Hello. On 2024/7/9 20:46, Rohit Singh wrote: > Hello. > I am looking around ext4 code and I observed the following issue. > > Within ext4_insert_range(), EXT4_I(inode)->i_disksize is being updated > without acquiring i_data_sem. > > I have seen code where this operation is done after acquiring > i_data_sem such as in > ext4_update_i_disksize() > > So, is this as expected or is it problematic? > Thanks for pointing this out, At the moment, IIUC,I don't think it will cause any real problem since inode->i_rwsem could protect i_disksize updating from most of race conditions except the write back. ext4_do_writepages()->mpage_map_and_submit_extent() doesn't hold inode->i_rwsem when updating i_disksize, but we have flushed dirty blocks through filemap_write_and_wait_range() in ext4_insert_range() and can prevent from generating new dirty pages beyond current i_disksize, so this race is also closed. However, I suppose we'd still better to move the updating under i_data_sem to prevent some potential race conditions in the future. Thanks, Yi.
