The patch titled
Subject: mm/migrate_device: return number of migrating pages in args->cpages
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-migrate_device-return-number-of-migrating-pages-in-args-cpages.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-migrate_device-return-number-of-migrating-pages-in-args-cpages.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Alistair Popple <apopple@xxxxxxxxxx>
Subject: mm/migrate_device: return number of migrating pages in args->cpages
Date: Fri, 11 Nov 2022 11:51:35 +1100
migrate_vma->cpages originally contained a count of the number of pages
migrating including non-present pages which can be populated directly on
the target.
Commit 241f68859656 ("mm/migrate_device.c: refactor migrate_vma and
migrate_device_coherent_page()") inadvertantly changed this to contain
just the number of pages that were unmapped. Usage of migrate_vma->cpages
isn't documented, but most drivers use it to see if all the requested
addresses can be migrated so restore the original behaviour.
Link: https://lkml.kernel.org/r/20221111005135.1344004-1-apopple@xxxxxxxxxx
Fixes: 241f68859656 ("mm/migrate_device.c: refactor migrate_vma and migrate_deivce_coherent_page()")
Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx>
Reported-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
Reviewed-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Alex Sierra <alex.sierra@xxxxxxx>
Cc: Ben Skeggs <bskeggs@xxxxxxxxxx>
Cc: Felix Kuehling <Felix.Kuehling@xxxxxxx>
Cc: Lyude Paul <lyude@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/migrate_device.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
--- a/mm/migrate_device.c~mm-migrate_device-return-number-of-migrating-pages-in-args-cpages
+++ a/mm/migrate_device.c
@@ -357,7 +357,8 @@ static bool migrate_vma_check_page(struc
}
/*
- * Unmaps pages for migration. Returns number of unmapped pages.
+ * Unmaps pages for migration. Returns number of source pfns marked as
+ * migrating.
*/
static unsigned long migrate_device_unmap(unsigned long *src_pfns,
unsigned long npages,
@@ -373,8 +374,11 @@ static unsigned long migrate_device_unma
struct page *page = migrate_pfn_to_page(src_pfns[i]);
struct folio *folio;
- if (!page)
+ if (!page) {
+ if (src_pfns[i] & MIGRATE_PFN_MIGRATE)
+ unmapped++;
continue;
+ }
/* ZONE_DEVICE pages are not on LRU */
if (!is_zone_device_page(page)) {
_
Patches currently in -mm which might be from apopple@xxxxxxxxxx are
mm-memory-return-vm_fault_t-result-from-migrate_to_ram-callback.patch
mm-migrate_device-return-number-of-migrating-pages-in-args-cpages.patch
mm-khugepaged-refactor-mm_khugepaged_scan_file-tracepoint-to-remove-filename-from-function-call-fix.patch
