On Tue, Apr 29, 2025 at 07:49:53PM -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.
This is pushing it. I would not expect this to go to stable. At all.
BTW you had mentioned the code for auto-sel would be published a while ago, is it available anywhere?
Luis