On Tue, Jan 02 2007, Jens Axboe wrote:
> On Tue, Jan 02 2007, Rene Herman wrote:
> > Jens Axboe wrote:
> >
> > >On Mon, Jan 01 2007, Andrew Morton wrote:
> >
> > >>The patch would appear to need this fix:
> > >>
> > >>--- a/block/cfq-iosched.c~a
> > >>+++ a/block/cfq-iosched.c
> > >>@@ -592,7 +592,7 @@ static int cfq_allow_merge(request_queue
> > >> if (cfqq == RQ_CFQQ(rq))
> > >> return 1;
> > >>
> > >>- return 1;
> > >>+ return 0;
> > >> }
> > >>
> > >> static inline void
> > >>_
> > >>
> > >>But that might not fix things...
> > >
> > >Yeah it is, but I don't think it'll fix it (if anything, it'll be more
> > >conservative).
> >
> > (to possibly save others from trying -- no, doesn't fix any)
>
> As expected. The issue is rq_is_sync(rq) takes the data direction into
> account as well, while bio_sync() only checks the sync bit. This should
> fix it.
And here a little more relaxed version, as Mark Lord suggested. We allow
merge of async bio into a sync request, but not vice versa.
Both patches pending testing, will do so now.
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 4b4217d..07b7062 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -577,9 +577,9 @@ static int cfq_allow_merge(request_queue
pid_t key;
/*
- * Disallow merge, if bio and rq aren't both sync or async
+ * Disallow merge of a sync bio into an async request.
*/
- if (!!bio_sync(bio) != !!rq_is_sync(rq))
+ if ((bio_data_dir(bio) == READ || bio_sync(bio)) && !rq_is_sync(rq))
return 0;
/*
@@ -592,7 +592,7 @@ static int cfq_allow_merge(request_queue
if (cfqq == RQ_CFQQ(rq))
return 1;
- return 1;
+ return 0;
}
static inline void
--
Jens Axboe
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
