xfs: more reserved blocks fixups

This mangles the reserved blocks counts a little more.

1) add a helper function for the default reserved count
2) add helper functions to save/restore counts on ro/rw
3) save/restore reserved blocks on freeze/thaw
4) disallow changing reserved count while readonly

V2: changed field name to match Dave's changes

Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Signed-off-by: Alex Elder <aelder@sgi.com>

1 files changed, 23 insertions, 11 deletions

diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 7f81ed72c875..5061149b2cc4 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -1091,6 +1091,22 @@ xfs_mount_reset_sbqflags(
         return xfs_trans_commit(tp, 0);
 }
 
+__uint64_t
+xfs_default_resblks(xfs_mount_t *mp)
+{
+        __uint64_t resblks;
+
+        /*
+         * We default to 5% or 1024 fsbs of space reserved, whichever is smaller.
+         * This may drive us straight to ENOSPC on mount, but that implies
+         * we were already there on the last unmount. Warn if this occurs.
+         */
+        resblks = mp->m_sb.sb_dblocks;
+        do_div(resblks, 20);
+        resblks = min_t(__uint64_t, resblks, 1024);
+        return resblks;
+}
+
 /*
  * This function does the following on an initial mount of a file system:
  *      - reads the superblock from disk and init the mount struct
@@ -1401,18 +1417,14 @@ xfs_mountfs(
          * when at ENOSPC. This is needed for operations like create with
          * attr, unwritten extent conversion at ENOSPC, etc. Data allocations
          * are not allowed to use this reserved space.
-         *
-         * We default to 5% or 1024 fsbs of space reserved, whichever is smaller.
-         * This may drive us straight to ENOSPC on mount, but that implies
-         * we were already there on the last unmount. Warn if this occurs.
          */
-        resblks = mp->m_sb.sb_dblocks;
-        do_div(resblks, 20);
-        resblks = min_t(__uint64_t, resblks, 1024);
-        error = xfs_reserve_blocks(mp, &resblks, NULL);
-        if (error)
-                cmn_err(CE_WARN, "XFS: Unable to allocate reserve blocks. "
-                                "Continuing without a reserve pool.");
+        if (!(mp->m_flags & XFS_MOUNT_RDONLY)) {
+                resblks = xfs_default_resblks(mp);
+                error = xfs_reserve_blocks(mp, &resblks, NULL);
+                if (error)
+                        cmn_err(CE_WARN, "XFS: Unable to allocate reserve "
+                                "blocks. Continuing without a reserve pool.");
+        }
 
         return 0;