Hello! On Sat 25-11-23 20:17:39, Zhang Yi wrote: > From: Zhang Yi <yi.zhang@xxxxxxxxxx> > > Current jbd2 only add REQ_SYNC for descriptor block, metadata log > buffer, commit buffer and superblock buffer, the submitted IO could be > throttled by writeback throttle in block layer, that could lead to > priority inversion in some cases. The log IO looks like a kind of high > priority metadata IO, so it should not be throttled by WBT like QOS > policies in block layer, let's add REQ_SYNC | REQ_IDLE to exempt from > writeback throttle, and also add REQ_META together indicates it's a > metadata IO. So I agree about REQ_META but with REQ_IDLE I'm not so sure. __REQ_IDLE is documented as "anticipate more IO after this one" so that is a good fit for normal transaction writes but not so much for journal superblock writes. OTOH as far as I'm checking XFS uses REQ_IDLE as well for its log IO and the only places where REQ_IDLE is really checked is in blk-wbt... So I guess this makes sense. > diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h > index 52772c826c86..f7e8274b46ae 100644 > --- a/include/linux/jbd2.h > +++ b/include/linux/jbd2.h > @@ -1374,6 +1374,9 @@ JBD2_FEATURE_INCOMPAT_FUNCS(csum2, CSUM_V2) > JBD2_FEATURE_INCOMPAT_FUNCS(csum3, CSUM_V3) > JBD2_FEATURE_INCOMPAT_FUNCS(fast_commit, FAST_COMMIT) > > +/* Journal high priority write IO operation flags */ > +#define JBD2_REQ_HIPRIO (REQ_META | REQ_SYNC | REQ_IDLE) Since all journal IO is submitted with these flags I'd maybe name this JBD2_JOURNAL_REQ_FLAGS? Otherwise the patch looks good to me so feel free to add: Reviewed-by: Jan Kara <jack@xxxxxxx> Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
