I wonder why nobody complained about the build warning... sorry. ----8<---- From: Vlastimil Babka <vbabka@xxxxxxx> Date: Mon, 19 May 2014 12:02:38 +0200 Subject: mm-compaction-avoid-rescanning-pageblocks-in-isolate_freepages-fix MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Fix a (spurious) build warning: mm/compaction.c:860:15: warning: ‘next_free_pfn’ may be used uninitialized in this function [-Wmaybe-uninitialized] Seems like the compiler cannot prove that exiting the for loop without updating next_free_pfn there will mean that the check for crossing the scanners will trigger. So let's not confuse people who try to see why this warning occurs. Instead of initializing next_free_pfn to zero with an explaining comment, just drop the damned variable altogether and work with cc->free_pfn directly as Nayoa originally suggested. Suggested-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx> --- mm/compaction.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index 8db9820..b0f939b 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -760,7 +760,6 @@ static void isolate_freepages(struct zone *zone, unsigned long block_start_pfn; /* start of current pageblock */ unsigned long block_end_pfn; /* end of current pageblock */ unsigned long low_pfn; /* lowest pfn scanner is able to scan */ - unsigned long next_free_pfn; /* start pfn for scaning at next round */ int nr_freepages = cc->nr_freepages; struct list_head *freelist = &cc->freepages; @@ -822,7 +821,7 @@ static void isolate_freepages(struct zone *zone, continue; /* Found a block suitable for isolating free pages from */ - next_free_pfn = block_start_pfn; + cc->free_pfn = block_start_pfn; isolated = isolate_freepages_block(cc, block_start_pfn, block_end_pfn, freelist, false); nr_freepages += isolated; @@ -852,9 +851,8 @@ static void isolate_freepages(struct zone *zone, * so that compact_finished() may detect this */ if (block_start_pfn < low_pfn) - next_free_pfn = cc->migrate_pfn; + cc->free_pfn = cc->migrate_pfn; - cc->free_pfn = next_free_pfn; cc->nr_freepages = nr_freepages; } -- 1.8.4.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>