The function set_migratetype_isolate() has special handling for
pageblocks of MIGRATE_CMA type that protects them from being
isolated for MIGRATE_MOVABLE requests.
Since isolate_single_pageblock() doesn't receive the migratetype
argument of start_isolate_page_range() it used the migratetype
of the pageblock instead of the requested migratetype which
defeats this MIGRATE_CMA check.
This allows an attempt to create a gigantic page within a CMA
region to change the migratetype of the first and last pageblocks
from MIGRATE_CMA to MIGRATE_MOVABLE when they are restored after
failure, which corrupts the CMA region.
The calls to (un)set_migratetype_isolate() for the first and last
pageblocks of the start_isolate_page_range() are moved back into
that function to allow access to its migratetype argument and make
it easier to see how all of the pageblocks in the range are
isolated.
Fixes: b2c9e2fbba32 ("mm: make alloc_contig_range work at pageblock granularity")
Signed-off-by: Doug Berger <opendmb@xxxxxxxxx>
---
mm/page_isolation.c | 75 +++++++++++++++++++++------------------------
1 file changed, 35 insertions(+), 40 deletions(-)
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 9d73dc38e3d7..8e16aa22cb61 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -286,8 +286,6 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
* @flags: isolation flags
* @gfp_flags: GFP flags used for migrating pages
* @isolate_before: isolate the pageblock before the boundary_pfn
- * @skip_isolation: the flag to skip the pageblock isolation in second
- * isolate_single_pageblock()
*
* Free and in-use pages can be as big as MAX_ORDER-1 and contain more than one
* pageblock. When not all pageblocks within a page are isolated at the same
@@ -302,9 +300,8 @@ __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, bool skip_isolation)
+ gfp_t gfp_flags, bool isolate_before)
{
- unsigned char saved_mt;
unsigned long start_pfn;
unsigned long isolate_pageblock;
unsigned long pfn;
@@ -328,18 +325,6 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
start_pfn = max(ALIGN_DOWN(isolate_pageblock, MAX_ORDER_NR_PAGES),
zone->zone_start_pfn);
- saved_mt = get_pageblock_migratetype(pfn_to_page(isolate_pageblock));
-
- 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
* a free or in-use page across boundary_pfn:
@@ -428,7 +413,7 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
ret = set_migratetype_isolate(page, page_mt,
flags, head_pfn, head_pfn + nr_pages);
if (ret)
- goto failed;
+ return ret;
}
ret = __alloc_contig_migrate_range(&cc, head_pfn,
@@ -443,7 +428,7 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
unset_migratetype_isolate(page, page_mt);
if (ret)
- goto failed;
+ return -EBUSY;
/*
* reset pfn to the head of the free page, so
* that the free page handling code above can split
@@ -459,24 +444,19 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
while (!PageBuddy(pfn_to_page(outer_pfn))) {
/* stop if we cannot find the free page */
if (++order >= MAX_ORDER)
- goto failed;
+ return -EBUSY;
outer_pfn &= ~0UL << order;
}
pfn = outer_pfn;
continue;
} else
#endif
- goto failed;
+ return -EBUSY;
}
pfn++;
}
return 0;
-failed:
- /* restore the original migratetype */
- if (!skip_isolation)
- unset_migratetype_isolate(pfn_to_page(isolate_pageblock), saved_mt);
- return -EBUSY;
}
/**
@@ -534,21 +514,30 @@ 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, skip_isolation);
+ ret = set_migratetype_isolate(pfn_to_page(isolate_start), migratetype,
+ flags, isolate_start, isolate_start + pageblock_nr_pages);
if (ret)
return ret;
-
- if (isolate_start == isolate_end - pageblock_nr_pages)
- skip_isolation = true;
+ ret = isolate_single_pageblock(isolate_start, flags, gfp_flags, false);
+ if (ret)
+ goto unset_start_block;
/* isolate [isolate_end - pageblock_nr_pages, isolate_end) pageblock */
- ret = isolate_single_pageblock(isolate_end, flags, gfp_flags, true, skip_isolation);
+ pfn = isolate_end - pageblock_nr_pages;
+ if (isolate_start != pfn) {
+ ret = set_migratetype_isolate(pfn_to_page(pfn), migratetype,
+ flags, pfn, pfn + pageblock_nr_pages);
+ if (ret)
+ goto unset_start_block;
+ }
+ ret = isolate_single_pageblock(isolate_end, flags, gfp_flags, true);
if (ret) {
- unset_migratetype_isolate(pfn_to_page(isolate_start), migratetype);
- return ret;
+ if (isolate_start != pfn)
+ goto unset_end_block;
+ else
+ goto unset_start_block;
}
/* skip isolated pageblocks at the beginning and end */
@@ -557,15 +546,21 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
pfn += pageblock_nr_pages) {
page = __first_valid_page(pfn, pageblock_nr_pages);
if (page && set_migratetype_isolate(page, migratetype, flags,
- start_pfn, end_pfn)) {
- undo_isolate_page_range(isolate_start, pfn, migratetype);
- unset_migratetype_isolate(
- pfn_to_page(isolate_end - pageblock_nr_pages),
- migratetype);
- return -EBUSY;
- }
+ start_pfn, end_pfn))
+ goto unset_isolated_blocks;
}
return 0;
+
+unset_isolated_blocks:
+ ret = -EBUSY;
+ undo_isolate_page_range(isolate_start + pageblock_nr_pages, pfn,
+ migratetype);
+unset_end_block:
+ unset_migratetype_isolate(pfn_to_page(isolate_end - pageblock_nr_pages),
+ migratetype);
+unset_start_block:
+ unset_migratetype_isolate(pfn_to_page(isolate_start), migratetype);
+ return ret;
}
/*
--
2.25.1
