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Linux 2.6.26 compat, lookup_bdev()

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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
This commit is contained in:
Brian Behlendorf 2013-01-28 14:15:39 -08:00
parent 930b6fec21
commit 2b7ab9d4d9
3 changed files with 27 additions and 0 deletions
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17
config/kernel-lookup-bdev.m4 Normal file
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@ -0,0 +1,17 @@
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)
])
])

1
config/kernel.m4
View File

@ -12,6 +12,7 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
ZFS_AC_KERNEL_3ARG_BLKDEV_GET
ZFS_AC_KERNEL_BLKDEV_GET_BY_PATH
ZFS_AC_KERNEL_OPEN_BDEV_EXCLUSIVE
ZFS_AC_KERNEL_LOOKUP_BDEV
ZFS_AC_KERNEL_INVALIDATE_BDEV_ARGS
ZFS_AC_KERNEL_BDEV_LOGICAL_BLOCK_SIZE
ZFS_AC_KERNEL_BDEV_PHYSICAL_BLOCK_SIZE

9
include/linux/blkdev_compat.h
View File

@ -392,6 +392,15 @@ bio_set_flags_failfast(struct block_device *bdev, int *flags)
# define vdev_bdev_invalidate(bdev) invalidate_bdev(bdev, 1)
#endif /* HAVE_1ARG_INVALIDATE_BDEV */
/*
* 2.6.27 API change
* The function was exported for use, prior to this it existed by the
* symbol was not exported.
*/
#ifndef HAVE_LOOKUP_BDEV
# define lookup_bdev(path) ERR_PTR(-ENOTSUP)
#endif
/*
* 2.6.30 API change
* To ensure good performance preferentially use the physical block size