This is a note to let you know that I've just added the patch titled
io_uring: get rid of double locking
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
io_uring-get-rid-of-double-locking.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From f10ba483becae0b8c7de0e9fe3e0f6d07a405b7a Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@xxxxxxxxx>
Date: Wed, 7 Dec 2022 03:53:34 +0000
Subject: io_uring: get rid of double locking
From: Pavel Begunkov <asml.silence@xxxxxxxxx>
Commit 11373026f2960390d5e330df4e92735c4265c440 upstream.
We don't need to take both uring_locks at once, msg_ring can be split in
two parts, first getting a file from the filetable of the first ring and
then installing it into the second one.
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
Link: https://lore.kernel.org/r/a80ecc2bc99c3b3f2cf20015d618b7c51419a797.1670384893.git.asml.silence@xxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
io_uring/msg_ring.c | 85 +++++++++++++++++++++++++++++-----------------------
io_uring/msg_ring.h | 1
io_uring/opdef.c | 1
3 files changed, 51 insertions(+), 36 deletions(-)
--- a/io_uring/msg_ring.c
+++ b/io_uring/msg_ring.c
@@ -15,6 +15,7 @@
struct io_msg {
struct file *file;
+ struct file *src_file;
u64 user_data;
u32 len;
u32 cmd;
@@ -23,6 +24,17 @@ struct io_msg {
u32 flags;
};
+void io_msg_ring_cleanup(struct io_kiocb *req)
+{
+ struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
+
+ if (WARN_ON_ONCE(!msg->src_file))
+ return;
+
+ fput(msg->src_file);
+ msg->src_file = NULL;
+}
+
static int io_msg_ring_data(struct io_kiocb *req)
{
struct io_ring_ctx *target_ctx = req->file->private_data;
@@ -39,17 +51,13 @@ static int io_msg_ring_data(struct io_ki
return -EOVERFLOW;
}
-static void io_double_unlock_ctx(struct io_ring_ctx *ctx,
- struct io_ring_ctx *octx,
+static void io_double_unlock_ctx(struct io_ring_ctx *octx,
unsigned int issue_flags)
{
- if (issue_flags & IO_URING_F_UNLOCKED)
- mutex_unlock(&ctx->uring_lock);
mutex_unlock(&octx->uring_lock);
}
-static int io_double_lock_ctx(struct io_ring_ctx *ctx,
- struct io_ring_ctx *octx,
+static int io_double_lock_ctx(struct io_ring_ctx *octx,
unsigned int issue_flags)
{
/*
@@ -62,17 +70,28 @@ static int io_double_lock_ctx(struct io_
return -EAGAIN;
return 0;
}
+ mutex_lock(&octx->uring_lock);
+ return 0;
+}
- /* Always grab smallest value ctx first. We know ctx != octx. */
- if (ctx < octx) {
- mutex_lock(&ctx->uring_lock);
- mutex_lock(&octx->uring_lock);
- } else {
- mutex_lock(&octx->uring_lock);
- mutex_lock(&ctx->uring_lock);
- }
+static struct file *io_msg_grab_file(struct io_kiocb *req, unsigned int issue_flags)
+{
+ struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
+ struct io_ring_ctx *ctx = req->ctx;
+ struct file *file = NULL;
+ unsigned long file_ptr;
+ int idx = msg->src_fd;
- return 0;
+ io_ring_submit_lock(ctx, issue_flags);
+ if (likely(idx < ctx->nr_user_files)) {
+ idx = array_index_nospec(idx, ctx->nr_user_files);
+ file_ptr = io_fixed_file_slot(&ctx->file_table, idx)->file_ptr;
+ file = (struct file *) (file_ptr & FFS_MASK);
+ if (file)
+ get_file(file);
+ }
+ io_ring_submit_unlock(ctx, issue_flags);
+ return file;
}
static int io_msg_send_fd(struct io_kiocb *req, unsigned int issue_flags)
@@ -80,8 +99,7 @@ static int io_msg_send_fd(struct io_kioc
struct io_ring_ctx *target_ctx = req->file->private_data;
struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
struct io_ring_ctx *ctx = req->ctx;
- unsigned long file_ptr;
- struct file *src_file;
+ struct file *src_file = msg->src_file;
int ret;
if (msg->len)
@@ -90,28 +108,22 @@ static int io_msg_send_fd(struct io_kioc
return -EINVAL;
if (target_ctx->flags & IORING_SETUP_R_DISABLED)
return -EBADFD;
+ if (!src_file) {
+ src_file = io_msg_grab_file(req, issue_flags);
+ if (!src_file)
+ return -EBADF;
+ msg->src_file = src_file;
+ req->flags |= REQ_F_NEED_CLEANUP;
+ }
- ret = io_double_lock_ctx(ctx, target_ctx, issue_flags);
- if (unlikely(ret))
- return ret;
-
- ret = -EBADF;
- if (unlikely(msg->src_fd >= ctx->nr_user_files))
- goto out_unlock;
-
- msg->src_fd = array_index_nospec(msg->src_fd, ctx->nr_user_files);
- file_ptr = io_fixed_file_slot(&ctx->file_table, msg->src_fd)->file_ptr;
- if (!file_ptr)
- goto out_unlock;
-
- src_file = (struct file *) (file_ptr & FFS_MASK);
- get_file(src_file);
+ if (unlikely(io_double_lock_ctx(target_ctx, issue_flags)))
+ return -EAGAIN;
ret = __io_fixed_fd_install(target_ctx, src_file, msg->dst_fd);
- if (ret < 0) {
- fput(src_file);
+ if (ret < 0)
goto out_unlock;
- }
+ msg->src_file = NULL;
+ req->flags &= ~REQ_F_NEED_CLEANUP;
if (msg->flags & IORING_MSG_RING_CQE_SKIP)
goto out_unlock;
@@ -125,7 +137,7 @@ static int io_msg_send_fd(struct io_kioc
if (!io_post_aux_cqe(target_ctx, msg->user_data, ret, 0, true))
ret = -EOVERFLOW;
out_unlock:
- io_double_unlock_ctx(ctx, target_ctx, issue_flags);
+ io_double_unlock_ctx(target_ctx, issue_flags);
return ret;
}
@@ -136,6 +148,7 @@ int io_msg_ring_prep(struct io_kiocb *re
if (unlikely(sqe->buf_index || sqe->personality))
return -EINVAL;
+ msg->src_file = NULL;
msg->user_data = READ_ONCE(sqe->off);
msg->len = READ_ONCE(sqe->len);
msg->cmd = READ_ONCE(sqe->addr);
--- a/io_uring/msg_ring.h
+++ b/io_uring/msg_ring.h
@@ -2,3 +2,4 @@
int io_msg_ring_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
int io_msg_ring(struct io_kiocb *req, unsigned int issue_flags);
+void io_msg_ring_cleanup(struct io_kiocb *req);
--- a/io_uring/opdef.c
+++ b/io_uring/opdef.c
@@ -445,6 +445,7 @@ const struct io_op_def io_op_defs[] = {
.name = "MSG_RING",
.prep = io_msg_ring_prep,
.issue = io_msg_ring,
+ .cleanup = io_msg_ring_cleanup,
},
[IORING_OP_FSETXATTR] = {
.needs_file = 1,
Patches currently in stable-queue which might be from asml.silence@xxxxxxxxx are
queue-6.1/io_uring-extract-a-io_msg_install_complete-helper.patch
queue-6.1/io_uring-get-rid-of-double-locking.patch
