ublk selftests: add --no_ublk_fixed_fd for not using registered ublk char device
Add a new command line option --no_ublk_fixed_fd that excludes the ublk
control device (/dev/ublkcN) from io_uring's registered files array.
When this option is used, only backing files are registered starting
from index 1, while the ublk control device is accessed using its raw
file descriptor.
Add ublk_get_registered_fd() helper function that returns the appropriate
file descriptor for use with io_uring operations.
Key optimizations implemented:
- Cache UBLKS_Q_NO_UBLK_FIXED_FD flag in ublk_queue.flags to avoid
reading dev->no_ublk_fixed_fd in fast path
- Cache ublk char device fd in ublk_queue.ublk_fd for fast access
- Update ublk_get_registered_fd() to use ublk_queue * parameter
- Update io_uring_prep_buf_register/unregister() to use ublk_queue *
- Replace ublk_device * access with ublk_queue * access in fast paths
Also pass --no_ublk_fixed_fd to test_stress_04.sh for covering
plain ublk char device mode.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20250827121602.2619736-3-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/tools/testing/selftests/ublk/file_backed.c b/tools/testing/selftests/ublk/file_backed.c
index 2d93ac8..cd9fe69 100644
--- a/tools/testing/selftests/ublk/file_backed.c
+++ b/tools/testing/selftests/ublk/file_backed.c
@@ -20,7 +20,7 @@ static int loop_queue_flush_io(struct ublk_thread *t, struct ublk_queue *q,
struct io_uring_sqe *sqe[1];
ublk_io_alloc_sqes(t, sqe, 1);
- io_uring_prep_fsync(sqe[0], 1 /*fds[1]*/, IORING_FSYNC_DATASYNC);
+ io_uring_prep_fsync(sqe[0], ublk_get_registered_fd(q, 1) /*fds[1]*/, IORING_FSYNC_DATASYNC);
io_uring_sqe_set_flags(sqe[0], IOSQE_FIXED_FILE);
/* bit63 marks us as tgt io */
sqe[0]->user_data = build_user_data(tag, ublk_op, 0, q->q_id, 1);
@@ -42,7 +42,7 @@ static int loop_queue_tgt_rw_io(struct ublk_thread *t, struct ublk_queue *q,
if (!sqe[0])
return -ENOMEM;
- io_uring_prep_rw(op, sqe[0], 1 /*fds[1]*/,
+ io_uring_prep_rw(op, sqe[0], ublk_get_registered_fd(q, 1) /*fds[1]*/,
addr,
iod->nr_sectors << 9,
iod->start_sector << 9);
@@ -56,19 +56,19 @@ static int loop_queue_tgt_rw_io(struct ublk_thread *t, struct ublk_queue *q,
ublk_io_alloc_sqes(t, sqe, 3);
- io_uring_prep_buf_register(sqe[0], 0, tag, q->q_id, ublk_get_io(q, tag)->buf_index);
+ io_uring_prep_buf_register(sqe[0], q, tag, q->q_id, ublk_get_io(q, tag)->buf_index);
sqe[0]->flags |= IOSQE_CQE_SKIP_SUCCESS | IOSQE_IO_HARDLINK;
sqe[0]->user_data = build_user_data(tag,
ublk_cmd_op_nr(sqe[0]->cmd_op), 0, q->q_id, 1);
- io_uring_prep_rw(op, sqe[1], 1 /*fds[1]*/, 0,
+ io_uring_prep_rw(op, sqe[1], ublk_get_registered_fd(q, 1) /*fds[1]*/, 0,
iod->nr_sectors << 9,
iod->start_sector << 9);
sqe[1]->buf_index = tag;
sqe[1]->flags |= IOSQE_FIXED_FILE | IOSQE_IO_HARDLINK;
sqe[1]->user_data = build_user_data(tag, ublk_op, 0, q->q_id, 1);
- io_uring_prep_buf_unregister(sqe[2], 0, tag, q->q_id, ublk_get_io(q, tag)->buf_index);
+ io_uring_prep_buf_unregister(sqe[2], q, tag, q->q_id, ublk_get_io(q, tag)->buf_index);
sqe[2]->user_data = build_user_data(tag, ublk_cmd_op_nr(sqe[2]->cmd_op), 0, q->q_id, 1);
return 2;
diff --git a/tools/testing/selftests/ublk/kublk.c b/tools/testing/selftests/ublk/kublk.c
index 6512dfb..b71faba 100644
--- a/tools/testing/selftests/ublk/kublk.c
+++ b/tools/testing/selftests/ublk/kublk.c
@@ -432,7 +432,7 @@ static void ublk_thread_deinit(struct ublk_thread *t)
}
}
-static int ublk_queue_init(struct ublk_queue *q, unsigned extra_flags)
+static int ublk_queue_init(struct ublk_queue *q, unsigned long long extra_flags)
{
struct ublk_dev *dev = q->dev;
int depth = dev->dev_info.queue_depth;
@@ -446,6 +446,9 @@ static int ublk_queue_init(struct ublk_queue *q, unsigned extra_flags)
q->flags = dev->dev_info.flags;
q->flags |= extra_flags;
+ /* Cache fd in queue for fast path access */
+ q->ublk_fd = dev->fds[0];
+
cmd_buf_size = ublk_queue_cmd_buf_sz(q);
off = UBLKSRV_CMD_BUF_OFFSET + q->q_id * ublk_queue_max_cmd_buf_sz();
q->io_cmd_buf = mmap(0, cmd_buf_size, PROT_READ,
@@ -481,9 +484,10 @@ static int ublk_queue_init(struct ublk_queue *q, unsigned extra_flags)
return -ENOMEM;
}
-static int ublk_thread_init(struct ublk_thread *t)
+static int ublk_thread_init(struct ublk_thread *t, unsigned long long extra_flags)
{
struct ublk_dev *dev = t->dev;
+ unsigned long long flags = dev->dev_info.flags | extra_flags;
int ring_depth = dev->tgt.sq_depth, cq_depth = dev->tgt.cq_depth;
int ret;
@@ -512,7 +516,17 @@ static int ublk_thread_init(struct ublk_thread *t)
io_uring_register_ring_fd(&t->ring);
- ret = io_uring_register_files(&t->ring, dev->fds, dev->nr_fds);
+ if (flags & UBLKS_Q_NO_UBLK_FIXED_FD) {
+ /* Register only backing files starting from index 1, exclude ublk control device */
+ if (dev->nr_fds > 1) {
+ ret = io_uring_register_files(&t->ring, &dev->fds[1], dev->nr_fds - 1);
+ } else {
+ /* No backing files to register, skip file registration */
+ ret = 0;
+ }
+ } else {
+ ret = io_uring_register_files(&t->ring, dev->fds, dev->nr_fds);
+ }
if (ret) {
ublk_err("ublk dev %d thread %d register files failed %d\n",
t->dev->dev_info.dev_id, t->idx, ret);
@@ -626,9 +640,12 @@ int ublk_queue_io_cmd(struct ublk_thread *t, struct ublk_io *io)
/* These fields should be written once, never change */
ublk_set_sqe_cmd_op(sqe[0], cmd_op);
- sqe[0]->fd = 0; /* dev->fds[0] */
+ sqe[0]->fd = ublk_get_registered_fd(q, 0); /* dev->fds[0] */
sqe[0]->opcode = IORING_OP_URING_CMD;
- sqe[0]->flags = IOSQE_FIXED_FILE;
+ if (q->flags & UBLKS_Q_NO_UBLK_FIXED_FD)
+ sqe[0]->flags = 0; /* Use raw FD, not fixed file */
+ else
+ sqe[0]->flags = IOSQE_FIXED_FILE;
sqe[0]->rw_flags = 0;
cmd->tag = io->tag;
cmd->q_id = q->q_id;
@@ -832,6 +849,7 @@ struct ublk_thread_info {
unsigned idx;
sem_t *ready;
cpu_set_t *affinity;
+ unsigned long long extra_flags;
};
static void *ublk_io_handler_fn(void *data)
@@ -844,7 +862,7 @@ static void *ublk_io_handler_fn(void *data)
t->dev = info->dev;
t->idx = info->idx;
- ret = ublk_thread_init(t);
+ ret = ublk_thread_init(t, info->extra_flags);
if (ret) {
ublk_err("ublk dev %d thread %u init failed\n",
dev_id, t->idx);
@@ -934,6 +952,8 @@ static int ublk_start_daemon(const struct dev_ctx *ctx, struct ublk_dev *dev)
if (ctx->auto_zc_fallback)
extra_flags = UBLKS_Q_AUTO_BUF_REG_FALLBACK;
+ if (ctx->no_ublk_fixed_fd)
+ extra_flags |= UBLKS_Q_NO_UBLK_FIXED_FD;
for (i = 0; i < dinfo->nr_hw_queues; i++) {
dev->q[i].dev = dev;
@@ -951,6 +971,7 @@ static int ublk_start_daemon(const struct dev_ctx *ctx, struct ublk_dev *dev)
tinfo[i].dev = dev;
tinfo[i].idx = i;
tinfo[i].ready = &ready;
+ tinfo[i].extra_flags = extra_flags;
/*
* If threads are not tied 1:1 to queues, setting thread
@@ -1471,7 +1492,7 @@ static void __cmd_create_help(char *exe, bool recovery)
printf("%s %s -t [null|loop|stripe|fault_inject] [-q nr_queues] [-d depth] [-n dev_id]\n",
exe, recovery ? "recover" : "add");
printf("\t[--foreground] [--quiet] [-z] [--auto_zc] [--auto_zc_fallback] [--debug_mask mask] [-r 0|1 ] [-g]\n");
- printf("\t[-e 0|1 ] [-i 0|1]\n");
+ printf("\t[-e 0|1 ] [-i 0|1] [--no_ublk_fixed_fd]\n");
printf("\t[--nthreads threads] [--per_io_tasks]\n");
printf("\t[target options] [backfile1] [backfile2] ...\n");
printf("\tdefault: nr_queues=2(max 32), depth=128(max 1024), dev_id=-1(auto allocation)\n");
@@ -1534,6 +1555,7 @@ int main(int argc, char *argv[])
{ "size", 1, NULL, 's'},
{ "nthreads", 1, NULL, 0 },
{ "per_io_tasks", 0, NULL, 0 },
+ { "no_ublk_fixed_fd", 0, NULL, 0 },
{ 0, 0, 0, 0 }
};
const struct ublk_tgt_ops *ops = NULL;
@@ -1613,6 +1635,8 @@ int main(int argc, char *argv[])
ctx.nthreads = strtol(optarg, NULL, 10);
if (!strcmp(longopts[option_idx].name, "per_io_tasks"))
ctx.per_io_tasks = 1;
+ if (!strcmp(longopts[option_idx].name, "no_ublk_fixed_fd"))
+ ctx.no_ublk_fixed_fd = 1;
break;
case '?':
/*
diff --git a/tools/testing/selftests/ublk/kublk.h b/tools/testing/selftests/ublk/kublk.h
index 219233f..5e55484 100644
--- a/tools/testing/selftests/ublk/kublk.h
+++ b/tools/testing/selftests/ublk/kublk.h
@@ -77,6 +77,7 @@ struct dev_ctx {
unsigned int recovery:1;
unsigned int auto_zc_fallback:1;
unsigned int per_io_tasks:1;
+ unsigned int no_ublk_fixed_fd:1;
int _evtfd;
int _shmid;
@@ -166,7 +167,9 @@ struct ublk_queue {
/* borrow one bit of ublk uapi flags, which may never be used */
#define UBLKS_Q_AUTO_BUF_REG_FALLBACK (1ULL << 63)
+#define UBLKS_Q_NO_UBLK_FIXED_FD (1ULL << 62)
__u64 flags;
+ int ublk_fd; /* cached ublk char device fd */
struct ublk_io ios[UBLK_QUEUE_DEPTH];
};
@@ -273,34 +276,48 @@ static inline int ublk_io_alloc_sqes(struct ublk_thread *t,
return nr_sqes;
}
-static inline void io_uring_prep_buf_register(struct io_uring_sqe *sqe,
- int dev_fd, int tag, int q_id, __u64 index)
+static inline int ublk_get_registered_fd(struct ublk_queue *q, int fd_index)
+{
+ if (q->flags & UBLKS_Q_NO_UBLK_FIXED_FD) {
+ if (fd_index == 0)
+ /* Return the raw ublk FD for index 0 */
+ return q->ublk_fd;
+ /* Adjust index for backing files (index 1 becomes 0, etc.) */
+ return fd_index - 1;
+ }
+ return fd_index;
+}
+
+static inline void __io_uring_prep_buf_reg_unreg(struct io_uring_sqe *sqe,
+ struct ublk_queue *q, int tag, int q_id, __u64 index)
{
struct ublksrv_io_cmd *cmd = (struct ublksrv_io_cmd *)sqe->cmd;
+ int dev_fd = ublk_get_registered_fd(q, 0);
io_uring_prep_read(sqe, dev_fd, 0, 0, 0);
sqe->opcode = IORING_OP_URING_CMD;
- sqe->flags |= IOSQE_FIXED_FILE;
- sqe->cmd_op = UBLK_U_IO_REGISTER_IO_BUF;
+ if (q->flags & UBLKS_Q_NO_UBLK_FIXED_FD)
+ sqe->flags &= ~IOSQE_FIXED_FILE;
+ else
+ sqe->flags |= IOSQE_FIXED_FILE;
cmd->tag = tag;
cmd->addr = index;
cmd->q_id = q_id;
}
-static inline void io_uring_prep_buf_unregister(struct io_uring_sqe *sqe,
- int dev_fd, int tag, int q_id, __u64 index)
+static inline void io_uring_prep_buf_register(struct io_uring_sqe *sqe,
+ struct ublk_queue *q, int tag, int q_id, __u64 index)
{
- struct ublksrv_io_cmd *cmd = (struct ublksrv_io_cmd *)sqe->cmd;
+ __io_uring_prep_buf_reg_unreg(sqe, q, tag, q_id, index);
+ sqe->cmd_op = UBLK_U_IO_REGISTER_IO_BUF;
+}
- io_uring_prep_read(sqe, dev_fd, 0, 0, 0);
- sqe->opcode = IORING_OP_URING_CMD;
- sqe->flags |= IOSQE_FIXED_FILE;
+static inline void io_uring_prep_buf_unregister(struct io_uring_sqe *sqe,
+ struct ublk_queue *q, int tag, int q_id, __u64 index)
+{
+ __io_uring_prep_buf_reg_unreg(sqe, q, tag, q_id, index);
sqe->cmd_op = UBLK_U_IO_UNREGISTER_IO_BUF;
-
- cmd->tag = tag;
- cmd->addr = index;
- cmd->q_id = q_id;
}
static inline void *ublk_get_sqe_cmd(const struct io_uring_sqe *sqe)
diff --git a/tools/testing/selftests/ublk/null.c b/tools/testing/selftests/ublk/null.c
index f0e0003..280043f 100644
--- a/tools/testing/selftests/ublk/null.c
+++ b/tools/testing/selftests/ublk/null.c
@@ -63,7 +63,7 @@ static int null_queue_zc_io(struct ublk_thread *t, struct ublk_queue *q,
ublk_io_alloc_sqes(t, sqe, 3);
- io_uring_prep_buf_register(sqe[0], 0, tag, q->q_id, ublk_get_io(q, tag)->buf_index);
+ io_uring_prep_buf_register(sqe[0], q, tag, q->q_id, ublk_get_io(q, tag)->buf_index);
sqe[0]->user_data = build_user_data(tag,
ublk_cmd_op_nr(sqe[0]->cmd_op), 0, q->q_id, 1);
sqe[0]->flags |= IOSQE_CQE_SKIP_SUCCESS | IOSQE_IO_HARDLINK;
@@ -71,7 +71,7 @@ static int null_queue_zc_io(struct ublk_thread *t, struct ublk_queue *q,
__setup_nop_io(tag, iod, sqe[1], q->q_id);
sqe[1]->flags |= IOSQE_IO_HARDLINK;
- io_uring_prep_buf_unregister(sqe[2], 0, tag, q->q_id, ublk_get_io(q, tag)->buf_index);
+ io_uring_prep_buf_unregister(sqe[2], q, tag, q->q_id, ublk_get_io(q, tag)->buf_index);
sqe[2]->user_data = build_user_data(tag, ublk_cmd_op_nr(sqe[2]->cmd_op), 0, q->q_id, 1);
// buf register is marked as IOSQE_CQE_SKIP_SUCCESS
diff --git a/tools/testing/selftests/ublk/stripe.c b/tools/testing/selftests/ublk/stripe.c
index 1fb9b7c..791fa8d 100644
--- a/tools/testing/selftests/ublk/stripe.c
+++ b/tools/testing/selftests/ublk/stripe.c
@@ -142,7 +142,7 @@ static int stripe_queue_tgt_rw_io(struct ublk_thread *t, struct ublk_queue *q,
ublk_io_alloc_sqes(t, sqe, s->nr + extra);
if (zc) {
- io_uring_prep_buf_register(sqe[0], 0, tag, q->q_id, io->buf_index);
+ io_uring_prep_buf_register(sqe[0], q, tag, q->q_id, io->buf_index);
sqe[0]->flags |= IOSQE_CQE_SKIP_SUCCESS | IOSQE_IO_HARDLINK;
sqe[0]->user_data = build_user_data(tag,
ublk_cmd_op_nr(sqe[0]->cmd_op), 0, q->q_id, 1);
@@ -168,7 +168,7 @@ static int stripe_queue_tgt_rw_io(struct ublk_thread *t, struct ublk_queue *q,
if (zc) {
struct io_uring_sqe *unreg = sqe[s->nr + 1];
- io_uring_prep_buf_unregister(unreg, 0, tag, q->q_id, io->buf_index);
+ io_uring_prep_buf_unregister(unreg, q, tag, q->q_id, io->buf_index);
unreg->user_data = build_user_data(
tag, ublk_cmd_op_nr(unreg->cmd_op), 0, q->q_id, 1);
}
diff --git a/tools/testing/selftests/ublk/test_stress_04.sh b/tools/testing/selftests/ublk/test_stress_04.sh
index 40d1437..3f901db 100755
--- a/tools/testing/selftests/ublk/test_stress_04.sh
+++ b/tools/testing/selftests/ublk/test_stress_04.sh
@@ -28,14 +28,14 @@
_create_backfile 1 128M
_create_backfile 2 128M
-ublk_io_and_kill_daemon 8G -t null -q 4 -z &
-ublk_io_and_kill_daemon 256M -t loop -q 4 -z "${UBLK_BACKFILES[0]}" &
+ublk_io_and_kill_daemon 8G -t null -q 4 -z --no_ublk_fixed_fd &
+ublk_io_and_kill_daemon 256M -t loop -q 4 -z --no_ublk_fixed_fd "${UBLK_BACKFILES[0]}" &
ublk_io_and_kill_daemon 256M -t stripe -q 4 -z "${UBLK_BACKFILES[1]}" "${UBLK_BACKFILES[2]}" &
if _have_feature "AUTO_BUF_REG"; then
ublk_io_and_kill_daemon 8G -t null -q 4 --auto_zc &
ublk_io_and_kill_daemon 256M -t loop -q 4 --auto_zc "${UBLK_BACKFILES[0]}" &
- ublk_io_and_kill_daemon 256M -t stripe -q 4 --auto_zc "${UBLK_BACKFILES[1]}" "${UBLK_BACKFILES[2]}" &
+ ublk_io_and_kill_daemon 256M -t stripe -q 4 --auto_zc --no_ublk_fixed_fd "${UBLK_BACKFILES[1]}" "${UBLK_BACKFILES[2]}" &
ublk_io_and_kill_daemon 8G -t null -q 4 -z --auto_zc --auto_zc_fallback &
fi
