linux-kernel - Re: [PATCH 0/2] fs: make the i_size_read/write helpers be smp_load_acquire/store

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Message-ID: <20240122-gepokert-mitmachen-6d6ba8d2f0a8@brauner>
Date: Mon, 22 Jan 2024 12:14:52 +0100
From: Christian Brauner <brauner@...nel.org>
To: Baokun Li <libaokun1@...wei.com>
Cc: Christian Brauner <brauner@...nel.org>,
	torvalds@...ux-foundation.org,
	viro@...iv.linux.org.uk,
	jack@...e.cz,
	willy@...radead.org,
	akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org,
	yi.zhang@...wei.com,
	yangerkun@...wei.com,
	yukuai3@...wei.com,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 0/2] fs: make the i_size_read/write helpers be smp_load_acquire/store_release()

On Mon, 22 Jan 2024 17:45:34 +0800, Baokun Li wrote:
> This patchset follows the linus suggestion to make the i_size_read/write
> helpers be smp_load_acquire/store_release(), after which the extra smp_rmb
> in filemap_read() is no longer needed, so it is removed.
> 
> Functional tests were performed and no new problems were found.
> 
> Here are the results of unixbench tests based on 6.7.0-next-20240118 on
> arm64, with some degradation in single-threading and some optimization in
> multi-threading, but overall the impact is not significant.
> 
> [...]

Hm, we can certainly try but I wouldn't rule it out that someone will
complain aobut the "non-significant" degradation in single-threading.
We'll see. Let that performance bot chew on it for a bit as well.

But I agree that the smp_load_acquire()/smp_store_release() is clearer
than the open-coded smp_rmb().

---

Applied to the vfs.misc branch of the vfs/vfs.git tree.
Patches in the vfs.misc branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs.misc

[1/2] fs: make the i_size_read/write helpers be smp_load_acquire/store_release()
      https://git.kernel.org/vfs/vfs/c/7d7825fde8ba
[2/2] Revert "mm/filemap: avoid buffered read/write race to read inconsistent data"
      https://git.kernel.org/vfs/vfs/c/83dfed690b90