On Fri, Jan 08, 2016 at 02:49:44PM -0500, Matthew Wilcox wrote:

From: Matthew Wilcox <redacted>

Andrew, I think this is ready for a spin in -mm.

v3: Rebased against current mmtom
v2: Reduced churn in filesystems by switching to ->huge_fault interface
    Addressed concerns from Kirill

We have customer demand to use 1GB pages to map DAX files.  Unlike the 2MB
page support, the Linux MM does not currently support PUD pages, so I have
attempted to add support for the necessary pieces for DAX huge PUD pages.

Filesystems still need work to allocate 1GB pages.  With ext4, I can
only get 16MB of contiguous space, although it is aligned.  With XFS,
I can get 80MB less than 1GB, and it's not aligned.  The XFS problem
may be due to the small amount of RAM in my test machine.

"It's not aligned"... I don't know the details of what you're trying to do, but
are you trying to create a file where each GB of logical address space maps to
a contiguous GB of physical space, and both logical and physical offsets align
to a 1GB boundary?

If the XFS is formatted with stripe unit/width of 1G, an extent size hint of 1G
is put on the file, and the whole file is allocated in 1G chunks, I think
you're supposed to be able to make the above happen:

# mkfs.xfs /dev/mapper/moo -f -d su=1g,sw=1
meta-data=/dev/mapper/moo        isize=512    agcount=34, agsize=8126464 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=1, sparse=0, rmapbt=0, reflink=0
data     =                       bsize=4096   blocks=268435456, imaxpct=5
         =                       sunit=262144 swidth=262144 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=1
log      =internal log           bsize=4096   blocks=131072, version=2
         =                       sectsz=512   sunit=8 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
# mount /dev/mapper/moo /mnt
# xfs_io -f -c 'extsize 1g' -c 'falloc 0 200g' /mnt/urk
# filefrag -v /mnt/urk
Filesystem type is: 58465342
File size of /mnt/urk is 214748364800 (52428800 blocks of 4096 bytes)
 ext:     logical_offset:        physical_offset: length:   expected: flags:
   0:        0.. 7340031:     524288..   7864319: 7340032:             unwritten
   1:  7340032..14680063:    8388608..  15728639: 7340032:    7864320: unwritten
   2: 14680064..22020095:   16515072..  23855103: 7340032:   15728640: unwritten
   3: 22020096..29360127:   24641536..  31981567: 7340032:   23855104: unwritten
   4: 29360128..36700159:   32768000..  40108031: 7340032:   31981568: unwritten
   5: 36700160..40370175:   40894464..  44564479: 3670016:   40108032: unwritten
   6: 40370176..44040191:   44826624..  48496639: 3670016:   44564480: unwritten
   7: 44040192..51380223:   49020928..  56360959: 7340032:   48496640: unwritten
   8: 51380224..52428799:   57147392..  58195967: 1048576:   56360960: last,unwritten,eof
/mnt/urk: 9 extents found

AFAICT each extent's logical and physical offsets are aligned to a 1G boundary.

<shrug> Just a shot in the dark.

(This VM has 2G of memory and 1T of fake disk.)

--D

This patch set is against something approximately current -mm.  I'd like
to thank Dave Chinner & Kirill Shutemov for their reviews of v1.
The conversion of pmd_fault & pud_fault to huge_fault is thanks to
Dave's poking, and Kirill spotted a couple of problems in the MM code.
Version 2 of the patch set is about 200 lines smaller (1016 insertions,
23 deletions in v1).

I've done some light testing using a program to mmap a block device
with DAX enabled, calling mincore() and examining /proc/smaps and
/proc/pagemap.

Matthew Wilcox (8):
  mm: Convert an open-coded VM_BUG_ON_VMA
  mm,fs,dax: Change ->pmd_fault to ->huge_fault
  mm: Add support for PUD-sized transparent hugepages
  mincore: Add support for PUDs
  procfs: Add support for PUDs to smaps, clear_refs and pagemap
  x86: Add support for PUD-sized transparent hugepages
  dax: Support for transparent PUD pages
  ext4: Support for PUD-sized transparent huge pages

 Documentation/filesystems/dax.txt     |  12 +-
 arch/Kconfig                          |   3 +
 arch/x86/Kconfig                      |   1 +
 arch/x86/include/asm/paravirt.h       |  11 ++
 arch/x86/include/asm/paravirt_types.h |   2 +
 arch/x86/include/asm/pgtable.h        |  94 ++++++++++++
 arch/x86/include/asm/pgtable_64.h     |  13 ++
 arch/x86/kernel/paravirt.c            |   1 +
 arch/x86/mm/pgtable.c                 |  31 ++++
 fs/block_dev.c                        |  10 +-
 fs/dax.c                              | 272 +++++++++++++++++++++++++---------
 fs/ext2/file.c                        |  27 +---
 fs/ext4/file.c                        |  60 +++-----
 fs/proc/task_mmu.c                    | 109 ++++++++++++++
 fs/xfs/xfs_file.c                     |  25 ++--
 fs/xfs/xfs_trace.h                    |   2 +-
 include/asm-generic/pgtable.h         |  62 +++++++-
 include/asm-generic/tlb.h             |  14 ++
 include/linux/dax.h                   |  17 ---
 include/linux/huge_mm.h               |  50 +++++++
 include/linux/mm.h                    |  43 +++++-
 include/linux/mmu_notifier.h          |  13 ++
 include/linux/pfn_t.h                 |   8 +
 mm/huge_memory.c                      | 151 +++++++++++++++++++
 mm/memory.c                           | 101 +++++++++++--
 mm/mincore.c                          |  13 ++
 mm/pagewalk.c                         |  19 ++-
 mm/pgtable-generic.c                  |  14 ++
 28 files changed, 980 insertions(+), 198 deletions(-)

-- 
2.6.4

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