fs: hfs: initialize fsdata in hfs_file_truncate()

When aops->write_begin() does not initialize fsdata, KMSAN may report an
error passing the latter to aops->write_end().

Fix this by unconditionally initializing fsdata.

Link: https://lkml.kernel.org/r/20221121112134.407362-4-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Suggested-by: Eric Biggers <ebiggers@kernel.org>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Chao Yu <chao@kernel.org>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: ramosian-glider

fs/hfs/extent.c

@@ -486,7 +486,7 @@ void hfs_file_truncate(struct inode *inode)
 		inode->i_size);
 	if (inode->i_size > HFS_I(inode)->phys_size) {
 		struct address_space *mapping = inode->i_mapping;
-		void *fsdata;
+		void *fsdata = NULL;
 		struct page *page;
 
 		/* XXX: Can use generic_cont_expand? */