Revision 3770a42bb8ceb856877699257a43c0585a5d2996 authored by Sagi Grimberg on 05 September 2022, 15:07:06 UTC, committed by Christoph Hellwig on 06 September 2022, 04:40:44 UTC
When we queue requests, we strive to batch as much as possible and also signal the network stack that more data is about to be sent over a socket with MSG_SENDPAGE_NOTLAST. This flag looks at the pending requests queued as well as queue->more_requests that is derived from the block layer last-in-batch indication. We set more_request=true when we flush the request directly from .queue_rq submission context (in nvme_tcp_send_all), however this is wrongly assuming that no other requests may be queued during the execution of nvme_tcp_send_all. Due to this, a race condition may happen where: 1. request X is queued as !last-in-batch 2. request X submission context calls nvme_tcp_send_all directly 3. nvme_tcp_send_all is preempted and schedules to a different cpu 4. request Y is queued as last-in-batch 5. nvme_tcp_send_all context sends request X+Y, however signals for both MSG_SENDPAGE_NOTLAST because queue->more_requests=true. ==> none of the requests is pushed down to the wire as the network stack is waiting for more data, both requests timeout. To fix this, we eliminate queue->more_requests and only rely on the queue req_list and send_list to be not-empty. Fixes: 122e5b9f3d37 ("nvme-tcp: optimize network stack with setting msg flags according to batch size") Reported-by: Jonathan Nicklin <jnicklin@blockbridge.com> Signed-off-by: Sagi Grimberg <sagi@grimberg.me> Tested-by: Jonathan Nicklin <jnicklin@blockbridge.com> Signed-off-by: Christoph Hellwig <hch@lst.de>
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Kbuild
# SPDX-License-Identifier: GPL-2.0
#
# Kbuild for top-level directory of the kernel
#####
# Generate bounds.h
bounds-file := include/generated/bounds.h
always-y := $(bounds-file)
targets := kernel/bounds.s
$(bounds-file): kernel/bounds.s FORCE
$(call filechk,offsets,__LINUX_BOUNDS_H__)
#####
# Generate timeconst.h
timeconst-file := include/generated/timeconst.h
filechk_gentimeconst = echo $(CONFIG_HZ) | bc -q $<
$(timeconst-file): kernel/time/timeconst.bc FORCE
$(call filechk,gentimeconst)
#####
# Generate asm-offsets.h
offsets-file := include/generated/asm-offsets.h
always-y += $(offsets-file)
targets += arch/$(SRCARCH)/kernel/asm-offsets.s
arch/$(SRCARCH)/kernel/asm-offsets.s: $(timeconst-file) $(bounds-file)
$(offsets-file): arch/$(SRCARCH)/kernel/asm-offsets.s FORCE
$(call filechk,offsets,__ASM_OFFSETS_H__)
#####
# Check for missing system calls
always-y += missing-syscalls
quiet_cmd_syscalls = CALL $<
cmd_syscalls = $(CONFIG_SHELL) $< $(CC) $(c_flags) $(missing_syscalls_flags)
missing-syscalls: scripts/checksyscalls.sh $(offsets-file) FORCE
$(call cmd,syscalls)
#####
# Check atomic headers are up-to-date
always-y += old-atomics
quiet_cmd_atomics = CALL $<
cmd_atomics = $(CONFIG_SHELL) $<
old-atomics: scripts/atomic/check-atomics.sh FORCE
$(call cmd,atomics)
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