On Sun, Sep 11, 2016 at 10:31:35AM -0700, Dan Williams wrote: > As evidenced by this bug report [1], userspace libraries are interested > in whether a mapping is DAX mapped, i.e. no intervening page cache. > Rather than using the ambiguous VM_MIXEDMAP flag in smaps, provide an > explicit "is dax" indication as a new flag in the page vector populated > by mincore. > > There are also cases, particularly for testing and validating a > configuration to know the hardware mapping geometry of the pages in a > given process address range. Consider filesystem-dax where a > configuration needs to take care to align partitions and block > allocations before huge page mappings might be used, or > anonymous-transparent-huge-pages where a process is opportunistically > assigned large pages. mincore2() allows these configurations to be > surveyed and validated. > > The implementation takes advantage of the unused bits in the per-page > byte returned for each PAGE_SIZE extent of a given address range. The > new format of each vector byte is: > > (TLB_SHIFT - PAGE_SHIFT) << 2 | vma_is_dax() << 1 | page_present > > [1]: https://lkml.org/lkml/2016/9/7/61 > > Cc: Arnd Bergmann <a...@arndb.de> > Cc: Andrea Arcangeli <aarca...@redhat.com> > Cc: Andrew Morton <a...@linux-foundation.org> > Cc: Dave Hansen <dave.han...@linux.intel.com> > Cc: Xiao Guangrong <guangrong.x...@linux.intel.com> > Cc: Kirill A. Shutemov <kirill.shute...@linux.intel.com> > Signed-off-by: Dan Williams <dan.j.willi...@intel.com> > --- > include/linux/syscalls.h | 2 + > include/uapi/asm-generic/mman-common.h | 3 + > kernel/sys_ni.c | 1 > mm/mincore.c | 126 > +++++++++++++++++++++++++------- > 4 files changed, 104 insertions(+), 28 deletions(-) > > diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h > index d02239022bd0..4aa2ee7e359a 100644 > --- a/include/linux/syscalls.h > +++ b/include/linux/syscalls.h > @@ -467,6 +467,8 @@ asmlinkage long sys_munlockall(void); > asmlinkage long sys_madvise(unsigned long start, size_t len, int behavior); > asmlinkage long sys_mincore(unsigned long start, size_t len, > unsigned char __user * vec); > +asmlinkage long sys_mincore2(unsigned long start, size_t len, > + unsigned char __user * vec, int flags);
We had few attempts to extand mincore(2) interface/functionality before. None of them ended up in upsteam. How this attempt compares to previous? -- Kirill A. Shutemov
