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authorJens Axboe <jens.axboe@oracle.com>2008-09-14 12:55:09 (GMT)
committerJens Axboe <jens.axboe@oracle.com>2008-10-09 06:56:13 (GMT)
commit242f9dcb8ba6f68fcd217a119a7648a4f69290e9 (patch)
tree1bfe245ffbc50d204d76665cd8f90d85100f86a1 /block/blk-timeout.c
parent608aeef17a91747d6303de4df5e2c2e6899a95e8 (diff)
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>
Diffstat (limited to 'block/blk-timeout.c')
-rw-r--r--block/blk-timeout.c155
1 files changed, 155 insertions, 0 deletions
diff --git a/block/blk-timeout.c b/block/blk-timeout.c
new file mode 100644
index 0000000..b36d07bf
--- /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);
+}

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