On Fri, Apr 22, 2016 at 06:21:22PM -0600, Toshi Kani wrote: > 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. > > thp_get_unmapped_area() can be extended for huge page cache support. > > The patch is based on Matthew Wilcox's change that allows adding > support of the pud page size easily. See Hugh's implementation: http://lkml.kernel.org/r/alpine.LSU.2.11.1604051420110.5965@eggly.anvils > [1]: https://github.com/axboe/fio/blob/master/engines/mmap.c > Signed-off-by: Toshi Kani <toshi.kani@xxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx> > Cc: Dan Williams <dan.j.williams@xxxxxxxxx> > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxxxx> > Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> > Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > Cc: Dave Chinner <david@xxxxxxxxxxxxx> > Cc: Jan Kara <jack@xxxxxxx> > Cc: Theodore Ts'o <tytso@xxxxxxx> > Cc: Andreas Dilger <adilger.kernel@xxxxxxxxx> > Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> > --- > include/linux/huge_mm.h | 7 +++++++ > mm/huge_memory.c | 43 +++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 50 insertions(+) > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h > index 7008623..3769674 100644 > --- a/include/linux/huge_mm.h > +++ b/include/linux/huge_mm.h > @@ -85,6 +85,10 @@ 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); > > @@ -163,6 +167,9 @@ struct page *get_huge_zero_page(void); > #define transparent_hugepage_enabled(__vma) 0 > > #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 86f9f8b..2181c7f 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -790,6 +790,49 @@ 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; Hugh has more sanity checks before and after call to get_unmapped_area(). Please, consider borrowing them. > +} > + > +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; I think it's too strong reaction to hint, isn't it? We definately need this for MAP_FIXED. But in general? Maybe. > + 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 mm_struct *mm, > struct vm_area_struct *vma, > unsigned long address, pmd_t *pmd, > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a> -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
