mm: Fix comments mentioning i_mutex

inode->i_mutex has been replaced with inode->i_rwsem long ago. Fix
comments still mentioning i_mutex.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/mm/truncate.c b/mm/truncate.c
index 234ddd8..0f9bece 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -412,7 +412,7 @@ EXPORT_SYMBOL(truncate_inode_pages_range);
  * @mapping: mapping to truncate
  * @lstart: offset from which to truncate
  *
- * Called under (and serialised by) inode->i_mutex.
+ * Called under (and serialised by) inode->i_rwsem.
  *
  * Note: When this function returns, there can be a page in the process of
  * deletion (inside __delete_from_page_cache()) in the specified range.  Thus
@@ -429,7 +429,7 @@ EXPORT_SYMBOL(truncate_inode_pages);
  * truncate_inode_pages_final - truncate *all* pages before inode dies
  * @mapping: mapping to truncate
  *
- * Called under (and serialized by) inode->i_mutex.
+ * Called under (and serialized by) inode->i_rwsem.
  *
  * Filesystems have to use this in the .evict_inode path to inform the
  * VM that this is the final truncate and the inode is going away.
@@ -748,7 +748,7 @@ EXPORT_SYMBOL(truncate_pagecache);
  * setattr function when ATTR_SIZE is passed in.
  *
  * Must be called with a lock serializing truncates and writes (generally
- * i_mutex but e.g. xfs uses a different lock) and before all filesystem
+ * i_rwsem but e.g. xfs uses a different lock) and before all filesystem
  * specific block truncation has been performed.
  */
 void truncate_setsize(struct inode *inode, loff_t newsize)
@@ -777,7 +777,7 @@ EXPORT_SYMBOL(truncate_setsize);
  *
  * The function must be called after i_size is updated so that page fault
  * coming after we unlock the page will already see the new i_size.
- * The function must be called while we still hold i_mutex - this not only
+ * The function must be called while we still hold i_rwsem - this not only
  * makes sure i_size is stable but also that userspace cannot observe new
  * i_size value before we are prepared to store mmap writes at new inode size.
  */