thp, dax: add thp_get_unmapped_area for pmd mappings

When CONFIG_FS_DAX_PMD is set, DAX supports mmap() using pmd page size.
This feature relies on both mmap virtual address and FS block (i.e.
physical address) to be aligned by the pmd page size.  Users can use mkfs
options to specify FS to align block allocations.  However, aligning mmap
address requires code changes to existing applications for providing a
pmd-aligned address to mmap().

For instance, fio with "ioengine=mmap" performs I/Os with mmap() [1].  It
calls mmap() with a NULL address, which needs to be changed to provide a
pmd-aligned address for testing with DAX pmd mappings.  Changing all
applications that call mmap() with NULL is undesirable.

Add thp_get_unmapped_area(), which can be called by filesystem's
get_unmapped_area to align an mmap address by the pmd size for a DAX file.
It calls the default handler, mm->get_unmapped_area(), to find a range
and then aligns it for a DAX file.

The patch is based on Matthew Wilcox's change that allows adding support
of the pud page size easily.

[1]: https://github.com/axboe/fio/blob/master/engines/mmap.c
Link: http://lkml.kernel.org/r/1472497881-9323-2-git-send-email-toshi.kani@hpe.com
Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 6f14de45b5ce0807e01f7c5093d46ab5c9a546bb..4fca5263fd4253fcfb7ac93b9b0d5a8fe2aac8bb 100644 (file)
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -87,6 +87,10 @@ extern bool is_vma_temporary_stack(struct vm_area_struct *vma);
 
 extern unsigned long transparent_hugepage_flags;
 
+extern unsigned long thp_get_unmapped_area(struct file *filp,
+               unsigned long addr, unsigned long len, unsigned long pgoff,
+               unsigned long flags);
+
 extern void prep_transhuge_page(struct page *page);
 extern void free_transhuge_page(struct page *page);
 
@@ -169,6 +173,9 @@ void put_huge_zero_page(void);
 static inline void prep_transhuge_page(struct page *page) {}
 
 #define transparent_hugepage_flags 0UL
+
+#define thp_get_unmapped_area  NULL
+
 static inline int
 split_huge_page_to_list(struct page *page, struct list_head *list)
 {

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 2db2112aa31ed5506b4aef572d8e8c70477a8aa7..883f0ee0e73b8d385d67ce0d0c4ab5919234a487 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -469,6 +469,49 @@ void prep_transhuge_page(struct page *page)
        set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR);
 }
 
+unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len,
+               loff_t off, unsigned long flags, unsigned long size)
+{
+       unsigned long addr;
+       loff_t off_end = off + len;
+       loff_t off_align = round_up(off, size);
+       unsigned long len_pad;
+
+       if (off_end <= off_align || (off_end - off_align) < size)
+               return 0;
+
+       len_pad = len + size;
+       if (len_pad < len || (off + len_pad) < off)
+               return 0;
+
+       addr = current->mm->get_unmapped_area(filp, 0, len_pad,
+                                             off >> PAGE_SHIFT, flags);
+       if (IS_ERR_VALUE(addr))
+               return 0;
+
+       addr += (off - addr) & (size - 1);
+       return addr;
+}
+
+unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
+               unsigned long len, unsigned long pgoff, unsigned long flags)
+{
+       loff_t off = (loff_t)pgoff << PAGE_SHIFT;
+
+       if (addr)
+               goto out;
+       if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
+               goto out;
+
+       addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
+       if (addr)
+               return addr;
+
+ out:
+       return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
+}
+EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
+
 static int __do_huge_pmd_anonymous_page(struct fault_env *fe, struct page *page,
                gfp_t gfp)
 {