Re: [PATCH 2/3] vmsplice: make vmsplice a trivial wrapper for preadv2/pwritev2

On Sun, May 31, 2026 at 01:01:06AM +0000, Askar Safin wrote:

> vmsplice behavior on writable pipe became equivalent to pwritev2.
> vmsplice behavior on readable pipe already was nearly
> equivalent to preadv2, but I made this explicit. I. e. I made it
> obvious from code that vmsplice now is equivalent to preadv2/pwritev2.

> Also I moved vmsplice to fs/read_write.c, because now it arguably
> belongs there.

> Note that SPLICE_F_NONBLOCK behavior slightly changed: previously
> vmsplice ignored whether the pipe was opened with O_NONBLOCK, and mode
> of operation depended on whether SPLICE_F_NONBLOCK was passed only.
> Now the operation will be non-blocking if O_NONBLOCK was passed when
> opening *or* SPLICE_F_NONBLOCK was passed to vmsplice. Previous
> behavior was arguably buggy, and new behavior is arguably better.

FWIW this is triggering a failure in the LTP vmsplice01 test case (which
sends with a vmsplice() and then tries to read that with a splice()) in
-next:

| tst_tmpdir.c:316: TINFO: Using /tmp/LTP_vmsp3vEmQ as tmpdir (tmpfs filesystem)
| L4471tst_test.c:2047: TINFO: LTP version: 20260130
| L4472tst_test.c:2050: TINFO: Tested kernel: 7.1.0-rc6-next-20260604 #1 SMP @1780589917 armv7l
| L4473tst_kconfig.c:71: TINFO: Couldn't locate kernel config!
| L4474tst_test.c:1875: TINFO: Overall timeout per run is 0h 00m 30s
| L4475tst_test.c:1632: TINFO: tmpfs is supported by the test
| L4476Test timeouted, sending SIGKILL!
| L4477tst_test.c:1947: TINFO: If you are running on slow machine, try exporting LTP_TIMEOUT_MUL > 1
| L4478tst_test.c:1949: TBROK: Test killed! (timeout?)

As the test itself notes it's not super realistic but thought it was
better to mention it since I didn't see any report on the list yet, I've
CCed the LTP list.

Full log:

   https://lava.sirena.org.uk/scheduler/job/2831199#L4468

bisect log:

# bad: [b99ae45861eccff1e1d8c7b05a13650be805d437] Add linux-next specific files for 20260604
# good: [5e9d583f58c8b56c9f5022639ac70cb7ae6e9fe9] Merge branch 'for-linux-next-fixes' of https://gitlab.freedesktop.org/drm/misc/kernel.git
# good: [a9f7db50ed2fff96727782456f49bf88def68510] tee: fs/splice.c: remove unused parameter "flags" from "link_pipe"
# good: [215701873a7ed1214bba82c8fadcd2583d0246c3] net: mdio: realtek-rtl9300: Add ports to info structure
# good: [b882d807fa443b529ae8bf917d7b640a8d555437] tools/nolibc: stackprotector: Avoid stalling program startup if crng is not init yet
# good: [835fa43a4d36bd66ad0dd052f9fa15f7bd365fa8] tools/nolibc: add ftruncate()
# good: [5d72c6a754ef488f88ad33c83d14556c6f38af3a] Merge branch 'pci/controller/dwc-qcom'
# good: [04b18289834f20bbed25813c4978833ca8bd6e82] Merge branch 'pci/controller/misc'
# good: [94bf692c483ffb325af0b110429ad37f445d40b0] Merge branch 'pci/endpoint'
# good: [1c996a37fd244d19e5dbb715328c1676e28ef607] tools/power turbostat: pmt: Improve sscanf() hygiene
# good: [083c9ab12c402efe9ed55c942ede92eb35f8bf2a] crypto: omap-des - add COMPILE_TEST and fix CONFIG_OF=n build
# good: [49e05bb00f2e8168695f7af4d694c39e1423e8a2] crypto: atmel-sha204a - fail on hwrng registration error in probe path
# good: [86ad8069366642fec18c1bc53c24cad3da720ce5] Documentation: qat_rl: make rate limiting wording clearer
# good: [d58b4a09d7f06750a706b70d068f5a678dad8233] crypto: atmel-sha204a - remove sysfs group before hwrng
# good: [34808ac8ddafc3e2c2a59e84eaab0a410e7a0fdc] regmap-i2c: fix sparse warning in regmap_smbus_word_write_reg16
# good: [dc3ec9af62a92a46378960e599521c2ac5f81343] hwrng: core - use MAX to simplify RNG_BUFFER_SIZE
# good: [513f49c33e91e58975ada7967b44512179f0e703] power: sequencing: print power sequencing device parent in debugfs
# good: [bb2d82d41894cb30d836e9796ff67d2f9a71eccf] Merge tag 'v7.1-rc2' into nolibc/for-next
# good: [07a1a6562ce29e2e0c134a57882d6e52e8758492] kcsan: Silence -Wmaybe-uninitialized when calling __kcsan_check_access()
git bisect start 'b99ae45861eccff1e1d8c7b05a13650be805d437' '5e9d583f58c8b56c9f5022639ac70cb7ae6e9fe9' 'a9f7db50ed2fff96727782456f49bf88def68510' '215701873a7ed1214bba82c8fadcd2583d0246c3' 'b882d807fa443b529ae8bf917d7b640a8d555437' '835fa43a4d36bd66ad0dd052f9fa15f7bd365fa8' '5d72c6a754ef488f88ad33c83d14556c6f38af3a' '04b18289834f20bbed25813c4978833ca8bd6e82' '94bf692c483ffb325af0b110429ad37f445d40b0' '1c996a37fd244d19e5dbb715328c1676e28ef607' '083c9ab12c402efe9ed55c942ede92eb35f8bf2a' '49e05bb00f2e8168695f7af4d694c39e1423e8a2' '86ad8069366642fec18c1bc53c24cad3da720ce5' 'd58b4a09d7f06750a706b70d068f5a678dad8233' '34808ac8ddafc3e2c2a59e84eaab0a410e7a0fdc' 'dc3ec9af62a92a46378960e599521c2ac5f81343' '513f49c33e91e58975ada7967b44512179f0e703' 'bb2d82d41894cb30d836e9796ff67d2f9a71eccf' '07a1a6562ce29e2e0c134a57882d6e52e8758492'
# test job: [a9f7db50ed2fff96727782456f49bf88def68510] https://lava.sirena.org.uk/scheduler/job/2827407
# test job: [215701873a7ed1214bba82c8fadcd2583d0246c3] https://lava.sirena.org.uk/scheduler/job/2804576
# test job: [b882d807fa443b529ae8bf917d7b640a8d555437] https://lava.sirena.org.uk/scheduler/job/2801267
# test job: [835fa43a4d36bd66ad0dd052f9fa15f7bd365fa8] https://lava.sirena.org.uk/scheduler/job/2801414
# test job: [5d72c6a754ef488f88ad33c83d14556c6f38af3a] https://lava.sirena.org.uk/scheduler/job/2827129
# test job: [04b18289834f20bbed25813c4978833ca8bd6e82] https://lava.sirena.org.uk/scheduler/job/2827205
# test job: [94bf692c483ffb325af0b110429ad37f445d40b0] https://lava.sirena.org.uk/scheduler/job/2827087
# test job: [1c996a37fd244d19e5dbb715328c1676e28ef607] https://lava.sirena.org.uk/scheduler/job/2801077
# test job: [083c9ab12c402efe9ed55c942ede92eb35f8bf2a] https://lava.sirena.org.uk/scheduler/job/2804905
# test job: [49e05bb00f2e8168695f7af4d694c39e1423e8a2] https://lava.sirena.org.uk/scheduler/job/2804997
# test job: [86ad8069366642fec18c1bc53c24cad3da720ce5] https://lava.sirena.org.uk/scheduler/job/2804815
# test job: [d58b4a09d7f06750a706b70d068f5a678dad8233] https://lava.sirena.org.uk/scheduler/job/2805032
# test job: [34808ac8ddafc3e2c2a59e84eaab0a410e7a0fdc] https://lava.sirena.org.uk/scheduler/job/2783569
# test job: [dc3ec9af62a92a46378960e599521c2ac5f81343] https://lava.sirena.org.uk/scheduler/job/2804763
# test job: [513f49c33e91e58975ada7967b44512179f0e703] https://lava.sirena.org.uk/scheduler/job/2801614
# test job: [bb2d82d41894cb30d836e9796ff67d2f9a71eccf] https://lava.sirena.org.uk/scheduler/job/2744679
# test job: [07a1a6562ce29e2e0c134a57882d6e52e8758492] https://lava.sirena.org.uk/scheduler/job/2745239
# test job: [b99ae45861eccff1e1d8c7b05a13650be805d437] https://lava.sirena.org.uk/scheduler/job/2831199
# bad: [b99ae45861eccff1e1d8c7b05a13650be805d437] Add linux-next specific files for 20260604
git bisect bad b99ae45861eccff1e1d8c7b05a13650be805d437
# test job: [2d4099641dbaed4b98711fc7d8ec94c5aec0a0f0] https://lava.sirena.org.uk/scheduler/job/2827279
# bad: [2d4099641dbaed4b98711fc7d8ec94c5aec0a0f0] Merge patch series "vmsplice: make vmsplice a trivial wrapper for preadv2/pwritev2"
git bisect bad 2d4099641dbaed4b98711fc7d8ec94c5aec0a0f0
# test job: [e2c0b2368081bef7d1f6758cc9e7edde8521237c] https://lava.sirena.org.uk/scheduler/job/2827345
# bad: [e2c0b2368081bef7d1f6758cc9e7edde8521237c] vmsplice: make vmsplice a trivial wrapper for preadv2/pwritev2
git bisect bad e2c0b2368081bef7d1f6758cc9e7edde8521237c
# first bad commit: [e2c0b2368081bef7d1f6758cc9e7edde8521237c] vmsplice: make vmsplice a trivial wrapper for preadv2/pwritev2
# test job: [7d75aa8edfce3e8ac4f0f8fe5728fd1eab8f7f23] https://lava.sirena.org.uk/scheduler/job/2829187
# skip: [7d75aa8edfce3e8ac4f0f8fe5728fd1eab8f7f23] splice: remove PIPE_BUF_FLAG_GIFT
git bisect skip 7d75aa8edfce3e8ac4f0f8fe5728fd1eab8f7f23
# first bad commit: [e2c0b2368081bef7d1f6758cc9e7edde8521237c] vmsplice: make vmsplice a trivial wrapper for preadv2/pwritev2

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