From b854f711f6b8b49674d494c5e6d706096dd38301 Mon Sep 17 00:00:00 2001 From: Joonsoo Kim Date: Tue, 21 Jan 2014 15:49:43 -0800 Subject: [PATCH] mm/rmap: recompute pgoff for huge page Rmap traversing is used in five different cases, try_to_unmap(), try_to_munlock(), page_referenced(), page_mkclean() and remove_migration_ptes(). Each one implements its own traversing functions for the cases, anon, file, ksm, respectively. These cause lots of duplications and cause maintenance overhead. They also make codes being hard to understand and error-prone. One example is hugepage handling. There is a code to compute hugepage offset correctly in try_to_unmap_file(), but, there isn't a code to compute hugepage offset in rmap_walk_file(). These are used pairwise in migration context, but we missed to modify pairwise. To overcome these drawbacks, we should unify these through one unified function. I decide rmap_walk() as main function since it has no unnecessity. And to control behavior of rmap_walk(), I introduce struct rmap_walk_control having some function pointers. These makes rmap_walk() working for their specific needs. This patchset remove a lot of duplicated code as you can see in below short-stat and kernel text size also decrease slightly. text data bss dec hex filename 10640 1 16 10657 29a1 mm/rmap.o 10047 1 16 10064 2750 mm/rmap.o 13823 705 8288 22816 5920 mm/ksm.o 13199 705 8288 22192 56b0 mm/ksm.o This patch (of 9): We have to recompute pgoff if the given page is huge, since result based on HPAGE_SIZE is not approapriate for scanning the vma interval tree, as shown by commit 36e4f20af833 ("hugetlb: do not use vma_hugecache_offset() for vma_prio_tree_foreach") and commit 369a713e ("rmap: recompute pgoff for unmapping huge page"). To handle both the cases, normal page for page cache and hugetlb page, by same way, we can use compound_page(). It returns 0 on non-compound page and it also returns proper value on compound page. Signed-off-by: Joonsoo Kim Cc: Naoya Horiguchi Cc: Mel Gorman Cc: Hugh Dickins Cc: Rik van Riel Cc: Ingo Molnar Cc: Hillf Danton Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/rmap.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/mm/rmap.c b/mm/rmap.c index 068522d8502a..edc0aea2c4e3 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1512,7 +1512,7 @@ static int try_to_unmap_anon(struct page *page, enum ttu_flags flags) static int try_to_unmap_file(struct page *page, enum ttu_flags flags) { struct address_space *mapping = page->mapping; - pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); + pgoff_t pgoff = page->index << compound_order(page); struct vm_area_struct *vma; int ret = SWAP_AGAIN; unsigned long cursor; @@ -1520,9 +1520,6 @@ static int try_to_unmap_file(struct page *page, enum ttu_flags flags) unsigned long max_nl_size = 0; unsigned int mapcount; - if (PageHuge(page)) - pgoff = page->index << compound_order(page); - mutex_lock(&mapping->i_mmap_mutex); vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) { unsigned long address = vma_address(page, vma); @@ -1712,7 +1709,7 @@ static int rmap_walk_file(struct page *page, int (*rmap_one)(struct page *, struct vm_area_struct *, unsigned long, void *), void *arg) { struct address_space *mapping = page->mapping; - pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); + pgoff_t pgoff = page->index << compound_order(page); struct vm_area_struct *vma; int ret = SWAP_AGAIN; -- 2.30.2