linux-kernel - Re: [PATCH v3] mm: shmem: skip swapcache for swapin of synchronous swap device

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Message-Id: <20250107182943.a36b6876985dac7d34ef07a2@linux-foundation.org>
Date: Tue, 7 Jan 2025 18:29:43 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: hughd@...gle.com, willy@...radead.org, david@...hat.com,
 wangkefeng.wang@...wei.com, kasong@...cent.com,
 ying.huang@...ux.alibaba.com, 21cnbao@...il.com, ryan.roberts@....com,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] mm: shmem: skip swapcache for swapin of synchronous
 swap device

On Wed,  8 Jan 2025 10:16:49 +0800 Baolin Wang <baolin.wang@...ux.alibaba.com> wrote:

> +static struct folio *shmem_swap_alloc_folio(struct inode *inode,
> +		struct vm_area_struct *vma, pgoff_t index,
> +		swp_entry_t entry, int order, gfp_t gfp)
> +{
> +	struct shmem_inode_info *info = SHMEM_I(inode);
> +	struct folio *new;
> +	void *shadow;
> +	int nr_pages;
> +
> +	/*
> +	 * We have arrived here because our zones are constrained, so don't
> +	 * limit chance of success by further cpuset and node constraints.
> +	 */
> +	gfp &= ~GFP_CONSTRAINT_MASK;
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +	if (order > 0) {
> +		gfp_t huge_gfp = vma_thp_gfp_mask(vma);
> +
> +		gfp = limit_gfp_mask(huge_gfp, gfp);
> +	}
> +#endif
> +

Can we do this?

--- a/mm/shmem.c~mm-shmem-skip-swapcache-for-swapin-of-synchronous-swap-device-fix
+++ a/mm/shmem.c
@@ -1978,16 +1978,14 @@ static struct folio *shmem_swap_alloc_fo
 
 	/*
 	 * We have arrived here because our zones are constrained, so don't
-	 * limit chance of success by further cpuset and node constraints.
+	 * limit chance of success with further cpuset and node constraints.
 	 */
 	gfp &= ~GFP_CONSTRAINT_MASK;
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-	if (order > 0) {
+	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && order > 0) {
 		gfp_t huge_gfp = vma_thp_gfp_mask(vma);
 
 		gfp = limit_gfp_mask(huge_gfp, gfp);
 	}
-#endif
 
 	new = shmem_alloc_folio(gfp, order, info, index);
 	if (!new)
_