mirror_zfs/config/kernel-lookup-bdev.m4
Brian Behlendorf 2b7ab9d4d9 Linux 2.6.26 compat, lookup_bdev()
It's doubtful many people were impacted by this but commit 6c28567
accidentally broke ZFS builds for 2.6.26 and earlier kernels.  This
commit depends on the lookup_bdev() function which exists in 2.6.26
but wasn't exported until 2.6.27.

The availability of the function isn't critical so a wrapper is
introduced which returns ERR_PTR(-ENOTSUP) when the function isn't
defined.  This will have the effect of causing zvol_is_zvol() to
always fail for 2.6.26 kernels.  This in turn means vdevs will
always get opened concurrently which is good for normal usage.
This will only become an issue if your using a zvol as a vdev in
another pool.  In which case you really should be using a newer
kernel anyway.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1205
2013-01-28 15:35:00 -08:00

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dnl #
dnl # 2.6.27 API change
dnl # lookup_bdev() was exported.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_LOOKUP_BDEV],
[AC_MSG_CHECKING([whether lookup_bdev() is available])
ZFS_LINUX_TRY_COMPILE_SYMBOL([
#include <linux/fs.h>
], [
lookup_bdev(NULL);
], [lookup_bdev], [fs/block_dev.c], [
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_LOOKUP_BDEV, 1, [lookup_bdev() is available])
], [
AC_MSG_RESULT(no)
])
])