Man page 9 : truncate_setsize

truncate_setsize - update inode and pagecache for a new file size

void truncate_setsize(struct inode *  inode , loff_t  newsize );

inode
    inode

newsize
    new file size

truncate_setsize updates i_size and performs pagecache truncation (if necessary) to newsize. It will be typically be called from the filesystemAqs setattr function when ATTR_SIZE is passed in.

Must be called with inode_mutex held and before all filesystem specific block truncation has been performed.