From: Sagi Grimberg <sagi@grimberg.me>
To: Christoph Hellwig <hch@lst.de>
Cc: Keith Busch <kbusch@kernel.org>,
Anton Eidelman <anton@lightbitslabs.com>,
linux-nvme@lists.infradead.org
Subject: Re: [PATCH v2 for-5.8-rc 3/6] nvme: don't protect ns mutation with ns->head->lock
Date: Wed, 24 Jun 2020 01:24:33 -0700 [thread overview]
Message-ID: <6d2f4e5e-9d0a-e145-2913-45f3699ff89c@grimberg.me> (raw)
In-Reply-To: <20200624063719.GC17594@lst.de>
>> Right now ns->head->lock is protecting namespace mutation
>> which is wrong and unneeded. Move it to only protect
>> against head mutations. While we're at it, remove unnecessary
>> ns->head reference as we already have head pointer.
>
> The changes look reasonable (nitpick below), but this changelog doesn't
> sway what the problem is and how it it fixed.
I'll add to v3:
The problem with this is that the head->lock spans
mpath disk node I/O that may block under some conditions (if
for example the controller is disconnecting or the path
became inaccessible), The locking scheme does not allow any
other path to enable itself, preventing blocked I/O to complete
and forward-progress from there.
This is a preparation patch for the fix in a subsequent patch
where the disk I/O will also be done outside the head->lock.
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next prev parent reply other threads:[~2020-06-24 8:24 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-24 0:18 [PATCH v2 for-5.8-rc 0/6] address deadlocks in high stress ns scanning and ana updates Sagi Grimberg
2020-06-24 0:18 ` [PATCH v2 for-5.8-rc 1/6] nvme: fix possible deadlock when I/O is blocked Sagi Grimberg
2020-06-24 6:29 ` Christoph Hellwig
2020-06-24 6:54 ` Sagi Grimberg
2020-06-24 6:57 ` Christoph Hellwig
2020-06-24 7:09 ` Sagi Grimberg
2020-07-07 10:57 ` Anthony Iliopoulos
2020-07-08 14:42 ` Christoph Hellwig
2020-07-10 4:47 ` Sagi Grimberg
2020-07-14 11:12 ` Christoph Hellwig
2020-06-24 0:18 ` [PATCH v2 for-5.8-rc 2/6] nvme-multipath: fix deadlock between ana_work and scan_work Sagi Grimberg
2020-06-24 6:34 ` Christoph Hellwig
2020-06-24 6:56 ` Sagi Grimberg
2020-06-24 0:18 ` [PATCH v2 for-5.8-rc 3/6] nvme: don't protect ns mutation with ns->head->lock Sagi Grimberg
2020-06-24 6:37 ` Christoph Hellwig
2020-06-24 6:58 ` Sagi Grimberg
2020-06-24 8:24 ` Sagi Grimberg [this message]
2020-06-24 0:18 ` [PATCH v2 for-5.8-rc 4/6] nvme-multipath: fix deadlock due to head->lock Sagi Grimberg
2020-06-24 6:39 ` Christoph Hellwig
2020-06-24 7:00 ` Sagi Grimberg
2020-06-24 0:18 ` [PATCH v2 for-5.8-rc 5/6] nvme-multipath: fix bogus request queue reference put Sagi Grimberg
2020-06-24 6:40 ` Christoph Hellwig
2020-06-24 0:18 ` [PATCH v2 RFC 6/6] nvme-core: fix deadlock in disconnect during scan_work and/or ana_work Sagi Grimberg
2020-06-24 6:43 ` Christoph Hellwig
2020-06-24 7:13 ` Sagi Grimberg
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