On Tue 06-06-23 14:14:46, Zhang Yi wrote: > From: Zhang Yi <yi.zhang@xxxxxxxxxx> > > Before removing checkpoint buffer from the t_checkpoint_list, we have to > check both BH_Dirty and BH_Lock bits together to distinguish buffers > have not been or were being written back. But __cp_buffer_busy() checks > them separately, it first check lock state and then check dirty, the > window between these two checks could be raced by writing back > procedure, which locks buffer and clears buffer dirty before I/O > completes. So it cannot guarantee checkpointing buffers been written > back to disk if some error happens later. Finally, it may clean > checkpoint transactions and lead to inconsistent filesystem. > > jbd2_journal_forget() and __journal_try_to_free_buffer() also have the > same problem (journal_unmap_buffer() escape from this issue since it's > running under the buffer lock), so fix them through introducing a new > helper to try holding the buffer lock and remove really clean buffer. > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=217490 > Cc: stable@xxxxxxxxxxxxxxx > Suggested-by: Jan Kara <jack@xxxxxxx> > Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx> Looks good. Feel free to add: Reviewed-by: Jan Kara <jack@xxxxxxx> Just a type correction below: > @@ -615,6 +619,34 @@ int __jbd2_journal_remove_checkpoint(struct journal_head *jh) > return 1; > } > > +/* > + * Check the checkpoint buffer and try to remove it from the checkpoint > + * list if it's clean. Returns -EBUSY if it is not clean, returns 1 if > + * it frees the transaction, 0 otherwise. > + * > + * This function is called with j_list_lock held. > + */ > +int jbd2_journal_try_remove_checkpoint(struct journal_head *jh) > +{ > + struct buffer_head *bh = jh2bh(jh); > + > + if (!trylock_buffer(bh)) > + return -EBUSY; > + if (buffer_dirty(bh)) { > + unlock_buffer(bh); > + return -EBUSY; > + } > + unlock_buffer(bh); > + > + /* > + * Buffer is clean and the IO has finished (we hold the buffer ^^^ held > + * lock) so the checkpoint is done. We can safely remove the > + * buffer from this transaction. > + */ > + JBUFFER_TRACE(jh, "remove from checkpoint list"); > + return __jbd2_journal_remove_checkpoint(jh); > +} Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
