+ mm-gup-longterm-pin-migration-cleanup.patch added to -mm tree

* + mm-gup-longterm-pin-migration-cleanup.patch added to -mm tree
@ 2021-03-08 21:30 akpm
  0 siblings, 0 replies; 2+ messages in thread
From: akpm @ 2021-03-08 21:30 UTC (permalink / raw)
  To: dan.j.williams, david, iamjoonsoo.kim, ira.weiny, jgg, jgg,
	jhubbard, jmorris, mgorman, mhocko, mhocko, mike.kravetz, mingo,
	mm-commits, osalvador, pasha.tatashin, peterz, rientjes, rostedt,
	sashal, tyhicks, vbabka, willy


The patch titled
     Subject: mm/gup: longterm pin migration cleanup
has been added to the -mm tree.  Its filename is
     mm-gup-longterm-pin-migration-cleanup.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-gup-longterm-pin-migration-cleanup.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-gup-longterm-pin-migration-cleanup.patch

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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

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------------------------------------------------------
From: Pavel Tatashin <pasha.tatashin@soleen.com>
Subject: mm/gup: longterm pin migration cleanup

When pages are longterm pinned, we must migrated them out of movable zone.
The function that migrates them has a hidden loop with goto.  The loop is
to retry on isolation failures, and after successful migration.

Make this code better by moving this loop to the caller.

Link: https://lkml.kernel.org/r/20210215161349.246722-13-pasha.tatashin@soleen.com
Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/gup.c |   93 +++++++++++++++++++++--------------------------------
 1 file changed, 37 insertions(+), 56 deletions(-)

--- a/mm/gup.c~mm-gup-longterm-pin-migration-cleanup
+++ a/mm/gup.c
@@ -1541,27 +1541,28 @@ struct page *get_dump_page(unsigned long
 #endif /* CONFIG_ELF_CORE */
 
 #ifdef CONFIG_MIGRATION
-static long check_and_migrate_movable_pages(struct mm_struct *mm,
-					    unsigned long start,
-					    unsigned long nr_pages,
+/*
+ * Check whether all pages are pinnable, if so return number of pages.  If some
+ * pages are not pinnable, migrate them, and unpin all pages. Return zero if
+ * pages were migrated, or if some pages were not successfully isolated.
+ * Return negative error if migration fails.
+ */
+static long check_and_migrate_movable_pages(unsigned long nr_pages,
 					    struct page **pages,
-					    struct vm_area_struct **vmas,
 					    unsigned int gup_flags)
 {
-	unsigned long i, isolation_error_count;
-	bool drain_allow;
+	unsigned long i;
+	unsigned long isolation_error_count = 0;
+	bool drain_allow = true;
 	LIST_HEAD(movable_page_list);
-	long ret = nr_pages;
-	struct page *prev_head, *head;
+	long ret = 0;
+	struct page *prev_head = NULL;
+	struct page *head;
 	struct migration_target_control mtc = {
 		.nid = NUMA_NO_NODE,
 		.gfp_mask = GFP_USER | __GFP_NOWARN,
 	};
 
-check_again:
-	prev_head = NULL;
-	isolation_error_count = 0;
-	drain_allow = true;
 	for (i = 0; i < nr_pages; i++) {
 		head = compound_head(pages[i]);
 		if (head == prev_head)
@@ -1599,47 +1600,27 @@ check_again:
 	 * in the correct zone.
 	 */
 	if (list_empty(&movable_page_list) && !isolation_error_count)
-		return ret;
+		return nr_pages;
 
+	if (gup_flags & FOLL_PIN) {
+		unpin_user_pages(pages, nr_pages);
+	} else {
+		for (i = 0; i < nr_pages; i++)
+			put_page(pages[i]);
+	}
 	if (!list_empty(&movable_page_list)) {
-		/*
-		 * drop the above get_user_pages reference.
-		 */
-		if (gup_flags & FOLL_PIN)
-			unpin_user_pages(pages, nr_pages);
-		else
-			for (i = 0; i < nr_pages; i++)
-				put_page(pages[i]);
-
 		ret = migrate_pages(&movable_page_list, alloc_migration_target,
 				    NULL, (unsigned long)&mtc, MIGRATE_SYNC,
 				    MR_LONGTERM_PIN);
-		if (ret) {
-			if (!list_empty(&movable_page_list))
-				putback_movable_pages(&movable_page_list);
-			return ret > 0 ? -ENOMEM : ret;
-		}
-
-		/* We unpinned pages before migration, pin them again */
-		ret = __get_user_pages_locked(mm, start, nr_pages, pages, vmas,
-					      NULL, gup_flags);
-		if (ret <= 0)
-			return ret;
-		nr_pages = ret;
+		if (ret && !list_empty(&movable_page_list))
+			putback_movable_pages(&movable_page_list);
 	}
 
-	/*
-	 * check again because pages were unpinned, and we also might have
-	 * had isolation errors and need more pages to migrate.
-	 */
-	goto check_again;
+	return ret > 0 ? -ENOMEM : ret;
 }
 #else
-static long check_and_migrate_movable_pages(struct mm_struct *mm,
-					    unsigned long start,
-					    unsigned long nr_pages,
+static long check_and_migrate_movable_pages(unsigned long nr_pages,
 					    struct page **pages,
-					    struct vm_area_struct **vmas,
 					    unsigned int gup_flags)
 {
 	return nr_pages;
@@ -1657,22 +1638,22 @@ static long __gup_longterm_locked(struct
 				  struct vm_area_struct **vmas,
 				  unsigned int gup_flags)
 {
-	unsigned long flags = 0;
+	unsigned int flags;
 	long rc;
 
-	if (gup_flags & FOLL_LONGTERM)
-		flags = memalloc_pin_save();
-
-	rc = __get_user_pages_locked(mm, start, nr_pages, pages, vmas, NULL,
-				     gup_flags);
+	if (!(gup_flags & FOLL_LONGTERM))
+		return __get_user_pages_locked(mm, start, nr_pages, pages, vmas,
+					       NULL, gup_flags);
+	flags = memalloc_pin_save();
+	do {
+		rc = __get_user_pages_locked(mm, start, nr_pages, pages, vmas,
+					     NULL, gup_flags);
+		if (rc <= 0)
+			break;
+		rc = check_and_migrate_movable_pages(rc, pages, gup_flags);
+	} while (!rc);
+	memalloc_pin_restore(flags);
 
-	if (gup_flags & FOLL_LONGTERM) {
-		if (rc > 0)
-			rc = check_and_migrate_movable_pages(mm, start, rc,
-							     pages, vmas,
-							     gup_flags);
-		memalloc_pin_restore(flags);
-	}
 	return rc;
 }
 
_

Patches currently in -mm which might be from pasha.tatashin@soleen.com are

mm-gup-dont-pin-migrated-cma-pages-in-movable-zone.patch
mm-gup-check-every-subpage-of-a-compound-page-during-isolation.patch
mm-gup-return-an-error-on-migration-failure.patch
mm-gup-check-for-isolation-errors.patch
mm-cma-rename-pf_memalloc_nocma-to-pf_memalloc_pin.patch
mm-apply-per-task-gfp-constraints-in-fast-path.patch
mm-honor-pf_memalloc_pin-for-all-movable-pages.patch
mm-gup-do-not-migrate-zero-page.patch
mm-gup-migrate-pinned-pages-out-of-movable-zone.patch
memory-hotplugrst-add-a-note-about-zone_movable-and-page-pinning.patch
mm-gup-change-index-type-to-long-as-it-counts-pages.patch
mm-gup-longterm-pin-migration-cleanup.patch
selftests-vm-gup_test-fix-test-flag.patch
selftests-vm-gup_test-test-faulting-in-kernel-and-verify-pinnable-pages.patch


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