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io_uring: share fixed_file_refs b/w multiple rsrcs

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Double fixed files for splice/tee are done in a nasty way, it takes 2
ref_node refs, and during the second time it blindly overrides
req->fixed_file_refs hoping that it haven't changed. That works because
all that is done under iouring_lock in a single go but is error-prone.

Bind everything explicitly to a single ref_node and take only one ref,
with current ref_node ordering it's guaranteed to keep all files valid
awhile the request is inflight.

That's mainly a cleanup + preparation for generic resource handling,
but also saves pcpu_ref get/put for splice/tee with 2 fixed files.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2020-11-18 19:57:26 +00:00 committed by Jens Axboe
parent c98de08c99
commit 36f72fe279
1 changed files with 15 additions and 8 deletions
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23
fs/io_uring.c
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@ -1037,6 +1037,16 @@ static inline void io_clean_op(struct io_kiocb *req)
__io_clean_op(req);
}
static inline void io_set_resource_node(struct io_kiocb *req)
{
struct io_ring_ctx *ctx = req->ctx;
if (!req->fixed_file_refs) {
req->fixed_file_refs = &ctx->file_data->node->refs;
percpu_ref_get(req->fixed_file_refs);
}
}
static bool io_match_task(struct io_kiocb *head,
struct task_struct *task,
struct files_struct *files)
@ -1919,9 +1929,7 @@ static struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx,
static inline void io_put_file(struct io_kiocb *req, struct file *file,
bool fixed)
{
if (fixed)
percpu_ref_put(req->fixed_file_refs);
else
if (!fixed)
fput(file);
}
@ -1933,7 +1941,8 @@ static void io_dismantle_req(struct io_kiocb *req)
kfree(req->async_data);
if (req->file)
io_put_file(req, req->file, (req->flags & REQ_F_FIXED_FILE));
if (req->fixed_file_refs)
percpu_ref_put(req->fixed_file_refs);
io_req_clean_work(req);
}
@ -6310,10 +6319,7 @@ static struct file *io_file_get(struct io_submit_state *state,
return NULL;
fd = array_index_nospec(fd, ctx->nr_user_files);
file = io_file_from_index(ctx, fd);
if (file) {
req->fixed_file_refs = &ctx->file_data->node->refs;
percpu_ref_get(req->fixed_file_refs);
}
io_set_resource_node(req);
} else {
trace_io_uring_file_get(ctx, fd);
file = __io_file_get(state, fd);
@ -6691,6 +6697,7 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
req->ctx = ctx;
req->flags = 0;
req->link = NULL;
req->fixed_file_refs = NULL;
/* one is dropped after submission, the other at completion */
refcount_set(&req->refs, 2);
req->task = current;