block: unify request timeout handling

Right now SCSI and others do their own command timeout handling.
Move those bits to the block layer.

Instead of having a timer per command, we try to be a bit more clever
and simply have one per-queue. This avoids the overhead of having to
tear down and setup a timer for each command, so it will result in a lot
less timer fiddling.

Signed-off-by: Mike Anderson <andmike@linux.vnet.ibm.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 155 insertions, 0 deletions

diff --git a/block/blk-timeout.c b/block/blk-timeout.c
new file mode 100644
index 000000000000..b36d07bf0afb
--- /dev/null
+++ b/block/blk-timeout.c
@@ -0,0 +1,155 @@
+/*
+ * Functions related to generic timeout handling of requests.
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/blkdev.h>
+
+#include "blk.h"
+
+/*
+ * blk_delete_timer - Delete/cancel timer for a given function.
+ * @req:        request that we are canceling timer for
+ *
+ */
+void blk_delete_timer(struct request *req)
+{
+        struct request_queue *q = req->q;
+
+        /*
+         * Nothing to detach
+         */
+        if (!q->rq_timed_out_fn || !req->deadline)
+                return;
+
+        list_del_init(&req->timeout_list);
+
+        if (list_empty(&q->timeout_list))
+                del_timer(&q->timeout);
+}
+
+static void blk_rq_timed_out(struct request *req)
+{
+        struct request_queue *q = req->q;
+        enum blk_eh_timer_return ret;
+
+        ret = q->rq_timed_out_fn(req);
+        switch (ret) {
+        case BLK_EH_HANDLED:
+                __blk_complete_request(req);
+                break;
+        case BLK_EH_RESET_TIMER:
+                blk_clear_rq_complete(req);
+                blk_add_timer(req);
+                break;
+        case BLK_EH_NOT_HANDLED:
+                /*
+                 * LLD handles this for now but in the future
+                 * we can send a request msg to abort the command
+                 * and we can move more of the generic scsi eh code to
+                 * the blk layer.
+                 */
+                break;
+        default:
+                printk(KERN_ERR "block: bad eh return: %d\n", ret);
+                break;
+        }
+}
+
+void blk_rq_timed_out_timer(unsigned long data)
+{
+        struct request_queue *q = (struct request_queue *) data;
+        unsigned long flags, uninitialized_var(next), next_set = 0;
+        struct request *rq, *tmp;
+
+        spin_lock_irqsave(q->queue_lock, flags);
+
+        list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list) {
+                if (time_after_eq(jiffies, rq->deadline)) {
+                        list_del_init(&rq->timeout_list);
+
+                        /*
+                         * Check if we raced with end io completion
+                         */
+                        if (blk_mark_rq_complete(rq))
+                                continue;
+                        blk_rq_timed_out(rq);
+                }
+                if (!next_set) {
+                        next = rq->deadline;
+                        next_set = 1;
+                } else if (time_after(next, rq->deadline))
+                        next = rq->deadline;
+        }
+
+        if (next_set && !list_empty(&q->timeout_list))
+                mod_timer(&q->timeout, round_jiffies(next));
+
+        spin_unlock_irqrestore(q->queue_lock, flags);
+}
+
+/**
+ * blk_abort_request -- Request request recovery for the specified command
+ * @req:        pointer to the request of interest
+ *
+ * This function requests that the block layer start recovery for the
+ * request by deleting the timer and calling the q's timeout function.
+ * LLDDs who implement their own error recovery MAY ignore the timeout
+ * event if they generated blk_abort_req. Must hold queue lock.
+ */
+void blk_abort_request(struct request *req)
+{
+        blk_delete_timer(req);
+        blk_rq_timed_out(req);
+}
+EXPORT_SYMBOL_GPL(blk_abort_request);
+
+/**
+ * blk_add_timer - Start timeout timer for a single request
+ * @req:        request that is about to start running.
+ *
+ * Notes:
+ *    Each request has its own timer, and as it is added to the queue, we
+ *    set up the timer. When the request completes, we cancel the timer.
+ */
+void blk_add_timer(struct request *req)
+{
+        struct request_queue *q = req->q;
+        unsigned long expiry;
+
+        if (!q->rq_timed_out_fn)
+                return;
+
+        BUG_ON(!list_empty(&req->timeout_list));
+        BUG_ON(test_bit(REQ_ATOM_COMPLETE, &req->atomic_flags));
+
+        if (req->timeout)
+                req->deadline = jiffies + req->timeout;
+        else {
+                req->deadline = jiffies + q->rq_timeout;
+                /*
+                 * Some LLDs, like scsi, peek at the timeout to prevent
+                 * a command from being retried forever.
+                 */
+                req->timeout = q->rq_timeout;
+        }
+        list_add_tail(&req->timeout_list, &q->timeout_list);
+
+        /*
+         * If the timer isn't already pending or this timeout is earlier
+         * than an existing one, modify the timer. Round to next nearest
+         * second.
+         */
+        expiry = round_jiffies(req->deadline);
+
+        /*
+         * We use ->deadline == 0 to detect whether a timer was added or
+         * not, so just increase to next jiffy for that specific case
+         */
+        if (unlikely(!req->deadline))
+                req->deadline = 1;
+
+        if (!timer_pending(&q->timeout) ||
+            time_before(expiry, q->timeout.expires))
+                mod_timer(&q->timeout, expiry);
+}