fs: fixes from testing

1. Don't allow rmdir .
2. Don't allow rmdir of a directory with a file in it (we stopped only subdirs)
3. Don't consider unreferenced inodes when checking if a remount is valid
4. Fix the case of

	process A
		cd /tmp/foo
	process B
		rmdir /tmp/foo
	process A
		ls .   (stale entry)

diff --git a/Kernel/syscall_other.c b/Kernel/syscall_other.c
index f951714..7079c7b 100644 (file)
--- a/Kernel/syscall_other.c
+++ b/Kernel/syscall_other.c
@@ -89,10 +89,13 @@ arg_t _rename(void)
                        udata.u_error = EISDIR;
                        goto nogood;
                }
-               if (unlinki(dsti, dstp, lastname) == -1)
+               i_lock(dstp);
+               if (unlinki(dsti, dstp, lastname) == -1) {
+                       i_unlock(dstp);
                        goto nogood;
+               }
                /* Drop the reference to the unlinked file */
-               i_deref(dsti);
+               i_unlock_deref(dstp);
        }
        i_lock(dstp);
        /* Ok we may proceed: we set up fname earlier */
@@ -164,6 +167,7 @@ arg_t _mkdir(void)
                goto nogood2;
        }
 
+
        i_ref(parent);          /* We need it again in a minute */
        if (!(ino = newfile(parent, lastname))) {
 //             i_deref(parent);
@@ -173,6 +177,7 @@ arg_t _mkdir(void)
        /* Initialize mode and dev */
        ino->c_node.i_mode = F_DIR | 0200;      /* so ch_link is allowed */
        setftime(ino, A_TIME | M_TIME | C_TIME);
+       /* Ensure the directory is fully formed before anyone can see it */
        if (ch_link(ino, "", ".", ino) == 0 ||
            ch_link(ino, "", "..", parent) == 0)
                goto cleanup;
@@ -187,13 +192,17 @@ arg_t _mkdir(void)
        return (0);
 
 cleanup:
-       i_lock(parent);
-       if (!ch_link(parent, fname, "", NULLINODE))
-               kprintf("_mkdir: bad rec\n");
-       i_unlock(parent);
+       /* We need to unlock inode before we are allowed to lock the parent */
        /* i_deref will put the blocks */
        ino->c_node.i_nlink = 0;
        wr_inode(ino);
+       i_unlock_deref(ino);
+       /* In the error case it may be observed but it's consistently empty */
+       i_lock(parent);
+       if (!ch_link(parent, fname, "", NULLINODE))
+               kprintf("_mkdir: bad rec\n");
+       i_unlock_deref(parent);
+       return -1;
       nogood:
        i_unlock_deref(ino);
       nogood2:
@@ -220,18 +229,30 @@ arg_t _rmdir(void)
        inoptr ino;
        inoptr parent;
 
+       /* Q: rmdir . */
        ino = n_open(path, &parent);
 
        /* It and its parent must exist */
        if (!(parent && ino)) {
-               if (parent)     /* parent exist */
-                       i_deref(parent);
                udata.u_error = ENOENT;
-               return (-1);
+               goto nogood_early;
+       }
+
+       if (*lastname == '.' && !lastname[1]) {
+               udata.u_error = EINVAL;
+               i_deref(ino);
+               goto nogood_early;
        }
 
        i_lock(parent);
-       /* Fixme: check for rmdir of /. - ditto for unlink ? */
+       /* So nobody gets to access it while it's being dismantled */
+       i_lock(ino);
+
+       /* Make sure we don't remove a mount point */
+       if (ino->c_num == ROOTINODE) {
+               udata.u_error = EBUSY;
+               goto nogood;
+       }
 
        /* Not a directory */
        if (getmode(ino) != MODE_R(F_DIR)) {
@@ -240,7 +261,7 @@ arg_t _rmdir(void)
        }
 
        /* Busy */
-       if (ino->c_node.i_nlink != 2) {
+       if (ino->c_node.i_nlink != 2 || !emptydir(ino)) {
                udata.u_error = ENOTEMPTY;
                goto nogood;
        }
@@ -262,15 +283,24 @@ arg_t _rmdir(void)
                kputs("_rmdir: bad nlink\n");
        }
        setftime(ino, C_TIME);
+       /* We have a lock on the inode so we know nobody else is walking the
+          directory at the moment. We have to truncate it now rather than
+          only final de-reference as a user might have a cwd set here and
+          would have access to the invalid . and .. */
+       f_trunc(ino);
        wr_inode(parent);
        wr_inode(ino);
        i_unlock_deref(parent);
-       i_deref(ino);
+       i_unlock_deref(ino);
        return (0);
 
       nogood:
-       i_deref(parent);
-       i_deref(ino);
+       i_unlock_deref(parent);
+       i_unlock_deref(ino);
+       return (-1);
+      nogood_early:
+       if (parent)     /* parent exist */
+               i_deref(parent);
        return (-1);
 #else
        udata.u_error = -ENOSYS;
@@ -377,7 +407,7 @@ static int do_umount(uint16_t dev)
           can't remount it read only */
        if ((flags & (MS_RDONLY|MS_REMOUNT)) == (MS_RDONLY|MS_REMOUNT)) {
                for (ptr = i_tab ; ptr < i_tab + ITABSIZE; ++ptr) {
-                       if (ptr->c_dev == dev && !isdevice(ptr)) {
+                       if (ptr->c_refs && ptr->c_dev == dev && !isdevice(ptr)) {
                        /* Files being written block the remount ro, but so
                           do files that when closed will be deleted */
                                if (ptr->c_writers ||