diff options
| -rw-r--r-- | mm/page_alloc.c | 8 | ||||
| -rw-r--r-- | mm/page_isolation.c | 18 |
2 files changed, 21 insertions, 5 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 02c1a60d7937..0b97b8ece4a9 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7765,11 +7765,11 @@ static int __alloc_contig_migrate_range(struct compact_control *cc, * @gfp_mask: GFP mask to use during compaction * * The PFN range does not have to be pageblock or MAX_ORDER_NR_PAGES - * aligned, however it's the caller's responsibility to guarantee that - * we are the only thread that changes migrate type of pageblocks the - * pages fall in. + * aligned. The PFN range must belong to a single zone. * - * The PFN range must belong to a single zone. + * The first thing this routine does is attempt to MIGRATE_ISOLATE all + * pageblocks in the range. Once isolated, the pageblocks should not + * be modified by others. * * Returns zero on success or negative error code. On success all * pages which PFN is in [start, end) are allocated for the caller and diff --git a/mm/page_isolation.c b/mm/page_isolation.c index 165ed8117bd1..61dee77bb211 100644 --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -28,6 +28,14 @@ static int set_migratetype_isolate(struct page *page, int migratetype, spin_lock_irqsave(&zone->lock, flags); + /* + * We assume the caller intended to SET migrate type to isolate. + * If it is already set, then someone else must have raced and + * set it before us. Return -EBUSY + */ + if (is_migrate_isolate_page(page)) + goto out; + pfn = page_to_pfn(page); arg.start_pfn = pfn; arg.nr_pages = pageblock_nr_pages; @@ -166,7 +174,15 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages) * future will not be allocated again. * * start_pfn/end_pfn must be aligned to pageblock_order. - * Returns 0 on success and -EBUSY if any part of range cannot be isolated. + * Return 0 on success and -EBUSY if any part of range cannot be isolated. + * + * There is no high level synchronization mechanism that prevents two threads + * from trying to isolate overlapping ranges. If this happens, one thread + * will notice pageblocks in the overlapping range already set to isolate. + * This happens in set_migratetype_isolate, and set_migratetype_isolate + * returns an error. We then clean up by restoring the migration type on + * pageblocks we may have modified and return -EBUSY to caller. This + * prevents two threads from simultaneously working on overlapping ranges. */ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, unsigned migratetype, bool skip_hwpoisoned_pages) |