From 3f302388d45855c0b24802e7b414e3fb29f172e3 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Thu, 11 Jan 2024 13:34:33 -0700
Subject: [PATCH] io_uring/rsrc: improve code generation for fixed file
assignment
For the normal read/write path, we have already locked the ring
submission side when assigning the file. This causes branch
mispredictions when we then check and try and lock again in
io_req_set_rsrc_node(). As this is a very hot path, this matters.
Add a basic helper that already assumes we already have it locked,
and use that in io_file_get_fixed().
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
io_uring/io_uring.c | 5 +++--
io_uring/rsrc.h | 14 +++++++++-----
2 files changed, 12 insertions(+), 7 deletions(-)
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 4afb911fc042b..50c9f04bc193c 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -2000,9 +2000,10 @@ inline struct file *io_file_get_fixed(struct io_kiocb *req, int fd,
goto out;
fd = array_index_nospec(fd, ctx->nr_user_files);
slot = io_fixed_file_slot(&ctx->file_table, fd);
- file = io_slot_file(slot);
+ if (!req->rsrc_node)
+ __io_req_set_rsrc_node(req, ctx);
req->flags |= io_slot_flags(slot);
- io_req_set_rsrc_node(req, ctx, 0);
+ file = io_slot_file(slot);
out:
io_ring_submit_unlock(ctx, issue_flags);
return file;
diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
index 7238b9cfe33b6..c6f199bbee284 100644
--- a/io_uring/rsrc.h
+++ b/io_uring/rsrc.h
@@ -102,17 +102,21 @@ static inline void io_charge_rsrc_node(struct io_ring_ctx *ctx,
node->refs++;
}
+static inline void __io_req_set_rsrc_node(struct io_kiocb *req,
+ struct io_ring_ctx *ctx)
+{
+ lockdep_assert_held(&ctx->uring_lock);
+ req->rsrc_node = ctx->rsrc_node;
+ io_charge_rsrc_node(ctx, ctx->rsrc_node);
+}
+
static inline void io_req_set_rsrc_node(struct io_kiocb *req,
struct io_ring_ctx *ctx,
unsigned int issue_flags)
{
if (!req->rsrc_node) {
io_ring_submit_lock(ctx, issue_flags);
-
- lockdep_assert_held(&ctx->uring_lock);
-
- req->rsrc_node = ctx->rsrc_node;
- io_charge_rsrc_node(ctx, ctx->rsrc_node);
+ __io_req_set_rsrc_node(req, ctx);
io_ring_submit_unlock(ctx, issue_flags);
}
}
--
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