shmem: add huge pages support
Here's basic implementation of huge pages support for shmem/tmpfs.
It's all pretty streight-forward:
- shmem_getpage() allcoates huge page if it can and try to inserd into
radix tree with shmem_add_to_page_cache();
- shmem_add_to_page_cache() puts the page onto radix-tree if there's
space for it;
- shmem_undo_range() removes huge pages, if it fully within range.
Partial truncate of huge pages zero out this part of THP.
This have visible effect on fallocate(FALLOC_FL_PUNCH_HOLE)
behaviour. As we don't really create hole in this case,
lseek(SEEK_HOLE) may have inconsistent results depending what
pages happened to be allocated.
- no need to change shmem_fault: core-mm will map an compound page as
huge if VMA is suitable;
Link: http://lkml.kernel.org/r/1466021202-61880-30-git-send-email-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/filemap.c b/mm/filemap.c
index 21508ea..e90c154 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -219,8 +219,13 @@
/* hugetlb pages do not participate in page cache accounting. */
if (!PageHuge(page))
__mod_zone_page_state(page_zone(page), NR_FILE_PAGES, -nr);
- if (PageSwapBacked(page))
+ if (PageSwapBacked(page)) {
__mod_zone_page_state(page_zone(page), NR_SHMEM, -nr);
+ if (PageTransHuge(page))
+ __dec_zone_page_state(page, NR_SHMEM_THPS);
+ } else {
+ VM_BUG_ON_PAGE(PageTransHuge(page) && !PageHuge(page), page);
+ }
/*
* At this point page must be either written or cleaned by truncate.