From: Yoav Cohen Date: Mon, 12 Jan 2026 22:05:01 +0000 (+0200) Subject: ublk: add UBLK_CMD_TRY_STOP_DEV command X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=93ada1b3da398b492c45429cef1a1c9651d5c7ba;p=thirdparty%2Fkernel%2Flinux.git ublk: add UBLK_CMD_TRY_STOP_DEV command Add a best-effort stop command, UBLK_CMD_TRY_STOP_DEV, which only stops a ublk device when it has no active openers. Unlike UBLK_CMD_STOP_DEV, this command does not disrupt existing users. New opens are blocked only after disk_openers has reached zero; if the device is busy, the command returns -EBUSY and leaves it running. The ub->block_open flag is used only to close a race with an in-progress open and does not otherwise change open behavior. Advertise support via the UBLK_F_SAFE_STOP_DEV feature flag. Signed-off-by: Yoav Cohen Reviewed-by: Ming Lei Signed-off-by: Jens Axboe --- diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c index 73490890242b8..aaf94d2fb7897 100644 --- a/drivers/block/ublk_drv.c +++ b/drivers/block/ublk_drv.c @@ -56,6 +56,7 @@ #define UBLK_CMD_DEL_DEV_ASYNC _IOC_NR(UBLK_U_CMD_DEL_DEV_ASYNC) #define UBLK_CMD_UPDATE_SIZE _IOC_NR(UBLK_U_CMD_UPDATE_SIZE) #define UBLK_CMD_QUIESCE_DEV _IOC_NR(UBLK_U_CMD_QUIESCE_DEV) +#define UBLK_CMD_TRY_STOP_DEV _IOC_NR(UBLK_U_CMD_TRY_STOP_DEV) #define UBLK_IO_REGISTER_IO_BUF _IOC_NR(UBLK_U_IO_REGISTER_IO_BUF) #define UBLK_IO_UNREGISTER_IO_BUF _IOC_NR(UBLK_U_IO_UNREGISTER_IO_BUF) @@ -76,7 +77,8 @@ | UBLK_F_QUIESCE \ | UBLK_F_PER_IO_DAEMON \ | UBLK_F_BUF_REG_OFF_DAEMON \ - | (IS_ENABLED(CONFIG_BLK_DEV_INTEGRITY) ? UBLK_F_INTEGRITY : 0)) + | (IS_ENABLED(CONFIG_BLK_DEV_INTEGRITY) ? UBLK_F_INTEGRITY : 0) \ + | UBLK_F_SAFE_STOP_DEV) #define UBLK_F_ALL_RECOVERY_FLAGS (UBLK_F_USER_RECOVERY \ | UBLK_F_USER_RECOVERY_REISSUE \ @@ -243,6 +245,8 @@ struct ublk_device { struct delayed_work exit_work; struct work_struct partition_scan_work; + bool block_open; /* protected by open_mutex */ + struct ublk_queue *queues[]; }; @@ -984,6 +988,9 @@ static int ublk_open(struct gendisk *disk, blk_mode_t mode) return -EPERM; } + if (ub->block_open) + return -ENXIO; + return 0; } @@ -3343,7 +3350,8 @@ static int ublk_ctrl_add_dev(const struct ublksrv_ctrl_cmd *header) ub->dev_info.flags |= UBLK_F_CMD_IOCTL_ENCODE | UBLK_F_URING_CMD_COMP_IN_TASK | UBLK_F_PER_IO_DAEMON | - UBLK_F_BUF_REG_OFF_DAEMON; + UBLK_F_BUF_REG_OFF_DAEMON | + UBLK_F_SAFE_STOP_DEV; /* GET_DATA isn't needed any more with USER_COPY or ZERO COPY */ if (ub->dev_info.flags & (UBLK_F_USER_COPY | UBLK_F_SUPPORT_ZERO_COPY | @@ -3464,6 +3472,34 @@ static void ublk_ctrl_stop_dev(struct ublk_device *ub) ublk_stop_dev(ub); } +static int ublk_ctrl_try_stop_dev(struct ublk_device *ub) +{ + struct gendisk *disk; + int ret = 0; + + disk = ublk_get_disk(ub); + if (!disk) + return -ENODEV; + + mutex_lock(&disk->open_mutex); + if (disk_openers(disk) > 0) { + ret = -EBUSY; + goto unlock; + } + ub->block_open = true; + /* release open_mutex as del_gendisk() will reacquire it */ + mutex_unlock(&disk->open_mutex); + + ublk_ctrl_stop_dev(ub); + goto out; + +unlock: + mutex_unlock(&disk->open_mutex); +out: + ublk_put_disk(disk); + return ret; +} + static int ublk_ctrl_get_dev_info(struct ublk_device *ub, const struct ublksrv_ctrl_cmd *header) { @@ -3859,6 +3895,7 @@ static int ublk_ctrl_uring_cmd_permission(struct ublk_device *ub, case UBLK_CMD_END_USER_RECOVERY: case UBLK_CMD_UPDATE_SIZE: case UBLK_CMD_QUIESCE_DEV: + case UBLK_CMD_TRY_STOP_DEV: mask = MAY_READ | MAY_WRITE; break; default: @@ -3972,6 +4009,9 @@ static int ublk_ctrl_uring_cmd(struct io_uring_cmd *cmd, case UBLK_CMD_QUIESCE_DEV: ret = ublk_ctrl_quiesce_dev(ub, header); break; + case UBLK_CMD_TRY_STOP_DEV: + ret = ublk_ctrl_try_stop_dev(ub); + break; default: ret = -EOPNOTSUPP; break; diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h index 61ac5d8e10788..90f47da4f435f 100644 --- a/include/uapi/linux/ublk_cmd.h +++ b/include/uapi/linux/ublk_cmd.h @@ -55,7 +55,8 @@ _IOWR('u', 0x15, struct ublksrv_ctrl_cmd) #define UBLK_U_CMD_QUIESCE_DEV \ _IOWR('u', 0x16, struct ublksrv_ctrl_cmd) - +#define UBLK_U_CMD_TRY_STOP_DEV \ + _IOWR('u', 0x17, struct ublksrv_ctrl_cmd) /* * 64bits are enough now, and it should be easy to extend in case of * running out of feature flags @@ -321,6 +322,12 @@ */ #define UBLK_F_INTEGRITY (1ULL << 16) +/* + * The device supports the UBLK_CMD_TRY_STOP_DEV command, which + * allows stopping the device only if there are no openers. + */ +#define UBLK_F_SAFE_STOP_DEV (1ULL << 17) + /* device state */ #define UBLK_S_DEV_DEAD 0 #define UBLK_S_DEV_LIVE 1