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Diffstat (limited to 'drivers/block/ublk_drv.c')
-rw-r--r--drivers/block/ublk_drv.c342
1 files changed, 215 insertions, 127 deletions
diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 630ddfe665..83600b45e1 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -75,6 +75,7 @@ struct ublk_rq_data {
struct ublk_uring_cmd_pdu {
struct ublk_queue *ubq;
+ u16 tag;
};
/*
@@ -115,6 +116,9 @@ struct ublk_uring_cmd_pdu {
*/
#define UBLK_IO_FLAG_NEED_GET_DATA 0x08
+/* atomic RW with ubq->cancel_lock */
+#define UBLK_IO_FLAG_CANCELED 0x80000000
+
struct ublk_io {
/* userspace buffer address from io cmd */
__u64 addr;
@@ -138,13 +142,13 @@ struct ublk_queue {
unsigned int max_io_sz;
bool force_abort;
bool timeout;
+ bool canceling;
unsigned short nr_io_ready; /* how many ios setup */
+ spinlock_t cancel_lock;
struct ublk_device *dev;
struct ublk_io ios[];
};
-#define UBLK_DAEMON_MONITOR_PERIOD (5 * HZ)
-
struct ublk_device {
struct gendisk *ub_disk;
@@ -166,7 +170,7 @@ struct ublk_device {
struct mutex mutex;
- spinlock_t mm_lock;
+ spinlock_t lock;
struct mm_struct *mm;
struct ublk_params params;
@@ -175,11 +179,6 @@ struct ublk_device {
unsigned int nr_queues_ready;
unsigned int nr_privileged_daemon;
- /*
- * Our ubq->daemon may be killed without any notification, so
- * monitor each queue's daemon periodically
- */
- struct delayed_work monitor_work;
struct work_struct quiesce_work;
struct work_struct stop_work;
};
@@ -190,10 +189,11 @@ struct ublk_params_header {
__u32 types;
};
+static bool ublk_abort_requests(struct ublk_device *ub, struct ublk_queue *ubq);
+
static inline unsigned int ublk_req_build_flags(struct request *req);
static inline struct ublksrv_io_desc *ublk_get_iod(struct ublk_queue *ubq,
int tag);
-
static inline bool ublk_dev_is_user_copy(const struct ublk_device *ub)
{
return ub->dev_info.flags & UBLK_F_USER_COPY;
@@ -470,6 +470,7 @@ static DEFINE_MUTEX(ublk_ctl_mutex);
* It can be extended to one per-user limit in future or even controlled
* by cgroup.
*/
+#define UBLK_MAX_UBLKS UBLK_MINORS
static unsigned int ublks_max = 64;
static unsigned int ublks_added; /* protected by ublk_ctl_mutex */
@@ -1083,13 +1084,10 @@ static void __ublk_fail_req(struct ublk_queue *ubq, struct ublk_io *io,
{
WARN_ON_ONCE(io->flags & UBLK_IO_FLAG_ACTIVE);
- if (!(io->flags & UBLK_IO_FLAG_ABORTED)) {
- io->flags |= UBLK_IO_FLAG_ABORTED;
- if (ublk_queue_can_use_recovery_reissue(ubq))
- blk_mq_requeue_request(req, false);
- else
- ublk_put_req_ref(ubq, req);
- }
+ if (ublk_queue_can_use_recovery_reissue(ubq))
+ blk_mq_requeue_request(req, false);
+ else
+ ublk_put_req_ref(ubq, req);
}
static void ubq_complete_io_cmd(struct ublk_io *io, int res,
@@ -1118,8 +1116,6 @@ static inline void __ublk_abort_rq(struct ublk_queue *ubq,
blk_mq_requeue_request(rq, false);
else
blk_mq_end_request(rq, BLK_STS_IOERR);
-
- mod_delayed_work(system_wq, &ubq->dev->monitor_work, 0);
}
static inline void __ublk_rq_task_work(struct request *req,
@@ -1212,15 +1208,6 @@ static inline void ublk_forward_io_cmds(struct ublk_queue *ubq,
__ublk_rq_task_work(blk_mq_rq_from_pdu(data), issue_flags);
}
-static inline void ublk_abort_io_cmds(struct ublk_queue *ubq)
-{
- struct llist_node *io_cmds = llist_del_all(&ubq->io_cmds);
- struct ublk_rq_data *data, *tmp;
-
- llist_for_each_entry_safe(data, tmp, io_cmds, node)
- __ublk_abort_rq(ubq, blk_mq_rq_from_pdu(data));
-}
-
static void ublk_rq_task_work_cb(struct io_uring_cmd *cmd, unsigned issue_flags)
{
struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
@@ -1232,38 +1219,19 @@ static void ublk_rq_task_work_cb(struct io_uring_cmd *cmd, unsigned issue_flags)
static void ublk_queue_cmd(struct ublk_queue *ubq, struct request *rq)
{
struct ublk_rq_data *data = blk_mq_rq_to_pdu(rq);
- struct ublk_io *io;
- if (!llist_add(&data->node, &ubq->io_cmds))
- return;
+ if (llist_add(&data->node, &ubq->io_cmds)) {
+ struct ublk_io *io = &ubq->ios[rq->tag];
- io = &ubq->ios[rq->tag];
- /*
- * If the check pass, we know that this is a re-issued request aborted
- * previously in monitor_work because the ubq_daemon(cmd's task) is
- * PF_EXITING. We cannot call io_uring_cmd_complete_in_task() anymore
- * because this ioucmd's io_uring context may be freed now if no inflight
- * ioucmd exists. Otherwise we may cause null-deref in ctx->fallback_work.
- *
- * Note: monitor_work sets UBLK_IO_FLAG_ABORTED and ends this request(releasing
- * the tag). Then the request is re-started(allocating the tag) and we are here.
- * Since releasing/allocating a tag implies smp_mb(), finding UBLK_IO_FLAG_ABORTED
- * guarantees that here is a re-issued request aborted previously.
- */
- if (unlikely(io->flags & UBLK_IO_FLAG_ABORTED)) {
- ublk_abort_io_cmds(ubq);
- } else {
- struct io_uring_cmd *cmd = io->cmd;
- struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
-
- pdu->ubq = ubq;
- io_uring_cmd_complete_in_task(cmd, ublk_rq_task_work_cb);
+ io_uring_cmd_complete_in_task(io->cmd, ublk_rq_task_work_cb);
}
}
static enum blk_eh_timer_return ublk_timeout(struct request *rq)
{
struct ublk_queue *ubq = rq->mq_hctx->driver_data;
+ unsigned int nr_inflight = 0;
+ int i;
if (ubq->flags & UBLK_F_UNPRIVILEGED_DEV) {
if (!ubq->timeout) {
@@ -1274,6 +1242,29 @@ static enum blk_eh_timer_return ublk_timeout(struct request *rq)
return BLK_EH_DONE;
}
+ if (!ubq_daemon_is_dying(ubq))
+ return BLK_EH_RESET_TIMER;
+
+ for (i = 0; i < ubq->q_depth; i++) {
+ struct ublk_io *io = &ubq->ios[i];
+
+ if (!(io->flags & UBLK_IO_FLAG_ACTIVE))
+ nr_inflight++;
+ }
+
+ /* cancelable uring_cmd can't help us if all commands are in-flight */
+ if (nr_inflight == ubq->q_depth) {
+ struct ublk_device *ub = ubq->dev;
+
+ if (ublk_abort_requests(ub, ubq)) {
+ if (ublk_can_use_recovery(ub))
+ schedule_work(&ub->quiesce_work);
+ else
+ schedule_work(&ub->stop_work);
+ }
+ return BLK_EH_DONE;
+ }
+
return BLK_EH_RESET_TIMER;
}
@@ -1301,13 +1292,12 @@ static blk_status_t ublk_queue_rq(struct blk_mq_hw_ctx *hctx,
if (ublk_queue_can_use_recovery(ubq) && unlikely(ubq->force_abort))
return BLK_STS_IOERR;
- blk_mq_start_request(bd->rq);
-
- if (unlikely(ubq_daemon_is_dying(ubq))) {
+ if (unlikely(ubq->canceling)) {
__ublk_abort_rq(ubq, rq);
return BLK_STS_OK;
}
+ blk_mq_start_request(bd->rq);
ublk_queue_cmd(ubq, rq);
return BLK_STS_OK;
@@ -1357,12 +1347,12 @@ static int ublk_ch_mmap(struct file *filp, struct vm_area_struct *vma)
unsigned long pfn, end, phys_off = vma->vm_pgoff << PAGE_SHIFT;
int q_id, ret = 0;
- spin_lock(&ub->mm_lock);
+ spin_lock(&ub->lock);
if (!ub->mm)
ub->mm = current->mm;
if (current->mm != ub->mm)
ret = -EINVAL;
- spin_unlock(&ub->mm_lock);
+ spin_unlock(&ub->lock);
if (ret)
return ret;
@@ -1411,17 +1401,14 @@ static void ublk_commit_completion(struct ublk_device *ub,
}
/*
- * When ->ubq_daemon is exiting, either new request is ended immediately,
- * or any queued io command is drained, so it is safe to abort queue
- * lockless
+ * Called from ubq_daemon context via cancel fn, meantime quiesce ublk
+ * blk-mq queue, so we are called exclusively with blk-mq and ubq_daemon
+ * context, so everything is serialized.
*/
static void ublk_abort_queue(struct ublk_device *ub, struct ublk_queue *ubq)
{
int i;
- if (!ublk_get_device(ub))
- return;
-
for (i = 0; i < ubq->q_depth; i++) {
struct ublk_io *io = &ubq->ios[i];
@@ -1433,72 +1420,114 @@ static void ublk_abort_queue(struct ublk_device *ub, struct ublk_queue *ubq)
* will do it
*/
rq = blk_mq_tag_to_rq(ub->tag_set.tags[ubq->q_id], i);
- if (rq)
+ if (rq && blk_mq_request_started(rq)) {
+ io->flags |= UBLK_IO_FLAG_ABORTED;
__ublk_fail_req(ubq, io, rq);
+ }
}
}
- ublk_put_device(ub);
}
-static void ublk_daemon_monitor_work(struct work_struct *work)
+static bool ublk_abort_requests(struct ublk_device *ub, struct ublk_queue *ubq)
{
- struct ublk_device *ub =
- container_of(work, struct ublk_device, monitor_work.work);
- int i;
+ struct gendisk *disk;
- for (i = 0; i < ub->dev_info.nr_hw_queues; i++) {
- struct ublk_queue *ubq = ublk_get_queue(ub, i);
+ spin_lock(&ubq->cancel_lock);
+ if (ubq->canceling) {
+ spin_unlock(&ubq->cancel_lock);
+ return false;
+ }
+ ubq->canceling = true;
+ spin_unlock(&ubq->cancel_lock);
- if (ubq_daemon_is_dying(ubq)) {
- if (ublk_queue_can_use_recovery(ubq))
- schedule_work(&ub->quiesce_work);
- else
- schedule_work(&ub->stop_work);
+ spin_lock(&ub->lock);
+ disk = ub->ub_disk;
+ if (disk)
+ get_device(disk_to_dev(disk));
+ spin_unlock(&ub->lock);
- /* abort queue is for making forward progress */
- ublk_abort_queue(ub, ubq);
- }
- }
+ /* Our disk has been dead */
+ if (!disk)
+ return false;
- /*
- * We can't schedule monitor work after ub's state is not UBLK_S_DEV_LIVE.
- * after ublk_remove() or __ublk_quiesce_dev() is started.
- *
- * No need ub->mutex, monitor work are canceled after state is marked
- * as not LIVE, so new state is observed reliably.
- */
- if (ub->dev_info.state == UBLK_S_DEV_LIVE)
- schedule_delayed_work(&ub->monitor_work,
- UBLK_DAEMON_MONITOR_PERIOD);
-}
+ /* Now we are serialized with ublk_queue_rq() */
+ blk_mq_quiesce_queue(disk->queue);
+ /* abort queue is for making forward progress */
+ ublk_abort_queue(ub, ubq);
+ blk_mq_unquiesce_queue(disk->queue);
+ put_device(disk_to_dev(disk));
-static inline bool ublk_queue_ready(struct ublk_queue *ubq)
-{
- return ubq->nr_io_ready == ubq->q_depth;
+ return true;
}
-static void ublk_cmd_cancel_cb(struct io_uring_cmd *cmd, unsigned issue_flags)
+static void ublk_cancel_cmd(struct ublk_queue *ubq, struct ublk_io *io,
+ unsigned int issue_flags)
{
- io_uring_cmd_done(cmd, UBLK_IO_RES_ABORT, 0, issue_flags);
+ bool done;
+
+ if (!(io->flags & UBLK_IO_FLAG_ACTIVE))
+ return;
+
+ spin_lock(&ubq->cancel_lock);
+ done = !!(io->flags & UBLK_IO_FLAG_CANCELED);
+ if (!done)
+ io->flags |= UBLK_IO_FLAG_CANCELED;
+ spin_unlock(&ubq->cancel_lock);
+
+ if (!done)
+ io_uring_cmd_done(io->cmd, UBLK_IO_RES_ABORT, 0, issue_flags);
}
-static void ublk_cancel_queue(struct ublk_queue *ubq)
+/*
+ * The ublk char device won't be closed when calling cancel fn, so both
+ * ublk device and queue are guaranteed to be live
+ */
+static void ublk_uring_cmd_cancel_fn(struct io_uring_cmd *cmd,
+ unsigned int issue_flags)
{
- int i;
+ struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
+ struct ublk_queue *ubq = pdu->ubq;
+ struct task_struct *task;
+ struct ublk_device *ub;
+ bool need_schedule;
+ struct ublk_io *io;
- if (!ublk_queue_ready(ubq))
+ if (WARN_ON_ONCE(!ubq))
return;
- for (i = 0; i < ubq->q_depth; i++) {
- struct ublk_io *io = &ubq->ios[i];
+ if (WARN_ON_ONCE(pdu->tag >= ubq->q_depth))
+ return;
+
+ task = io_uring_cmd_get_task(cmd);
+ if (WARN_ON_ONCE(task && task != ubq->ubq_daemon))
+ return;
+
+ ub = ubq->dev;
+ need_schedule = ublk_abort_requests(ub, ubq);
+
+ io = &ubq->ios[pdu->tag];
+ WARN_ON_ONCE(io->cmd != cmd);
+ ublk_cancel_cmd(ubq, io, issue_flags);
- if (io->flags & UBLK_IO_FLAG_ACTIVE)
- io_uring_cmd_complete_in_task(io->cmd,
- ublk_cmd_cancel_cb);
+ if (need_schedule) {
+ if (ublk_can_use_recovery(ub))
+ schedule_work(&ub->quiesce_work);
+ else
+ schedule_work(&ub->stop_work);
}
+}
- /* all io commands are canceled */
- ubq->nr_io_ready = 0;
+static inline bool ublk_queue_ready(struct ublk_queue *ubq)
+{
+ return ubq->nr_io_ready == ubq->q_depth;
+}
+
+static void ublk_cancel_queue(struct ublk_queue *ubq)
+{
+ int i;
+
+ for (i = 0; i < ubq->q_depth; i++)
+ ublk_cancel_cmd(ubq, &ubq->ios[i], IO_URING_F_UNLOCKED);
}
/* Cancel all pending commands, must be called after del_gendisk() returns */
@@ -1545,16 +1574,6 @@ static void __ublk_quiesce_dev(struct ublk_device *ub)
blk_mq_quiesce_queue(ub->ub_disk->queue);
ublk_wait_tagset_rqs_idle(ub);
ub->dev_info.state = UBLK_S_DEV_QUIESCED;
- ublk_cancel_dev(ub);
- /* we are going to release task_struct of ubq_daemon and resets
- * ->ubq_daemon to NULL. So in monitor_work, check on ubq_daemon causes UAF.
- * Besides, monitor_work is not necessary in QUIESCED state since we have
- * already scheduled quiesce_work and quiesced all ubqs.
- *
- * Do not let monitor_work schedule itself if state it QUIESCED. And we cancel
- * it here and re-schedule it in END_USER_RECOVERY to avoid UAF.
- */
- cancel_delayed_work_sync(&ub->monitor_work);
}
static void ublk_quiesce_work_fn(struct work_struct *work)
@@ -1568,6 +1587,7 @@ static void ublk_quiesce_work_fn(struct work_struct *work)
__ublk_quiesce_dev(ub);
unlock:
mutex_unlock(&ub->mutex);
+ ublk_cancel_dev(ub);
}
static void ublk_unquiesce_dev(struct ublk_device *ub)
@@ -1593,6 +1613,8 @@ static void ublk_unquiesce_dev(struct ublk_device *ub)
static void ublk_stop_dev(struct ublk_device *ub)
{
+ struct gendisk *disk;
+
mutex_lock(&ub->mutex);
if (ub->dev_info.state == UBLK_S_DEV_DEAD)
goto unlock;
@@ -1602,14 +1624,18 @@ static void ublk_stop_dev(struct ublk_device *ub)
ublk_unquiesce_dev(ub);
}
del_gendisk(ub->ub_disk);
+
+ /* Sync with ublk_abort_queue() by holding the lock */
+ spin_lock(&ub->lock);
+ disk = ub->ub_disk;
ub->dev_info.state = UBLK_S_DEV_DEAD;
ub->dev_info.ublksrv_pid = -1;
- put_disk(ub->ub_disk);
ub->ub_disk = NULL;
+ spin_unlock(&ub->lock);
+ put_disk(disk);
unlock:
- ublk_cancel_dev(ub);
mutex_unlock(&ub->mutex);
- cancel_delayed_work_sync(&ub->monitor_work);
+ ublk_cancel_dev(ub);
}
/* device can only be started after all IOs are ready */
@@ -1660,6 +1686,21 @@ static inline void ublk_fill_io_cmd(struct ublk_io *io,
io->addr = buf_addr;
}
+static inline void ublk_prep_cancel(struct io_uring_cmd *cmd,
+ unsigned int issue_flags,
+ struct ublk_queue *ubq, unsigned int tag)
+{
+ struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
+
+ /*
+ * Safe to refer to @ubq since ublk_queue won't be died until its
+ * commands are completed
+ */
+ pdu->ubq = ubq;
+ pdu->tag = tag;
+ io_uring_cmd_mark_cancelable(cmd, issue_flags);
+}
+
static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
unsigned int issue_flags,
const struct ublksrv_io_cmd *ub_cmd)
@@ -1775,6 +1816,7 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
default:
goto out;
}
+ ublk_prep_cancel(cmd, issue_flags, ubq, tag);
return -EIOCBQUEUED;
out:
@@ -1814,7 +1856,8 @@ fail_put:
return NULL;
}
-static int ublk_ch_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
+static inline int ublk_ch_uring_cmd_local(struct io_uring_cmd *cmd,
+ unsigned int issue_flags)
{
/*
* Not necessary for async retry, but let's keep it simple and always
@@ -1828,9 +1871,33 @@ static int ublk_ch_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
.addr = READ_ONCE(ub_src->addr)
};
+ WARN_ON_ONCE(issue_flags & IO_URING_F_UNLOCKED);
+
return __ublk_ch_uring_cmd(cmd, issue_flags, &ub_cmd);
}
+static void ublk_ch_uring_cmd_cb(struct io_uring_cmd *cmd,
+ unsigned int issue_flags)
+{
+ ublk_ch_uring_cmd_local(cmd, issue_flags);
+}
+
+static int ublk_ch_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
+{
+ if (unlikely(issue_flags & IO_URING_F_CANCEL)) {
+ ublk_uring_cmd_cancel_fn(cmd, issue_flags);
+ return 0;
+ }
+
+ /* well-implemented server won't run into unlocked */
+ if (unlikely(issue_flags & IO_URING_F_UNLOCKED)) {
+ io_uring_cmd_complete_in_task(cmd, ublk_ch_uring_cmd_cb);
+ return -EIOCBQUEUED;
+ }
+
+ return ublk_ch_uring_cmd_local(cmd, issue_flags);
+}
+
static inline bool ublk_check_ubuf_dir(const struct request *req,
int ubuf_dir)
{
@@ -1962,6 +2029,7 @@ static int ublk_init_queue(struct ublk_device *ub, int q_id)
void *ptr;
int size;
+ spin_lock_init(&ubq->cancel_lock);
ubq->flags = ub->dev_info.flags;
ubq->q_id = q_id;
ubq->q_depth = ub->dev_info.queue_depth;
@@ -2026,7 +2094,8 @@ static int ublk_alloc_dev_number(struct ublk_device *ub, int idx)
if (err == -ENOSPC)
err = -EEXIST;
} else {
- err = idr_alloc(&ublk_index_idr, ub, 0, 0, GFP_NOWAIT);
+ err = idr_alloc(&ublk_index_idr, ub, 0, UBLK_MAX_UBLKS,
+ GFP_NOWAIT);
}
spin_unlock(&ublk_idr_lock);
@@ -2151,8 +2220,6 @@ static int ublk_ctrl_start_dev(struct ublk_device *ub, struct io_uring_cmd *cmd)
if (wait_for_completion_interruptible(&ub->completion) != 0)
return -EINTR;
- schedule_delayed_work(&ub->monitor_work, UBLK_DAEMON_MONITOR_PERIOD);
-
mutex_lock(&ub->mutex);
if (ub->dev_info.state == UBLK_S_DEV_LIVE ||
test_bit(UB_STATE_USED, &ub->state)) {
@@ -2305,6 +2372,12 @@ static int ublk_ctrl_add_dev(struct io_uring_cmd *cmd)
return -EINVAL;
}
+ if (header->dev_id != U32_MAX && header->dev_id >= UBLK_MAX_UBLKS) {
+ pr_warn("%s: dev id is too large. Max supported is %d\n",
+ __func__, UBLK_MAX_UBLKS - 1);
+ return -EINVAL;
+ }
+
ublk_dump_dev_info(&info);
ret = mutex_lock_killable(&ublk_ctl_mutex);
@@ -2320,10 +2393,9 @@ static int ublk_ctrl_add_dev(struct io_uring_cmd *cmd)
if (!ub)
goto out_unlock;
mutex_init(&ub->mutex);
- spin_lock_init(&ub->mm_lock);
+ spin_lock_init(&ub->lock);
INIT_WORK(&ub->quiesce_work, ublk_quiesce_work_fn);
INIT_WORK(&ub->stop_work, ublk_stop_work_fn);
- INIT_DELAYED_WORK(&ub->monitor_work, ublk_daemon_monitor_work);
ret = ublk_alloc_dev_number(ub, header->dev_id);
if (ret < 0)
@@ -2569,13 +2641,15 @@ static void ublk_queue_reinit(struct ublk_device *ub, struct ublk_queue *ubq)
int i;
WARN_ON_ONCE(!(ubq->ubq_daemon && ubq_daemon_is_dying(ubq)));
+
/* All old ioucmds have to be completed */
- WARN_ON_ONCE(ubq->nr_io_ready);
+ ubq->nr_io_ready = 0;
/* old daemon is PF_EXITING, put it now */
put_task_struct(ubq->ubq_daemon);
/* We have to reset it to NULL, otherwise ub won't accept new FETCH_REQ */
ubq->ubq_daemon = NULL;
ubq->timeout = false;
+ ubq->canceling = false;
for (i = 0; i < ubq->q_depth; i++) {
struct ublk_io *io = &ubq->ios[i];
@@ -2661,7 +2735,6 @@ static int ublk_ctrl_end_recovery(struct ublk_device *ub,
__func__, header->dev_id);
blk_mq_kick_requeue_list(ub->ub_disk->queue);
ub->dev_info.state = UBLK_S_DEV_LIVE;
- schedule_delayed_work(&ub->monitor_work, UBLK_DAEMON_MONITOR_PERIOD);
ret = 0;
out_unlock:
mutex_unlock(&ub->mutex);
@@ -2932,7 +3005,22 @@ static void __exit ublk_exit(void)
module_init(ublk_init);
module_exit(ublk_exit);
-module_param(ublks_max, int, 0444);
+static int ublk_set_max_ublks(const char *buf, const struct kernel_param *kp)
+{
+ return param_set_uint_minmax(buf, kp, 0, UBLK_MAX_UBLKS);
+}
+
+static int ublk_get_max_ublks(char *buf, const struct kernel_param *kp)
+{
+ return sysfs_emit(buf, "%u\n", ublks_max);
+}
+
+static const struct kernel_param_ops ublk_max_ublks_ops = {
+ .set = ublk_set_max_ublks,
+ .get = ublk_get_max_ublks,
+};
+
+module_param_cb(ublks_max, &ublk_max_ublks_ops, &ublks_max, 0644);
MODULE_PARM_DESC(ublks_max, "max number of ublk devices allowed to add(default: 64)");
MODULE_AUTHOR("Ming Lei <ming.lei@redhat.com>");