+/*
+ * Try to write out the superblock using barriers.
+ */
+STATIC int
+xfs_barrier_test(
+ xfs_mount_t *mp)
+{
+ xfs_buf_t *sbp = xfs_getsb(mp, 0);
+ int error;
+
+ XFS_BUF_UNDONE(sbp);
+ XFS_BUF_UNREAD(sbp);
+ XFS_BUF_UNDELAYWRITE(sbp);
+ XFS_BUF_WRITE(sbp);
+ XFS_BUF_UNASYNC(sbp);
+ XFS_BUF_ORDERED(sbp);
+
+ xfsbdstrat(mp, sbp);
+ error = xfs_iowait(sbp);
+
+ /*
+ * Clear all the flags we set and possible error state in the
+ * buffer. We only did the write to try out whether barriers
+ * worked and shouldn't leave any traces in the superblock
+ * buffer.
+ */
+ XFS_BUF_DONE(sbp);
+ XFS_BUF_ERROR(sbp, 0);
+ XFS_BUF_UNORDERED(sbp);
+
+ xfs_buf_relse(sbp);
+ return error;
+}
+
+void
+xfs_mountfs_check_barriers(xfs_mount_t *mp)
+{
+ int error;
+
+ if (mp->m_logdev_targp != mp->m_ddev_targp) {
+ xfs_fs_cmn_err(CE_NOTE, mp,
+ "Disabling barriers, not supported with external log device");
+ mp->m_flags &= ~XFS_MOUNT_BARRIER;
+ return;
+ }
+
+ if (mp->m_ddev_targp->bt_bdev->bd_disk->queue->ordered ==
+ QUEUE_ORDERED_NONE) {
+ xfs_fs_cmn_err(CE_NOTE, mp,
+ "Disabling barriers, not supported by the underlying device");
+ mp->m_flags &= ~XFS_MOUNT_BARRIER;
+ return;
+ }
+
+ if (xfs_readonly_buftarg(mp->m_ddev_targp)) {
+ xfs_fs_cmn_err(CE_NOTE, mp,
+ "Disabling barriers, underlying device is readonly");
+ mp->m_flags &= ~XFS_MOUNT_BARRIER;
+ return;
+ }
+
+ error = xfs_barrier_test(mp);
+ if (error) {
+ xfs_fs_cmn_err(CE_NOTE, mp,
+ "Disabling barriers, trial barrier write failed");
+ mp->m_flags &= ~XFS_MOUNT_BARRIER;
+ return;
+ }
+}
+
+void
+xfs_blkdev_issue_flush(
+ xfs_buftarg_t *buftarg)
+{
+ blkdev_issue_flush(buftarg->bt_bdev, NULL);
+}