From: Christoph Hellwig <hch@infradead.org>
To: Logan Gunthorpe <logang@deltatee.com>
Cc: linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org,
Song Liu <song@kernel.org>, Christoph Hellwig <hch@infradead.org>,
Donald Buczek <buczek@molgen.mpg.de>,
Guoqing Jiang <guoqing.jiang@linux.dev>, Xiao Ni <xni@redhat.com>,
Stephen Bates <sbates@raithlin.com>,
Martin Oliveira <Martin.Oliveira@eideticom.com>,
David Sloan <David.Sloan@eideticom.com>
Subject: Re: [PATCH v2 13/17] md/raid5-cache: Add RCU protection to conf->log accesses
Date: Sun, 29 May 2022 23:01:19 -0700 [thread overview]
Message-ID: <YpRdrytEQkw/0vMH@infradead.org> (raw)
In-Reply-To: <20220526163604.32736-14-logang@deltatee.com>
On Thu, May 26, 2022 at 10:36:00AM -0600, Logan Gunthorpe wrote:
> The mdadm test 21raid5cache randomly fails with NULL pointer accesses
> of conf->log when run repeatedly. conf->log was sort of protected with
> RCU, but most dereferences were not done with the correct functions.
>
> Add rcu_read_locks(), rcu_dereference_protected() and rcu_access_pointers()
> calls to the appropriate places and mark the pointer with __rcu.
Looking at the code a bit more, is this really enough? Calls to
r5c_is_writeback / r5c_confi_is_writeback are sprinkled all over the
code, and my gut feeling is the value is not expected to change over
way longer critical sections than this. So maybe the answer here is to
fix up the release to be properly locked as it only affects the non-I/O
slow path anyway.
next prev parent reply other threads:[~2022-05-30 6:01 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-26 16:35 [PATCH v2 00/17] Bug fixes for mdadm tests Logan Gunthorpe
2022-05-26 16:35 ` [PATCH v2 01/17] md/raid5-log: Drop extern decorators for function prototypes Logan Gunthorpe
2022-05-26 16:35 ` [PATCH v2 02/17] md/raid5-cache: Add r5c_conf_is_writeback() helper Logan Gunthorpe
2022-05-30 5:56 ` Christoph Hellwig
2022-05-26 16:35 ` [PATCH v2 03/17] md/raid5-cache: Refactor r5l_start() to take a struct r5conf Logan Gunthorpe
2022-05-26 16:35 ` [PATCH v2 04/17] md/raid5-cache: Refactor r5l_flush_stripe_to_raid() " Logan Gunthorpe
2022-05-26 16:35 ` [PATCH v2 05/17] md/raid5-cache: Refactor r5l_wake_reclaim() " Logan Gunthorpe
2022-05-26 16:35 ` [PATCH v2 06/17] md/raid5-cache: Refactor remaining functions to take a r5conf Logan Gunthorpe
2022-05-26 16:35 ` [PATCH v2 07/17] md/raid5-ppl: Drop unused argument from ppl_handle_flush_request() Logan Gunthorpe
2022-05-26 16:35 ` [PATCH v2 08/17] md/raid5-cache: Pass the log through to r5c_finish_cache_stripe() Logan Gunthorpe
2022-05-26 16:35 ` [PATCH v2 09/17] md/raid5-cache: Don't pass conf to r5c_calculate_new_cp() Logan Gunthorpe
2022-05-26 16:35 ` [PATCH v2 10/17] md/raid5-cache: Take struct r5l_log in r5c_log_required_to_flush_cache() Logan Gunthorpe
2022-05-26 16:35 ` [PATCH v2 11/17] md/raid5: Ensure array is suspended for calls to log_exit() Logan Gunthorpe
2022-05-26 16:35 ` [PATCH v2 12/17] md/raid5-cache: Move struct r5l_log definition to raid5-log.h Logan Gunthorpe
2022-05-30 5:59 ` Christoph Hellwig
2022-05-30 15:48 ` Logan Gunthorpe
2022-06-01 22:36 ` Song Liu
2022-06-01 22:42 ` Logan Gunthorpe
2022-06-01 22:50 ` Song Liu
2022-05-26 16:36 ` [PATCH v2 13/17] md/raid5-cache: Add RCU protection to conf->log accesses Logan Gunthorpe
2022-05-30 6:01 ` Christoph Hellwig [this message]
2022-05-30 15:57 ` Logan Gunthorpe
2022-05-26 16:36 ` [PATCH v2 14/17] md/raid5-cache: Annotate pslot with __rcu notation Logan Gunthorpe
2022-05-26 16:36 ` [PATCH v2 15/17] md: Use enum for overloaded magic numbers used by mddev->curr_resync Logan Gunthorpe
2022-05-30 6:01 ` Christoph Hellwig
2022-05-30 15:43 ` Logan Gunthorpe
2022-05-26 16:36 ` [PATCH v2 16/17] md: Ensure resync is reported after it starts Logan Gunthorpe
2022-05-30 6:02 ` Christoph Hellwig
2022-05-26 16:36 ` [PATCH v2 17/17] md: Notify sysfs sync_completed in md_reap_sync_thread() Logan Gunthorpe
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