Messages in this thread | | | Date | Mon, 03 Nov 2014 10:49:21 -0500 | From | Boris Ostrovsky <> | Subject | Re: [PATCH] xen/blkfront: improve protection against issuing unsupported REQ_FUA |
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On 11/03/2014 07:22 AM, Laszlo Ersek wrote: > On 10/27/14 14:44, Vitaly Kuznetsov wrote: >> Guard against issuing unsupported REQ_FUA and REQ_FLUSH was introduced >> in d11e61583 and was factored out into blkif_request_flush_valid() in >> 0f1ca65ee. However: >> 1) This check in incomplete. In case we negotiated to feature_flush = REQ_FLUSH >> and flush_op = BLKIF_OP_FLUSH_DISKCACHE (so FUA is unsupported) FUA request >> will still pass the check. >> 2) blkif_request_flush_valid() is misnamed. It is bool but returns true when >> the request is invalid. >> 3) When blkif_request_flush_valid() fails -EIO is being returned. It seems that >> -EOPNOTSUPP is more appropriate here. >> Fix all of the above issues. >> >> This patch is based on the original patch by Laszlo Ersek and a comment by >> Jeff Moyer. >> >> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> >> --- >> drivers/block/xen-blkfront.c | 14 ++++++++------ >> 1 file changed, 8 insertions(+), 6 deletions(-) >> >> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c >> index 5ac312f..2e6c103 100644 >> --- a/drivers/block/xen-blkfront.c >> +++ b/drivers/block/xen-blkfront.c >> @@ -582,12 +582,14 @@ static inline void flush_requests(struct blkfront_info *info) >> notify_remote_via_irq(info->irq); >> } >> >> -static inline bool blkif_request_flush_valid(struct request *req, >> - struct blkfront_info *info) >> +static inline bool blkif_request_flush_invalid(struct request *req, >> + struct blkfront_info *info) >> { >> return ((req->cmd_type != REQ_TYPE_FS) || >> - ((req->cmd_flags & (REQ_FLUSH | REQ_FUA)) && >> - !info->flush_op)); >> + ((req->cmd_flags & REQ_FLUSH) && >> + !(info->feature_flush & REQ_FLUSH)) || >> + ((req->cmd_flags & REQ_FUA) && >> + !(info->feature_flush & REQ_FUA)));
Somewhat unrelated to the patch, but I am wondering whether we actually need flush_op field at all as it seems that it is unambiguously defined by REQ_FLUSH/REQ_FUA.
-boris
>> } >> >> /* >> @@ -612,8 +614,8 @@ static void do_blkif_request(struct request_queue *rq) >> >> blk_start_request(req); >> >> - if (blkif_request_flush_valid(req, info)) { >> - __blk_end_request_all(req, -EIO); >> + if (blkif_request_flush_invalid(req, info)) { >> + __blk_end_request_all(req, -EOPNOTSUPP); >> continue; >> } >> >> > Not sure if there has been some feedback yet (I can't see anything > threaded with this message in my inbox). > > FWIW I consulted "Documentation/block/writeback_cache_control.txt" for > this review. Apparently, REQ_FLUSH forces out "previously completed > write requests", whereas REQ_FUA delays the IO completion signal for > *this* request until "the data has been committed to non-volatile > storage". So, indeed, support for REQ_FLUSH only does not guarantee that > REQ_FUA can be served. > > Reviewed-by: Laszlo Ersek <lersek@redhat.com> > > Thanks > Laszlo
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