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mm/percpu: make cached pages lookup explicit

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pcpu_depopulate_chunk() only needs the temporary pages array that was
already allocated by an earlier successful population attempt.  Passing
GFP_KERNEL to pcpu_get_pages() in this path is misleading because the
depopulation path is not expected to allocate the array.

Teach pcpu_get_pages() to treat a zero gfp mask as a cached-only lookup
and add pcpu_get_pages_cached() for that use case.  This keeps allocation
on the populate path tied to the caller supplied GFP mask while making the
depopulate path's dependency on the cached array explicit.

Link: https://lore.kernel.org/20260618130414.96383-4-kaitao.cheng@linux.dev
Signed-off-by: Kaitao Cheng <chengkaitao@kylinos.cn>
Suggested-by: Dennis Zhou <dennis@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Christoph Lameter <cl@gentwo.org>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Shivam Kalra <shivamkalra98@zohomail.in>
Cc: Tejun Heo <tj@kernel.org>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Kaitao Cheng
2026-06-18 21:04:13 +08:00
committed by Andrew Morton
parent 881adc51b2
commit 17fcdd8699
1 changed files with 9 additions and 3 deletions
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12
mm/percpu-vm.c
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@@ -21,7 +21,8 @@ static struct page *pcpu_chunk_page(struct pcpu_chunk *chunk,
/**
* pcpu_get_pages - get temp pages array
* @gfp: allocation flags passed to the underlying allocator
* @gfp: allocation flags passed to the underlying allocator, 0 to only
* return the cached array
*
* Returns pointer to array of pointers to struct page which can be indexed
* with pcpu_page_idx(). Note that there is only one array and accesses
@@ -37,11 +38,16 @@ static struct page **pcpu_get_pages(gfp_t gfp)
lockdep_assert_held(&pcpu_alloc_mutex);
if (!pages)
if (!pages && gfp)
pages = pcpu_mem_zalloc(pages_size, gfp);
return pages;
}
static struct page **pcpu_get_pages_cached(void)
{
return pcpu_get_pages(0);
}
/**
* pcpu_free_pages - free pages which were allocated for @chunk
* @chunk: chunk pages were allocated for
@@ -333,7 +339,7 @@ static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk,
* successful population attempt so the temp pages array must
* be available now.
*/
pages = pcpu_get_pages(GFP_KERNEL);
pages = pcpu_get_pages_cached();
BUG_ON(!pages);
/* unmap and free */