Currently cloning a buffer table will fail if the destination already has
a table. But it should be possible to use it to replace existing elements.
Add a IORING_REGISTER_DST_REPLACE cloning flag, which if set, will allow
the destination to already having a buffer table. If that is the case,
then entries designated by offset + nr buffers will be replaced if they
already exist.
Note that it's allowed to use IORING_REGISTER_DST_REPLACE and not have
an existing table, in which case it'll work just like not having the
flag set and an empty table - it'll just assign the newly created table
for that case.
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
include/uapi/linux/io_uring.h | 3 ++-
io_uring/rsrc.c | 24 ++++++++++++++++++++----
2 files changed, 22 insertions(+), 5 deletions(-)
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index cc8dbe78c126..ce58c4590de6 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -713,7 +713,8 @@ struct io_uring_clock_register {
};
enum {
- IORING_REGISTER_SRC_REGISTERED = 1,
+ IORING_REGISTER_SRC_REGISTERED = (1U << 0),
+ IORING_REGISTER_DST_REPLACE = (1U << 1),
};
struct io_uring_clone_buffers {
diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index 4c149dc42fd7..9829c51105ed 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -990,9 +990,25 @@ static int io_clone_buffers(struct io_ring_ctx *ctx, struct io_ring_ctx *src_ctx
/* Have a ref on the bufs now, drop src lock and re-grab our own lock */
mutex_unlock(&src_ctx->uring_lock);
mutex_lock(&ctx->uring_lock);
- if (!ctx->buf_table.nr) {
+
+ /*
+ * Not replacing, or replacing an empty table. Just install the
+ * new table.
+ */
+ if (!(arg->flags & IORING_REGISTER_DST_REPLACE) || !ctx->buf_table.nr) {
ctx->buf_table = data;
return 0;
+ } else if (arg->flags & IORING_REGISTER_DST_REPLACE) {
+ /* put nodes in overlapping spots, if any */
+ for (i = arg->src_off; i < arg->nr; i++) {
+ if (data.nodes[i] == rsrc_empty_node)
+ continue;
+ io_reset_rsrc_node(&ctx->buf_table, i);
+ ctx->buf_table.nodes[i] = data.nodes[i];
+ data.nodes[i] = NULL;
+ }
+ io_rsrc_data_free(&data);
+ return 0;
}
mutex_unlock(&ctx->uring_lock);
@@ -1026,12 +1042,12 @@ int io_register_clone_buffers(struct io_ring_ctx *ctx, void __user *arg)
struct file *file;
int ret;
- if (ctx->buf_table.nr)
- return -EBUSY;
if (copy_from_user(&buf, arg, sizeof(buf)))
return -EFAULT;
- if (buf.flags & ~IORING_REGISTER_SRC_REGISTERED)
+ if (buf.flags & ~(IORING_REGISTER_SRC_REGISTERED|IORING_REGISTER_DST_REPLACE))
return -EINVAL;
+ if (!(buf.flags & IORING_REGISTER_DST_REPLACE) && ctx->buf_table.nr)
+ return -EBUSY;
if (memchr_inv(buf.pad, 0, sizeof(buf.pad)))
return -EINVAL;
--
2.45.2
