github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-11-06 21:58:01 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

io_uring/dma-buf: allow cloning registered dma-bufs

Browse Source 
One problem that was brought up is that the file table size is often a
limiting factor when working with dma-bufs, which is quite an old
problem. With a single io_uring people can work it around by closing
the dma-buf fd after registration, but for more complex cases we need
a way to dynamically register it into another ring. We also need to
deduplicate internal registrations as each creates a new attachment and
related structures, which could involve large allocations and iommu
mappings. Solve it by enabling io_uring buffer cloning.

I made dma-bufs registered for io_uring not cloneable between rings
because the implementation could modify parts of struct io_buf_dma
without any locking and sharing it would've created races. That was an
optimisation that got dropped at some point for simplicity, so we can
safely enable cloning back as long as IORING_SETUP_IOPOLL rejection
is honoured. Kill the uncloneable flag as unused as well.

Reported-by: William Power <william.power@intel.com>
Reported-by: Tushar Gohad <tushar.gohad@intel.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://patch.msgid.link/b76cf21ee0e2362489c864e43781b20d95fd75f7.1792142588.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2026-10-16 10:26:55 +01:00 committed by Jens Axboe
parent aeef964d73
commit f57b957778
3 changed files with 10 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
io_uring/dma-buf.c
View File

@ -18,6 +18,11 @@ int __io_register_dmabuf(struct io_ring_ctx *ctx,
struct dma_buf *dmabuf = NULL;
int ret;
/*
* We have to drop the dma-buf map early when IO is finished. Disable
* IOPOLL for now as we can't wait potentially infintely for a task
* to do that.
*/
if (ctx->flags & IORING_SETUP_IOPOLL)
return -EOPNOTSUPP;
if (desc->uaddr || desc->size)
@ -51,7 +56,7 @@ int __io_register_dmabuf(struct io_ring_ctx *ctx,
imu->len = dmabuf->size;
imu->release = io_release_dmabuf;
imu->priv = bd;
imu->flags = IO_REGBUF_F_DMABUF | IO_REGBUF_F_UNCLONEABLE;
imu->flags = IO_REGBUF_F_DMABUF;
imu->dir = IO_BUF_DEST | IO_BUF_SOURCE;
dma_buf_put(dmabuf);
return 0;

4
io_uring/rsrc.c
View File

@ -1507,7 +1507,9 @@ static int io_clone_buffers(struct io_ring_ctx *ctx, struct io_ring_ctx *src_ctx
if (!src_node) {
dst_node = NULL;
} else {
if (src_node->buf->flags & IO_REGBUF_F_UNCLONEABLE) {
/* we don't allow IOPOLL rw with dma-buf for now */
if ((src_node->buf->flags & IO_REGBUF_F_DMABUF) &&
(ctx->flags & IORING_SETUP_IOPOLL)) {
io_rsrc_data_free(ctx, &data);
return -EOPNOTSUPP;
}

3
io_uring/rsrc.h
View File

@ -27,8 +27,7 @@ struct io_rsrc_node {
enum {
IO_REGBUF_F_KBUF = 1 << 0,
IO_REGBUF_F_UNCLONEABLE = 1 << 1,
IO_REGBUF_F_DMABUF = 1 << 3,
IO_REGBUF_F_DMABUF = 1 << 1,
};
enum {