vfs: pull ext4's double-i_mutex-locking into common code

We want to do this elsewhere as well.

Also catch any attempts to use it for directories (where this ordering
would conflict with ancestor-first directory ordering in lock_rename).

Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Dave Chinner <david@fromorbit.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Acked-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

5 files changed, 43 insertions, 42 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index af815ea9d7cc..d01d62315f7e 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2734,8 +2734,6 @@ extern void ext4_double_down_write_data_sem(struct inode *first,
                                             struct inode *second);
 extern void ext4_double_up_write_data_sem(struct inode *orig_inode,
                                           struct inode *donor_inode);
-void ext4_inode_double_lock(struct inode *inode1, struct inode *inode2);
-void ext4_inode_double_unlock(struct inode *inode1, struct inode *inode2);
 extern int ext4_move_extents(struct file *o_filp, struct file *d_filp,
                              __u64 start_orig, __u64 start_donor,
                              __u64 len, __u64 *moved_len);
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index a569d335f804..60589b60e9b0 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -130,7 +130,7 @@ static long swap_inode_boot_loader(struct super_block *sb,
 
         /* Protect orig inodes against a truncate and make sure,
          * that only 1 swap_inode_boot_loader is running. */
-        ext4_inode_double_lock(inode, inode_bl);
+        lock_two_nondirectories(inode, inode_bl);
 
         truncate_inode_pages(&inode->i_data, 0);
         truncate_inode_pages(&inode_bl->i_data, 0);
@@ -205,7 +205,7 @@ static long swap_inode_boot_loader(struct super_block *sb,
         ext4_inode_resume_unlocked_dio(inode);
         ext4_inode_resume_unlocked_dio(inode_bl);
 
-        ext4_inode_double_unlock(inode, inode_bl);
+        unlock_two_nondirectories(inode, inode_bl);
 
         iput(inode_bl);
 
diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index 7fa4d855dbd5..773b503bd18c 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -1203,42 +1203,6 @@ mext_check_arguments(struct inode *orig_inode,
 }
 
 /**
- * ext4_inode_double_lock - Lock i_mutex on both @inode1 and @inode2
- *
- * @inode1:     the inode structure
- * @inode2:     the inode structure
- *
- * Lock two inodes' i_mutex
- */
-void
-ext4_inode_double_lock(struct inode *inode1, struct inode *inode2)
-{
-        BUG_ON(inode1 == inode2);
-        if (inode1 < inode2) {
-                mutex_lock_nested(&inode1->i_mutex, I_MUTEX_PARENT);
-                mutex_lock_nested(&inode2->i_mutex, I_MUTEX_CHILD);
-        } else {
-                mutex_lock_nested(&inode2->i_mutex, I_MUTEX_PARENT);
-                mutex_lock_nested(&inode1->i_mutex, I_MUTEX_CHILD);
-        }
-}
-
-/**
- * ext4_inode_double_unlock - Release i_mutex on both @inode1 and @inode2
- *
- * @inode1:     the inode that is released first
- * @inode2:     the inode that is released second
- *
- */
-
-void
-ext4_inode_double_unlock(struct inode *inode1, struct inode *inode2)
-{
-        mutex_unlock(&inode1->i_mutex);
-        mutex_unlock(&inode2->i_mutex);
-}
-
-/**
  * ext4_move_extents - Exchange the specified range of a file
  *
  * @o_filp:             file structure of the original file
@@ -1327,7 +1291,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
                 return -EINVAL;
         }
         /* Protect orig and donor inodes against a truncate */
-        ext4_inode_double_lock(orig_inode, donor_inode);
+        lock_two_nondirectories(orig_inode, donor_inode);
 
         /* Wait for all existing dio workers */
         ext4_inode_block_unlocked_dio(orig_inode);
@@ -1535,7 +1499,7 @@ out:
         ext4_double_up_write_data_sem(orig_inode, donor_inode);
         ext4_inode_resume_unlocked_dio(orig_inode);
         ext4_inode_resume_unlocked_dio(donor_inode);
-        ext4_inode_double_unlock(orig_inode, donor_inode);
+        unlock_two_nondirectories(orig_inode, donor_inode);
 
         return ret;
 }
diff --git a/fs/inode.c b/fs/inode.c
index bf7a8b3ab937..ef25afdf3906 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -943,6 +943,42 @@ void unlock_new_inode(struct inode *inode)
 EXPORT_SYMBOL(unlock_new_inode);
 
 /**
+ * lock_two_nondirectories - take two i_mutexes on non-directory objects
+ * @inode1: first inode to lock
+ * @inode2: second inode to lock
+ */
+void lock_two_nondirectories(struct inode *inode1, struct inode *inode2)
+{
+        WARN_ON_ONCE(S_ISDIR(inode1->i_mode));
+        if (inode1 == inode2 || !inode2) {
+                mutex_lock_nested(&inode1->i_mutex, I_MUTEX_PARENT);
+                return;
+        }
+        WARN_ON_ONCE(S_ISDIR(inode2->i_mode));
+        if (inode1 < inode2) {
+                mutex_lock_nested(&inode1->i_mutex, I_MUTEX_PARENT);
+                mutex_lock_nested(&inode2->i_mutex, I_MUTEX_CHILD);
+        } else {
+                mutex_lock_nested(&inode2->i_mutex, I_MUTEX_PARENT);
+                mutex_lock_nested(&inode1->i_mutex, I_MUTEX_CHILD);
+        }
+}
+EXPORT_SYMBOL(lock_two_nondirectories);
+
+/**
+ * unlock_two_nondirectories - release locks from lock_two_nondirectories()
+ * @inode1: first inode to unlock
+ * @inode2: second inode to unlock
+ */
+void unlock_two_nondirectories(struct inode *inode1, struct inode *inode2)
+{
+        mutex_unlock(&inode1->i_mutex);
+        if (inode2 && inode2 != inode1)
+                mutex_unlock(&inode2->i_mutex);
+}
+EXPORT_SYMBOL(unlock_two_nondirectories);
+
+/**
  * iget5_locked - obtain an inode from a mounted file system
  * @sb:         super block of file system
  * @hashval:    hash value (usually inode number) to get
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 5e44b0893db8..4e1a0b41f966 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -637,6 +637,9 @@ enum inode_i_mutex_lock_class
         I_MUTEX_QUOTA
 };
 
+void lock_two_nondirectories(struct inode *, struct inode*);
+void unlock_two_nondirectories(struct inode *, struct inode*);
+
 /*
  * NOTE: in a 32bit arch with a preemptable kernel and
  * an UP compile the i_size_read/write must be atomic