Re: [PATCH AUTOSEL 6.12 25/37] fs/buffer: split locking for pagecache lookups

[Luis Chamberlain <mcgrof@kernel.org>]

On Tue, Apr 29, 2025 at 07:51:10PM -0400, Sasha Levin wrote:
> From: Davidlohr Bueso <dave@stgolabs.net>
> 
> [ Upstream commit 7ffe3de53a885dbb5836541c2178bd07d1bad7df ]
> 
> Callers of __find_get_block() may or may not allow for blocking
> semantics, and is currently assumed that it will not. Layout
> two paths based on this. The the private_lock scheme will
> continued to be used for atomic contexts. Otherwise take the
> folio lock instead, which protects the buffers, such as
> vs migration and try_to_free_buffers().
> 
> Per the "hack idea", the latter can alleviate contention on
> the private_lock for bdev mappings. For reasons of determinism
> and avoid making bugs hard to reproduce, the trylocking is not
> attempted.
> 
> No change in semantics. All lookup users still take the spinlock.
> 
> Reviewed-by: Jan Kara <jack@suse.cz>
> Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
> Link: https://kdevops.org/ext4/v6.15-rc2.html # [0]
> Link: https://lore.kernel.org/all/aAAEvcrmREWa1SKF@bombadil.infradead.org/ # [1]
> Link: https://lore.kernel.org/20250418015921.132400-2-dave@stgolabs.net
> Tested-by: kdevops@lists.linux.dev
> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
> Signed-off-by: Christian Brauner <brauner@kernel.org>
> Signed-off-by: Sasha Levin <sashal@kernel.org>

Same no way. This is pushing it.

  Luis