We could end up where all the devs with waiting_blocks
set hold all the blocks. find_free_blocks will always
fail. This just adds a force round where if the first
round fails, we then take pages from all devs.
Signed-off-by: Mike Christie <mchristi@xxxxxxxxxx>
---
drivers/target/target_core_user.c | 29 ++++++++++++++++++++++++++++-
1 file changed, 28 insertions(+), 1 deletion(-)
diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index dff7b14..9dad078 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -2040,10 +2040,12 @@ static struct target_backend_ops tcmu_ops = {
static uint32_t find_free_blocks(void)
{
struct tcmu_dev *udev;
+ bool force = false;
loff_t off;
uint32_t start, end, block, free_blocks = 0;
mutex_lock(&root_udev_mutex);
+retry:
list_for_each_entry(udev, &root_udev, node) {
mutex_lock(&udev->cmdr_lock);
@@ -2051,7 +2053,7 @@ static uint32_t find_free_blocks(void)
tcmu_handle_completions(udev);
/* Skip the udevs waiting the global pool or in idle */
- if (udev->waiting_blocks || !udev->dbi_thresh) {
+ if (!force && (udev->waiting_blocks || !udev->dbi_thresh)) {
mutex_unlock(&udev->cmdr_lock);
continue;
}
@@ -2080,10 +2082,35 @@ static uint32_t find_free_blocks(void)
/* Release the block pages */
tcmu_blocks_release(&udev->data_blocks, start, end);
+
+ if (list_empty(&udev->waiter)) {
+ /*
+ * if we had to take pages from a dev that hit its
+ * DATA_BLOCK_BITS limit put it on the waiter
+ * list so it gets rescheduled when pages are free.
+ */
+ spin_lock(&root_udev_waiter_lock);
+ list_add_tail(&udev->waiter, &root_udev_waiter);
+ spin_unlock(&root_udev_waiter_lock);
+ }
+
mutex_unlock(&udev->cmdr_lock);
+ pr_debug("Freed %u blocks from %s. Forced %d\n", end - start,
+ udev->name, force);
+
free_blocks += end - start;
}
+
+ if (!force && !free_blocks) {
+ /*
+ * if all pages were held by devs with waiting_blocks > 0
+ * then we have to force the release to prevent deadlock.
+ */
+ force = true;
+ goto retry;
+ }
+
mutex_unlock(&root_udev_mutex);
return free_blocks;
}
--
2.7.2
--
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