From: Robin Dong <sanbai@xxxxxxxxxx> 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 <sanbai@xxxxxxxxxx> --- 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 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
