f2fs: Convert to using invalidate_lock

Use invalidate_lock instead of f2fs' private i_mmap_sem. The intended
purpose is exactly the same. By this conversion we fix a long standing
race between hole punching and read(2) / readahead(2) paths that can
lead to stale page cache contents.

CC: Jaegeuk Kim <jaegeuk@kernel.org>
CC: Chao Yu <yuchao0@huawei.com>
CC: linux-f2fs-devel@lists.sourceforge.net
Acked-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index d2cf48c..eb222b3 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -3187,12 +3187,12 @@ static void f2fs_write_failed(struct address_space *mapping, loff_t to)
 	/* In the fs-verity case, f2fs_end_enable_verity() does the truncate */
 	if (to > i_size && !f2fs_verity_in_progress(inode)) {
 		down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
-		down_write(&F2FS_I(inode)->i_mmap_sem);
+		filemap_invalidate_lock(mapping);
 
 		truncate_pagecache(inode, i_size);
 		f2fs_truncate_blocks(inode, i_size, true);
 
-		up_write(&F2FS_I(inode)->i_mmap_sem);
+		filemap_invalidate_unlock(mapping);
 		up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
 	}
 }
@@ -3852,7 +3852,7 @@ static int f2fs_migrate_blocks(struct inode *inode, block_t start_blk,
 	int ret = 0;
 
 	down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
-	down_write(&F2FS_I(inode)->i_mmap_sem);
+	filemap_invalidate_lock(inode->i_mapping);
 
 	set_inode_flag(inode, FI_ALIGNED_WRITE);
 
@@ -3894,7 +3894,7 @@ static int f2fs_migrate_blocks(struct inode *inode, block_t start_blk,
 	clear_inode_flag(inode, FI_DO_DEFRAG);
 	clear_inode_flag(inode, FI_ALIGNED_WRITE);
 
-	up_write(&F2FS_I(inode)->i_mmap_sem);
+	filemap_invalidate_unlock(inode->i_mapping);
 	up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
 
 	return ret;