* Re: [PATCH 2/3] vmsplice: make vmsplice a trivial wrapper for preadv2/pwritev2
2026-06-08 17:19 ` [PATCH 2/3] vmsplice: make vmsplice a trivial wrapper for preadv2/pwritev2 Alexander Gordeev
@ 2026-06-08 18:42 ` David Hildenbrand (Arm)
2026-06-16 0:36 ` Askar Safin
1 sibling, 0 replies; 3+ messages in thread
From: David Hildenbrand (Arm) @ 2026-06-08 18:42 UTC (permalink / raw)
To: Alexander Gordeev, Askar Safin
Cc: linux-fsdevel, Christian Brauner, Alexander Viro, Jan Kara,
linux-kernel, linux-mm, linux-api, netdev, Linus Torvalds,
Matthew Wilcox, Jens Axboe, Christoph Hellwig, David Howells,
Andrew Morton, Pedro Falcato, Miklos Szeredi, patches, linux-s390,
linux-next
On 6/8/26 19:19, Alexander Gordeev wrote:
> 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.
>>
>> Now SPLICE_F_GIFT is always ignored by all 3 syscalls: splice, tee
>> and vmsplice.
>>
>> Signed-off-by: Askar Safin <safinaskar@gmail.com>
>> ---
>> fs/read_write.c | 23 +++++
>> fs/splice.c | 192 +--------------------------------------
>> include/linux/skbuff.h | 4 +-
>> include/linux/splice.h | 2 +-
>> include/linux/syscalls.h | 4 +-
>> 5 files changed, 29 insertions(+), 196 deletions(-)
>
> Hi All,
>
> This patch as commit e2c0b2368081b ("vmsplice: make vmsplice a trivial
> wrapper for preadv2/pwritev2") in linux-next on s390 causes the selftest
> tools/testing/selftests/mm/cow.c to hang:
>
> # [RUN] vmsplice() + unmap in child ... with PTE-mapped THP (128 kB)
>
> Recently there has been changes in THP area, so the problem is not
> necessary linked to this patch per se.
If we reach 128 kB, then 64 kB likely worked. Which might hint at a similar problem
as found by the vmsplice01 ltp test case (blocking instead of returning once the
pipe is full).
https://lore.kernel.org/r/20260603-raumfahrt-unmerklich-ertrugen-c4ecae70d5f9@brauner
--
Cheers,
David
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH 2/3] vmsplice: make vmsplice a trivial wrapper for preadv2/pwritev2
2026-06-08 17:19 ` [PATCH 2/3] vmsplice: make vmsplice a trivial wrapper for preadv2/pwritev2 Alexander Gordeev
2026-06-08 18:42 ` David Hildenbrand (Arm)
@ 2026-06-16 0:36 ` Askar Safin
1 sibling, 0 replies; 3+ messages in thread
From: Askar Safin @ 2026-06-16 0:36 UTC (permalink / raw)
To: agordeev
Cc: akpm, axboe, brauner, david, dhowells, hch, jack, linux-api,
linux-fsdevel, linux-kernel, linux-mm, linux-next, linux-s390,
miklos, netdev, patches, pfalcato, safinaskar, torvalds, viro,
willy
Alexander Gordeev <agordeev@linux.ibm.com>:
> Hi All,
>
> This patch as commit e2c0b2368081b ("vmsplice: make vmsplice a trivial
> wrapper for preadv2/pwritev2") in linux-next on s390 causes the selftest
> tools/testing/selftests/mm/cow.c to hang:
>
> # [RUN] vmsplice() + unmap in child ... with PTE-mapped THP (128 kB)
>
> Recently there has been changes in THP area, so the problem is not
> necessary linked to this patch per se.
>
> Please, let me know if you need any additional information.
>
> Thanks!
As well as I understand, this test uses vmsplice to pin pages.
I. e. if my patch lands, then this test should be rewriten to use
some other mechanism.
--
Askar Safin
^ permalink raw reply [flat|nested] 3+ messages in thread