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authorMikulas Patocka <mpatocka@redhat.com>2011-08-02 15:32:04 +0400
committerAlasdair G Kergon <agk@redhat.com>2011-08-02 15:32:04 +0400
commita6e50b409d3f9e0833e69c3c9cca822e8fa4adbb (patch)
tree82ca807c21156437270e6a1ed255b18ccf8b3672 /drivers/md/dm-kcopyd.c
parentd5b9dd04bd74b774b8e8d93ced7a0d15ad403fa9 (diff)
downloadlinux-a6e50b409d3f9e0833e69c3c9cca822e8fa4adbb.tar.xz
dm snapshot: skip reading origin when overwriting complete chunk
If we write a full chunk in the snapshot, skip reading the origin device because the whole chunk will be overwritten anyway. This patch changes the snapshot write logic when a full chunk is written. In this case: 1. allocate the exception 2. dispatch the bio (but don't report the bio completion to device mapper) 3. write the exception record 4. report bio completed Callbacks must be done through the kcopyd thread, because callbacks must not race with each other. So we create two new functions: dm_kcopyd_prepare_callback: allocate a job structure and prepare the callback. (This function must not be called from interrupt context.) dm_kcopyd_do_callback: submit callback. (This function may be called from interrupt context.) Performance test (on snapshots with 4k chunk size): without the patch: non-direct-io sequential write (dd): 17.7MB/s direct-io sequential write (dd): 20.9MB/s non-direct-io random write (mkfs.ext2): 0.44s with the patch: non-direct-io sequential write (dd): 26.5MB/s direct-io sequential write (dd): 33.2MB/s non-direct-io random write (mkfs.ext2): 0.27s Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md/dm-kcopyd.c')
-rw-r--r--drivers/md/dm-kcopyd.c31
1 files changed, 31 insertions, 0 deletions
diff --git a/drivers/md/dm-kcopyd.c b/drivers/md/dm-kcopyd.c
index 98725e119324..f82147029636 100644
--- a/drivers/md/dm-kcopyd.c
+++ b/drivers/md/dm-kcopyd.c
@@ -617,6 +617,37 @@ int dm_kcopyd_copy(struct dm_kcopyd_client *kc, struct dm_io_region *from,
}
EXPORT_SYMBOL(dm_kcopyd_copy);
+void *dm_kcopyd_prepare_callback(struct dm_kcopyd_client *kc,
+ dm_kcopyd_notify_fn fn, void *context)
+{
+ struct kcopyd_job *job;
+
+ job = mempool_alloc(kc->job_pool, GFP_NOIO);
+
+ memset(job, 0, sizeof(struct kcopyd_job));
+ job->kc = kc;
+ job->fn = fn;
+ job->context = context;
+
+ atomic_inc(&kc->nr_jobs);
+
+ return job;
+}
+EXPORT_SYMBOL(dm_kcopyd_prepare_callback);
+
+void dm_kcopyd_do_callback(void *j, int read_err, unsigned long write_err)
+{
+ struct kcopyd_job *job = j;
+ struct dm_kcopyd_client *kc = job->kc;
+
+ job->read_err = read_err;
+ job->write_err = write_err;
+
+ push(&kc->complete_jobs, job);
+ wake(kc);
+}
+EXPORT_SYMBOL(dm_kcopyd_do_callback);
+
/*
* Cancels a kcopyd job, eg. someone might be deactivating a
* mirror.