ping 2012/9/20 Robin Dong <robin.k.d...@gmail.com>: > From: Robin Dong <san...@taobao.com> > > We are now trying to modify flashcache(https://github.com/facebook/flashcache) > to make it request based so that > we can let cfq io-controller control the bandwidth between different > io cgroups. > > A search in the dm directory tells me that only multipath is a request > based dm target and its functionality > is very simple and map_rq() is used to map the request to different > underlying devices. > We can't work in this way because: > > 1. the request which processed by map_rq() need to be issued to > different lower devices (disk device and cache device, in > flashcache), therefore the request > can't be totally remapped by simply changing its queue and returning > DM_MAPIO_REMAPPED in map_rq() like multipath_map() > 2. to submit bios drectly in map_rq() (by return DM_MAPIO_SUBMITTED) will > cause BUG_ON(!irqs_disabled()) > in dm_request_fn() because the > submit_bio()->generic_make_request()->blk_queue_bio() will definitly call > spin_unlock_irq to enable the irqs > > As above,the interface map_rq() provided by devcie-mapper framework > is not enough for an autonomous target, like flashcache. > > We propose to add a new > mk_rq interface so that we can make the requests > by ourselves. > > Signed-off-by: Robin Dong <san...@taobao.com> > --- > drivers/md/dm-io.c | 58 ++++++++++++++++++++++++++++-------------------- > drivers/md/dm-log.c | 1 + > include/linux/dm-io.h | 3 ++ > 3 files changed, 38 insertions(+), 24 deletions(-) > > diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c > index ea5dd28..f767792 100644 > --- a/drivers/md/dm-io.c > +++ b/drivers/md/dm-io.c > @@ -287,8 +287,8 @@ static void km_dp_init(struct dpages *dp, void *data) > /*----------------------------------------------------------------- > * IO routines that accept a list of pages. > *---------------------------------------------------------------*/ > -static void do_region(int rw, unsigned region, struct dm_io_region *where, > - struct dpages *dp, struct io *io) > +static void do_region(struct dm_io_request *io_req, unsigned region, > + struct dm_io_region *where, struct dpages *dp, struct io *io) > { > struct bio *bio; > struct page *page; > @@ -298,6 +298,7 @@ static void do_region(int rw, unsigned region, struct > dm_io_region *where, > sector_t remaining = where->count; > struct request_queue *q = bdev_get_queue(where->bdev); > sector_t discard_sectors; > + int rw = io_req->bi_rw; > > /* > * where->count may be zero if rw holds a flush and we need to > @@ -339,15 +340,26 @@ static void do_region(int rw, unsigned region, struct > dm_io_region *where, > } > > atomic_inc(&io->count); > - submit_bio(rw, bio); > + if (!io_req->only_create_bio) > + submit_bio(rw, bio); > + else { > + bio->bi_rw |= rw; > + if (io_req->start) { > + io_req->end->bi_next = bio; > + io_req->end = bio; > + } else > + io_req->start = io_req->end = bio; > + bio->bi_next = NULL; > + } > } while (remaining); > } > > -static void dispatch_io(int rw, unsigned int num_regions, > +static void dispatch_io(struct dm_io_request *io_req, unsigned int > num_regions, > struct dm_io_region *where, struct dpages *dp, > struct io *io, int sync) > { > int i; > + int rw = io_req->bi_rw; > struct dpages old_pages = *dp; > > BUG_ON(num_regions > DM_IO_MAX_REGIONS); > @@ -362,7 +374,7 @@ static void dispatch_io(int rw, unsigned int num_regions, > for (i = 0; i < num_regions; i++) { > *dp = old_pages; > if (where[i].count || (rw & REQ_FLUSH)) > - do_region(rw, i, where + i, dp, io); > + do_region(io_req, i, where + i, dp, io); > } > > /* > @@ -372,8 +384,8 @@ static void dispatch_io(int rw, unsigned int num_regions, > dec_count(io, 0, 0); > } > > -static int sync_io(struct dm_io_client *client, unsigned int num_regions, > - struct dm_io_region *where, int rw, struct dpages *dp, > +static int sync_io(struct dm_io_request *io_req, unsigned int num_regions, > + struct dm_io_region *where, struct dpages *dp, > unsigned long *error_bits) > { > /* > @@ -385,7 +397,7 @@ static int sync_io(struct dm_io_client *client, unsigned > int num_regions, > volatile char io_[sizeof(struct io) + __alignof__(struct io) - 1]; > struct io *io = (struct io *)PTR_ALIGN(&io_, __alignof__(struct io)); > > - if (num_regions > 1 && (rw & RW_MASK) != WRITE) { > + if (num_regions > 1 && (io_req->bi_rw & RW_MASK) != WRITE) { > WARN_ON(1); > return -EIO; > } > @@ -393,12 +405,12 @@ static int sync_io(struct dm_io_client *client, > unsigned int num_regions, > io->error_bits = 0; > atomic_set(&io->count, 1); /* see dispatch_io() */ > io->sleeper = current; > - io->client = client; > + io->client = io_req->client; > > io->vma_invalidate_address = dp->vma_invalidate_address; > io->vma_invalidate_size = dp->vma_invalidate_size; > > - dispatch_io(rw, num_regions, where, dp, io, 1); > + dispatch_io(io_req, num_regions, where, dp, io, 1); > > while (1) { > set_current_state(TASK_UNINTERRUPTIBLE); > @@ -416,30 +428,29 @@ static int sync_io(struct dm_io_client *client, > unsigned int num_regions, > return io->error_bits ? -EIO : 0; > } > > -static int async_io(struct dm_io_client *client, unsigned int num_regions, > - struct dm_io_region *where, int rw, struct dpages *dp, > - io_notify_fn fn, void *context) > +static int async_io(struct dm_io_request *io_req, unsigned int num_regions, > + struct dm_io_region *where, struct dpages *dp) > { > struct io *io; > > - if (num_regions > 1 && (rw & RW_MASK) != WRITE) { > + if (num_regions > 1 && (io_req->bi_rw & RW_MASK) != WRITE) { > WARN_ON(1); > - fn(1, context); > + io_req->notify.fn(1, io_req->notify.context); > return -EIO; > } > > - io = mempool_alloc(client->pool, GFP_NOIO); > + io = mempool_alloc(io_req->client->pool, GFP_NOIO); > io->error_bits = 0; > atomic_set(&io->count, 1); /* see dispatch_io() */ > io->sleeper = NULL; > - io->client = client; > - io->callback = fn; > - io->context = context; > + io->client = io_req->client; > + io->callback = io_req->notify.fn; > + io->context = io_req->notify.context; > > io->vma_invalidate_address = dp->vma_invalidate_address; > io->vma_invalidate_size = dp->vma_invalidate_size; > > - dispatch_io(rw, num_regions, where, dp, io, 0); > + dispatch_io(io_req, num_regions, where, dp, io, 0); > return 0; > } > > @@ -499,11 +510,10 @@ int dm_io(struct dm_io_request *io_req, unsigned > num_regions, > return r; > > if (!io_req->notify.fn) > - return sync_io(io_req->client, num_regions, where, > - io_req->bi_rw, &dp, sync_error_bits); > + return sync_io(io_req, num_regions, where, > + &dp, sync_error_bits); > > - return async_io(io_req->client, num_regions, where, io_req->bi_rw, > - &dp, io_req->notify.fn, io_req->notify.context); > + return async_io(io_req, num_regions, where, &dp); > } > EXPORT_SYMBOL(dm_io); > > diff --git a/drivers/md/dm-log.c b/drivers/md/dm-log.c > index 627d191..3bf065a 100644 > --- a/drivers/md/dm-log.c > +++ b/drivers/md/dm-log.c > @@ -463,6 +463,7 @@ static int create_log_context(struct dm_dirty_log *log, > struct dm_target *ti, > kfree(lc); > return r; > } > + lc->io_req.only_create_bio = 0; > > lc->disk_header = vmalloc(buf_size); > if (!lc->disk_header) { > diff --git a/include/linux/dm-io.h b/include/linux/dm-io.h > index f4b0aa3..8782163 100644 > --- a/include/linux/dm-io.h > +++ b/include/linux/dm-io.h > @@ -61,6 +61,9 @@ struct dm_io_request { > struct dm_io_memory mem; /* Memory to use for io */ > struct dm_io_notify notify; /* Synchronous if notify.fn is NULL */ > struct dm_io_client *client; /* Client memory handler */ > + int only_create_bio; > + struct bio *start; > + struct bio *end; > }; > > /* > -- > 1.7.1 >
-- -- Best Regard Robin Dong -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
