Re: [PATCH v3 06/18] mm/huge_memory: consolidate irq and locking for folio split

[Kiryl Shutsemau <kirill@shutemov.name>]

On Fri, Aug 21, 2026 at 02:55:19AM +0800, Kairui Song via B4 Relay wrote:
> From: Kairui Song <kasong@tencent.com>
> 
> Let each split helper handle its own locking instead of relying on
> the caller, so both helpers manage their own irq and locking state.
> This lets __folio_split() drop its local irq handling and fail label,
> preparing for further cleanup.
> 
> The file path now uses xas_lock_irq() instead of local_irq_disable()
> with xas_lock(). The two are equivalent on non-RT, and
> TRANSPARENT_HUGEPAGE cannot be enabled on RT anyway. This conversion
> also buys consistency: every other place in mm/ that freezes a folio
> while it is still reachable through the page cache already takes the
> lock this way. This was actually the last plain xas_lock() on
> mapping->i_pages left in mm. If we are going to support RT, spinning
> on frozen folio refs could be a problem, but it already exists in
> many places and should be fixed generically.
> 
> The anon helper keeps a single local_irq_disable() as before, because
> it has to cover several plain spinlocks at once.
> 
> The dropped xas_reset() was a no-op as the xa_state is not walked
> before the xas_load() under the lock.
> 
> Reviewed-by: Zi Yan <ziy@nvidia.com>
> Signed-off-by: Kairui Song <kasong@tencent.com>

Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>

-- 
  Kiryl Shutsemau / Kirill A. Shutemov