Re: tunefs -p doesn't work for read-write mounts

[Luoqi Chen]

> Hi folks,
> 
> Shouldn't I be able to show the current tuneables for a given filesystem?
> 
> # tunefs -p /usr
> tunefs: cannot work on read-write mounted file system
> 
> This is on a recent CURRENT.
> 
> Ciao,
> Sheldon.
> 
You were supposed to use a raw device for a mounted fs, but that no longer
works after the elimination of block device. I have a quick fix for this
problem: open the device read-only to read the superblock and later re-open
it read-write before writing back.

-lq

Index: tunefs.c
===================================================================
RCS file: /home/ncvs/src/sbin/tunefs/tunefs.c,v
retrieving revision 1.11
diff -u -r1.11 tunefs.c
--- tunefs.c    2000/01/30 05:24:55     1.11
+++ tunefs.c    2000/03/03 16:04:04
@@ -75,9 +75,10 @@
 int fi;
 long dev_bsize = 1;
 
-void bwrite(daddr_t, char *, int);
-int bread(daddr_t, char *, int);
-void getsb(struct fs *, char *);
+void bwrite __P((daddr_t, char *, int));
+int bread __P((daddr_t, char *, int));
+void getsb __P((struct fs *, char *));
+void putsb __P((struct fs *, char *, int));
 void usage __P((void));
 void printfs __P((void));
 
@@ -103,9 +104,6 @@
        if (fs) {
                if (statfs(special, &stfs) == 0 &&
                    strcmp(special, stfs.f_mntonname) == 0) {
-                       if ((stfs.f_flags & MNT_RDONLY) == 0) {
-                               errx(1, "cannot work on read-write mounted file 
system");
-                       }
                        active = 1;
                }
                special = fs->fs_spec;
@@ -251,12 +249,7 @@
        }
        if (argc != 1)
                usage();
-       bwrite((daddr_t)SBOFF / dev_bsize, (char *)&sblock, SBSIZE);
-       if (Aflag)
-               for (i = 0; i < sblock.fs_ncg; i++)
-                       bwrite(fsbtodb(&sblock, cgsblock(&sblock, i)),
-                           (char *)&sblock, SBSIZE);
-       close(fi);
+       putsb(&sblock, special, Aflag);
        if (active) {
                bzero(&args, sizeof(args));
                if (mount("ufs", fs->fs_file,
@@ -283,7 +276,7 @@
        char *file;
 {
 
-       fi = open(file, 2);
+       fi = open(file, 0);
        if (fi < 0)
                err(3, "cannot open %s", file);
        if (bread((daddr_t)SBOFF, (char *)fs, SBSIZE))
@@ -291,6 +284,30 @@
        if (fs->fs_magic != FS_MAGIC)
                err(5, "%s: bad magic number", file);
        dev_bsize = fs->fs_fsize / fsbtodb(fs, 1);
+}
+
+void
+putsb(fs, file, all)
+       register struct fs *fs;
+       char *file;
+       int all;
+{
+       int i;
+
+       /*
+        * Re-open the device read-write. Use the read-only file
+        * descriptor as an interlock to prevent the device from
+        * being mounted while we are switching mode.
+        */
+       i = fi; fi = open(file, 2); close(i);
+       if (fi < 0)
+               err(3, "cannot open %s", file);
+       bwrite((daddr_t)SBOFF / dev_bsize, (char *)fs, SBSIZE);
+       if (all)
+               for (i = 0; i < fs->fs_ncg; i++)
+                       bwrite(fsbtodb(fs, cgsblock(fs, i)),
+                           (char *)fs, SBSIZE);
+       close(fi);
 }
 
 void


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