[PATCH v3 12/18] xfs_db: do not reset current lsn from uuid command on v5 supers

[Brian Foster <bfoster@xxxxxxxxxx>]

The xfs_db uuid command modifes the uuid of the filesystem. As part of
this process, it is required to clear the log and format it with records
that use the new uuid. It currently resets the log to cycle 1, which is
not safe for v5 superblocks.

Update the uuid log clearing implementation to bump the current cycle
when the log is formatted on v5 superblock filesystems. This ensures
that the current LSN remains ahead of metadata LSNs on the subsequent
mount. Since the log is checked and cleared across a couple different
functions, also add a new global xlog structure, associate it with the
preexisting global mount structure and reference it to get and use the
current log cycle.

Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
---
 db/init.c | 25 ++++++++++++++-----------
 db/sb.c   | 19 +++++++++++++++----
 2 files changed, 29 insertions(+), 15 deletions(-)

diff --git a/db/init.c b/db/init.c
index 9537a38..c0472c8 100644
--- a/db/init.c
+++ b/db/init.c
@@ -17,6 +17,7 @@
  */
 
 #include "libxfs.h"
+#include "libxlog.h"
 #include <signal.h>
 #include "command.h"
 #include "init.h"
@@ -28,17 +29,18 @@
 #include "malloc.h"
 #include "type.h"
 
-static char    **cmdline;
-static int     ncmdline;
-char           *fsdevice;
-int            blkbb;
-int            exitcode;
-int            expert_mode;
-int            force;
-xfs_mount_t    xmount;
-xfs_mount_t    *mp;
-libxfs_init_t  x;
-xfs_agnumber_t cur_agno = NULLAGNUMBER;
+static char            **cmdline;
+static int             ncmdline;
+char                   *fsdevice;
+int                    blkbb;
+int                    exitcode;
+int                    expert_mode;
+int                    force;
+struct xfs_mount       xmount;
+struct xfs_mount       *mp;
+struct xlog            xlog;
+libxfs_init_t          x;
+xfs_agnumber_t         cur_agno = NULLAGNUMBER;
 
 static void
 usage(void)
@@ -154,6 +156,7 @@ init(
                        progname, fsdevice);
                exit(1);
        }
+       mp->m_log = &xlog;
        blkbb = 1 << mp->m_blkbb_log;
 
        /*
diff --git a/db/sb.c b/db/sb.c
index 9c585ca..30c622d 100644
--- a/db/sb.c
+++ b/db/sb.c
@@ -229,7 +229,6 @@ int xlog_recover_do_trans(struct xlog *log, xlog_recover_t 
*t, int p)
 int
 sb_logcheck(void)
 {
-       struct xlog     log;
        int             dirty;
 
        if (mp->m_sb.sb_logstart) {
@@ -248,7 +247,7 @@ sb_logcheck(void)
 
        libxfs_buftarg_init(mp, x.ddev, x.logdev, x.rtdev);
 
-       dirty = xlog_is_dirty(mp, &log, &x, 0);
+       dirty = xlog_is_dirty(mp, mp->m_log, &x, 0);
        if (dirty == -1) {
                dbprintf(_("ERROR: cannot find log head/tail, run 
xfs_repair\n"));
                return 0;
@@ -269,20 +268,32 @@ sb_logcheck(void)
 static int
 sb_logzero(uuid_t *uuidp)
 {
+       int     cycle = XLOG_INIT_CYCLE;
+       int     error;
+
        if (!sb_logcheck())
                return 0;
 
+       /*
+        * The log must always move forward on v5 superblocks. Bump it to the
+        * next cycle.
+        */
+       if (xfs_sb_version_hascrc(&mp->m_sb))
+               cycle = mp->m_log->l_curr_cycle + 1;
+
        dbprintf(_("Clearing log and setting UUID\n"));
 
-       if (libxfs_log_clear(mp->m_logdev_targp,
+       error =  libxfs_log_clear(mp->m_logdev_targp,
                        XFS_FSB_TO_DADDR(mp, mp->m_sb.sb_logstart),
                        (xfs_extlen_t)XFS_FSB_TO_BB(mp, mp->m_sb.sb_logblocks),
                        uuidp,
                        xfs_sb_version_haslogv2(&mp->m_sb) ? 2 : 1,
-                       mp->m_sb.sb_logsunit, XLOG_FMT, XLOG_INIT_CYCLE)) {
+                       mp->m_sb.sb_logsunit, XLOG_FMT, cycle);
+       if (error) {
                dbprintf(_("ERROR: cannot clear the log\n"));
                return 0;
        }
+
        return 1;
 }
 
-- 
2.1.0