3.16.63-rc1 review patch. If anyone has any objections, please let me know.
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From: Mike Kravetz mike.kravetz@oracle.com
commit 22146c3ce98962436e401f7b7016a6f664c9ffb5 upstream.
Some test systems were experiencing negative huge page reserve counts and incorrect file block counts. This was traced to /proc/sys/vm/drop_caches removing clean pages from hugetlbfs file pagecaches. When non-hugetlbfs explicit code removes the pages, the appropriate accounting is not performed.
This can be recreated as follows: fallocate -l 2M /dev/hugepages/foo echo 1 > /proc/sys/vm/drop_caches fallocate -l 2M /dev/hugepages/foo grep -i huge /proc/meminfo AnonHugePages: 0 kB ShmemHugePages: 0 kB HugePages_Total: 2048 HugePages_Free: 2047 HugePages_Rsvd: 18446744073709551615 HugePages_Surp: 0 Hugepagesize: 2048 kB Hugetlb: 4194304 kB ls -lsh /dev/hugepages/foo 4.0M -rw-r--r--. 1 root root 2.0M Oct 17 20:05 /dev/hugepages/foo
To address this issue, dirty pages as they are added to pagecache. This can easily be reproduced with fallocate as shown above. Read faulted pages will eventually end up being marked dirty. But there is a window where they are clean and could be impacted by code such as drop_caches. So, just dirty them all as they are added to the pagecache.
Link: http://lkml.kernel.org/r/b5be45b8-5afe-56cd-9482-28384699a049@oracle.com Fixes: 6bda666a03f0 ("hugepages: fold find_or_alloc_pages into huge_no_page()") Signed-off-by: Mike Kravetz mike.kravetz@oracle.com Acked-by: Mihcla Hocko mhocko@suse.com Reviewed-by: Khalid Aziz khalid.aziz@oracle.com Cc: Hugh Dickins hughd@google.com Cc: Naoya Horiguchi n-horiguchi@ah.jp.nec.com Cc: "Aneesh Kumar K . V" aneesh.kumar@linux.vnet.ibm.com Cc: Andrea Arcangeli aarcange@redhat.com Cc: "Kirill A . Shutemov" kirill.shutemov@linux.intel.com Cc: Davidlohr Bueso dave@stgolabs.net Cc: Alexander Viro viro@zeniv.linux.org.uk Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org [bwh: Backported to 3.16: adjust context, indentation] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- mm/hugetlb.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -3085,6 +3085,12 @@ retry: } ClearPagePrivate(page);
+ /* + * set page dirty so that it will not be removed from + * cache/file by non-hugetlbfs specific code paths. + */ + set_page_dirty(page); + spin_lock(&inode->i_lock); inode->i_blocks += blocks_per_huge_page(h); spin_unlock(&inode->i_lock);