On 3/3/25 10:37, Pavel Tikhomirov wrote:
This eventfd can be used to get an event when merge_backward start work
have finished and is waiting for completion.
Note: The eventfd can be changed even while work is running.
Locking:
The backward_merge.eventfd_ctx is protected from being released by
tgt->ctl_mutex.
https://virtuozzo.atlassian.net/browse/VSTOR-100466
Signed-off-by: Pavel Tikhomirov <ptikhomi...@virtuozzo.com>
--
v2: Always report that work finished, e.g. also on error or then it was
canceled, this should be more consistent from the userspace perspective.
v4: Address Andrey's reveiw: signal that we are at completion waiting on
change of eventfd.
---
drivers/md/dm-qcow2-cmd.c | 42 ++++++++++++++++++++++++++++++++++++++-
drivers/md/dm-qcow2.h | 2 ++
2 files changed, 43 insertions(+), 1 deletion(-)
diff --git a/drivers/md/dm-qcow2-cmd.c b/drivers/md/dm-qcow2-cmd.c
index 04a992f3ebba6..f16b4f731ca5a 100644
--- a/drivers/md/dm-qcow2-cmd.c
+++ b/drivers/md/dm-qcow2-cmd.c
@@ -5,6 +5,8 @@
#include <linux/device-mapper.h>
#include <linux/sched/signal.h>
#include <linux/file.h>
+#include <linux/eventfd.h>
+#include <linux/minmax.h>
#include <linux/error-injection.h>
#include "dm-qcow2.h"
@@ -197,6 +199,8 @@ void qcow2_merge_backward_work(struct work_struct *work)
mutex_lock(&tgt->ctl_mutex);
if (tgt->backward_merge.state != BACKWARD_MERGE_START) {
+ if (tgt->backward_merge.eventfd_ctx)
+ eventfd_signal(tgt->backward_merge.eventfd_ctx, 1);
mutex_unlock(&tgt->ctl_mutex);
return;
}
@@ -249,6 +253,8 @@ void qcow2_merge_backward_work(struct work_struct *work)
/* Finish merge */
tgt->backward_merge.state = BACKWARD_MERGE_WAIT_COMPLETION;
}
+ if (tgt->backward_merge.eventfd_ctx)
+ eventfd_signal(tgt->backward_merge.eventfd_ctx, 1);
It would be a bit better if we also set a different values for error or
success, but it is not necessary, as either complete will fail or we do
get_progress and see error
mutex_unlock(&tgt->ctl_mutex);
}
@@ -312,6 +318,27 @@ static bool qcow2_backward_merge_should_stop(struct qcow2_target *tgt)
return READ_ONCE(tgt->backward_merge.state) == BACKWARD_MERGE_STOP;
}
+#define QCOW2_FILE_UNBIND -1
+
+static int qcow2_merge_backward_set_eventfd(struct qcow2_target *tgt, int efd)
+{
+ struct eventfd_ctx *ctx = NULL;
+
+ ctx = efd == QCOW2_FILE_UNBIND ? NULL : eventfd_ctx_fdget(efd);
+ if (IS_ERR(ctx))
+ return PTR_ERR(ctx);
+
+ mutex_lock(&tgt->ctl_mutex);
+ swap(ctx, tgt->backward_merge.eventfd_ctx);
+ if (ctx)
+ eventfd_ctx_put(ctx);
+ if (tgt->backward_merge.eventfd_ctx &&
+ tgt->backward_merge.state == BACKWARD_MERGE_WAIT_COMPLETION)
+ eventfd_signal(tgt->backward_merge.eventfd_ctx, 1);
+ mutex_unlock(&tgt->ctl_mutex);
+ return 0;
+}
+
static struct qcow2 *qcow2_get_img(struct qcow2_target *tgt, u32 img_id, u8
*ref_index)
{
struct qcow2 *qcow2;
@@ -470,14 +497,27 @@ int qcow2_message(struct dm_target *ti, unsigned int
argc, char **argv,
ret = qcow2_get_event(tgt, result, maxlen);
goto out;
} else if (!strcmp(argv[0], "merge_backward")) {
- if (argc != 2) {
+ if (argc < 2) {
ret = -EINVAL;
goto out;
}
if (!strcmp(argv[1], "cancel")) {
+ if (argc != 2) {
+ ret = -EINVAL;
+ goto out;
+ }
qcow2_merge_backward_cancel(tgt);
ret = 0;
goto out;
+ } else if (!strcmp(argv[1], "set_eventfd")) {
+ int efd;
+
+ if (argc != 3 || kstrtoint(argv[2], 10, &efd)) {
+ ret = -EINVAL;
+ goto out;
+ }
+ ret = qcow2_merge_backward_set_eventfd(tgt, efd);
+ goto out;
}
}
diff --git a/drivers/md/dm-qcow2.h b/drivers/md/dm-qcow2.h
index bebfdc50ed6d4..c4956e3fd0eb7 100644
--- a/drivers/md/dm-qcow2.h
+++ b/drivers/md/dm-qcow2.h
@@ -5,6 +5,7 @@
#include <linux/percpu-refcount.h>
#include <linux/device-mapper.h>
#include <linux/fs.h>
+#include <linux/eventfd.h>
#include "dm-core.h"
#define DM_MSG_PREFIX "qcow2"
@@ -161,6 +162,7 @@ struct qcow2_backward_merge {
struct work_struct work;
enum qcow2_backward_merge_state state;
int error;
+ struct eventfd_ctx *eventfd_ctx;
};
struct qcow2_target {
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