Thread (19 messages) 19 messages, 3 authors, 2018-05-28

Re: [PATCH v2 1/4] mm: change type of free_contig_range(nr_pages) to unsigned long

From: Vlastimil Babka <hidden>
Date: 2018-05-18 09:15:05
Also in: linux-mm, lkml

On 05/04/2018 01:29 AM, Mike Kravetz wrote:
quoted hunk ↗ jump to hunk
free_contig_range() is currently defined as:
void free_contig_range(unsigned long pfn, unsigned nr_pages);
change to,
void free_contig_range(unsigned long pfn, unsigned long nr_pages);

Some callers are passing a truncated unsigned long today.  It is
highly unlikely that these values will overflow an unsigned int.
However, this should be changed to an unsigned long to be consistent
with other page counts.

Signed-off-by: Mike Kravetz <redacted>
---
 include/linux/gfp.h | 2 +-
 mm/cma.c            | 2 +-
 mm/hugetlb.c        | 2 +-
 mm/page_alloc.c     | 6 +++---
 4 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 1a4582b44d32..86a0d06463ab 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -572,7 +572,7 @@ static inline bool pm_suspended_storage(void)
 /* The below functions must be run on a range from a single zone. */
 extern int alloc_contig_range(unsigned long start, unsigned long end,
 			      unsigned migratetype, gfp_t gfp_mask);
-extern void free_contig_range(unsigned long pfn, unsigned nr_pages);
+extern void free_contig_range(unsigned long pfn, unsigned long nr_pages);
 #endif
 
 #ifdef CONFIG_CMA
diff --git a/mm/cma.c b/mm/cma.c
index aa40e6c7b042..f473fc2b7cbd 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -563,7 +563,7 @@ bool cma_release(struct cma *cma, const struct page *pages, unsigned int count)
 
 	VM_BUG_ON(pfn + count > cma->base_pfn + cma->count);
 
-	free_contig_range(pfn, count);
+	free_contig_range(pfn, (unsigned long)count);
I guess this cast from uint to ulong doesn't need to be explicit? But
instead, cma_release() signature could be also changed to ulong, because
some of its callers do pass those?
quoted hunk ↗ jump to hunk
 	cma_clear_bitmap(cma, pfn, count);
 	trace_cma_release(pfn, pages, count);
 
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 218679138255..c81072ce7510 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1055,7 +1055,7 @@ static void destroy_compound_gigantic_page(struct page *page,
 
 static void free_gigantic_page(struct page *page, unsigned int order)
 {
-	free_contig_range(page_to_pfn(page), 1 << order);
+	free_contig_range(page_to_pfn(page), 1UL << order);
 }
 
 static int __alloc_gigantic_page(unsigned long start_pfn,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 905db9d7962f..0fd5e8e2456e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7937,9 +7937,9 @@ int alloc_contig_range(unsigned long start, unsigned long end,
 	return ret;
 }
 
-void free_contig_range(unsigned long pfn, unsigned nr_pages)
+void free_contig_range(unsigned long pfn, unsigned long nr_pages)
 {
-	unsigned int count = 0;
+	unsigned long count = 0;
 
 	for (; nr_pages--; pfn++) {
 		struct page *page = pfn_to_page(pfn);
@@ -7947,7 +7947,7 @@ void free_contig_range(unsigned long pfn, unsigned nr_pages)
 		count += page_count(page) != 1;
 		__free_page(page);
 	}
-	WARN(count != 0, "%d pages are still in use!\n", count);
+	WARN(count != 0, "%ld pages are still in use!\n", count);
Maybe change to %lu while at it?
BTW, this warning can theoretically produce false positives, because
page users have to deal with page_count() being incremented by e.g.
parallel pfn scanners using get_page_unless_zero(). We also don't detect
refcount leaks in general. Should we remove it or change it to VM_WARN
if it's still useful for debugging?
 }
 #endif
 
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