On Tue, Sep 05, 2017 at 04:54:42PM +0200, Christoph Hellwig wrote: > On Tue, Sep 05, 2017 at 10:40:07AM -0400, Brian Foster wrote: > > Thanks.. I agree that a rework of the optimization can come later now > > that the bug is fixed. > > I agree in principle, but I don't think the patch in for-next is enough, > given that it doesn't take ic_refcnt into account. > Hmm.. Ok, I might be missing something here. In xfs_log_force() at least it looks like we only set log_flushed if the refcnt has reached zero. In xfs_log_force_lsn(), the iclog has to be ACTIVE. We switch it to WANT_SYNC, bump the refcnt and call release_iclog(). The latter may or may not do anything depending on the refcount. We set log_flushed immediately after the release before we know whether an xlog_sync() has actually occurred (is that your concern?). If XFS_LOG_SYNC is set, we wait on the iclog before _force_lsn() returns, which means the log buffer I/O has to have completed before we return either way. If the iclog is still WANT_SYNC, the release didn't do anything, but we wait on ic_force_wait which is triggered during I/O completion handling. If the iclog is already DIRTY/ACTIVE, then the I/O has already submitted and completed. fsync looks like the only the user of log_flushed and it also uses XFS_LOG_SYNC. ISTM that the code is probably still bogus in principle, but in practice the fsync code may be safe. Thoughts? Am I missing something else? > > Christoph, are you planning to continue with your flushseq based patch? > > I think it is fundamentally the right thing to do, but given how > much I've got on my plate I wouldn't mind someone else looking into it :) Ok, I may be able to take a crack at it... Brian > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
