config/kernel-bdev-physical-size.m4

   1 dnl #
   2 dnl # 2.6.30 API change
   3 dnl #
   4 dnl # The bdev_physical_block_size() interface was added to provide a way
   5 dnl # to determine the smallest write which can be performed without a
   6 dnl # read-modify-write operation.  From the kernel documentation:
   7 dnl #
   8 dnl # What:          /sys/block/<disk>/queue/physical_block_size
   9 dnl # Date:          May 2009
  10 dnl # Contact:       Martin K. Petersen <martin.petersen@oracle.com>
  11 dnl # Description:
  12 dnl #                This is the smallest unit the storage device can write
  13 dnl #                without resorting to read-modify-write operation.  It is
  14 dnl #                usually the same as the logical block size but may be
  15 dnl #                bigger.  One example is SATA drives with 4KB sectors
  16 dnl #                that expose a 512-byte logical block size to the
  17 dnl #                operating system.
  18 dnl #
  19 dnl # Unfortunately, this interface isn't entirely reliable because
  20 dnl # drives are sometimes known to misreport this value.
  21 dnl #
  22 AC_DEFUN([ZFS_AC_KERNEL_BDEV_PHYSICAL_BLOCK_SIZE], [
  23         AC_MSG_CHECKING([whether bdev_physical_block_size() is available])
  24         tmp_flags="$EXTRA_KCFLAGS"
  25         EXTRA_KCFLAGS="${NO_UNUSED_BUT_SET_VARIABLE}"
  26         ZFS_LINUX_TRY_COMPILE([
  27                 #include <linux/blkdev.h>
  28         ],[
  29                 struct block_device *bdev = NULL;
  30                 bdev_physical_block_size(bdev);
  31         ],[
  32                 AC_MSG_RESULT(yes)
  33                 AC_DEFINE(HAVE_BDEV_PHYSICAL_BLOCK_SIZE, 1,
  34                           [bdev_physical_block_size() is available])
  35         ],[
  36                 AC_MSG_RESULT(no)
  37         ])
  38         EXTRA_KCFLAGS="$tmp_flags"
  39 ])