Re: [PATCH 1/2] md: add new interface 'mk_rq' in target_type

From: Robin Dong
Date: Tue Nov 13 2012 - 22:08:11 EST

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ping

2012/9/20 Robin Dong <robin.k.dong@xxxxxxxxx>:
> 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
>

--
--
Best Regard
Robin Dong
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Next message: Robin Dong: "Re: [PATCH 2/2] md: modify dm_io() so it could return bios instead ofsubmitting it"
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