summaryrefslogtreecommitdiffstats
path: root/Documentation/admin-guide/device-mapper/kcopyd.rst
diff options
context:
space:
mode:
authorJoel Fernandes <joelagnelf@nvidia.com>2026-07-18 13:15:36 -0400
committerPaul E. McKenney <paulmck@kernel.org>2026-07-23 10:39:57 -0700
commit34ff636f322c6d5e4f0a52338fa63a7dff09a495 (patch)
tree7629759c1ec7148b95bc8ab3080df20a5ecd2273 /Documentation/admin-guide/device-mapper/kcopyd.rst
downloadlinux-stable-34ff636f322c6d5e4f0a52338fa63a7dff09a495.tar.gz
linux-stable-34ff636f322c6d5e4f0a52338fa63a7dff09a495.zip
scftorture: Count single_rpc offline failures in statistics outputgrafted
scf_torture_stats_print() aggregates each invoker thread's counters into a local scf_statistics structure before printing, but the n_single_rpc_ofl field is missing from the aggregation loop. As a result, the "single_rpc_ofl" value printed in the statistics line is always zero, even when smp_call_function_single() invocations for the RPC test have failed due to offline CPUs and been counted by the invoker threads. Add the missing accumulation so that the printed value reflects the actual counts. Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'Documentation/admin-guide/device-mapper/kcopyd.rst')
-rw-r--r--Documentation/admin-guide/device-mapper/kcopyd.rst47
1 files changed, 47 insertions, 0 deletions
diff --git a/Documentation/admin-guide/device-mapper/kcopyd.rst b/Documentation/admin-guide/device-mapper/kcopyd.rst
new file mode 100644
index 000000000..7651d3951
--- /dev/null
+++ b/Documentation/admin-guide/device-mapper/kcopyd.rst
@@ -0,0 +1,47 @@
+======
+kcopyd
+======
+
+Kcopyd provides the ability to copy a range of sectors from one block-device
+to one or more other block-devices, with an asynchronous completion
+notification. It is used by dm-snapshot and dm-mirror.
+
+Users of kcopyd must first create a client and indicate how many memory pages
+to set aside for their copy jobs. This is done with a call to
+kcopyd_client_create()::
+
+ int kcopyd_client_create(unsigned int num_pages,
+ struct kcopyd_client **result);
+
+To start a copy job, the user must set up io_region structures to describe
+the source and destinations of the copy. Each io_region indicates a
+block-device along with the starting sector and size of the region. The source
+of the copy is given as one io_region structure, and the destinations of the
+copy are given as an array of io_region structures::
+
+ struct io_region {
+ struct block_device *bdev;
+ sector_t sector;
+ sector_t count;
+ };
+
+To start the copy, the user calls kcopyd_copy(), passing in the client
+pointer, pointers to the source and destination io_regions, the name of a
+completion callback routine, and a pointer to some context data for the copy::
+
+ int kcopyd_copy(struct kcopyd_client *kc, struct io_region *from,
+ unsigned int num_dests, struct io_region *dests,
+ unsigned int flags, kcopyd_notify_fn fn, void *context);
+
+ typedef void (*kcopyd_notify_fn)(int read_err, unsigned int write_err,
+ void *context);
+
+When the copy completes, kcopyd will call the user's completion routine,
+passing back the user's context pointer. It will also indicate if a read or
+write error occurred during the copy.
+
+When a user is done with all their copy jobs, they should call
+kcopyd_client_destroy() to delete the kcopyd client, which will release the
+associated memory pages::
+
+ void kcopyd_client_destroy(struct kcopyd_client *kc);