[PATCH V4 1/1] nvmet: support reservation feature
Guixin Liu
kanie at linux.alibaba.com
Mon Jan 29 19:09:35 PST 2024
在 2024/1/29 18:40, Sagi Grimberg 写道:
>
>
> On 1/23/24 11:45, Guixin Liu wrote:
>>
>> 在 2024/1/22 21:03, Sagi Grimberg 写道:
>>>
>>>> This patch implements the reservation feature, includes:
>>>> 1. reservation register(register, unregister and replace).
>>>> 2. reservation acquire(acquire, preempt, preempt and abort).
>>>> 3. reservation release(release and clear).
>>>> 4. reservation report.
>>>>
>>>> And also make reservation configurable, one can set ns to support
>>>> reservation before enable ns. The default of resv_enable is false.
>>>>
>>>> Signed-off-by: Guixin Liu <kanie at linux.alibaba.com>
>>>> ---
>>>> drivers/nvme/target/Makefile | 2 +-
>>>> drivers/nvme/target/admin-cmd.c | 14 +-
>>>> drivers/nvme/target/configfs.c | 27 +
>>>> drivers/nvme/target/core.c | 50 +-
>>>> drivers/nvme/target/nvmet.h | 35 ++
>>>> drivers/nvme/target/pr.c | 956
>>>> ++++++++++++++++++++++++++++++++
>>>> include/linux/nvme.h | 48 ++
>>>> 7 files changed, 1125 insertions(+), 7 deletions(-)
>>>> create mode 100644 drivers/nvme/target/pr.c
>>>>
>>>> diff --git a/drivers/nvme/target/Makefile
>>>> b/drivers/nvme/target/Makefile
>>>> index c66820102493..f9bfc904a5b3 100644
>>>> --- a/drivers/nvme/target/Makefile
>>>> +++ b/drivers/nvme/target/Makefile
>>>> @@ -10,7 +10,7 @@ obj-$(CONFIG_NVME_TARGET_FCLOOP) += nvme-fcloop.o
>>>> obj-$(CONFIG_NVME_TARGET_TCP) += nvmet-tcp.o
>>>> nvmet-y += core.o configfs.o admin-cmd.o fabrics-cmd.o \
>>>> - discovery.o io-cmd-file.o io-cmd-bdev.o
>>>> + discovery.o io-cmd-file.o io-cmd-bdev.o pr.o
>>>> nvmet-$(CONFIG_NVME_TARGET_PASSTHRU) += passthru.o
>>>> nvmet-$(CONFIG_BLK_DEV_ZONED) += zns.o
>>>> nvmet-$(CONFIG_NVME_TARGET_AUTH) += fabrics-cmd-auth.o auth.o
>>>> diff --git a/drivers/nvme/target/admin-cmd.c
>>>> b/drivers/nvme/target/admin-cmd.c
>>>> index 39cb570f833d..791bc7e740c0 100644
>>>> --- a/drivers/nvme/target/admin-cmd.c
>>>> +++ b/drivers/nvme/target/admin-cmd.c
>>>> @@ -176,6 +176,10 @@ static void nvmet_get_cmd_effects_nvm(struct
>>>> nvme_effects_log *log)
>>>> log->iocs[nvme_cmd_read] =
>>>> log->iocs[nvme_cmd_flush] =
>>>> log->iocs[nvme_cmd_dsm] =
>>>> + log->iocs[nvme_cmd_resv_acquire] =
>>>> + log->iocs[nvme_cmd_resv_register] =
>>>> + log->iocs[nvme_cmd_resv_release] =
>>>> + log->iocs[nvme_cmd_resv_report] =
>>>> cpu_to_le32(NVME_CMD_EFFECTS_CSUPP);
>>>> log->iocs[nvme_cmd_write] =
>>>> log->iocs[nvme_cmd_write_zeroes] =
>>>> @@ -340,6 +344,8 @@ static void nvmet_execute_get_log_page(struct
>>>> nvmet_req *req)
>>>> return nvmet_execute_get_log_cmd_effects_ns(req);
>>>> case NVME_LOG_ANA:
>>>> return nvmet_execute_get_log_page_ana(req);
>>>> + case NVME_LOG_RESERVATION:
>>>> + return nvmet_execute_get_log_page_resv(req);
>>>> }
>>>> pr_debug("unhandled lid %d on qid %d\n",
>>>> req->cmd->get_log_page.lid, req->sq->qid);
>>>> @@ -550,7 +556,13 @@ static void nvmet_execute_identify_ns(struct
>>>> nvmet_req *req)
>>>> */
>>>> id->nmic = NVME_NS_NMIC_SHARED;
>>>> id->anagrpid = cpu_to_le32(req->ns->anagrpid);
>>>> -
>>>> + id->rescap = NVME_PR_SUPPORT_WRITE_EXCLUSIVE |
>>>> + NVME_PR_SUPPORT_EXCLUSIVE_ACCESS |
>>>> + NVME_PR_SUPPORT_WRITE_EXCLUSIVE_REG_ONLY |
>>>> + NVME_PR_SUPPORT_EXCLUSIVE_ACCESS_REG_ONLY |
>>>> + NVME_PR_SUPPORT_WRITE_EXCLUSIVE_ALL_REGS |
>>>> + NVME_PR_SUPPORT_EXCLUSIVE_ACCESS_ALL_REGS |
>>>> + NVME_PR_SUPPORT_IEKEY_VER_1_3_DEF;
>>>> memcpy(&id->nguid, &req->ns->nguid, sizeof(id->nguid));
>>>> id->lbaf[0].ds = req->ns->blksize_shift;
>>>> diff --git a/drivers/nvme/target/configfs.c
>>>> b/drivers/nvme/target/configfs.c
>>>> index d937fe05129e..1ac4802ec818 100644
>>>> --- a/drivers/nvme/target/configfs.c
>>>> +++ b/drivers/nvme/target/configfs.c
>>>> @@ -714,6 +714,32 @@ static ssize_t
>>>> nvmet_ns_revalidate_size_store(struct config_item *item,
>>>> CONFIGFS_ATTR_WO(nvmet_ns_, revalidate_size);
>>>> +static ssize_t nvmet_ns_resv_enable_show(struct config_item
>>>> *item, char *page)
>>>> +{
>>>> + return sprintf(page, "%d\n", to_nvmet_ns(item)->pr.enable);
>>>> +}
>>>> +
>>>> +static ssize_t nvmet_ns_resv_enable_store(struct config_item *item,
>>>> + const char *page, size_t count)
>>>> +{
>>>> + struct nvmet_ns *ns = to_nvmet_ns(item);
>>>> + bool val;
>>>> +
>>>> + if (kstrtobool(page, &val))
>>>> + return -EINVAL;
>>>> +
>>>> + mutex_lock(&ns->subsys->lock);
>>>> + if (ns->enabled) {
>>>> + pr_err("the ns:%d is already enabled.\n", ns->nsid);
>>>> + mutex_unlock(&ns->subsys->lock);
>>>> + return -EINVAL;
>>>> + }
>>>> + ns->pr.enable = val;
>>>> + mutex_unlock(&ns->subsys->lock);
>>>> + return count;
>>>> +}
>>>> +CONFIGFS_ATTR(nvmet_ns_, resv_enable);
>>>> +
>>>> static struct configfs_attribute *nvmet_ns_attrs[] = {
>>>> &nvmet_ns_attr_device_path,
>>>> &nvmet_ns_attr_device_nguid,
>>>> @@ -722,6 +748,7 @@ static struct configfs_attribute
>>>> *nvmet_ns_attrs[] = {
>>>> &nvmet_ns_attr_enable,
>>>> &nvmet_ns_attr_buffered_io,
>>>> &nvmet_ns_attr_revalidate_size,
>>>> + &nvmet_ns_attr_resv_enable,
>>>> #ifdef CONFIG_PCI_P2PDMA
>>>> &nvmet_ns_attr_p2pmem,
>>>> #endif
>>>> diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
>>>> index 3935165048e7..5bacffc59848 100644
>>>> --- a/drivers/nvme/target/core.c
>>>> +++ b/drivers/nvme/target/core.c
>>>> @@ -591,6 +591,8 @@ int nvmet_ns_enable(struct nvmet_ns *ns)
>>>> if (ns->nsid > subsys->max_nsid)
>>>> subsys->max_nsid = ns->nsid;
>>>> + nvmet_pr_init_ns(ns);
>>>> +
>>>> ret = xa_insert(&subsys->namespaces, ns->nsid, ns, GFP_KERNEL);
>>>> if (ret)
>>>> goto out_restore_subsys_maxnsid;
>>>> @@ -651,6 +653,7 @@ void nvmet_ns_disable(struct nvmet_ns *ns)
>>>> subsys->nr_namespaces--;
>>>> nvmet_ns_changed(subsys, ns->nsid);
>>>> + nvmet_pr_exit_ns(ns);
>>>> nvmet_ns_dev_disable(ns);
>>>> out_unlock:
>>>> mutex_unlock(&subsys->lock);
>>>> @@ -904,18 +907,34 @@ static u16 nvmet_parse_io_cmd(struct
>>>> nvmet_req *req)
>>>> return ret;
>>>> }
>>>> + if (req->ns->pr.enable) {
>>>> + ret = nvmet_parse_pr_cmd(req);
>>>> + if (!ret)
>>>> + return ret;
>>>> + }
>>>> +
>>>> switch (req->ns->csi) {
>>>> case NVME_CSI_NVM:
>>>> if (req->ns->file)
>>>> - return nvmet_file_parse_io_cmd(req);
>>>> - return nvmet_bdev_parse_io_cmd(req);
>>>> + ret = nvmet_file_parse_io_cmd(req);
>>>> + else
>>>> + ret = nvmet_bdev_parse_io_cmd(req);
>>>> + break;
>>>> case NVME_CSI_ZNS:
>>>> if (IS_ENABLED(CONFIG_BLK_DEV_ZONED))
>>>> - return nvmet_bdev_zns_parse_io_cmd(req);
>>>> - return NVME_SC_INVALID_IO_CMD_SET;
>>>> + ret = nvmet_bdev_zns_parse_io_cmd(req);
>>>> + else
>>>> + ret = NVME_SC_INVALID_IO_CMD_SET;
>>>> + break;
>>>> default:
>>>> - return NVME_SC_INVALID_IO_CMD_SET;
>>>> + ret = NVME_SC_INVALID_IO_CMD_SET;
>>>> }
>>>> + if (ret)
>>>> + return ret;
>>>> +
>>>> + if (req->ns->pr.enable)
>>>> + ret = nvmet_pr_check_cmd_access(req);
>>>> + return ret;
>>>> }
>>>> bool nvmet_req_init(struct nvmet_req *req, struct nvmet_cq *cq,
>>>> @@ -1231,6 +1250,21 @@ static void nvmet_init_cap(struct nvmet_ctrl
>>>> *ctrl)
>>>> nvmet_passthrough_override_cap(ctrl);
>>>> }
>>>> +bool nvmet_is_host_still_connected(uuid_t *hostid, struct
>>>> nvmet_subsys *subsys)
>>>> +{
>>>> + struct nvmet_ctrl *ctrl;
>>>> +
>>>> + mutex_lock(&subsys->lock);
>>>> + list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry) {
>>>> + if (uuid_equal(hostid, &ctrl->hostid)) {
>>>> + mutex_unlock(&subsys->lock);
>>>> + return true;
>>>
>>> Perhaps its cleaner to do:
>>> ret = true;
>>> break;
>>>
>> OK, changed in v5.
>>>> + }
>>>> + }
>>>> + mutex_unlock(&subsys->lock);
>>>> + return false;
>>>> +}
>>>> +
>>>> struct nvmet_ctrl *nvmet_ctrl_find_get(const char *subsysnqn,
>>>> const char *hostnqn, u16 cntlid,
>>>> struct nvmet_req *req)
>>>> @@ -1450,6 +1484,11 @@ u16 nvmet_alloc_ctrl(const char *subsysnqn,
>>>> const char *hostnqn,
>>>> ctrl->err_counter = 0;
>>>> spin_lock_init(&ctrl->error_lock);
>>>> + ctrl->pr_log_mgr.counter = 0;
>>>> + ctrl->pr_log_mgr.lost_count = 0;
>>>> + mutex_init(&ctrl->pr_log_mgr.lock);
>>>> + INIT_KFIFO(ctrl->pr_log_mgr.log_queue);
>>>> +
>>>> nvmet_start_keep_alive_timer(ctrl);
>>>> mutex_lock(&subsys->lock);
>>>> @@ -1488,6 +1527,7 @@ static void nvmet_ctrl_free(struct kref *ref)
>>>> cancel_work_sync(&ctrl->fatal_err_work);
>>>> nvmet_destroy_auth(ctrl);
>>>> + nvmet_ctrl_destroy_pr(ctrl);
>>>> ida_free(&cntlid_ida, ctrl->cntlid);
>>>> diff --git a/drivers/nvme/target/nvmet.h
>>>> b/drivers/nvme/target/nvmet.h
>>>> index 6c8acebe1a1a..b6facb243977 100644
>>>> --- a/drivers/nvme/target/nvmet.h
>>>> +++ b/drivers/nvme/target/nvmet.h
>>>> @@ -20,6 +20,7 @@
>>>> #include <linux/blkdev.h>
>>>> #include <linux/radix-tree.h>
>>>> #include <linux/t10-pi.h>
>>>> +#include <linux/kfifo.h>
>>>> #define NVMET_DEFAULT_VS NVME_VS(1, 3, 0)
>>>> @@ -30,6 +31,7 @@
>>>> #define NVMET_MN_MAX_SIZE 40
>>>> #define NVMET_SN_MAX_SIZE 20
>>>> #define NVMET_FR_MAX_SIZE 8
>>>> +#define NVMET_PR_LOG_QUEUE_SIZE 64
>>>> /*
>>>> * Supported optional AENs:
>>>> @@ -56,6 +58,22 @@
>>>> #define IPO_IATTR_CONNECT_SQE(x) \
>>>> (cpu_to_le32(offsetof(struct nvmf_connect_command, x)))
>>>> +struct nvmet_pr_registrant {
>>>> + u64 rkey;
>>>> + uuid_t hostid;
>>>> + enum nvme_pr_type rtype;
>>>> + struct list_head entry;
>>>> + struct rcu_head rcu;
>>>> +};
>>>> +
>>>> +struct nvmet_pr {
>>>> + bool enable;
>>>> + atomic_t generation;
>>>> + struct nvmet_pr_registrant __rcu *holder;
>>>> + struct mutex pr_lock;
>>>> + struct list_head registrant_list;
>>>> +};
>>>> +
>>>> struct nvmet_ns {
>>>> struct percpu_ref ref;
>>>> struct bdev_handle *bdev_handle;
>>>> @@ -85,6 +103,7 @@ struct nvmet_ns {
>>>> int pi_type;
>>>> int metadata_size;
>>>> u8 csi;
>>>> + struct nvmet_pr pr;
>>>> };
>>>> static inline struct nvmet_ns *to_nvmet_ns(struct config_item
>>>> *item)
>>>> @@ -190,6 +209,13 @@ static inline bool
>>>> nvmet_port_secure_channel_required(struct nvmet_port *port)
>>>> return nvmet_port_disc_addr_treq_secure_channel(port) ==
>>>> NVMF_TREQ_REQUIRED;
>>>> }
>>>> +struct nvmet_pr_log_mgr {
>>>> + struct mutex lock;
>>>> + u64 lost_count;
>>>> + u64 counter;
>>>> + DECLARE_KFIFO(log_queue, struct nvme_pr_log,
>>>> NVMET_PR_LOG_QUEUE_SIZE);
>>>> +};
>>>> +
>>>> struct nvmet_ctrl {
>>>> struct nvmet_subsys *subsys;
>>>> struct nvmet_sq **sqs;
>>>> @@ -243,6 +269,7 @@ struct nvmet_ctrl {
>>>> u8 *dh_key;
>>>> size_t dh_keysize;
>>>> #endif
>>>> + struct nvmet_pr_log_mgr pr_log_mgr;
>>>> };
>>>> struct nvmet_subsys {
>>>> @@ -750,4 +777,12 @@ static inline bool nvmet_has_auth(struct
>>>> nvmet_ctrl *ctrl)
>>>> static inline const char *nvmet_dhchap_dhgroup_name(u8 dhgid) {
>>>> return NULL; }
>>>> #endif
>>>> +void nvmet_pr_init_ns(struct nvmet_ns *ns);
>>>> +u16 nvmet_parse_pr_cmd(struct nvmet_req *req);
>>>> +u16 nvmet_pr_check_cmd_access(struct nvmet_req *req);
>>>> +void nvmet_ctrl_destroy_pr(struct nvmet_ctrl *ctrl);
>>>> +void nvmet_pr_exit_ns(struct nvmet_ns *ns);
>>>> +bool nvmet_is_host_still_connected(uuid_t *hostid, struct
>>>> nvmet_subsys *subsys);
>>>> +void nvmet_execute_get_log_page_resv(struct nvmet_req *req);
>>>> +
>>>> #endif /* _NVMET_H */
>>>> diff --git a/drivers/nvme/target/pr.c b/drivers/nvme/target/pr.c
>>>> new file mode 100644
>>>> index 000000000000..df71fd23ee47
>>>> --- /dev/null
>>>> +++ b/drivers/nvme/target/pr.c
>>>> @@ -0,0 +1,956 @@
>>>> +// SPDX-License-Identifier: GPL-2.0
>>>> +/*
>>>> + * NVMe over Fabrics Persist Reservation.
>>>> + * Copyright (c) 2024 Guixin Liu, Alibaba Group.
>>>> + * All rights reserved.
>>>> + */
>>>> +#include "nvmet.h"
>>>> +#include <linux/slab.h>
>>>> +#include <asm/unaligned.h>
>>>> +
>>>> +struct nvmet_pr_register_data {
>>>> + __le64 crkey;
>>>> + __le64 nrkey;
>>>> +};
>>>> +
>>>> +struct nvmet_pr_acquire_data {
>>>> + __le64 crkey;
>>>> + __le64 prkey;
>>>> +};
>>>> +
>>>> +struct nvmet_pr_release_data {
>>>> + __le64 crkey;
>>>> +};
>>>> +
>>>> +static inline struct nvmet_ns *nvmet_pr_to_ns(struct nvmet_pr *pr)
>>>> +{
>>>> + return container_of(pr, struct nvmet_ns, pr);
>>>> +}
>>>> +
>>>> +static u16 nvmet_pr_validate_rtype(u8 rtype)
>>>> +{
>>>> + if (rtype < NVME_PR_WRITE_EXCLUSIVE ||
>>>> + rtype > NVME_PR_EXCLUSIVE_ACCESS_ALL_REGS)
>>>> + return NVME_SC_INVALID_FIELD | NVME_SC_DNR;
>>>> +
>>>> + return NVME_SC_SUCCESS;
>>>> +}
>>>> +
>>>> +static u16 nvmet_pr_set_rtype_and_holder(struct nvmet_pr *pr, u8
>>>> rtype,
>>>> + struct nvmet_pr_registrant *reg)
>>>> +{
>>>> + u16 status;
>>>> +
>>>> + status = nvmet_pr_validate_rtype(rtype);
>>>> + if (!status) {
>>>> + reg->rtype = rtype;
>>>> + rcu_assign_pointer(pr->holder, reg);
>>>
>>> synchronize_rcu to have rcu grace period elapse?
>>>
>> rcu_assign_pointer ensures that all reads after it will see the new
>> value,
>>
>> we only need to ensure that there are no reads before the old value
>> free, the
>>
>> kfree_rcu can make sure that.
>>
>>>> + }
>>>> + return status;
>>>> +}
>>>> +
>>>> +static struct nvmet_pr_registrant *
>>>> +nvmet_pr_find_registrant_by_hostid(struct nvmet_pr *pr, uuid_t
>>>> *hostid)
>>>> +{
>>>> + struct nvmet_pr_registrant *reg;
>>>
>>> Perhaps lockdep_assert_held annotation here?
>>>
>> OK, it will be added in v5.
>>>> +
>>>> + list_for_each_entry_rcu(reg, &pr->registrant_list, entry) {
>>>
>>> is registrant_list protected by rcu?
>> Yes.
>>>
>>>> + if (uuid_equal(®->hostid, hostid))
>>>> + return reg;
>>>> + }
>>>> + return NULL;
>>>> +}
>>>> +
>>>> +void nvmet_execute_get_log_page_resv(struct nvmet_req *req)
>>>> +{
>>>> + struct nvmet_pr_log_mgr *log_mgr = &req->sq->ctrl->pr_log_mgr;
>>>> + struct nvme_pr_log next_log = {0};
>>>> + struct nvme_pr_log log = {0};
>>>> + u16 status = NVME_SC_SUCCESS;
>>>> + u64 lost_count;
>>>> + u64 cur_count;
>>>> + u64 next_count;
>>>> +
>>>> + mutex_lock(&log_mgr->lock);
>>>> + if (!kfifo_get(&log_mgr->log_queue, &log))
>>>> + goto out;
>>>> +
>>>> + cur_count = le64_to_cpu(log.count);
>>>> + if (kfifo_peek(&log_mgr->log_queue, &next_log)) {
>>>> + next_count = le64_to_cpu(next_log.count);
>>>> + if (next_count > cur_count)
>>>> + lost_count = next_count - cur_count - 1;
>>>> + else
>>>> + lost_count = U64_MAX - cur_count + next_count - 1;
>>>> + } else {
>>>> + lost_count = log_mgr->lost_count;
>>>> + }
>>>> +
>>>> + log.count = cpu_to_le64(cur_count + lost_count);
>>>> + log_mgr->lost_count -= lost_count;
>>>
>>> We need some code comments to say how the count/lost_count are managed
>>> because it looks slightly convoluted here.
>>>
>> Sure, it will be added in v5.
>>>> +
>>>> + log.nr_pages = min(kfifo_len(&log_mgr->log_queue) /
>>>> + sizeof(struct nvme_pr_log), 255);
>>>> +
>>>> + status = nvmet_copy_to_sgl(req, 0, &log, sizeof(log));
>>>> +
>>>> +out:
>>>> + mutex_unlock(&log_mgr->lock);
>>>> + nvmet_req_complete(req, status);
>>>> +}
>>>> +
>>>> +static void nvmet_pr_add_resv_log(struct nvmet_ctrl *ctrl, u8
>>>> log_type, u32 nsid)
>>>> +{
>>>> + struct nvmet_pr_log_mgr *log_mgr = &ctrl->pr_log_mgr;
>>>> + struct nvme_pr_log log = {0};
>>>> +
>>>> + mutex_lock(&log_mgr->lock);
>>>> + log_mgr->counter++;
>>>> + if (log_mgr->counter == 0)
>>>> + log_mgr->counter = 1;
>>>> +
>>>> + log.count = cpu_to_le64(log_mgr->counter);
>>>> + log.type = log_type;
>>>> + log.nsid = cpu_to_le32(nsid);
>>>> +
>>>> + if (!kfifo_put(&log_mgr->log_queue, log)) {
>>>> + pr_warn("a reservation log lost, cntlid:%d, log_type:%d,
>>>> nsid:%d\n",
>>>> + ctrl->cntlid, log_type, nsid);
>>>> + log_mgr->lost_count++;
>>>> + }
>>>
>>> It'd be good to have a blktest for lost events.
>>>
>> I have write a script to test this, but when I use v2.0 nvme-cli to
>> establish two
>>
>> connections to a same target with different hostnqn and hostid, the
>> v1.6 nvme-cli
>>
>> still work, I found that the 07d6b911e in nvme-cli limited this.
>>
>> And I should close the nvme-multipath also.
>>
>>>> +
>>>> + mutex_unlock(&log_mgr->lock);
>>>> +}
>>>> +
>>>> +static void nvmet_pr_send_resv_released(struct nvmet_pr *pr,
>>>> uuid_t *hostid)
>>>> +{
>>>> + struct nvmet_ns *ns = nvmet_pr_to_ns(pr);
>>>> + struct nvmet_subsys *subsys = ns->subsys;
>>>> + struct nvmet_ctrl *ctrl;
>>>> +
>>>> + mutex_lock(&subsys->lock);
>>>> + list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry) {
>>>> + if (!uuid_equal(&ctrl->hostid, hostid) &&
>>>> + nvmet_pr_find_registrant_by_hostid(pr, &ctrl->hostid)) {
>>>> + nvmet_pr_add_resv_log(ctrl,
>>>> + NVME_PR_LOG_RESERVATION_RELEASED, ns->nsid);
>>>> + nvmet_add_async_event(ctrl, NVME_AER_CSS,
>>>> + NVME_AEN_RESV_LOG_PAGE_AVALIABLE,
>>>> + NVME_LOG_RESERVATION);
>>>> + }
>>>> + }
>>>> + mutex_unlock(&subsys->lock);
>>>
>>> Wondering if this can consolidate also to nvmet_pr_send_event_by_hostid
>>> but with a filter? Not a must though (don't want to make the interface
>>> too complicated).
>>>
>>>
>> Yes, this will make function too complicated, so I didn't do that.
>>>> +}
>>>> +
>>>> +static void nvmet_pr_send_event_by_hostid(struct nvmet_pr *pr,
>>>> uuid_t *hostid,
>>>> + u8 log_type)
>>>> +{
>>>> + struct nvmet_ns *ns = nvmet_pr_to_ns(pr);
>>>> + struct nvmet_subsys *subsys = ns->subsys;
>>>> + struct nvmet_ctrl *ctrl;
>>>> +
>>>> + mutex_lock(&subsys->lock);
>>>> + list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry) {
>>>> + if (uuid_equal(hostid, &ctrl->hostid)) {
>>>> + nvmet_pr_add_resv_log(ctrl, log_type, ns->nsid);
>>>> + nvmet_add_async_event(ctrl, NVME_AER_CSS,
>>>> + NVME_AEN_RESV_LOG_PAGE_AVALIABLE,
>>>> + NVME_LOG_RESERVATION);
>>>> + }
>>>> + }
>>>> + mutex_unlock(&subsys->lock);
>>>> +}
>>>> +
>>>> +static void nvmet_pr_send_resv_preempted(struct nvmet_pr *pr,
>>>> uuid_t *hostid)
>>>> +{
>>>> + nvmet_pr_send_event_by_hostid(pr, hostid,
>>>> + NVME_PR_LOG_RESERVATOPM_PREEMPTED);
>>>> +}
>>>> +
>>>> +static void nvmet_pr_send_registration_preempted(struct nvmet_pr *pr,
>>>> + uuid_t *hostid)
>>>> +{
>>>> + nvmet_pr_send_event_by_hostid(pr, hostid,
>>>> + NVME_PR_LOG_REGISTRATION_PREEMPTED);
>>>> +}
>>>> +
>>>> +static u16 nvmet_pr_register_check_rkey(struct nvmet_req *req,
>>>> + struct nvmet_pr_register_data *d)
>>>> +{
>>>> + struct nvmet_ctrl *ctrl = req->sq->ctrl;
>>>> + struct nvmet_pr *pr = &req->ns->pr;
>>>> + struct nvmet_pr_registrant *reg;
>>>> +
>>>> + reg = nvmet_pr_find_registrant_by_hostid(pr, &ctrl->hostid);
>>>> + if (!reg || reg->rkey == le64_to_cpu(d->nrkey))
>>>> + return NVME_SC_SUCCESS;
>>>> +
>>>> + return NVME_SC_RESERVATION_CONFLICT | NVME_SC_DNR;
>>>> +}
>>>> +
>>>> +static u16 nvmet_pr_register(struct nvmet_req *req,
>>>> + struct nvmet_pr_register_data *d)
>>>> +{
>>>> + struct nvmet_ctrl *ctrl = req->sq->ctrl;
>>>> + struct nvmet_pr *pr = &req->ns->pr;
>>>> + struct nvmet_pr_registrant *reg;
>>>> + u16 status;
>>>> +
>>>> + status = nvmet_pr_register_check_rkey(req, d);
>>>> + if (status)
>>>> + return status;
>>>> +
>>>> + reg = kmalloc(sizeof(*reg), GFP_KERNEL);
>>>> + if (!reg)
>>>> + return NVME_SC_INTERNAL;
>>>> +
>>>> + memset(reg, 0, sizeof(*reg));
>>>> + INIT_LIST_HEAD(®->entry);
>>>> + reg->rkey = le64_to_cpu(d->nrkey);
>>>> + uuid_copy(®->hostid, &ctrl->hostid);
>>>> +
>>>> + mutex_lock(&pr->pr_lock);
>>>> + list_add_tail_rcu(®->entry, &pr->registrant_list);
>>>
>>> Can you explain why this is rculist operation?
>>>
>> I will explain this in bottom.
>>>> + mutex_unlock(&pr->pr_lock);
>>>> + return NVME_SC_SUCCESS;
>>>> +}
>>>> +
>>>> +static void __nvmet_pr_unregister_one(struct nvmet_pr *pr,
>>>> + struct nvmet_pr_registrant *reg)
>>>> +{
>>>> + struct nvmet_pr_registrant *first_reg;
>>>> + struct nvmet_pr_registrant *holder;
>>>> + u8 original_rtype;
>>>> +
>>>> + list_del_rcu(®->entry);
>>>> +
>>>> + holder = rcu_dereference_protected(pr->holder,
>>>> + lockdep_is_held(&pr->pr_lock));
>>>> + if (reg != holder) {
>>>> + kfree_rcu(reg, rcu);
>>>> + return;
>>>
>>> goto [out] label instead?
>>>
>> OK.
>>>> + }
>>>> +
>>>> + original_rtype = holder->rtype;
>>>> + if (original_rtype == NVME_PR_WRITE_EXCLUSIVE_ALL_REGS ||
>>>> + original_rtype == NVME_PR_EXCLUSIVE_ACCESS_ALL_REGS) {
>>>> + first_reg = list_first_entry_or_null(&pr->registrant_list,
>>>> + struct nvmet_pr_registrant, entry);
>>>> + if (first_reg)
>>>> + first_reg->rtype = original_rtype;
>>>> + rcu_assign_pointer(pr->holder, first_reg);
>>>
>>> synchronize_rcu() ?
>>>
>>>> + } else {
>>>> + rcu_assign_pointer(pr->holder, NULL);
>>>
>>> synchronize_rcu() ?
>>>
>>>> +
>>>> + if (original_rtype == NVME_PR_WRITE_EXCLUSIVE_REG_ONLY ||
>>>> + original_rtype == NVME_PR_WRITE_EXCLUSIVE_REG_ONLY)
>>>> + nvmet_pr_send_resv_released(pr, ®->hostid);
>>>> + }
>>>
>>> out:
>>>
>>>> + kfree_rcu(reg, rcu);
>>>> +}
>>>> +
>>>> +static u16 nvmet_pr_unregister(struct nvmet_req *req,
>>>> + struct nvmet_pr_register_data *d,
>>>> + bool ignore_key)
>>>> +{
>>>> + u16 status = NVME_SC_RESERVATION_CONFLICT | NVME_SC_DNR;
>>>> + struct nvmet_ctrl *ctrl = req->sq->ctrl;
>>>> + struct nvmet_pr *pr = &req->ns->pr;
>>>> + struct nvmet_pr_registrant *reg;
>>>> + struct nvmet_pr_registrant *tmp;
>>>> +
>>>> + mutex_lock(&pr->pr_lock);
>>>> + list_for_each_entry_safe(reg, tmp, &pr->registrant_list, entry) {
>>>
>>> You are mixing list/rculist traversals, it can't be correct.
>>
>> You are right, I should use rculist whether hold the pr_lock or not.
>>
>>>
>>>> + if (uuid_equal(®->hostid, &ctrl->hostid)) {
>>>> + if (ignore_key || reg->rkey == le64_to_cpu(d->crkey)) {
>>>> + status = NVME_SC_SUCCESS;
>>>> + __nvmet_pr_unregister_one(pr, reg);
>>>> + }
>>>> + break;
>>>> + }
>>>> + }
>>>> + mutex_unlock(&pr->pr_lock);
>>>> +
>>>> + return status;
>>>> +}
>>>> +
>>>> +static u16 __nvmet_pr_do_replace(struct nvmet_pr *pr,
>>>> + struct nvmet_pr_registrant *reg,
>>>> + u64 nrkey)
>>>> +{
>>>> + struct nvmet_pr_registrant *holder;
>>>> + struct nvmet_pr_registrant *new;
>>>> +
>>>> + holder = rcu_dereference_protected(pr->holder,
>>>> + lockdep_is_held(&pr->pr_lock));
>>>> + if (reg != holder) {
>>>> + reg->rkey = nrkey;
>>>> + return NVME_SC_SUCCESS;
>>>> + }
>>>> +
>>>> + new = kmalloc(sizeof(*new), GFP_ATOMIC);
>>>> + if (!new)
>>>> + return NVME_SC_INTERNAL;
>>>> + memcpy(new, reg, sizeof(*new));
>>>> + new->rkey = nrkey;
>>>> + list_del_rcu(®->entry);
>>>> + list_add_rcu(&new->entry, &pr->registrant_list);
>>>> + rcu_assign_pointer(pr->holder, new);
>>>> + kfree_rcu(reg, rcu);
>>>
>>> I still think that the correct ordering is:
>>> rcu_assign_pointer(pr->holder, new);
>>> synchronize_rcu();
>>> kfree(reg);
>>>
>>> Because what you want is rcu grace period to elapse is after you
>>> (re)assign pr->holder. Then you can safely use a normal kfree for
>>> reg.
>>>
>> The kfree_rcu can achieve the same effect,
>>
>> Could you plz tell me why should change to like this?
>>
>>>> + return NVME_SC_SUCCESS;
>>>> +}
>>>> +
>>>> +static u16 nvmet_pr_replace(struct nvmet_req *req,
>>>> + struct nvmet_pr_register_data *d,
>>>> + bool ignore_key)
>>>> +{
>>>> + u16 status = NVME_SC_RESERVATION_CONFLICT | NVME_SC_DNR;
>>>> + struct nvmet_ctrl *ctrl = req->sq->ctrl;
>>>> + struct nvmet_pr *pr = &req->ns->pr;
>>>> + struct nvmet_pr_registrant *reg;
>>>> +
>>>> + mutex_lock(&pr->pr_lock);
>>>> + list_for_each_entry_rcu(reg, &pr->registrant_list, entry) {
>>>> + if (uuid_equal(®->hostid, &ctrl->hostid)) {
>>>> + if (ignore_key || reg->rkey == le64_to_cpu(d->crkey)) {
>>>> + reg->rkey = le64_to_cpu(d->nrkey);
>>>> + status = __nvmet_pr_do_replace(pr, reg,
>>>> + le64_to_cpu(d->nrkey));
>>>
>>> So you assign reg->rkey here and then assign it again in
>>> _do_replace() ?
>>> I don't understand the logic here.
>>>
>> My bad, this is an oversight, it will be changed in v5.
>>>> + }
>>>> + break;
>>>> + }
>>>> + }
>>>> + mutex_unlock(&pr->pr_lock);
>>>> + return status;
>>>> +}
>>>> +
>>>> +static void nvmet_execute_pr_register(struct nvmet_req *req)
>>>> +{
>>>> + u32 cdw10 = le32_to_cpu(req->cmd->common.cdw10);
>>>> + bool ignore_key = (bool)((cdw10 >> 3) & 1); /* Ignore existing
>>>> key, bit 03 */
>>>> + struct nvmet_pr_register_data *d;
>>>> + u8 reg_act = cdw10 & 0x07; /* Reservation Register Action, bit
>>>> 02:00 */
>>>> + u16 status;
>>>> +
>>>> + d = kmalloc(sizeof(*d), GFP_KERNEL);
>>>> + if (!d) {
>>>> + status = NVME_SC_INTERNAL;
>>>> + goto out;
>>>> + }
>>>> +
>>>> + status = nvmet_copy_from_sgl(req, 0, d, sizeof(*d));
>>>> + if (status)
>>>> + goto free_data;
>>>> +
>>>> + switch (reg_act) {
>>>> + case NVME_PR_REGISTER_ACT_REG:
>>>> + status = nvmet_pr_register(req, d);
>>>> + break;
>>>> + case NVME_PR_REGISTER_ACT_UNREG:
>>>> + status = nvmet_pr_unregister(req, d, ignore_key);
>>>> + break;
>>>> + case NVME_PR_REGISTER_ACT_REPLACE:
>>>> + status = nvmet_pr_replace(req, d, ignore_key);
>>>> + break;
>>>> + default:
>>>> + req->error_loc = offsetof(struct nvme_common_command, cdw10);
>>>> + status = NVME_SC_INVALID_OPCODE | NVME_SC_DNR;
>>>> + break;
>>>> + }
>>>> +free_data:
>>>> + kfree(d);
>>>> +out:
>>>> + if (!status)
>>>> + atomic_inc(&req->ns->pr.generation);
>>>> + nvmet_req_complete(req, status);
>>>> +}
>>>> +
>>>> +static u16 nvmet_pr_acquire(struct nvmet_req *req,
>>>> + struct nvmet_pr_registrant *reg,
>>>> + u8 rtype)
>>>> +{
>>>> + struct nvmet_pr *pr = &req->ns->pr;
>>>> + struct nvmet_pr_registrant *holder;
>>>> +
>>>> + holder = rcu_dereference_protected(pr->holder,
>>>> + lockdep_is_held(&pr->pr_lock));
>>>> + if (holder && reg != holder)
>>>> + return NVME_SC_RESERVATION_CONFLICT | NVME_SC_DNR;
>>>> + if (holder && reg == holder) {
>>>> + if (holder->rtype == rtype)
>>>> + return NVME_SC_SUCCESS;
>>>> + return NVME_SC_RESERVATION_CONFLICT | NVME_SC_DNR;
>>>> + }
>>>> +
>>>> + return nvmet_pr_set_rtype_and_holder(pr, rtype, reg);
>>>> +}
>>>> +
>>>> +static u16 nvmet_pr_unreg_by_prkey(struct nvmet_pr *pr, u64 prkey,
>>>> + uuid_t *send_hostid)
>>>> +{
>>>> + u16 status = NVME_SC_RESERVATION_CONFLICT | NVME_SC_DNR;
>>>> + struct nvmet_pr_registrant *reg;
>>>> + struct nvmet_pr_registrant *tmp;
>>>> +
>>>
>>> lockdep_assert_held ?
>> OK
>>>
>>>> + list_for_each_entry_safe(reg, tmp,
>>>> + &pr->registrant_list, entry) {
>>>> + if (reg->rkey == prkey) {
>>>> + status = NVME_SC_SUCCESS;
>>>> + if (!uuid_equal(®->hostid, send_hostid))
>>>> + nvmet_pr_send_registration_preempted(pr,
>>>> + ®->hostid);
>>>> + __nvmet_pr_unregister_one(pr, reg);
>>>> + }
>>>> + }
>>>> + return status;
>>>> +}
>>>> +
>>>> +static u16 nvmet_pr_unreg_by_prkey_except_hostid(struct nvmet_pr
>>>> *pr, u64 prkey,
>>>> + uuid_t *send_hostid)
>>>> +{
>>>> + u16 status = NVME_SC_RESERVATION_CONFLICT | NVME_SC_DNR;
>>>> + struct nvmet_pr_registrant *reg;
>>>> + struct nvmet_pr_registrant *tmp;
>>>> +
>>>
>>> lockdep_assert_held ?
>> OK
>>>
>>>> + list_for_each_entry_safe(reg, tmp,
>>>> + &pr->registrant_list, entry) {
>>>> + if (reg->rkey == prkey &&
>>>> + !uuid_equal(®->hostid, send_hostid)) {
>>>> + status = NVME_SC_SUCCESS;
>>>> + nvmet_pr_send_registration_preempted(pr, ®->hostid);
>>>> + __nvmet_pr_unregister_one(pr, reg);
>>>> + }
>>>> + }
>>>> + return status;
>>>> +}
>>>> +
>>>> +static void nvmet_pr_unreg_except_hostid(struct nvmet_pr *pr,
>>>> + uuid_t *send_hostid)
>>>> +{
>>>> + struct nvmet_pr_registrant *reg;
>>>> + struct nvmet_pr_registrant *tmp;
>>>> +
>>>
>>> lockdep_assert_held ?
>> OK
>>>
>>>> + list_for_each_entry_safe(reg, tmp,
>>>> + &pr->registrant_list, entry) {
>>>> + if (!uuid_equal(®->hostid, send_hostid)) {
>>>> + nvmet_pr_send_registration_preempted(pr, ®->hostid);
>>>> + __nvmet_pr_unregister_one(pr, reg);
>>>> + }
>>>> + }
>>>> +}
>>>> +
>>>> +static u16 nvmet_pr_create_new_resv(struct nvmet_pr *pr,
>>>> + u8 original_rtype,
>>>> + u8 new_rtype,
>>>> + struct nvmet_pr_registrant *reg)
>>>> +{
>>>> + u16 status;
>>>> +
>>>> + status = nvmet_pr_set_rtype_and_holder(pr, new_rtype, reg);
>>>> + if (!status && original_rtype != new_rtype)
>>>> + nvmet_pr_send_resv_released(pr, ®->hostid);
>>>> + return status;
>>>> +}
>>>> +
>>>> +static u16 nvmet_pr_update_holder_rtype(struct nvmet_pr *pr,
>>>> + struct nvmet_pr_registrant *holder,
>>>> + u8 rtype)
>>>> +{
>>>> + u16 status;
>>>> + struct nvmet_pr_registrant *new;
>>>> +
>>>> + status = nvmet_pr_validate_rtype(rtype);
>>>> + if (status)
>>>> + return status;
>>>> +
>>>> + new = kmalloc(sizeof(*new), GFP_ATOMIC);
>>>> + if (!new)
>>>> + return NVME_SC_INTERNAL;
>>>> +
>>>> + list_del_rcu(&holder->entry);
>>>> + memcpy(new, holder, sizeof(*new));
>>>> + new->rtype = rtype;
>>>> + list_add_tail_rcu(&new->entry, &pr->registrant_list);
>>>> + rcu_assign_pointer(pr->holder, new);
>>>> + kfree_rcu(holder, rcu);
>>>
>>> Same comment as before.
>>>
>>>> + return NVME_SC_SUCCESS;
>>>> +}
>>>
>>> Why do you need this btw? shouldn't this one call
>>> __nvmet_pr_do_replace ?
>>>
>> OK, it will be changed in v5.
>>>> +
>>>> +static u16 nvmet_pr_preempt(struct nvmet_req *req,
>>>> + struct nvmet_pr_registrant *reg,
>>>> + u8 rtype,
>>>> + struct nvmet_pr_acquire_data *d)
>>>> +{
>>>> + struct nvmet_ctrl *ctrl = req->sq->ctrl;
>>>> + struct nvmet_pr *pr = &req->ns->pr;
>>>> + struct nvmet_pr_registrant *holder;
>>>> + enum nvme_pr_type original_rtype;
>>>> + u16 status;
>>>> +
>>>> + holder = rcu_dereference_protected(pr->holder,
>>>> + lockdep_is_held(&pr->pr_lock));
>>>> + if (!holder)
>>>> + return nvmet_pr_unreg_by_prkey(pr, le64_to_cpu(d->prkey),
>>>> + &ctrl->hostid);
>>>> +
>>>> + original_rtype = holder->rtype;
>>>> + if (original_rtype == NVME_PR_WRITE_EXCLUSIVE_ALL_REGS ||
>>>> + original_rtype == NVME_PR_EXCLUSIVE_ACCESS_ALL_REGS) {
>>>> + if (!le64_to_cpu(d->prkey)) {
>>>> + nvmet_pr_unreg_except_hostid(pr, &ctrl->hostid);
>>>> + return nvmet_pr_create_new_resv(pr, original_rtype,
>>>> + rtype, reg);
>>>> + }
>>>> + return nvmet_pr_unreg_by_prkey(pr, le64_to_cpu(d->prkey),
>>>> + &ctrl->hostid);
>>>> + }
>>>> +
>>>> + if (holder == reg) {
>>>> + status = nvmet_pr_update_holder_rtype(pr, holder, rtype);
>>>> + if (status)
>>>> + return status;
>>>> + if (original_rtype != rtype)
>>>> + nvmet_pr_send_resv_released(pr, ®->hostid);
>>>> + return status;
>>>> + }
>>>> +
>>>> + if (le64_to_cpu(d->prkey) == holder->rkey) {
>>>> + status = nvmet_pr_unreg_by_prkey_except_hostid(pr,
>>>> + le64_to_cpu(d->prkey), &ctrl->hostid);
>>>> + if (status)
>>>> + return status;
>>>> + return nvmet_pr_create_new_resv(pr, original_rtype, rtype,
>>>> reg);
>>>> + }
>>>> +
>>>> + if (le64_to_cpu(d->prkey))
>>>> + return nvmet_pr_unreg_by_prkey(pr, le64_to_cpu(d->prkey),
>>>> + &ctrl->hostid);
>>>> + return NVME_SC_INVALID_FIELD | NVME_SC_DNR;
>>>> +}
>>>> +
>>>> +static u16 __nvmet_execute_pr_acquire(struct nvmet_req *req,
>>>> + struct nvmet_pr_registrant *reg,
>>>> + u8 acquire_act,
>>>> + u8 rtype,
>>>> + struct nvmet_pr_acquire_data *d)
>>>> +{
>>>> + u16 status;
>>>> +
>>>> + switch (acquire_act) {
>>>> + case NVME_PR_ACQUIRE_ACT_ACQUIRE:
>>>> + status = nvmet_pr_acquire(req, reg, rtype);
>>>> + goto out;
>>>> + case NVME_PR_ACQUIRE_ACT_PREEMPT:
>>>> + status = nvmet_pr_preempt(req, reg, rtype, d);
>>>> + goto inc_gen;
>>>> + case NVME_PR_ACQUIRE_ACT_PREEMPT_AND_ABORT:
>>>> + status = nvmet_pr_preempt(req, reg, rtype, d);
>>>> + goto inc_gen;
>>>> + default:
>>>> + req->error_loc = offsetof(struct nvme_common_command, cdw10);
>>>> + status = NVME_SC_INVALID_OPCODE | NVME_SC_DNR;
>>>> + goto out;
>>>> + }
>>>> +inc_gen:
>>>> + if (!status)
>>>> + atomic_inc(&req->ns->pr.generation);
>>>> +out:
>>>> + return status;
>>>> +}
>>>> +
>>>> +static void nvmet_execute_pr_acquire(struct nvmet_req *req)
>>>> +{
>>>> + u32 cdw10 = le32_to_cpu(req->cmd->common.cdw10);
>>>> + bool ignore_key = (bool)((cdw10 >> 3) & 1); /* Ignore existing
>>>> key, bit 03 */
>>>> + u8 rtype = (u8)((cdw10 >> 8) & 0xff); /* Reservation type, bit
>>>> 15:08 */
>>>> + u8 acquire_act = cdw10 & 0x07; /* Reservation acquire action,
>>>> bit 02:00 */
>>>> + struct nvmet_ctrl *ctrl = req->sq->ctrl;
>>>> + struct nvmet_pr_acquire_data *d = NULL;
>>>> + struct nvmet_pr *pr = &req->ns->pr;
>>>> + struct nvmet_pr_registrant *reg;
>>>> + u16 status = NVME_SC_SUCCESS;
>>>> +
>>>> + if (ignore_key) {
>>>> + status = NVME_SC_INVALID_FIELD | NVME_SC_DNR;
>>>> + goto out;
>>>> + }
>>>> +
>>>> + d = kmalloc(sizeof(*d), GFP_KERNEL);
>>>> + if (!d) {
>>>> + status = NVME_SC_INTERNAL;
>>>> + goto out;
>>>> + }
>>>> +
>>>> + status = nvmet_copy_from_sgl(req, 0, d, sizeof(*d));
>>>> + if (status)
>>>> + goto free_data;
>>>> +
>>>> + status = NVME_SC_RESERVATION_CONFLICT | NVME_SC_DNR;
>>>> + mutex_lock(&pr->pr_lock);
>>>> + list_for_each_entry_rcu(reg, &pr->registrant_list, entry) {
>>>> + if (uuid_equal(®->hostid, &ctrl->hostid) &&
>>>> + reg->rkey == le64_to_cpu(d->crkey)) {
>>>> + status = __nvmet_execute_pr_acquire(req, reg,
>>>> + acquire_act, rtype, d);
>>>> + break;
>>>> + }
>>>> + }
>>>> + mutex_unlock(&pr->pr_lock);
>>>> +
>>>> +free_data:
>>>> + kfree(d);
>>>> +out:
>>>> + nvmet_req_complete(req, status);
>>>> +}
>>>> +
>>>> +static u16 nvmet_pr_release(struct nvmet_req *req,
>>>> + struct nvmet_pr_registrant *reg,
>>>> + u8 rtype)
>>>> +{
>>>> + struct nvmet_pr *pr = &req->ns->pr;
>>>> + struct nvmet_pr_registrant *holder;
>>>> + u8 original_rtype;
>>>> +
>>>> + holder = rcu_dereference_protected(pr->holder,
>>>> + lockdep_is_held(&pr->pr_lock));
>>>> + if (!holder || reg != holder)
>>>> + return NVME_SC_SUCCESS;
>>>> +
>>>> + original_rtype = holder->rtype;
>>>> + if (original_rtype != rtype)
>>>> + return NVME_SC_RESERVATION_CONFLICT | NVME_SC_DNR;
>>>> +
>>>> + rcu_assign_pointer(pr->holder, NULL);
>>>
>>> synchronize_rcu ?
>>>
>>>> +
>>>> + if (original_rtype != NVME_PR_WRITE_EXCLUSIVE &&
>>>> + original_rtype != NVME_PR_EXCLUSIVE_ACCESS)
>>>> + nvmet_pr_send_resv_released(pr, ®->hostid);
>>>> +
>>>> + return NVME_SC_SUCCESS;
>>>> +}
>>>> +
>>>> +static void nvmet_pr_clear(struct nvmet_req *req)
>>>> +{
>>>> + struct nvmet_pr *pr = &req->ns->pr;
>>>> + struct nvmet_pr_registrant *reg;
>>>> + struct nvmet_pr_registrant *tmp;
>>>> +
>>>
>>> lockdep_assert_held ?
>> OK
>>>
>>>> + list_for_each_entry_safe(reg, tmp, &pr->registrant_list, entry) {
>>>> + list_del_rcu(®->entry);
>>>
>>> Now registrant_list is an rculist ? I'm not following the logic here.
>>>
>> Yes
>>>> + if (!uuid_equal(&req->sq->ctrl->hostid, ®->hostid))
>>>> + nvmet_pr_send_resv_preempted(pr, ®->hostid);
>>>> + kfree_rcu(reg, rcu);
>>>
>>> Why are you calling kfree_rcu ?
>>>
>>>> + }
>>>> + rcu_assign_pointer(pr->holder, NULL);
>>>
>>> synchronize_rcu() ?
>>>
>>>> +
>>>> + atomic_inc(&pr->generation);
>>>> +}
>>>
>>> ...
>>>
>>> I'm stopping here, I think you want to either sort out or explain how
>>> you are managing pr, pr->holder, pr->registrant_list etc. It is
>>> difficult for me to follow and make sense of it.
>>
>> Hi Sagi,
>>
>> Thank you for the careful review. My bad, I'm not very familiar
>> with RCU, I wasn't aware
>>
>> of the many restrictions involved.I will do a deep research on RCU to
>> see what is correct to do.
>>
>> I use pr->pr_lock to protect pr->registrant_list and pr->holder
>> writing, and both of holder
>>
>> and registrant_list are rcu protected, so they can be read lightly in
>> nvmet_pr_check_cmd_access.
>
> Can you please explain where are the write side and read side critical
> sections for the registrant_list and where exactly a dereference occurs
> that is synchronized via rcu and is _not_ protected with a mutex?
>
1. write:
1) executing register、acquire、release commands.
2）disabling namespace in nvmet_pr_exit_ns().
When doing above, I will use mutex pr_lock to protect holder and
registrant_list both, because there are multi writers.
I use rcu_dereference_protected to get holder if locked pr_lock.
2. read:
1) executing report command, nvmet_execute_pr_report().
2) checking admin and IO command access, nvmet_pr_check_cmd_access().
When doing above, I use rcu_read_lock to read holder and registrant_list
lightly.
>>
>> I was misled by the __dev_exception_clean() into thinking that
>> if I added a mutex lock, I
>>
>> wouldn't have to use the rculist marcros anymore, I will change this
>> in v5, sorry for the trouble...
>>
>> And I still dont know why we should call synchronize_rcu after
>> rcu_assign_pointer, if it is for
>>
>> safely kfree(reg), the kfree_rcu can ensure that. Could you plz
>> expain that Sagi? Thanks.
>
> Well, kfree_rcu does more than just wait the rcu_grace period, it
> actually batches free in a workqueue context and drains it
> asynchronously. First of all, I think its an overkill and second,
> there is no reason to defer the free to a different context given that
> this is not the data path.
What I've known is that we can not use synchronize_rcu() in mutex lock,
so I use kfree_rcu to free reg asynchronously.
Now it seems that it's not necessary if this is not the data path.
I will change this in v6, you can skip v5.
Best regards,
Guixin Liu
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