From: Nikolay Borisov <nborisov@suse.com>
To: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: Josef Bacik <josef@toxicpanda.com>, linux-btrfs@vger.kernel.org
Subject: Re: [PATCH 0/3] Balance vs device add fixes
Date: Tue, 2 Nov 2021 19:39:37 +0200 [thread overview]
Message-ID: <541927b1-ff40-4d5a-6d99-709b10e4c141@suse.com> (raw)
In-Reply-To: <20211102172528.se6voh75geqjjltf@zuko>
On 2.11.21 г. 19:25, Goldwyn Rodrigues wrote:
> But do we really need to use *_ONCE, assuming btrfs_exclusive_operation
> fits in 8 bits?
>
The way I understand it based on the LWN articles is that the effect of
_ONCE is twofold:
1. It prevents theoretical torn writes + forces the compiler to always
issue the access i.e prevent it being optimized out - this could be moot
in our case.
2. It serves a documentation purpose where it states "this variable is
accessed in multithreaded contexts, possibly without an explicit lock" -
and this IMO is quite helpful in this particular context.
prev parent reply other threads:[~2021-11-02 17:39 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-01 11:53 [PATCH 0/3] Balance vs device add fixes Nikolay Borisov
2021-11-01 11:53 ` [PATCH 1/3] btrfs: introduce BTRFS_EXCLOP_BALANCE_PAUSED exclusive state Nikolay Borisov
2021-11-01 11:53 ` [PATCH 2/3] btrfs: make device add compatible with paused balance in btrfs_exclop_start_try_lock Nikolay Borisov
2021-11-01 11:53 ` [PATCH 3/3] btrfs: allow device add if balance is paused Nikolay Borisov
2021-11-02 4:52 ` [PATCH 0/3] Balance vs device add fixes Anand Jain
2021-11-02 13:12 ` Josef Bacik
2021-11-02 14:30 ` Josef Bacik
2021-11-02 15:25 ` Nikolay Borisov
2021-11-02 16:10 ` Josef Bacik
2021-11-02 17:25 ` Goldwyn Rodrigues
2021-11-02 17:39 ` Nikolay Borisov [this message]
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