[PATCH 4/8] libxfs: enable tools to check that metadata updates have been committed

["Darrick J. Wong" <darrick.wong@oracle.com>]

From: Darrick J. Wong <darrick.wong@oracle.com>

Add a new function that will ensure that everything we changed has
landed on stable media, and report the results.  Subsequent commits will
teach the individual programs to report when things go wrong.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 include/xfs_mount.h |    3 +++
 libxfs/init.c       |   43 +++++++++++++++++++++++++++++++++++++++++++
 libxfs/libxfs_io.h  |    2 ++
 libxfs/rdwr.c       |   27 +++++++++++++++++++++++++--
 4 files changed, 73 insertions(+), 2 deletions(-)


diff --git a/include/xfs_mount.h b/include/xfs_mount.h
index 29b3cc1b..c80aaf69 100644
--- a/include/xfs_mount.h
+++ b/include/xfs_mount.h
@@ -187,4 +187,7 @@ extern xfs_mount_t	*libxfs_mount (xfs_mount_t *, xfs_sb_t *,
 extern void	libxfs_umount (xfs_mount_t *);
 extern void	libxfs_rtmount_destroy (xfs_mount_t *);
 
+void libxfs_flush_devices(struct xfs_mount *mp, int *datadev, int *logdev,
+		int *rtdev);
+
 #endif	/* __XFS_MOUNT_H__ */
diff --git a/libxfs/init.c b/libxfs/init.c
index a0d4b7f4..d1d3f4df 100644
--- a/libxfs/init.c
+++ b/libxfs/init.c
@@ -569,6 +569,8 @@ libxfs_buftarg_alloc(
 	}
 	btp->bt_mount = mp;
 	btp->dev = dev;
+	btp->lost_writes = false;
+
 	return btp;
 }
 
@@ -791,6 +793,47 @@ libxfs_rtmount_destroy(xfs_mount_t *mp)
 	mp->m_rsumip = mp->m_rbmip = NULL;
 }
 
+static inline int
+libxfs_flush_buftarg(
+	struct xfs_buftarg	*btp)
+{
+	if (btp->lost_writes)
+		return -ENOTRECOVERABLE;
+
+	return libxfs_blkdev_issue_flush(btp);
+}
+
+/*
+ * Purge the buffer cache to write all dirty buffers to disk and free all
+ * incore buffers.  Buffers that cannot be written will cause the lost_writes
+ * flag to be set in the buftarg.  If there were no lost writes, flush the
+ * device to make sure the writes made it to stable storage.
+ *
+ * For each device, the return code will be set to -ENOTRECOVERABLE if we
+ * couldn't write something to disk; or the results of the block device flush
+ * operation.
+ */
+void
+libxfs_flush_devices(
+	struct xfs_mount	*mp,
+	int			*datadev,
+	int			*logdev,
+	int			*rtdev)
+{
+	*datadev = *logdev = *rtdev = 0;
+
+	libxfs_bcache_purge();
+
+	if (mp->m_ddev_targp)
+		*datadev = libxfs_flush_buftarg(mp->m_ddev_targp);
+
+	if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp)
+		*logdev = libxfs_flush_buftarg(mp->m_logdev_targp);
+
+	if (mp->m_rtdev_targp)
+		*rtdev = libxfs_flush_buftarg(mp->m_rtdev_targp);
+}
+
 /*
  * Release any resource obtained during a mount.
  */
diff --git a/libxfs/libxfs_io.h b/libxfs/libxfs_io.h
index 579df52b..fc0fd060 100644
--- a/libxfs/libxfs_io.h
+++ b/libxfs/libxfs_io.h
@@ -23,10 +23,12 @@ struct xfs_perag;
 struct xfs_buftarg {
 	struct xfs_mount	*bt_mount;
 	dev_t			dev;
+	bool			lost_writes;
 };
 
 extern void	libxfs_buftarg_init(struct xfs_mount *mp, dev_t ddev,
 				    dev_t logdev, dev_t rtdev);
+int libxfs_blkdev_issue_flush(struct xfs_buftarg *btp);
 
 #define LIBXFS_BBTOOFF64(bbs)	(((xfs_off_t)(bbs)) << BBSHIFT)
 
diff --git a/libxfs/rdwr.c b/libxfs/rdwr.c
index 8b47d438..92e497f9 100644
--- a/libxfs/rdwr.c
+++ b/libxfs/rdwr.c
@@ -17,6 +17,7 @@
 #include "xfs_inode_fork.h"
 #include "xfs_inode.h"
 #include "xfs_trans.h"
+#include "libfrog/platform.h"
 
 #include "libxfs.h"		/* for LIBXFS_EXIT_ON_FAILURE */
 
@@ -1227,9 +1228,11 @@ libxfs_brelse(
 
 	if (!bp)
 		return;
-	if (bp->b_flags & LIBXFS_B_DIRTY)
+	if (bp->b_flags & LIBXFS_B_DIRTY) {
 		fprintf(stderr,
 			"releasing dirty buffer to free list!\n");
+		bp->b_target->lost_writes = true;
+	}
 
 	pthread_mutex_lock(&xfs_buf_freelist.cm_mutex);
 	list_add(&bp->b_node.cn_mru, &xfs_buf_freelist.cm_list);
@@ -1248,9 +1251,11 @@ libxfs_bulkrelse(
 		return 0 ;
 
 	list_for_each_entry(bp, list, b_node.cn_mru) {
-		if (bp->b_flags & LIBXFS_B_DIRTY)
+		if (bp->b_flags & LIBXFS_B_DIRTY) {
 			fprintf(stderr,
 				"releasing dirty buffer (bulk) to free list!\n");
+			bp->b_target->lost_writes = true;
+		}
 		count++;
 	}
 
@@ -1479,6 +1484,24 @@ libxfs_irele(
 	kmem_cache_free(xfs_inode_zone, ip);
 }
 
+/*
+ * Flush everything dirty in the kernel and disk write caches to stable media.
+ * Returns 0 for success or a negative error code.
+ */
+int
+libxfs_blkdev_issue_flush(
+	struct xfs_buftarg	*btp)
+{
+	int			fd, ret;
+
+	if (btp->dev == 0)
+		return 0;
+
+	fd = libxfs_device_to_fd(btp->dev);
+	ret = platform_flush_device(fd, btp->dev);
+	return ret ? -errno : 0;
+}
+
 /*
  * Write out a buffer list synchronously.
  *