If tcmu_dev 1 took exactly TCMU_GLOBAL_MAX_BLOCKS and then
tcmu_dev 2 tried to allocate blocks dev 2 would be put
on the waiter list. Later when dev 1's commands complete
tcmu_irqcontrol would see that dev 1 is not on the waiter list
and so it only runs the dev 1's queue. dev 2 could then be
starved.
This patch adds a check if we hit the global limit and have
waiters in tcmu_irqcontrol. In this case we will then put
the completing dev on the waiter list of needed and then
wake up the unmapping thread/wq.
Signed-off-by: Mike Christie <mchristi@xxxxxxxxxx>
---
drivers/target/target_core_user.c | 47 ++++++++++++++++++++++++++-------------
1 file changed, 32 insertions(+), 15 deletions(-)
diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index fc82df6..c2a15f4 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -1271,23 +1271,41 @@ static bool run_cmdr_queue(struct tcmu_dev *udev)
return drained;
}
+static bool tcmu_waiting_on_dev_blocks(struct tcmu_dev *udev)
+{
+ return list_empty(&udev->waiter) && !list_empty(&udev->cmdr_queue);
+}
+
static int tcmu_irqcontrol(struct uio_info *info, s32 irq_on)
{
- struct tcmu_dev *tcmu_dev = container_of(info, struct tcmu_dev, uio_info);
+ struct tcmu_dev *udev = container_of(info, struct tcmu_dev, uio_info);
+ bool run_local = true;
- mutex_lock(&tcmu_dev->cmdr_lock);
- /*
- * If the current udev is also in waiter list, this will
- * make sure that the other waiters in list be fed ahead
- * of it.
- */
- if (!list_empty(&tcmu_dev->waiter)) {
- schedule_work(&tcmu_unmap_work);
- } else {
- tcmu_handle_completions(tcmu_dev);
- run_cmdr_queue(tcmu_dev);
+ mutex_lock(&udev->cmdr_lock);
+
+ if (atomic_read(&global_db_count) == TCMU_GLOBAL_MAX_BLOCKS) {
+ spin_lock(&root_udev_waiter_lock);
+ if (!list_empty(&root_udev_waiter)) {
+ /*
+ * If we only hit the per block limit then make sure
+ * we are added to the global list so we get run
+ * after the other waiters.
+ */
+ if (tcmu_waiting_on_dev_blocks(udev))
+ list_add_tail(&udev->waiter, &root_udev_waiter);
+
+ run_local = false;
+ schedule_work(&tcmu_unmap_work);
+ }
+ spin_unlock(&root_udev_waiter_lock);
}
- mutex_unlock(&tcmu_dev->cmdr_lock);
+
+ if (run_local) {
+ tcmu_handle_completions(udev);
+ run_cmdr_queue(udev);
+ }
+
+ mutex_unlock(&udev->cmdr_lock);
return 0;
}
@@ -2186,8 +2204,7 @@ static uint32_t find_free_blocks(void)
/* Release the block pages */
tcmu_blocks_release(&udev->data_blocks, start, end);
- if (list_empty(&udev->waiter) &&
- !list_empty(&udev->cmdr_queue)) {
+ if (tcmu_waiting_on_dev_blocks(udev)) {
/*
* if we had to take pages from a dev that hit its
* DATA_BLOCK_BITS limit put it on the waiter
--
2.7.2
--
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