On Fri, Oct 04, 2019 at 12:05:51AM +0200, Jan Kara wrote: > Similarly to directories, EA inodes do only journalled modifications to > their data. Change ext4_should_journal_data() to return true for them so > that we don't have to special-case them during truncate. We are already special-casing EA inodes in ext4_clear_blocks() in fs/ext4/indirect.c, and get_default_free_blocks_flags() in fs/ext4/extents.c, and like S_ISDIR, we want to treat EA inode blocks as metadata. So I'm not sure I see the value of this change? As an aside, I was looking at fs/ext4/mballoc.c to see what the difference is for treating a block as a metadata block versus a journaled data block, and what I found made my hair rise on end: /* * We need to make sure we don't reuse the freed block until after the * transaction is committed. We make an exception if the inode is to be * written in writeback mode since writeback mode has weak data * consistency guarantees. */ So in data=writeback, if a file is deleted, its blocks are available for immediate reallocation, and if we are under heavy memory pressure, the deleted file's blocks could get overwritten --- even in the case where we crash and the transaction never committed. While it's true that date=writeback mode has weaker guarantees, my understanding is that it only applied to the exposure stale data, and not to a long-standing file's blocks getting corrupted if it is almost deleted, but not quite before a crash. Granted, the situation where this would happen is quite wrare, but it seems quite wrong.... - Ted
