On Thu 27-09-12 16:54:13, Dmitry Monakhov wrote: > On Thu, 27 Sep 2012 14:34:20 +0200, Jan Kara <jack@xxxxxxx> wrote: > > On Thu 27-09-12 16:19:01, Dmitry Monakhov wrote: > > > On Wed, 26 Sep 2012 15:07:14 +0200, Jan Kara <jack@xxxxxxx> wrote: > > > > On Mon 24-09-12 15:44:13, Dmitry Monakhov wrote: > > > > > ext4_set_io_unwritten_flag() will increment i_unwritten counter, so > > > > > once we mark end_io with END_IO_UNWRITTEN we have to revert it back > > > > ^^ EXT4_IO_END_UNWRITTEN > > > > > on error path. > > > > > > > > > > - add missed error checks to prevent counter leakage > > > > > - ext4_end_io_nolock() will clear END_IO_UNWRITTEN flag to signal > > > > ^^ EXT4_IO_END_UNWRITTEN > > > > > that conversion finished. > > > > > - add BUGON to free_end_io() to prevent similar leackage in future. > > > > ^^ BUG_ON ^^ext4_free_io_end() ^^ leakage > > > > > > > > > Visiable effect of this bug is that unaligned aio_stress may deadlock > > > > ^^ Visible > > > > > > > > Umm, and won't it be more foolproof it we just decrement i_unwritten in > > > > ext4_free_io_end() when we see EXT4_IO_END_UNWRITTEN set? > > > I'd like to consider BUG_ON inside ext4_free_io_end as a sanity check to > > > force all callers to perform all necessary error checks in known context. > > I'm not sure how "performing all necessary error checks in known context" > > relates to ext4_free_io_end() cleaning up the structure on its own or > > whether someone has to do it beforehand... Can you maybe elaborate a bit > > more? > I assume that if end_io was tagged with UNWRITTEN flag it should goes trough > complete_io_list and end_io_nolock(), or caller should cancel it by > itself in case of error, otherwise we may miss valid unwritten end_io > but was not scheduled to complete_end_io routine by occasion (and endup > in silent data loss). In my opinion at the time then ext4_free_io_end() > was called all possible conversions should be completed. Fair enough. I just hated verifying all the paths in extent.c and checking whether they could happen to have end_io with UNWRITTEN flag set. Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
