Re: BUG #19725: PostgreSQL 18.6: pg_restore read failure with io_uring, not observed with worker

After setting backtrace_functions=md_readv_report, I received more log information:
2026-10-04 17:46:08.322 CST [local] test001 postgres [154450]LOG: XX000: could not read blocks 143..158 in file "base/6406098/6407866": Operation canceled
2026-10-04 17:46:08.322 CST [local] test001 postgres [154450]LOCATION: md_readv_report, md.c:2059
2026-10-04 17:46:08.322 CST [local] test001 postgres [154450]BACKTRACE:
postgres: postgres test001 [local] CREATE INDEX() [0x92eafc]
postgres: postgres test001 [local] CREATE INDEX() [0x92f7ec]
postgres: postgres test001 [local] CREATE INDEX(pgaio_io_call_complete_shared+0xfa) [0x8ef3ea]
postgres: postgres test001 [local] CREATE INDEX() [0x8f209c]
postgres: postgres test001 [local] CREATE INDEX() [0x8f2b63]
postgres: postgres test001 [local] CREATE INDEX() [0x8f0127]
postgres: postgres test001 [local] CREATE INDEX(WaitReadBuffers+0x1f7) [0x8f5137]
postgres: postgres test001 [local] CREATE INDEX(read_stream_next_buffer+0x211) [0x8f6ac1]
postgres: postgres test001 [local] CREATE INDEX() [0x5874d6]
postgres: postgres test001 [local] CREATE INDEX(heap_getnext+0x88) [0x5878e8]
postgres: postgres test001 [local] CREATE INDEX() [0x58dcbd]
postgres: postgres test001 [local] CREATE INDEX() [0x5b11ae]
postgres: postgres test001 [local] CREATE INDEX(btbuild+0xb05) [0x5b7325]
postgres: postgres test001 [local] CREATE INDEX(index_build+0x19c) [0x61fa2c]
postgres: postgres test001 [local] CREATE INDEX(index_create+0x1328) [0x621608]
postgres: postgres test001 [local] CREATE INDEX(DefineIndex+0x9bb) [0x6d11cb]
postgres: postgres test001 [local] CREATE INDEX() [0xb18111]
postgres: postgres test001 [local] CREATE INDEX(standard_ProcessUtility+0x3f8) [0x93c1d8]
/usr/pgsql-18/lib/pg_stat_statements.so(+0x7375) [0x7f209b366375]
postgres: postgres test001 [local] CREATE INDEX() [0x93cc3a]
postgres: postgres test001 [local] CREATE INDEX() [0x93cdaf]
postgres: postgres test001 [local] CREATE INDEX(PortalRun+0x291) [0x93d371]
postgres: postgres test001 [local] CREATE INDEX() [0x935ab0]
postgres: postgres test001 [local] CREATE INDEX(PostgresMain+0x1f1b) [0x937f6b]
postgres: postgres test001 [local] CREATE INDEX() [0x9389d5]
postgres: postgres test001 [local] CREATE INDEX(postmaster_child_launch+0x12d) [0x888ced]
postgres: postgres test001 [local] CREATE INDEX() [0x891cb2]
postgres: postgres test001 [local] CREATE INDEX(PostmasterMain+0xce9) [0x894309]
postgres: postgres test001 [local] CREATE INDEX(main+0x1d0) [0x531bc0]
/lib64/libc.so.6(+0x2a610) [0x7f209b82a610]
/lib64/libc.so.6(__libc_start_main+0x80) [0x7f209b82a6c0]
postgres: postgres test001 [local] CREATE INDEX(_start+0x25) [0x5321b5]
2026-10-04 17:46:08.322 CST [local] test001 postgres [154450]STATEMENT: CREATE INDEX idx_sys_notification_channel_notification_id ON dhr.sys_notification_channel USING btree (c_notification_id);

> 2026年9月28日 11:34，PG Bug reporting form <noreply(at)postgresql(dot)org> 写道：
>
> The following bug has been logged on the website:
>
> Bug reference: 19725
> Logged by: weijie JL
> Email address: weijie1006jl(at)gmail(dot)com
> PostgreSQL version: 18.6
> Operating system: RockyLinux9
> Description:
>
> Hello,
>
> I can reproduce a read failure during pg_restore with io_method=io_uring.
> The error disappears with worker and recurs after switching back to
> io_uring.
>
> Environment:
> - PostgreSQL 18.6, x86_64
> - VMware VM: 8 vCPUs, 32 GB RAM
> - Kernel: 5.14.0-611.55.1.el9_7.x86_64
>
> Settings:
> effective_io_concurrency = 256
> maintenance_io_concurrency = 16
> max_parallel_maintenance_workers = 2
>
> Restore command:
> nohup pg_restore -d test001 dhr.dump/ -j8 -v > test.log 2>&1 &
>
> One failing statement:
> ALTER TABLE ONLY dhr.obj_permission_object
> ADD CONSTRAINT obj_permission_object_pkey PRIMARY KEY (id);
>
> Server error:
> ERROR: could not read blocks 143..158 in file "base/1684908/1686127":
> Operation canceled
> LOCATION: md_readv_report, md.c:2059
> SQLSTATE: XX000
>
> Observed test sequence:
> 1. io_method=io_uring: the read error occurred during index creation.
> 2. Changed io_method to worker: retried without errors.
> 3. Changed io_method back to io_uring: the read error was reproduced.
>
> I have not measured the failure rate or prepared a self-contained
> minimal reproducer.
>
> One earlier run also reported "could not map dynamic shared memory
> segment" from parallel workers immediately after the read error.
> Those DSM errors have not recurred in subsequent failing tests.
>
> Does this match a known PostgreSQL bug or kernel-side io_uring issue?
> What additional logs or tracing would help identify the cause?
>
> Thank you.
>
>