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From: Johannes Thumshirn <Johannes.Thumshirn@wdc.com>
To: Michal Hocko <mhocko@suse.com>
Cc: Damien Le Moal <Damien.LeMoal@wdc.com>,
	Dan Carpenter <dan.carpenter@oracle.com>,
	"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>
Subject: Re: [bug report] scsi: sd_zbc: emulate ZONE_APPEND commands
Date: Wed, 17 Feb 2021 09:08:07 +0000	[thread overview]
Message-ID: <SN4PR0401MB3598D86F05613F41049038BB9B869@SN4PR0401MB3598.namprd04.prod.outlook.com> (raw)
In-Reply-To: YCzN4qPicujdSJ7P@dhcp22.suse.cz

On 17/02/2021 09:03, Michal Hocko wrote:
>> No I don't think so. A mutex isn't a spinlock so we can sleep on the allocation.
>> We can't use GFP_KERNEL as we're about to do I/O. blk_revalidate_disk_zones() called
>> a few line below also does the memalloc_noio_{save,restore}() dance.
> 
> You should be extending noio scope then if this allocation falls into
> the same category. Ideally the scope should start at the recursion place
> and end where the scope really ened.

That means all callers of blk_revalidate_disk_zones() should do 
memalloc_noio_{save,restore}? If yes, can we somehow runtime assert
that this is done, so we don't end up with bad surprises?

>>
>> Would a kmem_cache for these revalidations help us in any way?
> 
> I am not sure what you mean here.
> 

Using a kmem_cache for the allocations passed into blk_revalidate_disk_zones().
I've looked into kmem_cache_alloc() and I couldn't find anything that speaks 
against it, but I'm not too familiar with the code.

  reply	other threads:[~2021-02-17  9:09 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-16 19:39 [bug report] scsi: sd_zbc: emulate ZONE_APPEND commands Dan Carpenter
2021-02-16 23:33 ` Damien Le Moal
2021-02-17  6:42   ` Johannes Thumshirn
2021-02-17  8:00     ` Damien Le Moal
2021-02-17  8:03     ` Michal Hocko
2021-02-17  9:08       ` Johannes Thumshirn [this message]
2021-02-17  9:36         ` Michal Hocko
2021-02-17  9:41           ` Johannes Thumshirn
2021-02-17 10:05             ` Michal Hocko
2021-02-17  9:13       ` Damien Le Moal
2021-02-17  9:18         ` Johannes Thumshirn
2021-02-17 11:16           ` Dan Carpenter
2021-02-17 11:18             ` Johannes Thumshirn
2021-02-17  9:32         ` Michal Hocko

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