1 files changed, 16 insertions, 8 deletions

diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 02df7b408a26..f96c05669a9e 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -282,22 +282,29 @@ xfs_readsb(
         struct xfs_sb   *sbp = &mp->m_sb;
         int             error;
         int             loud = !(flags & XFS_MFSI_QUIET);
+        const struct xfs_buf_ops *buf_ops;
 
         ASSERT(mp->m_sb_bp == NULL);
         ASSERT(mp->m_ddev_targp != NULL);
 
         /*
+         * For the initial read, we must guess at the sector
+         * size based on the block device.  It's enough to
+         * get the sb_sectsize out of the superblock and
+         * then reread with the proper length.
+         * We don't verify it yet, because it may not be complete.
+         */
+        sector_size = xfs_getsize_buftarg(mp->m_ddev_targp);
+        buf_ops = NULL;
+
+        /*
          * Allocate a (locked) buffer to hold the superblock.
          * This will be kept around at all times to optimize
          * access to the superblock.
          */
-        sector_size = xfs_getsize_buftarg(mp->m_ddev_targp);
-
 reread:
         bp = xfs_buf_read_uncached(mp->m_ddev_targp, XFS_SB_DADDR,
-                                   BTOBB(sector_size), 0,
-                                   loud ? &xfs_sb_buf_ops
-                                        : &xfs_sb_quiet_buf_ops);
+                                   BTOBB(sector_size), 0, buf_ops);
         if (!bp) {
                 if (loud)
                         xfs_warn(mp, "SB buffer read failed");
@@ -328,12 +335,13 @@ reread:
         }
 
         /*
-         * If device sector size is smaller than the superblock size,
-         * re-read the superblock so the buffer is correctly sized.
+         * Re-read the superblock so the buffer is correctly sized,
+         * and properly verified.
          */
-        if (sector_size < sbp->sb_sectsize) {
+        if (buf_ops == NULL) {
                 xfs_buf_relse(bp);
                 sector_size = sbp->sb_sectsize;
+                buf_ops = loud ? &xfs_sb_buf_ops : &xfs_sb_quiet_buf_ops;
                 goto reread;
         }