mm: page-isolation: skip isolated pageblock in start_isolate_page_range()

start_isolate_page_range() first isolates the first and the last
pageblocks in the range and ensure pages across range boundaries are split
during isolation.  But it missed the case when the range is <= a pageblock
and the first and the last pageblocks are the same one, so the second
isolate_single_pageblock() will always fail.  To fix it, skip the
pageblock isolation in second isolate_single_pageblock().

Link: https://lkml.kernel.org/r/20220526231531.2404977-1-zi.yan@sent.com
Fixes: 88ee134320b8 ("mm: fix a potential infinite loop in start_isolate_page_range()")
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/linux-mm/ac65adc0-a7e4-cdfe-a0d8-757195b86293@samsung.com/
Reported-by: Michael Walle <michael@walle.cc>
Tested-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/linux-mm/8ca048ca8b547e0dd1c95387ee05c23d@walle.cc/
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David Hildenbrand <david@redhat.com>
Cc: Doug Berger <opendmb@gmail.com>
Cc: Eric Ren <renzhengeek@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Qian Cai <quic_qiancai@quicinc.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index c643c84..fbd820b 100644 (file)
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -300,7 +300,7 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
  * the in-use page then splitting the free page.
  */
 static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
-                       gfp_t gfp_flags, bool isolate_before)
+                       gfp_t gfp_flags, bool isolate_before, bool skip_isolation)
 {
        unsigned char saved_mt;
        unsigned long start_pfn;
@@ -327,11 +327,16 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
                                      zone->zone_start_pfn);
 
        saved_mt = get_pageblock_migratetype(pfn_to_page(isolate_pageblock));
-       ret = set_migratetype_isolate(pfn_to_page(isolate_pageblock), saved_mt, flags,
-                       isolate_pageblock, isolate_pageblock + pageblock_nr_pages);
 
-       if (ret)
-               return ret;
+       if (skip_isolation)
+               VM_BUG_ON(!is_migrate_isolate(saved_mt));
+       else {
+               ret = set_migratetype_isolate(pfn_to_page(isolate_pageblock), saved_mt, flags,
+                               isolate_pageblock, isolate_pageblock + pageblock_nr_pages);
+
+               if (ret)
+                       return ret;
+       }
 
        /*
         * Bail out early when the to-be-isolated pageblock does not form
@@ -463,7 +468,8 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
        return 0;
 failed:
        /* restore the original migratetype */
-       unset_migratetype_isolate(pfn_to_page(isolate_pageblock), saved_mt);
+       if (!skip_isolation)
+               unset_migratetype_isolate(pfn_to_page(isolate_pageblock), saved_mt);
        return -EBUSY;
 }
 
@@ -522,14 +528,18 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
        unsigned long isolate_start = ALIGN_DOWN(start_pfn, pageblock_nr_pages);
        unsigned long isolate_end = ALIGN(end_pfn, pageblock_nr_pages);
        int ret;
+       bool skip_isolation = false;
 
        /* isolate [isolate_start, isolate_start + pageblock_nr_pages) pageblock */
-       ret = isolate_single_pageblock(isolate_start, flags, gfp_flags, false);
+       ret = isolate_single_pageblock(isolate_start, flags, gfp_flags, false, skip_isolation);
        if (ret)
                return ret;
 
+       if (isolate_start == isolate_end - pageblock_nr_pages)
+               skip_isolation = true;
+
        /* isolate [isolate_end - pageblock_nr_pages, isolate_end) pageblock */
-       ret = isolate_single_pageblock(isolate_end, flags, gfp_flags, true);
+       ret = isolate_single_pageblock(isolate_end, flags, gfp_flags, true, skip_isolation);
        if (ret) {
                unset_migratetype_isolate(pfn_to_page(isolate_start), migratetype);
                return ret;