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io_uring: add file set registration 

We normally have to fget/fput for each IO we do on a file. Even with
the batching we do, the cost of the atomic inc/dec of the file usage
count adds up.

This adds IORING_REGISTER_FILES, and IORING_UNREGISTER_FILES opcodes
for the io_uring_register(2) system call. The arguments passed in must
be an array of __s32 holding file descriptors, and nr_args should hold
the number of file descriptors the application wishes to pin for the
duration of the io_uring instance (or until IORING_UNREGISTER_FILES is
called).

When used, the application must set IOSQE_FIXED_FILE in the sqe->flags
member. Then, instead of setting sqe->fd to the real fd, it sets sqe->fd
to the index in the array passed in to IORING_REGISTER_FILES.

Files are automatically unregistered when the io_uring instance is torn
down. An application need only unregister if it wishes to register a new
set of fds.

Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
hifive-unleashed-5.1
Jens Axboe 2019-01-10 22:13:58 -07:00
parent f4e65870e5
commit 6b06314c47
2 changed files with 288 additions and 32 deletions
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311
fs/io_uring.c
View File

@ -49,6 +49,7 @@
#include <linux/net.h>
#include <net/sock.h>
#include <net/af_unix.h>
#include <net/scm.h>
#include <linux/anon_inodes.h>
#include <linux/sched/mm.h>
#include <linux/uaccess.h>
@ -61,6 +62,7 @@
#include "internal.h"
#define IORING_MAX_ENTRIES 4096
#define IORING_MAX_FIXED_FILES 1024
struct io_uring {
u32 head ____cacheline_aligned_in_smp;
@ -123,6 +125,14 @@ struct io_ring_ctx {
struct fasync_struct *cq_fasync;
} ____cacheline_aligned_in_smp;
/*
* If used, fixed file set. Writers must ensure that ->refs is dead,
* readers must ensure that ->refs is alive as long as the file* is
* used. Only updated through io_uring_register(2).
*/
struct file **user_files;
unsigned nr_user_files;
/* if used, fixed mapped user buffers */
unsigned nr_user_bufs;
struct io_mapped_ubuf *user_bufs;
@ -170,6 +180,7 @@ struct io_kiocb {
unsigned int flags;
#define REQ_F_FORCE_NONBLOCK 1 /* inline submission attempt */
#define REQ_F_IOPOLL_COMPLETED 2 /* polled IO has completed */
#define REQ_F_FIXED_FILE 4 /* ctx owns file */
u64 user_data;
u64 error;
@ -404,15 +415,17 @@ static void io_iopoll_complete(struct io_ring_ctx *ctx, unsigned int *nr_events,
* Batched puts of the same file, to avoid dirtying the
* file usage count multiple times, if avoidable.
*/
if (!file) {
file = req->rw.ki_filp;
file_count = 1;
} else if (file == req->rw.ki_filp) {
file_count++;
} else {
fput_many(file, file_count);
file = req->rw.ki_filp;
file_count = 1;
if (!(req->flags & REQ_F_FIXED_FILE)) {
if (!file) {
file = req->rw.ki_filp;
file_count = 1;
} else if (file == req->rw.ki_filp) {
file_count++;
} else {
fput_many(file, file_count);
file = req->rw.ki_filp;
file_count = 1;
}
}
if (to_free == ARRAY_SIZE(reqs))
@ -544,13 +557,19 @@ static void kiocb_end_write(struct kiocb *kiocb)
}
}
static void io_fput(struct io_kiocb *req)
{
if (!(req->flags & REQ_F_FIXED_FILE))
fput(req->rw.ki_filp);
}
static void io_complete_rw(struct kiocb *kiocb, long res, long res2)
{
struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw);
kiocb_end_write(kiocb);
fput(kiocb->ki_filp);
io_fput(req);
io_cqring_add_event(req->ctx, req->user_data, res, 0);
io_free_req(req);
}
@ -666,19 +685,29 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe,
{
struct io_ring_ctx *ctx = req->ctx;
struct kiocb *kiocb = &req->rw;
unsigned ioprio;
unsigned ioprio, flags;
int fd, ret;
/* For -EAGAIN retry, everything is already prepped */
if (kiocb->ki_filp)
return 0;
flags = READ_ONCE(sqe->flags);
fd = READ_ONCE(sqe->fd);
kiocb->ki_filp = io_file_get(state, fd);
if (unlikely(!kiocb->ki_filp))
return -EBADF;
if (force_nonblock && !io_file_supports_async(kiocb->ki_filp))
force_nonblock = false;
if (flags & IOSQE_FIXED_FILE) {
if (unlikely(!ctx->user_files ||
(unsigned) fd >= ctx->nr_user_files))
return -EBADF;
kiocb->ki_filp = ctx->user_files[fd];
req->flags |= REQ_F_FIXED_FILE;
} else {
kiocb->ki_filp = io_file_get(state, fd);
if (unlikely(!kiocb->ki_filp))
return -EBADF;
if (force_nonblock && !io_file_supports_async(kiocb->ki_filp))
force_nonblock = false;
}
kiocb->ki_pos = READ_ONCE(sqe->off);
kiocb->ki_flags = iocb_flags(kiocb->ki_filp);
kiocb->ki_hint = ki_hint_validate(file_write_hint(kiocb->ki_filp));
@ -718,10 +747,14 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe,
}
return 0;
out_fput:
/* in case of error, we didn't use this file reference. drop it. */
if (state)
state->used_refs--;
io_file_put(state, kiocb->ki_filp);
if (!(flags & IOSQE_FIXED_FILE)) {
/*
* in case of error, we didn't use this file reference. drop it.
*/
if (state)
state->used_refs--;
io_file_put(state, kiocb->ki_filp);
}
return ret;
}
@ -863,7 +896,7 @@ static ssize_t io_read(struct io_kiocb *req, const struct sqe_submit *s,
out_fput:
/* Hold on to the file for -EAGAIN */
if (unlikely(ret && ret != -EAGAIN))
fput(file);
io_fput(req);
return ret;
}
@ -917,7 +950,7 @@ static ssize_t io_write(struct io_kiocb *req, const struct sqe_submit *s,
kfree(iovec);
out_fput:
if (unlikely(ret))
fput(file);
io_fput(req);
return ret;
}
@ -940,7 +973,7 @@ static int io_nop(struct io_kiocb *req, u64 user_data)
*/
if (req->rw.ki_filp) {
err = -EBADF;
fput(req->rw.ki_filp);
io_fput(req);
}
io_cqring_add_event(ctx, user_data, err, 0);
io_free_req(req);
@ -949,21 +982,32 @@ static int io_nop(struct io_kiocb *req, u64 user_data)
static int io_prep_fsync(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
struct io_ring_ctx *ctx = req->ctx;
unsigned flags;
int fd;
/* Prep already done */
if (req->rw.ki_filp)
return 0;
if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
if (unlikely(ctx->flags & IORING_SETUP_IOPOLL))
return -EINVAL;
if (unlikely(sqe->addr || sqe->ioprio || sqe->buf_index))
return -EINVAL;
fd = READ_ONCE(sqe->fd);
req->rw.ki_filp = fget(fd);
if (unlikely(!req->rw.ki_filp))
return -EBADF;
flags = READ_ONCE(sqe->flags);
if (flags & IOSQE_FIXED_FILE) {
if (unlikely(!ctx->user_files || fd >= ctx->nr_user_files))
return -EBADF;
req->rw.ki_filp = ctx->user_files[fd];
req->flags |= REQ_F_FIXED_FILE;
} else {
req->rw.ki_filp = fget(fd);
if (unlikely(!req->rw.ki_filp))
return -EBADF;
}
return 0;
}
@ -993,7 +1037,7 @@ static int io_fsync(struct io_kiocb *req, const struct io_uring_sqe *sqe,
end > 0 ? end : LLONG_MAX,
fsync_flags & IORING_FSYNC_DATASYNC);
fput(req->rw.ki_filp);
io_fput(req);
io_cqring_add_event(req->ctx, sqe->user_data, ret, 0);
io_free_req(req);
return 0;
@ -1132,7 +1176,7 @@ static int io_submit_sqe(struct io_ring_ctx *ctx, struct sqe_submit *s,
ssize_t ret;
/* enforce forwards compatibility on users */
if (unlikely(s->sqe->flags))
if (unlikely(s->sqe->flags & ~IOSQE_FIXED_FILE))
return -EINVAL;
req = io_get_req(ctx, state);
@ -1344,6 +1388,201 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
return READ_ONCE(ring->r.head) == READ_ONCE(ring->r.tail) ? ret : 0;
}
static void __io_sqe_files_unregister(struct io_ring_ctx *ctx)
{
#if defined(CONFIG_UNIX)
if (ctx->ring_sock) {
struct sock *sock = ctx->ring_sock->sk;
struct sk_buff *skb;
while ((skb = skb_dequeue(&sock->sk_receive_queue)) != NULL)
kfree_skb(skb);
}
#else
int i;
for (i = 0; i < ctx->nr_user_files; i++)
fput(ctx->user_files[i]);
#endif
}
static int io_sqe_files_unregister(struct io_ring_ctx *ctx)
{
if (!ctx->user_files)
return -ENXIO;
__io_sqe_files_unregister(ctx);
kfree(ctx->user_files);
ctx->user_files = NULL;
ctx->nr_user_files = 0;
return 0;
}
static void io_finish_async(struct io_ring_ctx *ctx)
{
if (ctx->sqo_wq) {
destroy_workqueue(ctx->sqo_wq);
ctx->sqo_wq = NULL;
}
}
#if defined(CONFIG_UNIX)
static void io_destruct_skb(struct sk_buff *skb)
{
struct io_ring_ctx *ctx = skb->sk->sk_user_data;
io_finish_async(ctx);
unix_destruct_scm(skb);
}
/*
* Ensure the UNIX gc is aware of our file set, so we are certain that
* the io_uring can be safely unregistered on process exit, even if we have
* loops in the file referencing.
*/
static int __io_sqe_files_scm(struct io_ring_ctx *ctx, int nr, int offset)
{
struct sock *sk = ctx->ring_sock->sk;
struct scm_fp_list *fpl;
struct sk_buff *skb;
int i;
if (!capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) {
unsigned long inflight = ctx->user->unix_inflight + nr;
if (inflight > task_rlimit(current, RLIMIT_NOFILE))
return -EMFILE;
}
fpl = kzalloc(sizeof(*fpl), GFP_KERNEL);
if (!fpl)
return -ENOMEM;
skb = alloc_skb(0, GFP_KERNEL);
if (!skb) {
kfree(fpl);
return -ENOMEM;
}
skb->sk = sk;
skb->destructor = io_destruct_skb;
fpl->user = get_uid(ctx->user);
for (i = 0; i < nr; i++) {
fpl->fp[i] = get_file(ctx->user_files[i + offset]);
unix_inflight(fpl->user, fpl->fp[i]);
}
fpl->max = fpl->count = nr;
UNIXCB(skb).fp = fpl;
refcount_add(skb->truesize, &sk->sk_wmem_alloc);
skb_queue_head(&sk->sk_receive_queue, skb);
for (i = 0; i < nr; i++)
fput(fpl->fp[i]);
return 0;
}
/*
* If UNIX sockets are enabled, fd passing can cause a reference cycle which
* causes regular reference counting to break down. We rely on the UNIX
* garbage collection to take care of this problem for us.
*/
static int io_sqe_files_scm(struct io_ring_ctx *ctx)
{
unsigned left, total;
int ret = 0;
total = 0;
left = ctx->nr_user_files;
while (left) {
unsigned this_files = min_t(unsigned, left, SCM_MAX_FD);
int ret;
ret = __io_sqe_files_scm(ctx, this_files, total);
if (ret)
break;
left -= this_files;
total += this_files;
}
if (!ret)
return 0;
while (total < ctx->nr_user_files) {
fput(ctx->user_files[total]);
total++;
}
return ret;
}
#else
static int io_sqe_files_scm(struct io_ring_ctx *ctx)
{
return 0;
}
#endif
static int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg,
unsigned nr_args)
{
__s32 __user *fds = (__s32 __user *) arg;
int fd, ret = 0;
unsigned i;
if (ctx->user_files)
return -EBUSY;
if (!nr_args)
return -EINVAL;
if (nr_args > IORING_MAX_FIXED_FILES)
return -EMFILE;
ctx->user_files = kcalloc(nr_args, sizeof(struct file *), GFP_KERNEL);
if (!ctx->user_files)
return -ENOMEM;
for (i = 0; i < nr_args; i++) {
ret = -EFAULT;
if (copy_from_user(&fd, &fds[i], sizeof(fd)))
break;
ctx->user_files[i] = fget(fd);
ret = -EBADF;
if (!ctx->user_files[i])
break;
/*
* Don't allow io_uring instances to be registered. If UNIX
* isn't enabled, then this causes a reference cycle and this
* instance can never get freed. If UNIX is enabled we'll
* handle it just fine, but there's still no point in allowing
* a ring fd as it doesn't support regular read/write anyway.
*/
if (ctx->user_files[i]->f_op == &io_uring_fops) {
fput(ctx->user_files[i]);
break;
}
ctx->nr_user_files++;
ret = 0;
}
if (ret) {
for (i = 0; i < ctx->nr_user_files; i++)
fput(ctx->user_files[i]);
kfree(ctx->user_files);
ctx->nr_user_files = 0;
return ret;
}
ret = io_sqe_files_scm(ctx);
if (ret)
io_sqe_files_unregister(ctx);
return ret;
}
static int io_sq_offload_start(struct io_ring_ctx *ctx)
{
int ret;
@ -1612,13 +1851,13 @@ err:
static void io_ring_ctx_free(struct io_ring_ctx *ctx)
{
if (ctx->sqo_wq)
destroy_workqueue(ctx->sqo_wq);
io_finish_async(ctx);
if (ctx->sqo_mm)
mmdrop(ctx->sqo_mm);
io_iopoll_reap_events(ctx);
io_sqe_buffer_unregister(ctx);
io_sqe_files_unregister(ctx);
#if defined(CONFIG_UNIX)
if (ctx->ring_sock)
@ -1858,6 +2097,7 @@ static int io_uring_get_fd(struct io_ring_ctx *ctx)
#if defined(CONFIG_UNIX)
ctx->ring_sock->file = file;
ctx->ring_sock->sk->sk_user_data = ctx;
#endif
fd_install(ret, file);
return ret;
@ -2001,6 +2241,15 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
break;
ret = io_sqe_buffer_unregister(ctx);
break;
case IORING_REGISTER_FILES:
ret = io_sqe_files_register(ctx, arg, nr_args);
break;
case IORING_UNREGISTER_FILES:
ret = -EINVAL;
if (arg || nr_args)
break;
ret = io_sqe_files_unregister(ctx);
break;
default:
ret = -EINVAL;
break;

9
include/uapi/linux/io_uring.h
View File

@ -16,7 +16,7 @@
*/
struct io_uring_sqe {
__u8 opcode; /* type of operation for this sqe */
__u8 flags; /* as of now unused */
__u8 flags; /* IOSQE_ flags */
__u16 ioprio; /* ioprio for the request */
__s32 fd; /* file descriptor to do IO on */
__u64 off; /* offset into file */
@ -33,6 +33,11 @@ struct io_uring_sqe {
};
};
/*
* sqe->flags
*/
#define IOSQE_FIXED_FILE (1U << 0) /* use fixed fileset */
/*
* io_uring_setup() flags
*/
@ -113,5 +118,7 @@ struct io_uring_params {
*/
#define IORING_REGISTER_BUFFERS 0
#define IORING_UNREGISTER_BUFFERS 1
#define IORING_REGISTER_FILES 2
#define IORING_UNREGISTER_FILES 3
#endif