FAILED: patch "[PATCH] io_uring: Fix mm_fault with READ/WRITE_FIXED" failed to apply to 5.4-stable tree
Subsystems (2)
[email protected]
maintainerThe patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 95a1b3ff9a3e4ea2f26c4e802067d58831f415db Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <[email protected]>
Date: Sun, 27 Oct 2019 23:15:41 +0300
Subject: [PATCH] io_uring: Fix mm_fault with READ/WRITE_FIXED
Commit fb5ccc98782f ("io_uring: Fix broken links with offloading") introduced a potential performance regression with unconditionally taking mm even for READ/WRITE_FIXED operations.
Return the logic handling it back. mm-faulted requests will go through the generic submission path, so honoring links and drains, but will fail further on req->has_user check.
fs/io_uring.c +17 -24
@@ -2726,13 +2726,14 @@ static bool io_get_sqring(struct io_ring_ctx *ctx, struct sqe_submit *s) }static int io_submit_sqes (struct io_ring_ctx *ctx,unsigned int nr, -bool has_user,bool mm_fault) +struct mm_struct **mm) {struct io_submit_state state, *statep =NULL ;struct io_kiocb *link =NULL ;struct io_kiocb *shadow_req =NULL ;bool prev_was_link = false;int i, submitted =0 ; +bool mm_fault = false;if (nr >IO_PLUG_THRESHOLD ) {io_submit_state_start (&state, ctx, nr);
@@ -2745,6 +2746,14 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,if (!io_get_sqring (ctx, &s))break ; +if (io_sqe_needs_user (s.sqe) && !*mm) { + mm_fault = mm_fault || !mmget_not_zero (ctx->sqo_mm); +if (!mm_fault) { +use_mm (ctx->sqo_mm); + *mm = ctx->sqo_mm; + } + } +/* * If previous wasn't linked and we have a linked command, * that's the end of the chain. Submit the previous link.
@@ -2768,17 +2777,12 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr, } out: -if (unlikely (mm_fault)) { -io_cqring_add_event (ctx, s.sqe->user_data, - -EFAULT ); - }else { - s.has_user = has_user; - s.in_async = true; - s.needs_fixed_file = true; -trace_io_uring_submit_sqe (ctx, true, true); -io_submit_sqe (ctx, &s, statep, &link); - submitted++; - } + s.has_user = *mm !=NULL ; + s.in_async = true; + s.needs_fixed_file = true; +trace_io_uring_submit_sqe (ctx, true, true); +io_submit_sqe (ctx, &s, statep, &link); + submitted++; }if (link)
@@ -2805,7 +2809,6 @@ static int io_sq_thread(void *data) timeout = inflight =0 ;while (!kthread_should_park ()) { -bool mm_fault = false;unsigned int to_submit;if (inflight) {
@@ -2890,18 +2893,8 @@ static int io_sq_thread(void *data) ctx->rings->sq_flags &= ~IORING_SQ_NEED_WAKEUP ; } -/* Unless all new commands are FIXED regions, grab mm */ -if (!cur_mm) { - mm_fault = !mmget_not_zero (ctx->sqo_mm); -if (!mm_fault) { -use_mm (ctx->sqo_mm); - cur_mm = ctx->sqo_mm; - } - } - to_submit =min (to_submit, ctx->sq_entries); - inflight +=io_submit_sqes (ctx, to_submit, cur_mm !=NULL , - mm_fault); + inflight +=io_submit_sqes (ctx, to_submit, &cur_mm);/* Commit SQ ring head once we've consumed all SQEs */ io_commit_sqring (ctx);