BMC/Intel-BMC/linux.git/mm/hugetlb.c, branch dev

mm/hugetlb: remove unused arch hook prepare/release_hugepage

2015-06-26T00:00:35+00:00

With s390 dropping support for emulated hugepages, the last user of arch_prepare_hugepage and arch_release_hugepage is gone. Signed-off-by: Dominik Dingel Acked-by: Martin Schwidefsky Cc: Heiko Carstens Cc: Christian Borntraeger Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/hugetlb: handle races in alloc_huge_page and hugetlb_reserve_pages

2015-06-25T00:49:44+00:00

alloc_huge_page and hugetlb_reserve_pages use region_chg to calculate the number of pages which will be added to the reserve map. Subpool and global reserve counts are adjusted based on the output of region_chg. Before the pages are actually added to the reserve map, these routines could race and add fewer pages than expected. If this happens, the subpool and global reserve counts are not correct. Compare the number of pages actually added (region_add) to those expected to added (region_chg). If fewer pages are actually added, this indicates a race and adjust counters accordingly. Signed-off-by: Mike Kravetz Reviewed-by: Naoya Horiguchi Reviewed-by: Davidlohr Bueso Cc: David Rientjes Cc: Luiz Capitulino Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/hugetlb: compute/return the number of regions added by region_add()

2015-06-25T00:49:44+00:00

Modify region_add() to keep track of regions(pages) added to the reserve map and return this value. The return value can be compared to the return value of region_chg() to determine if the map was modified between calls. Make vma_commit_reservation() also pass along the return value of region_add(). In the normal case, we want vma_commit_reservation to return the same value as the preceding call to vma_needs_reservation. Create a common __vma_reservation_common routine to help keep the special case return values in sync Signed-off-by: Mike Kravetz Cc: Naoya Horiguchi Cc: Davidlohr Bueso Cc: David Rientjes Cc: Luiz Capitulino Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/hugetlb: document the reserve map/region tracking routines

2015-06-25T00:49:44+00:00

While working on hugetlbfs fallocate support, I noticed the following race in the existing code. It is unlikely that this race is hit very often in the current code. However, if more functionality to add and remove pages to hugetlbfs mappings (such as fallocate) is added the likelihood of hitting this race will increase. alloc_huge_page and hugetlb_reserve_pages use information from the reserve map to determine if there are enough available huge pages to complete the operation, as well as adjust global reserve and subpool usage counts. The order of operations is as follows: - call region_chg() to determine the expected change based on reserve map - determine if enough resources are available for this operation - adjust global counts based on the expected change - call region_add() to update the reserve map The issue is that reserve map could change between the call to region_chg and region_add. In this case, the counters which were adjusted based on the output of region_chg will not be correct. In order to hit this race today, there must be an existing shared hugetlb mmap created with the MAP_NORESERVE flag. A page fault to allocate a huge page via this mapping must occur at the same another task is mapping the same region without the MAP_NORESERVE flag. The patch set does not prevent the race from happening. Rather, it adds simple functionality to detect when the race has occurred. If a race is detected, then the incorrect counts are adjusted. Review comments pointed out the need for documentation of the existing region/reserve map routines. This patch set also adds documentation in this area. This patch (of 3): This is a documentation only patch and does not modify any code. Descriptions of the routines used for reserve map/region tracking are added. Signed-off-by: Mike Kravetz Cc: Naoya Horiguchi Cc: Davidlohr Bueso Cc: David Rientjes Cc: Luiz Capitulino Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/hugetlb: introduce minimum hugepage order

2015-06-25T00:49:42+00:00

Currently the initial value of order in dissolve_free_huge_page is 64 or 32, which leads to the following warning in static checker: mm/hugetlb.c:1203 dissolve_free_huge_pages() warn: potential right shift more than type allows '9,18,64' This is a potential risk of infinite loop, because 1 << order (== 0) is used in for-loop like this: for (pfn =3D start_pfn; pfn < end_pfn; pfn +=3D 1 << order) ... So this patch fixes it by using global minimum_order calculated at boot time. text data bss dec hex filename 28313 469 84236 113018 1b97a mm/hugetlb.o 28256 473 84236 112965 1b945 mm/hugetlb.o (patched) Fixes: c8721bbbdd36 ("mm: memory-hotplug: enable memory hotplug to handle hugepage") Reported-by: Dan Carpenter Signed-off-by: Naoya Horiguchi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/hugetlb: reduce arch dependent code about huge_pmd_unshare

2015-06-25T00:49:41+00:00

Currently we have many duplicates in definitions of huge_pmd_unshare. In all architectures this function just returns 0 when CONFIG_ARCH_WANT_HUGE_PMD_SHARE is N. This patch puts the default implementation in mm/hugetlb.c and lets these architectures use the common code. Signed-off-by: Zhang Zhen Cc: Russell King Cc: Catalin Marinas Cc: Tony Luck Cc: James Hogan Cc: Ralf Baechle Cc: Benjamin Herrenschmidt Cc: Martin Schwidefsky Cc: Chris Metcalf Cc: David Rientjes Cc: James Yang Cc: Aneesh Kumar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: hugetlb: cleanup using paeg_huge_active()

2015-04-15T23:35:19+00:00

Now we have an easy access to hugepages' activeness, so existing helpers to get the information can be cleaned up. [akpm@linux-foundation.org: s/PageHugeActive/page_huge_active/] Signed-off-by: Naoya Horiguchi Cc: Hugh Dickins Reviewed-by: Michal Hocko Cc: Mel Gorman Cc: Johannes Weiner Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: hugetlb: introduce page_huge_active

2015-04-15T23:35:19+00:00

We are not safe from calling isolate_huge_page() on a hugepage concurrently, which can make the victim hugepage in invalid state and results in BUG_ON(). The root problem of this is that we don't have any information on struct page (so easily accessible) about hugepages' activeness. Note that hugepages' activeness means just being linked to hstate->hugepage_activelist, which is not the same as normal pages' activeness represented by PageActive flag. Normal pages are isolated by isolate_lru_page() which prechecks PageLRU before isolation, so let's do similarly for hugetlb with a new paeg_huge_active(). set/clear_page_huge_active() should be called within hugetlb_lock. But hugetlb_cow() and hugetlb_no_page() don't do this, being justified because in these functions set_page_huge_active() is called right after the hugepage is allocated and no other thread tries to isolate it. [akpm@linux-foundation.org: s/PageHugeActive/page_huge_active/, make it return bool] [fengguang.wu@intel.com: set_page_huge_active() can be static] Signed-off-by: Naoya Horiguchi Cc: Hugh Dickins Reviewed-by: Michal Hocko Cc: Mel Gorman Cc: Johannes Weiner Cc: David Rientjes Signed-off-by: Fengguang Wu Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

hugetlbfs: accept subpool min_size mount option and setup accordingly

2015-04-15T23:35:18+00:00

Make 'min_size=' be an option when mounting a hugetlbfs. This option takes the same value as the 'size' option. min_size can be specified without specifying size. If both are specified, min_size must be less that or equal to size else the mount will fail. If min_size is specified, then at mount time an attempt is made to reserve min_size pages. If the reservation fails, the mount fails. At umount time, the reserved pages are released. Signed-off-by: Mike Kravetz Cc: Davidlohr Bueso Cc: Aneesh Kumar Cc: Joonsoo Kim Cc: Andi Kleen Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

hugetlbfs: add minimum size accounting to subpools

2015-04-15T23:35:17+00:00

The same routines that perform subpool maximum size accounting hugepage_subpool_get/put_pages() are modified to also perform minimum size accounting. When a delta value is passed to these routines, calculate how global reservations must be adjusted to maintain the subpool minimum size. The routines now return this global reserve count adjustment. This global reserve count adjustment is then passed to the global accounting routine hugetlb_acct_memory(). Signed-off-by: Mike Kravetz Cc: Davidlohr Bueso Cc: Aneesh Kumar Cc: Joonsoo Kim Cc: Andi Kleen Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds