On Tue, Sep 17, 2019 at 02:30:15PM +0530, Ritesh Harjani wrote: > So if we have a delayed buffered write to a file, > in that case we first only update inode->i_size and update > i_disksize at writeback time > (i.e. during block allocation). > In that case when we call for ext4_dio_write_iter > since offset + len > i_disksize, we call for ext4_update_i_disksize(). > > Now if writeback for some reason failed. And the system crashes, during the > DIO writes, after the blocks are allocated. Then during reboot we may have > an inconsistent inode, since we did not add the inode into the > orphan list before we updated the inode->i_disksize. And journal replay > may not succeed. > > 1. Can above actually happen? I am still not able to figure out the > race/inconsistency completely. > 2. Can you please help explain under what other cases > it was necessary to call ext4_update_i_disksize() in DIO write paths? > 3. When will i_disksize be out-of-sync with i_size during DIO writes? None of the above seems new in this patchset, does it? That being said I found the early size update odd. XFS updates the on-disk size only at I/O completion time to deal with various races including the potential exposure of stale data.
