From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
Josef Bacik <josef@toxicpanda.com>,
David Sterba <dsterba@suse.com>,
Naohiro Aota <naohiro.aota@wdc.com>,
linux-block@vger.kernel.org, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 3/9] block: unhash the whole device inode earlier
Date: Thu, 22 Jul 2021 15:12:27 +0200 [thread overview]
Message-ID: <20210722131227.GA27213@lst.de> (raw)
In-Reply-To: <YPkqHjNQpgvbUgBr@T590>
On Thu, Jul 22, 2021 at 04:19:42PM +0800, Ming Lei wrote:
> > goto bdput;
> > - if ((disk->flags & (GENHD_FL_UP | GENHD_FL_HIDDEN)) != GENHD_FL_UP)
> > + if (disk->flags & GENHD_FL_HIDDEN)
>
> But del_gendisk() can be called just between bdget() and checking GENHD_FL_UP.
>
> And not see difference by moving remove_inode_hash() with disk open_mutex held.
The difference is not about having the open_mutex held, but about doing
it earlier.
The only check that matters is the GENHD_FL_UP check in blkdev_get_by_dev.
The earlier check just reduces the amount of work we're doing for a disk
already being delete. With the early unhash there is no need for that
check as we won't even find the inode for a disk in del_gendisk. We still
need the non-racy check under the lock, but the patch doesn't touch that
one.
Maybe I need to split this into two patches and improve the commit log.
next prev parent reply other threads:[~2021-07-22 13:12 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-22 7:53 fixes and cleanups for block_device refcounting v2 Christoph Hellwig
2021-07-22 7:53 ` [PATCH 1/9] block: delay freeing the gendisk Christoph Hellwig
2021-07-22 7:53 ` [PATCH 2/9] block: assert the locking state in delete_partition Christoph Hellwig
2021-07-22 18:38 ` Chaitanya Kulkarni
2021-07-22 7:53 ` [PATCH 3/9] block: unhash the whole device inode earlier Christoph Hellwig
2021-07-22 8:19 ` Ming Lei
2021-07-22 13:12 ` Christoph Hellwig [this message]
2021-07-22 7:53 ` [PATCH 4/9] block: allocate bd_meta_info later in add_partitions Christoph Hellwig
2021-07-22 8:32 ` Ming Lei
2021-07-22 7:53 ` [PATCH 5/9] block: change the refcounting for partitions Christoph Hellwig
2021-07-22 8:41 ` Ming Lei
2021-07-22 13:12 ` Christoph Hellwig
2021-07-22 7:53 ` [PATCH 6/9] btrfs: store a block_device in struct btrfs_ordered_extent Christoph Hellwig
2021-07-22 12:58 ` David Sterba
2021-07-22 13:04 ` Christoph Hellwig
2021-07-22 7:54 ` [PATCH 7/9] loop: don't grab a reference to the block device Christoph Hellwig
2021-07-22 8:57 ` Ming Lei
2021-07-22 18:40 ` Chaitanya Kulkarni
2021-07-22 7:54 ` [PATCH 8/9] block: remove bdgrab Christoph Hellwig
2021-07-22 7:54 ` [PATCH 9/9] block: remove bdput Christoph Hellwig
2021-07-22 18:40 ` Chaitanya Kulkarni
2021-07-28 1:39 ` fixes and cleanups for block_device refcounting v2 Jens Axboe
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