Re: [PATCH v6 6/6] mm/page_isolation: remove migratetype parameter from more functions.

From: David Hildenbrand
Date: Mon Jun 02 2025 - 12:25:49 EST

On 02.06.25 16:18, Zi Yan wrote:
On 30 May 2025, at 16:55, David Hildenbrand wrote:

On 30.05.25 22:46, Zi Yan wrote:
On 30 May 2025, at 16:08, David Hildenbrand wrote:

On 30.05.25 21:58, Zi Yan wrote:
On 30 May 2025, at 15:56, David Hildenbrand wrote:

On 30.05.25 18:22, Zi Yan wrote:
migratetype is no longer overwritten during pageblock isolation,
start_isolate_page_range(), has_unmovable_pages(), and
set_migratetype_isolate() no longer need which migratetype to restore
during isolation failure.

For has_unmoable_pages(), it needs to know if the isolation is for CMA
allocation, so adding CMA_ALLOCATION to provide the information. At the
same time change isolation flags to enum pb_isolate_mode
(PB_ISOLATE_MODE_MEM_OFFLINE, PB_ISOLATE_MODE_CMA_ALLOC,
PB_ISOLATE_MODE_OTHER). Remove REPORT_FAILURE and check
MEMORY_OFFLINE instead, since only PB_ISOLATE_MODE_MEM_OFFLINE reports
isolation failures.

alloc_contig_range() no longer needs migratetype. Replace it with
enum acr_flags_t to tell if an allocation is for CMA. So does
__alloc_contig_migrate_range().

Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
---
drivers/virtio/virtio_mem.c | 2 +-
include/linux/gfp.h | 9 ++++-
include/linux/page-isolation.h | 20 ++++++++--
include/trace/events/kmem.h | 14 ++++---
mm/cma.c | 2 +-
mm/memory_hotplug.c | 6 +--
mm/page_alloc.c | 27 ++++++-------
mm/page_isolation.c | 70 +++++++++++++++-------------------
8 files changed, 82 insertions(+), 68 deletions(-)

diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index 56d0dbe62163..6bce70b139b2 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -1243,7 +1243,7 @@ static int virtio_mem_fake_offline(struct virtio_mem *vm, unsigned long pfn,
if (atomic_read(&vm->config_changed))
return -EAGAIN;
- rc = alloc_contig_range(pfn, pfn + nr_pages, MIGRATE_MOVABLE,
+ rc = alloc_contig_range(pfn, pfn + nr_pages, ACR_OTHER,
GFP_KERNEL);
if (rc == -ENOMEM)
/* whoops, out of memory */
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index be160e8d8bcb..51990d571e3e 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -423,9 +423,16 @@ static inline bool gfp_compaction_allowed(gfp_t gfp_mask)
extern gfp_t vma_thp_gfp_mask(struct vm_area_struct *vma);
#ifdef CONFIG_CONTIG_ALLOC
+
+enum acr_flags_t {
+ ACR_CMA, // CMA allocation
+ ACR_OTHER, // other allocation
+};

Hm, enum != flags.

If you want to use flags, then just have ACR_CMA. ACR_OTHER is implied if not set.

And ACR_CMA would then have to be "1" etc.

I have a fixup to change acr_flags_t to acr_mode.


+
/* The below functions must be run on a range from a single zone. */
extern int alloc_contig_range_noprof(unsigned long start, unsigned long end,
- unsigned migratetype, gfp_t gfp_mask);
+ enum acr_flags_t alloc_flags,
+ gfp_t gfp_mask);
#define alloc_contig_range(...) alloc_hooks(alloc_contig_range_noprof(__VA_ARGS__))
extern struct page *alloc_contig_pages_noprof(unsigned long nr_pages, gfp_t gfp_mask,
diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
index 7a681a49e73c..3e2f960e166c 100644
--- a/include/linux/page-isolation.h
+++ b/include/linux/page-isolation.h
@@ -38,8 +38,20 @@ static inline void set_pageblock_isolate(struct page *page)
}
#endif
-#define MEMORY_OFFLINE 0x1
-#define REPORT_FAILURE 0x2
+/*
+ * Pageblock isolation modes:
+ * PB_ISOLATE_MODE_MEM_OFFLINE - isolate to offline (!allocate) memory
+ * e.g., skip over PageHWPoison() pages and
+ * PageOffline() pages. Unmovable pages will be
+ * reported in this mode.
+ * PB_ISOLATE_MODE_CMA_ALLOC - isolate for CMA allocations
+ * PB_ISOLATE_MODE_OTHER - isolate for other purposes
+ */
+enum pb_isolate_mode {
+ PB_ISOLATE_MODE_MEM_OFFLINE,
+ PB_ISOLATE_MODE_CMA_ALLOC,
+ PB_ISOLATE_MODE_OTHER,
+};

It's late on friady, but it looks like we are duplicating things here.

Let me think about that once my brain is recharged :)

Sure. Take your time.

Could we abstract both settings and use a single one? Then, we could simply reject if MEM_OFFLINE is passed into alloc_contig_range().

alloc_contig_pages and page isolation, hmmmm, MEM_OFFLINE is kind-of an allocation. CMA is an allocation.

Just an idea, not sure ...

I think so.

This is the fixup of removing acr_flags_t. It is on top of the original
patch. Take your time. I guess I will send V7 with all fixups next week.

Only wondering if we should rename "pb_isolate_mode" to something more abstract, that covers both use cases clearer.

Hmmm.

It is specifying the purpose of either alloc_contig_range() or
test_pages_isolated(), but these two use cases do not have high level
connection AFAICT.

Hm, then maybe just keep it as is for now, and have the translation from ACP -> isolatetype.

isolation modes should probably be an enum.

acp might long-term benefit from flags, where we would essentially for now only have a single flag ("ACP_CMA").

--
Cheers,

David / dhildenb