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Old 06-23-2011, 03:24 PM
Mikulas Patocka
 
Default dm-kcopyd: optionally zero an area instead of copying

On Thu, 23 Jun 2011, Alasdair G Kergon wrote:

> On Thu, Jun 09, 2011 at 11:36:44AM -0400, Mikulas Patocka wrote:
> > Here it is ... but it duplicates some code in dm_kcopyd_copy..
>
> Obviously I don't want the duplication
>
> Presumably a wrapper function with the first patch will suffice?
>
> Alasdair

Hi

So you can use this patch that adds a new function, but internaly works as
passing NULL from to dm_kcopyd_copy.

Mikulas

---

dm-kcopyd: optionally zero an area instead of copying

This patch introduces new function "dm_kcopyd_zero" that zeroes a
requested.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

---
drivers/md/dm-kcopyd.c | 31 ++++++++++++++++++++++++++-----
include/linux/dm-kcopyd.h | 3 +++
2 files changed, 29 insertions(+), 5 deletions(-)

Index: linux-2.6.39-fast/drivers/md/dm-kcopyd.c
================================================== =================
--- linux-2.6.39-fast.orig/drivers/md/dm-kcopyd.c 2011-06-23 16:58:49.000000000 +0200
+++ linux-2.6.39-fast/drivers/md/dm-kcopyd.c 2011-06-23 17:02:47.000000000 +0200
@@ -69,6 +69,8 @@ struct dm_kcopyd_client {
struct list_head pages_jobs;
};

+static struct page_list zero_page_list;
+
static DEFINE_SPINLOCK(throttle_spinlock);

/*
@@ -339,6 +341,9 @@ int __init dm_kcopyd_init(void)
if (!_job_cache)
return -ENOMEM;

+ zero_page_list.next = &zero_page_list;
+ zero_page_list.page = ZERO_PAGE(0);
+
return 0;
}

@@ -407,7 +412,7 @@ static int run_complete_job(struct kcopy
dm_kcopyd_notify_fn fn = job->fn;
struct dm_kcopyd_client *kc = job->kc;

- if (job->pages)
+ if (job->pages && job->pages != &zero_page_list)
kcopyd_put_pages(kc, job->pages);
/* Do not free sub-jobs */
if (context != job)
@@ -570,6 +575,8 @@ static void dispatch_job(struct kcopyd_j
atomic_inc(&kc->nr_jobs);
if (unlikely(!job->source.count))
push(&kc->complete_jobs, job);
+ else if (job->pages == &zero_page_list)
+ push(&kc->io_jobs, job);
else
push(&kc->pages_jobs, job);
wake(kc);
@@ -679,14 +686,20 @@ int dm_kcopyd_copy(struct dm_kcopyd_clie
job->flags = flags;
job->read_err = 0;
job->write_err = 0;
- job->rw = READ;
-
- job->source = *from;

job->num_dests = num_dests;
memcpy(&job->dests, dests, sizeof(*dests) * num_dests);

- job->pages = NULL;
+ if (from) {
+ job->source = *from;
+ job->pages = NULL;
+ job->rw = READ;
+ } else {
+ memset(&job->source, 0, sizeof job->source);
+ job->source.count = job->dests[0].count;
+ job->pages = &zero_page_list;
+ job->rw = WRITE;
+ }

job->fn = fn;
job->context = context;
@@ -704,6 +717,14 @@ int dm_kcopyd_copy(struct dm_kcopyd_clie
}
EXPORT_SYMBOL(dm_kcopyd_copy);

+int dm_kcopyd_zero(struct dm_kcopyd_client *kc,
+ unsigned int num_dests, struct dm_io_region *dests,
+ unsigned int flags, dm_kcopyd_notify_fn fn, void *context)
+{
+ return dm_kcopyd_copy(kc, NULL, num_dests, dests, flags, fn, context);
+}
+EXPORT_SYMBOL(dm_kcopyd_zero);
+
/*
* Cancels a kcopyd job, eg. someone might be deactivating a
* mirror.
Index: linux-2.6.39-fast/include/linux/dm-kcopyd.h
================================================== =================
--- linux-2.6.39-fast.orig/include/linux/dm-kcopyd.h 2011-06-23 17:00:16.000000000 +0200
+++ linux-2.6.39-fast/include/linux/dm-kcopyd.h 2011-06-23 17:00:42.000000000 +0200
@@ -54,6 +54,9 @@ typedef void (*dm_kcopyd_notify_fn)(int
int dm_kcopyd_copy(struct dm_kcopyd_client *kc, struct dm_io_region *from,
unsigned num_dests, struct dm_io_region *dests,
unsigned flags, dm_kcopyd_notify_fn fn, void *context);
+int dm_kcopyd_zero(struct dm_kcopyd_client *kc,
+ unsigned num_dests, struct dm_io_region *dests,
+ unsigned flags, dm_kcopyd_notify_fn fn, void *context);

#endif /* __KERNEL__ */
#endif /* _LINUX_DM_KCOPYD_H */

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