mm: optimize dev_pagemap reference counting around get_dev_pagemap
Change the calling convention so that get_dev_pagemap always consumes the
previous reference instead of doing this using an explicit earlier call to
put_dev_pagemap in the callers.
The callers will still need to put the final reference after finishing the
loop over the pages.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/mm/gup.c b/mm/gup.c
index e0d82b6..3affe75 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1410,7 +1410,6 @@
VM_BUG_ON_PAGE(compound_head(page) != head, page);
- put_dev_pagemap(pgmap);
SetPageReferenced(page);
pages[*nr] = page;
(*nr)++;
@@ -1420,6 +1419,8 @@
ret = 1;
pte_unmap:
+ if (pgmap)
+ put_dev_pagemap(pgmap);
pte_unmap(ptem);
return ret;
}
@@ -1459,10 +1460,12 @@
SetPageReferenced(page);
pages[*nr] = page;
get_page(page);
- put_dev_pagemap(pgmap);
(*nr)++;
pfn++;
} while (addr += PAGE_SIZE, addr != end);
+
+ if (pgmap)
+ put_dev_pagemap(pgmap);
return 1;
}