[PATCH v2] xfs: up(ic_sema) if flushing data device fails

[Leah Rumancik <leah.rumancik@xxxxxxxxx>]

We flush the data device cache before we issue external log IO. If
the flush fails, we shut down the log immediately and return. However,
the iclog->ic_sema is left in a decremented state so let's add an up().
Prior to this patch, xfs/438 would fail consistently when running with
an external log device:

sync
  -> xfs_log_force
  -> xlog_write_iclog
      -> down(&iclog->ic_sema)
      -> blkdev_issue_flush (fail causes us to intiate shutdown)
          -> xlog_force_shutdown
          -> return

unmount
  -> xfs_log_umount
      -> xlog_wait_iclog_completion
          -> down(&iclog->ic_sema) --------> HANG

There is a second early return / shutdown. Make sure the up() happens
for it as well.

Fixes: b5d721eaae47 ("xfs: external logs need to flush data device")
Fixes: 842a42d126b4 ("xfs: shutdown on failure to add page to log bio")
Fixes: 7d839e325af2 ("xfs: check return codes when flushing block devices")
Signed-off-by: Leah Rumancik <leah.rumancik@xxxxxxxxx>
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---

Notes:
    v1->v2:
     - use goto instead of multiple returns
     - add Fixes tags

 fs/xfs/xfs_log.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 51c100c86177..8ae923e00eb6 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -1925,20 +1925,17 @@ xlog_write_iclog(
 		 * avoid shutdown re-entering this path and erroring out again.
 		 */
 		if (log->l_targ != log->l_mp->m_ddev_targp &&
-		    blkdev_issue_flush(log->l_mp->m_ddev_targp->bt_bdev)) {
-			xlog_force_shutdown(log, SHUTDOWN_LOG_IO_ERROR);
-			return;
-		}
+		    blkdev_issue_flush(log->l_mp->m_ddev_targp->bt_bdev))
+			goto shutdown;
 	}
 	if (iclog->ic_flags & XLOG_ICL_NEED_FUA)
 		iclog->ic_bio.bi_opf |= REQ_FUA;
 
 	iclog->ic_flags &= ~(XLOG_ICL_NEED_FLUSH | XLOG_ICL_NEED_FUA);
 
-	if (xlog_map_iclog_data(&iclog->ic_bio, iclog->ic_data, count)) {
-		xlog_force_shutdown(log, SHUTDOWN_LOG_IO_ERROR);
-		return;
-	}
+	if (xlog_map_iclog_data(&iclog->ic_bio, iclog->ic_data, count))
+		goto shutdown;
+
 	if (is_vmalloc_addr(iclog->ic_data))
 		flush_kernel_vmap_range(iclog->ic_data, count);
 
@@ -1959,6 +1956,10 @@ xlog_write_iclog(
 	}
 
 	submit_bio(&iclog->ic_bio);
+	return;
+shutdown:
+	up(&iclog->ic_sema);
+	xlog_force_shutdown(log, SHUTDOWN_LOG_IO_ERROR);
 }
 
 /*
-- 
2.42.0.820.g83a721a137-goog