This is a note to let you know that I've just added the patch titled
rbd: rework rbd_request_fn()
to the 3.16-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
rbd-rework-rbd_request_fn.patch
and it can be found in the queue-3.16 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From bc1ecc65a259fa9333dc8bd6a4ba0cf03b7d4bf8 Mon Sep 17 00:00:00 2001
From: Ilya Dryomov <ilya.dryomov@xxxxxxxxxxx>
Date: Mon, 4 Aug 2014 18:04:39 +0400
Subject: rbd: rework rbd_request_fn()
From: Ilya Dryomov <ilya.dryomov@xxxxxxxxxxx>
commit bc1ecc65a259fa9333dc8bd6a4ba0cf03b7d4bf8 upstream.
While it was never a good idea to sleep in request_fn(), commit
34c6bc2c919a ("locking/mutexes: Add extra reschedule point") made it
a *bad* idea. mutex_lock() since 3.15 may reschedule *before* putting
task on the mutex wait queue, which for tasks in !TASK_RUNNING state
means block forever. request_fn() may be called with !TASK_RUNNING on
the way to schedule() in io_schedule().
Offload request handling to a workqueue, one per rbd device, to avoid
calling blocking primitives from rbd_request_fn().
Fixes: http://tracker.ceph.com/issues/8818
Signed-off-by: Ilya Dryomov <ilya.dryomov@xxxxxxxxxxx>
Tested-by: Eric Eastman <eric0e@xxxxxxx>
Tested-by: Greg Wilson <greg.wilson@xxxxxxxxxxxxxx>
Reviewed-by: Alex Elder <elder@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/block/rbd.c | 194 +++++++++++++++++++++++++++++++---------------------
1 file changed, 118 insertions(+), 76 deletions(-)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -42,6 +42,7 @@
#include <linux/blkdev.h>
#include <linux/slab.h>
#include <linux/idr.h>
+#include <linux/workqueue.h>
#include "rbd_types.h"
@@ -332,7 +333,10 @@ struct rbd_device {
char name[DEV_NAME_LEN]; /* blkdev name, e.g. rbd3 */
+ struct list_head rq_queue; /* incoming rq queue */
spinlock_t lock; /* queue, flags, open_count */
+ struct workqueue_struct *rq_wq;
+ struct work_struct rq_work;
struct rbd_image_header header;
unsigned long flags; /* possibly lock protected */
@@ -3183,102 +3187,129 @@ out:
return ret;
}
-static void rbd_request_fn(struct request_queue *q)
- __releases(q->queue_lock) __acquires(q->queue_lock)
+static void rbd_handle_request(struct rbd_device *rbd_dev, struct request *rq)
{
- struct rbd_device *rbd_dev = q->queuedata;
- struct request *rq;
+ struct rbd_img_request *img_request;
+ u64 offset = (u64)blk_rq_pos(rq) << SECTOR_SHIFT;
+ u64 length = blk_rq_bytes(rq);
+ bool wr = rq_data_dir(rq) == WRITE;
int result;
- while ((rq = blk_fetch_request(q))) {
- bool write_request = rq_data_dir(rq) == WRITE;
- struct rbd_img_request *img_request;
- u64 offset;
- u64 length;
+ /* Ignore/skip any zero-length requests */
- /* Ignore any non-FS requests that filter through. */
+ if (!length) {
+ dout("%s: zero-length request\n", __func__);
+ result = 0;
+ goto err_rq;
+ }
- if (rq->cmd_type != REQ_TYPE_FS) {
- dout("%s: non-fs request type %d\n", __func__,
- (int) rq->cmd_type);
- __blk_end_request_all(rq, 0);
- continue;
+ /* Disallow writes to a read-only device */
+
+ if (wr) {
+ if (rbd_dev->mapping.read_only) {
+ result = -EROFS;
+ goto err_rq;
}
+ rbd_assert(rbd_dev->spec->snap_id == CEPH_NOSNAP);
+ }
- /* Ignore/skip any zero-length requests */
+ /*
+ * Quit early if the mapped snapshot no longer exists. It's
+ * still possible the snapshot will have disappeared by the
+ * time our request arrives at the osd, but there's no sense in
+ * sending it if we already know.
+ */
+ if (!test_bit(RBD_DEV_FLAG_EXISTS, &rbd_dev->flags)) {
+ dout("request for non-existent snapshot");
+ rbd_assert(rbd_dev->spec->snap_id != CEPH_NOSNAP);
+ result = -ENXIO;
+ goto err_rq;
+ }
- offset = (u64) blk_rq_pos(rq) << SECTOR_SHIFT;
- length = (u64) blk_rq_bytes(rq);
+ if (offset && length > U64_MAX - offset + 1) {
+ rbd_warn(rbd_dev, "bad request range (%llu~%llu)", offset,
+ length);
+ result = -EINVAL;
+ goto err_rq; /* Shouldn't happen */
+ }
- if (!length) {
- dout("%s: zero-length request\n", __func__);
- __blk_end_request_all(rq, 0);
- continue;
- }
+ if (offset + length > rbd_dev->mapping.size) {
+ rbd_warn(rbd_dev, "beyond EOD (%llu~%llu > %llu)", offset,
+ length, rbd_dev->mapping.size);
+ result = -EIO;
+ goto err_rq;
+ }
- spin_unlock_irq(q->queue_lock);
+ img_request = rbd_img_request_create(rbd_dev, offset, length, wr);
+ if (!img_request) {
+ result = -ENOMEM;
+ goto err_rq;
+ }
+ img_request->rq = rq;
- /* Disallow writes to a read-only device */
+ result = rbd_img_request_fill(img_request, OBJ_REQUEST_BIO, rq->bio);
+ if (result)
+ goto err_img_request;
- if (write_request) {
- result = -EROFS;
- if (rbd_dev->mapping.read_only)
- goto end_request;
- rbd_assert(rbd_dev->spec->snap_id == CEPH_NOSNAP);
- }
+ result = rbd_img_request_submit(img_request);
+ if (result)
+ goto err_img_request;
- /*
- * Quit early if the mapped snapshot no longer
- * exists. It's still possible the snapshot will
- * have disappeared by the time our request arrives
- * at the osd, but there's no sense in sending it if
- * we already know.
- */
- if (!test_bit(RBD_DEV_FLAG_EXISTS, &rbd_dev->flags)) {
- dout("request for non-existent snapshot");
- rbd_assert(rbd_dev->spec->snap_id != CEPH_NOSNAP);
- result = -ENXIO;
- goto end_request;
- }
+ return;
- result = -EINVAL;
- if (offset && length > U64_MAX - offset + 1) {
- rbd_warn(rbd_dev, "bad request range (%llu~%llu)\n",
- offset, length);
- goto end_request; /* Shouldn't happen */
- }
+err_img_request:
+ rbd_img_request_put(img_request);
+err_rq:
+ if (result)
+ rbd_warn(rbd_dev, "%s %llx at %llx result %d",
+ wr ? "write" : "read", length, offset, result);
+ blk_end_request_all(rq, result);
+}
- result = -EIO;
- if (offset + length > rbd_dev->mapping.size) {
- rbd_warn(rbd_dev, "beyond EOD (%llu~%llu > %llu)\n",
- offset, length, rbd_dev->mapping.size);
- goto end_request;
- }
+static void rbd_request_workfn(struct work_struct *work)
+{
+ struct rbd_device *rbd_dev =
+ container_of(work, struct rbd_device, rq_work);
+ struct request *rq, *next;
+ LIST_HEAD(requests);
- result = -ENOMEM;
- img_request = rbd_img_request_create(rbd_dev, offset, length,
- write_request);
- if (!img_request)
- goto end_request;
+ spin_lock_irq(&rbd_dev->lock); /* rq->q->queue_lock */
+ list_splice_init(&rbd_dev->rq_queue, &requests);
+ spin_unlock_irq(&rbd_dev->lock);
- img_request->rq = rq;
+ list_for_each_entry_safe(rq, next, &requests, queuelist) {
+ list_del_init(&rq->queuelist);
+ rbd_handle_request(rbd_dev, rq);
+ }
+}
- result = rbd_img_request_fill(img_request, OBJ_REQUEST_BIO,
- rq->bio);
- if (!result)
- result = rbd_img_request_submit(img_request);
- if (result)
- rbd_img_request_put(img_request);
-end_request:
- spin_lock_irq(q->queue_lock);
- if (result < 0) {
- rbd_warn(rbd_dev, "%s %llx at %llx result %d\n",
- write_request ? "write" : "read",
- length, offset, result);
+/*
+ * Called with q->queue_lock held and interrupts disabled, possibly on
+ * the way to schedule(). Do not sleep here!
+ */
+static void rbd_request_fn(struct request_queue *q)
+{
+ struct rbd_device *rbd_dev = q->queuedata;
+ struct request *rq;
+ int queued = 0;
+
+ rbd_assert(rbd_dev);
- __blk_end_request_all(rq, result);
+ while ((rq = blk_fetch_request(q))) {
+ /* Ignore any non-FS requests that filter through. */
+ if (rq->cmd_type != REQ_TYPE_FS) {
+ dout("%s: non-fs request type %d\n", __func__,
+ (int) rq->cmd_type);
+ __blk_end_request_all(rq, 0);
+ continue;
}
+
+ list_add_tail(&rq->queuelist, &rbd_dev->rq_queue);
+ queued++;
}
+
+ if (queued)
+ queue_work(rbd_dev->rq_wq, &rbd_dev->rq_work);
}
/*
@@ -3848,6 +3879,8 @@ static struct rbd_device *rbd_dev_create
return NULL;
spin_lock_init(&rbd_dev->lock);
+ INIT_LIST_HEAD(&rbd_dev->rq_queue);
+ INIT_WORK(&rbd_dev->rq_work, rbd_request_workfn);
rbd_dev->flags = 0;
atomic_set(&rbd_dev->parent_ref, 0);
INIT_LIST_HEAD(&rbd_dev->node);
@@ -5066,12 +5099,17 @@ static int rbd_dev_device_setup(struct r
ret = rbd_dev_mapping_set(rbd_dev);
if (ret)
goto err_out_disk;
+
set_capacity(rbd_dev->disk, rbd_dev->mapping.size / SECTOR_SIZE);
set_disk_ro(rbd_dev->disk, rbd_dev->mapping.read_only);
+ rbd_dev->rq_wq = alloc_workqueue(rbd_dev->disk->disk_name, 0, 0);
+ if (!rbd_dev->rq_wq)
+ goto err_out_mapping;
+
ret = rbd_bus_add_dev(rbd_dev);
if (ret)
- goto err_out_mapping;
+ goto err_out_workqueue;
/* Everything's ready. Announce the disk to the world. */
@@ -5083,6 +5121,9 @@ static int rbd_dev_device_setup(struct r
return ret;
+err_out_workqueue:
+ destroy_workqueue(rbd_dev->rq_wq);
+ rbd_dev->rq_wq = NULL;
err_out_mapping:
rbd_dev_mapping_clear(rbd_dev);
err_out_disk:
@@ -5314,6 +5355,7 @@ static void rbd_dev_device_release(struc
{
struct rbd_device *rbd_dev = dev_to_rbd_dev(dev);
+ destroy_workqueue(rbd_dev->rq_wq);
rbd_free_disk(rbd_dev);
clear_bit(RBD_DEV_FLAG_EXISTS, &rbd_dev->flags);
rbd_dev_mapping_clear(rbd_dev);
Patches currently in stable-queue which might be from ilya.dryomov@xxxxxxxxxxx are
queue-3.16/rbd-rework-rbd_request_fn.patch
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html