Re: [PATCH] REQ-flags to/from BIO-flags bugfix

Boaz Harrosh
2007-12-12T16:08:24Z

On Wed, Dec 12 2007 at 17:18 +0200, Matthew Wilcox <matthew@wil.cx> wrote:
> On Wed, Dec 12, 2007 at 01:03:10PM +0200, Boaz Harrosh wrote:
>> - BIO flags bio->bi_rw and REQ flags req->cmd_flags no longer match.
>> Remove comments and do a proper translation between the 2 systems.
>
> I'd rather see them resynchronised ... in a way that makes it obvious
> that they should be desynced again:
>
> I don't know whether BIO_RW_BARRIER is __REQ_SOFTBARRIER or
> __REQ_HARDBARRIER, so I didn't include that in this patch. There also
> doesn't seem to be a __REQ equivalent to BIO_RW_AHEAD, but we can do
> the other four bits (and leave gaps for those two).
>
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index d18ee67..6aef34b 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -167,11 +167,13 @@ enum {
> };
>
> /*
> - * request type modified bits. first three bits match BIO_RW* bits, important
> + * request type modified bits. Don't change without looking at bi_rw flags
> */
> enum rq_flag_bits {
> - __REQ_RW, /* not set, read. set, write */
> - __REQ_FAILFAST, /* no low level driver retries */
> + __REQ_RW = BIO_RW, /* not set, read. set, write */
> + __REQ_FAILFAST = BIO_RW_FAILFAST, /* no low level driver retries */
> + __REQ_RW_SYNC = BIO_RW_SYNC, /* request is sync (O_DIRECT) */
> + __REQ_RW_META = BIO_RW_META, /* metadata io request */
> __REQ_SORTED, /* elevator knows about this request */
> __REQ_SOFTBARRIER, /* may not be passed by ioscheduler */
> __REQ_HARDBARRIER, /* may not be passed by drive either */
> @@ -185,9 +187,7 @@ enum rq_flag_bits {
> __REQ_QUIET, /* don't worry about errors */
> __REQ_PREEMPT, /* set for "ide_preempt" requests */
> __REQ_ORDERED_COLOR, /* is before or after barrier */
> - __REQ_RW_SYNC, /* request is sync (O_DIRECT) */
> __REQ_ALLOCED, /* request came from our alloc pool */
> - __REQ_RW_META, /* metadata io request */
> __REQ_NR_BITS, /* stops here */
> };
>
>
Thats not enough You still need to fix code in ll_rw_blk(), I would
define a rq_flags_bio_match_mask = 0xf for that.
(and also add what Jens called "needed" with the
BIO_RW_AHEAD selects REQ_FAILFAST.)

And I still don't understand why, for example, "Domain Validation" fails
with the original patch. What sets BIO_RW_FAILFAST and than panics
on Errors?
(All I see is this flag set in dm/multipath.c & dm-mpath.c)

Boaz