X-Git-Url: https://git.karo-electronics.de/?a=blobdiff_plain;f=fs%2Fnamespace.c;h=e6081996c9a2f9d26525740545445630c4737583;hb=bcf8a3dfcb274cf6654a19e12e244f3af8c0d355;hp=db65e2e4921f22833eedb38934c1ee4f07e09c7a;hpb=34c80b1d93e6e20ca9dea0baf583a5b5510d92d4;p=karo-tx-linux.git

diff --git a/fs/namespace.c b/fs/namespace.c
index db65e2e4921f..e6081996c9a2 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -273,6 +273,15 @@ static unsigned int mnt_get_writers(struct mount *mnt)
 #endif
 }
 
+static int mnt_is_readonly(struct vfsmount *mnt)
+{
+	if (mnt->mnt_sb->s_readonly_remount)
+		return 1;
+	/* Order wrt setting s_flags/s_readonly_remount in do_remount() */
+	smp_rmb();
+	return __mnt_is_readonly(mnt);
+}
+
 /*
  * Most r/o checks on a fs are for operations that take
  * discrete amounts of time, like a write() or unlink().
@@ -312,12 +321,10 @@ int mnt_want_write(struct vfsmount *m)
 	 * MNT_WRITE_HOLD is cleared.
 	 */
 	smp_rmb();
-	if (__mnt_is_readonly(m)) {
+	if (mnt_is_readonly(m)) {
 		mnt_dec_writers(mnt);
 		ret = -EROFS;
-		goto out;
 	}
-out:
 	preempt_enable();
 	return ret;
 }
@@ -435,6 +442,42 @@ static void __mnt_unmake_readonly(struct mount *mnt)
 	br_write_unlock(vfsmount_lock);
 }
 
+int sb_prepare_remount_readonly(struct super_block *sb)
+{
+	struct mount *mnt;
+	int err = 0;
+
+	/* Racy optimization.  Recheck the counter under MNT_WRITE_HOLD */
+	if (atomic_long_read(&sb->s_remove_count))
+		return -EBUSY;
+
+	br_write_lock(vfsmount_lock);
+	list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
+		if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
+			mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
+			smp_mb();
+			if (mnt_get_writers(mnt) > 0) {
+				err = -EBUSY;
+				break;
+			}
+		}
+	}
+	if (!err && atomic_long_read(&sb->s_remove_count))
+		err = -EBUSY;
+
+	if (!err) {
+		sb->s_readonly_remount = 1;
+		smp_wmb();
+	}
+	list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
+		if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
+			mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
+	}
+	br_write_unlock(vfsmount_lock);
+
+	return err;
+}
+
 static void free_vfsmnt(struct mount *mnt)
 {
 	kfree(mnt->mnt_devname);
@@ -671,6 +714,9 @@ vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void
 	mnt->mnt.mnt_sb = root->d_sb;
 	mnt->mnt_mountpoint = mnt->mnt.mnt_root;
 	mnt->mnt_parent = mnt;
+	br_write_lock(vfsmount_lock);
+	list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts);
+	br_write_unlock(vfsmount_lock);
 	return &mnt->mnt;
 }
 EXPORT_SYMBOL_GPL(vfs_kern_mount);
@@ -699,6 +745,9 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
 		mnt->mnt.mnt_root = dget(root);
 		mnt->mnt_mountpoint = mnt->mnt.mnt_root;
 		mnt->mnt_parent = mnt;
+		br_write_lock(vfsmount_lock);
+		list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
+		br_write_unlock(vfsmount_lock);
 
 		if (flag & CL_SLAVE) {
 			list_add(&mnt->mnt_slave, &old->mnt_slave_list);
@@ -781,6 +830,7 @@ put_again:
 		acct_auto_close_mnt(&mnt->mnt);
 		goto put_again;
 	}
+	list_del(&mnt->mnt_instance);
 	br_write_unlock(vfsmount_lock);
 	mntfree(mnt);
 }