>,
	Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	linux-mtd@lists.infradead.org, linux-fsdevel@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: [PATCH 5/5] mm: simplify bdi refcounting
Date: Wed, 27 Oct 2021 09:42:07 +0200	[thread overview]
Message-ID: <20211027074207.GA12793@lst.de> (raw)
In-Reply-To: <20211022090203.GF1026@quack2.suse.cz>

On Fri, Oct 22, 2021 at 11:02:03AM +0200, Jan Kara wrote:
> On Thu 21-10-21 14:44:41, Christoph Hellwig wrote:
> > Move grabbing and releasing the bdi refcount out of the common
> > wb_init/wb_exit helpers into code that is only used for the non-default
> > memcg driven bdi_writeback structures.
> > 
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> 
> Can we perhaps add a comment to struct bdi_writeback definition (or maybe
> wb_init()?) mentioning that it holds a reference to 'bdi' if it is
> bdi_writeback struct for a cgroup? I don't see it mentioned anywhere and
> now that you've changed the code, it isn't that obvious from the code
> either... Otherwise the patch looks good so feel free to add:

Like this?

diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index 33207004cfded..a3d7dd1cc30a1 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -103,6 +103,9 @@ struct wb_completion {
  * change as blkcg is disabled and enabled higher up in the hierarchy, a wb
  * is tested for blkcg after lookup and removed from index on mismatch so
  * that a new wb for the combination can be created.
+ *
+ * Each bdi_writeback that is no embedded into the backing_dev_info must hold
+ * a reference to the parent backing_dev_info.  See cgwb_create() for details.
  */
 struct bdi_writeback {
 	struct backing_dev_info *bdi;	/* our parent bdi */

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WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@lst.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Miquel Raynal <miquel.raynal@bootlin.com>,
	Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	linux-mtd@lists.infradead.org, linux-fsdevel@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: [PATCH 5/5] mm: simplify bdi refcounting
Date: Wed, 27 Oct 2021 09:42:07 +0200	[thread overview]
Message-ID: <20211027074207.GA12793@lst.de> (raw)
In-Reply-To: <20211022090203.GF1026@quack2.suse.cz>

On Fri, Oct 22, 2021 at 11:02:03AM +0200, Jan Kara wrote:
> On Thu 21-10-21 14:44:41, Christoph Hellwig wrote:
> > Move grabbing and releasing the bdi refcount out of the common
> > wb_init/wb_exit helpers into code that is only used for the non-default
> > memcg driven bdi_writeback structures.
> > 
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> 
> Can we perhaps add a comment to struct bdi_writeback definition (or maybe
> wb_init()?) mentioning that it holds a reference to 'bdi' if it is
> bdi_writeback struct for a cgroup? I don't see it mentioned anywhere and
> now that you've changed the code, it isn't that obvious from the code
> either... Otherwise the patch looks good so feel free to add:

Like this?

diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index 33207004cfded..a3d7dd1cc30a1 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -103,6 +103,9 @@ struct wb_completion {
  * change as blkcg is disabled and enabled higher up in the hierarchy, a wb
  * is tested for blkcg after lookup and removed from index on mismatch so
  * that a new wb for the combination can be created.
+ *
+ * Each bdi_writeback that is no embedded into the backing_dev_info must hold
+ * a reference to the parent backing_dev_info.  See cgwb_create() for details.
  */
 struct bdi_writeback {
 	struct backing_dev_info *bdi;	/* our parent bdi */

  reply	other threads:[~2021-10-27  7:43 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-21 12:44 simplify bdi unregistation Christoph Hellwig
2021-10-21 12:44 ` Christoph Hellwig
2021-10-21 12:44 ` [PATCH 1/5] mm: export bdi_unregister Christoph Hellwig
2021-10-21 12:44   ` Christoph Hellwig
2021-10-22  8:41   ` Jan Kara
2021-10-22  8:41     ` Jan Kara
2021-10-21 12:44 ` [PATCH 2/5] mtd: call bdi_unregister explicitly Christoph Hellwig
2021-10-21 12:44   ` Christoph Hellwig
2021-10-22  8:43   ` Jan Kara
2021-10-22  8:43     ` Jan Kara
2021-10-21 12:44 ` [PATCH 3/5] fs: explicitly unregister per-superblock BDIs Christoph Hellwig
2021-10-21 12:44   ` Christoph Hellwig
2021-10-22  8:48   ` Jan Kara
2021-10-22  8:48     ` Jan Kara
2021-10-21 12:44 ` [PATCH 4/5] mm: don't automatically unregister bdis Christoph Hellwig
2021-10-21 12:44   ` Christoph Hellwig
2021-10-22  8:51   ` Jan Kara
2021-10-22  8:51     ` Jan Kara
2021-10-21 12:44 ` [PATCH 5/5] mm: simplify bdi refcounting Christoph Hellwig
2021-10-21 12:44   ` Christoph Hellwig
2021-10-22  9:02   ` Jan Kara
2021-10-22  9:02     ` Jan Kara
2021-10-27  7:42     ` Christoph Hellwig [this message]
2021-10-27  7:42       ` Christoph Hellwig
2021-10-27  9:47       ` Jan Kara
2021-10-27  9:47         ` Jan Kara

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