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io_uring: provide means of removing buffers

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We have IORING_OP_PROVIDE_BUFFERS, but the only way to remove buffers
is to trigger IO on them. The usual case of shrinking a buffer pool
would be to just not replenish the buffers when IO completes, and
instead just free it. But it may be nice to have a way to manually
remove a number of buffers from a given group, and
IORING_OP_REMOVE_BUFFERS provides that functionality.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2020-03-02 16:32:28 -07:00
parent 52de1fe122
commit 067524e914
2 changed files with 84 additions and 19 deletions
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102
fs/io_uring.c
View File

@ -827,6 +827,7 @@ static const struct io_op_def io_op_defs[] = {
.unbound_nonreg_file = 1,
},
[IORING_OP_PROVIDE_BUFFERS] = {},
[IORING_OP_REMOVE_BUFFERS] = {},
};
static void io_wq_submit_work(struct io_wq_work **workptr);
@ -2995,6 +2996,75 @@ static int io_openat(struct io_kiocb *req, bool force_nonblock)
return io_openat2(req, force_nonblock);
}
static int io_remove_buffers_prep(struct io_kiocb *req,
const struct io_uring_sqe *sqe)
{
struct io_provide_buf *p = &req->pbuf;
u64 tmp;
if (sqe->ioprio || sqe->rw_flags || sqe->addr || sqe->len || sqe->off)
return -EINVAL;
tmp = READ_ONCE(sqe->fd);
if (!tmp || tmp > USHRT_MAX)
return -EINVAL;
memset(p, 0, sizeof(*p));
p->nbufs = tmp;
p->bgid = READ_ONCE(sqe->buf_group);
return 0;
}
static int __io_remove_buffers(struct io_ring_ctx *ctx, struct io_buffer *buf,
int bgid, unsigned nbufs)
{
unsigned i = 0;
/* shouldn't happen */
if (!nbufs)
return 0;
/* the head kbuf is the list itself */
while (!list_empty(&buf->list)) {
struct io_buffer *nxt;
nxt = list_first_entry(&buf->list, struct io_buffer, list);
list_del(&nxt->list);
kfree(nxt);
if (++i == nbufs)
return i;
}
i++;
kfree(buf);
idr_remove(&ctx->io_buffer_idr, bgid);
return i;
}
static int io_remove_buffers(struct io_kiocb *req, bool force_nonblock)
{
struct io_provide_buf *p = &req->pbuf;
struct io_ring_ctx *ctx = req->ctx;
struct io_buffer *head;
int ret = 0;
io_ring_submit_lock(ctx, !force_nonblock);
lockdep_assert_held(&ctx->uring_lock);
ret = -ENOENT;
head = idr_find(&ctx->io_buffer_idr, p->bgid);
if (head)
ret = __io_remove_buffers(ctx, head, p->bgid, p->nbufs);
io_ring_submit_lock(ctx, !force_nonblock);
if (ret < 0)
req_set_fail_links(req);
io_cqring_add_event(req, ret);
io_put_req(req);
return 0;
}
static int io_provide_buffers_prep(struct io_kiocb *req,
const struct io_uring_sqe *sqe)
{
@ -3070,15 +3140,7 @@ static int io_provide_buffers(struct io_kiocb *req, bool force_nonblock)
ret = idr_alloc(&ctx->io_buffer_idr, head, p->bgid, p->bgid + 1,
GFP_KERNEL);
if (ret < 0) {
while (!list_empty(&head->list)) {
struct io_buffer *buf;
buf = list_first_entry(&head->list,
struct io_buffer, list);
list_del(&buf->list);
kfree(buf);
}
kfree(head);
__io_remove_buffers(ctx, head, p->bgid, -1U);
goto out;
}
}
@ -4825,6 +4887,9 @@ static int io_req_defer_prep(struct io_kiocb *req,
case IORING_OP_PROVIDE_BUFFERS:
ret = io_provide_buffers_prep(req, sqe);
break;
case IORING_OP_REMOVE_BUFFERS:
ret = io_remove_buffers_prep(req, sqe);
break;
default:
printk_once(KERN_WARNING "io_uring: unhandled opcode %d\n",
req->opcode);
@ -5120,6 +5185,14 @@ static int io_issue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
}
ret = io_provide_buffers(req, force_nonblock);
break;
case IORING_OP_REMOVE_BUFFERS:
if (sqe) {
ret = io_remove_buffers_prep(req, sqe);
if (ret)
break;
}
ret = io_remove_buffers(req, force_nonblock);
break;
default:
ret = -EINVAL;
break;
@ -6998,16 +7071,7 @@ static int __io_destroy_buffers(int id, void *p, void *data)
struct io_ring_ctx *ctx = data;
struct io_buffer *buf = p;
/* the head kbuf is the list itself */
while (!list_empty(&buf->list)) {
struct io_buffer *nxt;
nxt = list_first_entry(&buf->list, struct io_buffer, list);
list_del(&nxt->list);
kfree(nxt);
}
kfree(buf);
idr_remove(&ctx->io_buffer_idr, id);
__io_remove_buffers(ctx, buf, id, -1U);
return 0;
}

1
include/uapi/linux/io_uring.h
View File

@ -128,6 +128,7 @@ enum {
IORING_OP_EPOLL_CTL,
IORING_OP_SPLICE,
IORING_OP_PROVIDE_BUFFERS,
IORING_OP_REMOVE_BUFFERS,
/* this goes last, obviously */
IORING_OP_LAST,