diff options
author | Jens Axboe <axboe@kernel.dk> | 2020-10-12 20:15:07 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-11-01 14:45:35 +0300 |
commit | bf03059892415cd40eeabc0fed13bbcd05ba2602 (patch) | |
tree | ee2a108756a58f1a586efebcc5c926e1697b8bb7 | |
parent | dd1acc182c85633bebc222d14acaf3f816503f0d (diff) | |
download | linux-bf03059892415cd40eeabc0fed13bbcd05ba2602.tar.xz |
io_uring: stash ctx task reference for SQPOLL
commit 2aede0e417db846793c276c7a1bbf7262c8349b0 upstream.
We can grab a reference to the task instead of stashing away the task
files_struct. This is doable without creating a circular reference
between the ring fd and the task itself.
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r-- | fs/io_uring.c | 39 |
1 files changed, 29 insertions, 10 deletions
diff --git a/fs/io_uring.c b/fs/io_uring.c index 6e061d5cf856..171ea70d5350 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -264,7 +264,16 @@ struct io_ring_ctx { /* IO offload */ struct io_wq *io_wq; struct task_struct *sqo_thread; /* if using sq thread polling */ - struct mm_struct *sqo_mm; + + /* + * For SQPOLL usage - we hold a reference to the parent task, so we + * have access to the ->files + */ + struct task_struct *sqo_task; + + /* Only used for accounting purposes */ + struct mm_struct *mm_account; + wait_queue_head_t sqo_wait; /* @@ -4421,9 +4430,10 @@ static int io_sq_thread_acquire_mm(struct io_ring_ctx *ctx, { if (io_op_defs[req->opcode].needs_mm && !current->mm) { if (unlikely(!(ctx->flags & IORING_SETUP_SQPOLL) || - !mmget_not_zero(ctx->sqo_mm))) + !ctx->sqo_task->mm || + !mmget_not_zero(ctx->sqo_task->mm))) return -EFAULT; - kthread_use_mm(ctx->sqo_mm); + kthread_use_mm(ctx->sqo_task->mm); } return 0; @@ -7104,9 +7114,6 @@ static int io_sq_offload_start(struct io_ring_ctx *ctx, { int ret; - mmgrab(current->mm); - ctx->sqo_mm = current->mm; - if (ctx->flags & IORING_SETUP_SQPOLL) { ret = -EPERM; if (!capable(CAP_SYS_ADMIN)) @@ -7151,8 +7158,6 @@ static int io_sq_offload_start(struct io_ring_ctx *ctx, return 0; err: io_finish_async(ctx); - mmdrop(ctx->sqo_mm); - ctx->sqo_mm = NULL; return ret; } @@ -7482,8 +7487,12 @@ static void io_destroy_buffers(struct io_ring_ctx *ctx) static void io_ring_ctx_free(struct io_ring_ctx *ctx) { io_finish_async(ctx); - if (ctx->sqo_mm) - mmdrop(ctx->sqo_mm); + if (ctx->sqo_task) { + put_task_struct(ctx->sqo_task); + ctx->sqo_task = NULL; + mmdrop(ctx->mm_account); + ctx->mm_account = NULL; + } io_iopoll_reap_events(ctx); io_sqe_buffer_unregister(ctx); @@ -8256,6 +8265,16 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p, ctx->user = user; ctx->creds = get_current_cred(); + ctx->sqo_task = get_task_struct(current); + /* + * This is just grabbed for accounting purposes. When a process exits, + * the mm is exited and dropped before the files, hence we need to hang + * on to this mm purely for the purposes of being able to unaccount + * memory (locked/pinned vm). It's not used for anything else. + */ + mmgrab(current->mm); + ctx->mm_account = current->mm; + ret = io_allocate_scq_urings(ctx, p); if (ret) goto err; |