aufs: ioctl, ibusy

Because of some inode is in use, the deletion of a branch can fail.
For those who wants to test the inode is busy or not, aufs provides an
ioctl, and a utility 'aubusy' in aufs-util.git.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

fs/aufs/branch.c

@@ -7,6 +7,7 @@
  * branch management
  */
 
+#include <linux/compat.h>
 #include <linux/statfs.h>
 #include "aufs.h"
 
@@ -1088,6 +1089,78 @@ out:
 
 /* ---------------------------------------------------------------------- */
 
+static int au_ibusy(struct super_block *sb, struct aufs_ibusy __user *arg)
+{
+	int err;
+	aufs_bindex_t btop, bbot;
+	struct aufs_ibusy ibusy;
+	struct inode *inode, *h_inode;
+
+	err = -EPERM;
+	if (unlikely(!capable(CAP_SYS_ADMIN)))
+		goto out;
+
+	err = copy_from_user(&ibusy, arg, sizeof(ibusy));
+	if (!err)
+		/* VERIFY_WRITE */
+		err = !access_ok(&arg->h_ino, sizeof(arg->h_ino));
+	if (unlikely(err)) {
+		err = -EFAULT;
+		AuTraceErr(err);
+		goto out;
+	}
+
+	err = -EINVAL;
+	si_read_lock(sb, AuLock_FLUSH);
+	if (unlikely(ibusy.bindex < 0 || ibusy.bindex > au_sbbot(sb)))
+		goto out_unlock;
+
+	err = 0;
+	ibusy.h_ino = 0; /* invalid */
+	inode = ilookup(sb, ibusy.ino);
+	if (!inode
+	    || inode->i_ino == AUFS_ROOT_INO
+	    || au_is_bad_inode(inode))
+		goto out_unlock;
+
+	ii_read_lock_child(inode);
+	btop = au_ibtop(inode);
+	bbot = au_ibbot(inode);
+	if (btop <= ibusy.bindex && ibusy.bindex <= bbot) {
+		h_inode = au_h_iptr(inode, ibusy.bindex);
+		if (h_inode && au_test_ibusy(inode, btop, bbot))
+			ibusy.h_ino = h_inode->i_ino;
+	}
+	ii_read_unlock(inode);
+	iput(inode);
+
+out_unlock:
+	si_read_unlock(sb);
+	if (!err) {
+		err = __put_user(ibusy.h_ino, &arg->h_ino);
+		if (unlikely(err)) {
+			err = -EFAULT;
+			AuTraceErr(err);
+		}
+	}
+out:
+	return err;
+}
+
+long au_ibusy_ioctl(struct file *file, unsigned long arg)
+{
+	return au_ibusy(file->f_path.dentry->d_sb, (void __user *)arg);
+}
+
+#ifdef CONFIG_COMPAT
+long au_ibusy_compat_ioctl(struct file *file, unsigned long arg)
+{
+	return au_ibusy(file->f_path.dentry->d_sb, compat_ptr(arg));
+}
+#endif
+
+/* ---------------------------------------------------------------------- */
+
 /*
  * change a branch permission
  */

fs/aufs/branch.h

@@ -187,6 +187,10 @@ struct au_opt_add;
 int au_br_add(struct super_block *sb, struct au_opt_add *add, int remount);
 struct au_opt_del;
 int au_br_del(struct super_block *sb, struct au_opt_del *del, int remount);
+long au_ibusy_ioctl(struct file *file, unsigned long arg);
+#ifdef CONFIG_COMPAT
+long au_ibusy_compat_ioctl(struct file *file, unsigned long arg);
+#endif
 struct au_opt_mod;
 int au_br_mod(struct super_block *sb, struct au_opt_mod *mod, int remount,
 	      int *do_refresh);

fs/aufs/ioctl.c

@@ -120,6 +120,10 @@ long aufs_ioctl_dir(struct file *file, unsigned int cmd, unsigned long arg)
 		err = au_wbr_fd(&file->f_path, (void __user *)arg);
 		break;
 
+	case AUFS_CTL_IBUSY:
+		err = au_ibusy_ioctl(file, arg);
+		break;
+
 	case AUFS_CTL_BRINFO:
 		err = au_brinfo_ioctl(file, arg);
 		break;
@@ -165,6 +169,10 @@ long aufs_compat_ioctl_dir(struct file *file, unsigned int cmd,
 		err = au_rdu_compat_ioctl(file, cmd, arg);
 		break;
 
+	case AUFS_CTL_IBUSY:
+		err = au_ibusy_compat_ioctl(file, arg);
+		break;
+
 	case AUFS_CTL_BRINFO:
 		err = au_brinfo_compat_ioctl(file, arg);
 		break;

include/uapi/linux/aufs_type.h

@@ -198,6 +198,7 @@ enum {
 	AuCtl_RDU_INO,
 
 	AuCtl_WBR_FD,	/* pathconf wrapper */
+	AuCtl_IBUSY,	/* busy inode */
 	AuCtl_BR	/* info about branches */
 };
 
@@ -304,6 +305,13 @@ struct aufs_wbr_fd {
 
 /* ---------------------------------------------------------------------- */
 
+struct aufs_ibusy {
+	uint64_t	ino, h_ino;
+	int16_t		bindex;
+} __aligned(8);
+
+/* ---------------------------------------------------------------------- */
+
 union aufs_brinfo {
 	/* PATH_MAX may differ between kernel-space and user-space */
 	char	_spacer[4096];
@@ -321,6 +329,7 @@ union aufs_brinfo {
 #define AUFS_CTL_RDU_INO	_IOWR(AuCtlType, AuCtl_RDU_INO, struct aufs_rdu)
 #define AUFS_CTL_WBR_FD		_IOW(AuCtlType, AuCtl_WBR_FD, \
 				     struct aufs_wbr_fd)
+#define AUFS_CTL_IBUSY		_IOWR(AuCtlType, AuCtl_IBUSY, struct aufs_ibusy)
 #define AUFS_CTL_BRINFO		_IOW(AuCtlType, AuCtl_BR, union aufs_brinfo)
 
 #endif /* __AUFS_TYPE_H__ */