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Remove the bio_empty_barrier() check.

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To determine whether the kernel is capable of handling empty barrier
BIOs, we check for the presence of the bio_empty_barrier() macro,
which was introduced in 2.6.24. If this macro is defined, then we can
flush disk vdevs; if it isn't, then flushing is disabled.

Unfortunately, the bio_empty_barrier() macro was removed in 2.6.37,
even though the kernel is still capable of handling empty barrier BIOs.

As a result, flushing is effectively disabled on kernels >= 2.6.37,
meaning that starting from this kernel version, zfs doesn't use
barriers to guarantee on-disk data consistency. This is quite bad and
can lead to potential data corruption on power failures.

This patch fixes the issue by removing the configure check for
bio_empty_barrier(), as we don't support kernels <= 2.6.24 anymore.

Thanks to Richard Kojedzinszky for catching this nasty bug.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1318
This commit is contained in:
Etienne Dechamps 2013-02-24 11:22:07 +00:00 committed by Brian Behlendorf
parent d75af3c0eb
commit d9b0ebbe82
3 changed files with 0 additions and 29 deletions
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19
config/kernel-bio-empty-barrier.m4
View File

@ -1,19 +0,0 @@
dnl #
dnl # 2.6.24 API change
dnl # Empty write barriers are now supported and we should use them.
dnl #
AC_DEFUN([ZFS_AC_KERNEL_BIO_EMPTY_BARRIER], [
AC_MSG_CHECKING([whether bio_empty_barrier() is defined])
ZFS_LINUX_TRY_COMPILE([
#include <linux/bio.h>
],[
struct bio bio;
(void)bio_empty_barrier(&bio);
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_BIO_EMPTY_BARRIER, 1,
[bio_empy_barrier() is defined])
],[
AC_MSG_RESULT(no)
])
])

1
config/kernel.m4
View File

@ -16,7 +16,6 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
ZFS_AC_KERNEL_INVALIDATE_BDEV_ARGS
ZFS_AC_KERNEL_BDEV_LOGICAL_BLOCK_SIZE
ZFS_AC_KERNEL_BDEV_PHYSICAL_BLOCK_SIZE
ZFS_AC_KERNEL_BIO_EMPTY_BARRIER
ZFS_AC_KERNEL_BIO_FAILFAST
ZFS_AC_KERNEL_BIO_FAILFAST_DTD
ZFS_AC_KERNEL_REQ_FAILFAST_MASK

9
module/zfs/vdev_disk.c
View File

@ -604,8 +604,6 @@ vdev_disk_physio(struct block_device *bdev, caddr_t kbuf,
return __vdev_disk_physio(bdev, NULL, kbuf, size, offset, flags);
}
/* 2.6.24 API change */
#ifdef HAVE_BIO_EMPTY_BARRIER
BIO_END_IO_PROTO(vdev_disk_io_flush_completion, bio, size, rc)
{
zio_t *zio = bio->bi_private;
@ -646,13 +644,6 @@ vdev_disk_io_flush(struct block_device *bdev, zio_t *zio)
return 0;
}
#else
static int
vdev_disk_io_flush(struct block_device *bdev, zio_t *zio)
{
return ENOTSUP;
}
#endif /* HAVE_BIO_EMPTY_BARRIER */
static int
vdev_disk_io_start(zio_t *zio)