* [PATCH 1/2] md: add new interface 'mk_rq' in target_type
@ 2012-09-20 3:18 Robin Dong
2012-09-20 3:18 ` [PATCH 2/2] md: modify dm_io() so it could return bios instead of submitting it Robin Dong
2012-11-14 3:08 ` [PATCH 1/2] md: add new interface 'mk_rq' in target_type Robin Dong
0 siblings, 2 replies; 5+ messages in thread
From: Robin Dong @ 2012-09-20 3:18 UTC (permalink / raw)
To: linux-kernel, dm-devel; +Cc: Robin Dong
From: Robin Dong <sanbai@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 <sanbai@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
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH 2/2] md: modify dm_io() so it could return bios instead of submitting it
2012-09-20 3:18 [PATCH 1/2] md: add new interface 'mk_rq' in target_type Robin Dong
@ 2012-09-20 3:18 ` Robin Dong
2012-11-14 3:08 ` Robin Dong
2012-11-14 3:08 ` [PATCH 1/2] md: add new interface 'mk_rq' in target_type Robin Dong
1 sibling, 1 reply; 5+ messages in thread
From: Robin Dong @ 2012-09-20 3:18 UTC (permalink / raw)
To: linux-kernel, dm-devel; +Cc: Robin Dong
From: Robin Dong <sanbai@taobao.com>
When trying to modify flashcache to request based (current it's bio based), we need
to make request from bios by ourselves, but dm_io() will submit these bios directly,
so we propose to modify the dm_io() to return bios instead of submiting it.
This could also improve the flexibility of dm_io().
Signed-off-by: Robin Dong <sanbai@taobao.com>
---
drivers/md/dm.c | 11 +++++++++++
include/linux/device-mapper.h | 3 +++
2 files changed, 14 insertions(+), 0 deletions(-)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 4e09b6f..bf6e3bb 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1459,11 +1459,22 @@ static int dm_request_based(struct mapped_device *md)
static void dm_request(struct request_queue *q, struct bio *bio)
{
struct mapped_device *md = q->queuedata;
+ struct dm_table *map = dm_get_live_table(md);
+ struct dm_target *ti = dm_table_find_target(map, bio->bi_sector);
+
+ if (ti->type->mk_rq) {
+ ti->type->mk_rq(ti, q, bio);
+ goto out;
+ }
if (dm_request_based(md))
blk_queue_bio(q, bio);
else
_dm_request(q, bio);
+
+out:
+ dm_table_put(map);
+ return;
}
void dm_dispatch_request(struct request *rq)
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 38d27a1..2386389 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -50,6 +50,8 @@ typedef int (*dm_map_fn) (struct dm_target *ti, struct bio *bio,
union map_info *map_context);
typedef int (*dm_map_request_fn) (struct dm_target *ti, struct request *clone,
union map_info *map_context);
+typedef int (*dm_make_request_fn) (struct dm_target *ti,
+ struct request_queue *q, struct bio *bio);
/*
* Returns:
@@ -136,6 +138,7 @@ struct target_type {
dm_dtr_fn dtr;
dm_map_fn map;
dm_map_request_fn map_rq;
+ dm_make_request_fn mk_rq;
dm_endio_fn end_io;
dm_request_endio_fn rq_end_io;
dm_presuspend_fn presuspend;
--
1.7.1
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH 2/2] md: modify dm_io() so it could return bios instead of submitting it
2012-09-20 3:18 ` [PATCH 2/2] md: modify dm_io() so it could return bios instead of submitting it Robin Dong
@ 2012-11-14 3:08 ` Robin Dong
0 siblings, 0 replies; 5+ messages in thread
From: Robin Dong @ 2012-11-14 3:08 UTC (permalink / raw)
To: linux-kernel, dm-devel
ping
2012/9/20 Robin Dong <robin.k.dong@gmail.com>:
> From: Robin Dong <sanbai@taobao.com>
>
> When trying to modify flashcache to request based (current it's bio based), we need
> to make request from bios by ourselves, but dm_io() will submit these bios directly,
> so we propose to modify the dm_io() to return bios instead of submiting it.
>
> This could also improve the flexibility of dm_io().
>
> Signed-off-by: Robin Dong <sanbai@taobao.com>
> ---
> drivers/md/dm.c | 11 +++++++++++
> include/linux/device-mapper.h | 3 +++
> 2 files changed, 14 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 4e09b6f..bf6e3bb 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -1459,11 +1459,22 @@ static int dm_request_based(struct mapped_device *md)
> static void dm_request(struct request_queue *q, struct bio *bio)
> {
> struct mapped_device *md = q->queuedata;
> + struct dm_table *map = dm_get_live_table(md);
> + struct dm_target *ti = dm_table_find_target(map, bio->bi_sector);
> +
> + if (ti->type->mk_rq) {
> + ti->type->mk_rq(ti, q, bio);
> + goto out;
> + }
>
> if (dm_request_based(md))
> blk_queue_bio(q, bio);
> else
> _dm_request(q, bio);
> +
> +out:
> + dm_table_put(map);
> + return;
> }
>
> void dm_dispatch_request(struct request *rq)
> diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
> index 38d27a1..2386389 100644
> --- a/include/linux/device-mapper.h
> +++ b/include/linux/device-mapper.h
> @@ -50,6 +50,8 @@ typedef int (*dm_map_fn) (struct dm_target *ti, struct bio *bio,
> union map_info *map_context);
> typedef int (*dm_map_request_fn) (struct dm_target *ti, struct request *clone,
> union map_info *map_context);
> +typedef int (*dm_make_request_fn) (struct dm_target *ti,
> + struct request_queue *q, struct bio *bio);
>
> /*
> * Returns:
> @@ -136,6 +138,7 @@ struct target_type {
> dm_dtr_fn dtr;
> dm_map_fn map;
> dm_map_request_fn map_rq;
> + dm_make_request_fn mk_rq;
> dm_endio_fn end_io;
> dm_request_endio_fn rq_end_io;
> dm_presuspend_fn presuspend;
> --
> 1.7.1
>
--
--
Best Regard
Robin Dong
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/2] md: add new interface 'mk_rq' in target_type
2012-09-20 3:18 [PATCH 1/2] md: add new interface 'mk_rq' in target_type Robin Dong
2012-09-20 3:18 ` [PATCH 2/2] md: modify dm_io() so it could return bios instead of submitting it Robin Dong
@ 2012-11-14 3:08 ` Robin Dong
1 sibling, 0 replies; 5+ messages in thread
From: Robin Dong @ 2012-11-14 3:08 UTC (permalink / raw)
To: linux-kernel, dm-devel
ping
2012/9/20 Robin Dong <robin.k.dong@gmail.com>:
> From: Robin Dong <sanbai@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 <sanbai@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
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH 1/2] md: add new interface 'mk_rq' in target_type
@ 2012-09-03 2:12 Robin Dong
0 siblings, 0 replies; 5+ messages in thread
From: Robin Dong @ 2012-09-03 2:12 UTC (permalink / raw)
To: dm-devel, linux-kernel; +Cc: Robin Dong
From: Robin Dong <sanbai@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 <sanbai@taobao.com>
---
drivers/md/dm.c | 10 ++++++++++
include/linux/device-mapper.h | 3 +++
2 files changed, 13 insertions(+), 0 deletions(-)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 4e09b6f..3ae67de 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1459,11 +1459,21 @@ static int dm_request_based(struct mapped_device *md)
static void dm_request(struct request_queue *q, struct bio *bio)
{
struct mapped_device *md = q->queuedata;
+ struct dm_table *map = dm_get_live_table(md);
+ struct dm_target *ti = dm_table_find_target(map, bio->bi_sector);
+
+ if (ti->type->mk_rq) {
+ ti->type->mk_rq(ti, q, bio);
+ goto out;
+ }
if (dm_request_based(md))
blk_queue_bio(q, bio);
else
_dm_request(q, bio);
+
+out:
+ dm_table_put(map);
}
void dm_dispatch_request(struct request *rq)
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 38d27a1..2386389 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -50,6 +50,8 @@ typedef int (*dm_map_fn) (struct dm_target *ti, struct bio *bio,
union map_info *map_context);
typedef int (*dm_map_request_fn) (struct dm_target *ti, struct request *clone,
union map_info *map_context);
+typedef int (*dm_make_request_fn) (struct dm_target *ti,
+ struct request_queue *q, struct bio *bio);
/*
* Returns:
@@ -136,6 +138,7 @@ struct target_type {
dm_dtr_fn dtr;
dm_map_fn map;
dm_map_request_fn map_rq;
+ dm_make_request_fn mk_rq;
dm_endio_fn end_io;
dm_request_endio_fn rq_end_io;
dm_presuspend_fn presuspend;
--
1.7.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
end of thread, other threads:[~2012-11-14 3:08 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2012-09-20 3:18 [PATCH 1/2] md: add new interface 'mk_rq' in target_type Robin Dong
2012-09-20 3:18 ` [PATCH 2/2] md: modify dm_io() so it could return bios instead of submitting it Robin Dong
2012-11-14 3:08 ` Robin Dong
2012-11-14 3:08 ` [PATCH 1/2] md: add new interface 'mk_rq' in target_type Robin Dong
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2012-09-03 2:12 Robin Dong
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