* Re: + mips-c-r4k-do-no-use-mmap_sem-for-gup_fast.patch added to -mm tree
[not found] <20190208054407.gjyKBBYUS%akpm@linux-foundation.org>
@ 2019-02-08 5:57 ` Paul Burton
2019-02-08 22:57 ` Andrew Morton
0 siblings, 1 reply; 2+ messages in thread
From: Paul Burton @ 2019-02-08 5:57 UTC (permalink / raw)
To: akpm; +Cc: dave, dbueso, jhogan, mm-commits, ralf, linux-mips
Hi Andrew,
On Thu, Feb 07, 2019 at 09:44:07PM -0800, akpm@linux-foundation.org wrote:
>
> The patch titled
> Subject: arch/mips/mm/c-r4k.c: do not use mmap_sem for gup_fast()
> has been added to the -mm tree. Its filename is
> mips-c-r4k-do-no-use-mmap_sem-for-gup_fast.patch
>
> This patch should soon appear at
> http://ozlabs.org/~akpm/mmots/broken-out/mips-c-r4k-do-no-use-mmap_sem-for-gup_fast.patch
> and later at
> http://ozlabs.org/~akpm/mmotm/broken-out/mips-c-r4k-do-no-use-mmap_sem-for-gup_fast.patch
>
> Before you just go and hit "reply", please:
> a) Consider who else should be cc'ed
> b) Prefer to cc a suitable mailing list as well
> c) Ideally: find the original patch on the mailing list and do a
> reply-to-all to that, adding suitable additional cc's
>
> *** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
>
> The -mm tree is included into linux-next and is updated
> there every 3-4 working days
>
> ------------------------------------------------------
> From: Davidlohr Bueso <dave@stgolabs.net>
> Subject: arch/mips/mm/c-r4k.c: do not use mmap_sem for gup_fast()
>
> It is well known that because the mm can internally call the regular
> gup_unlocked if the lockless approach fails and take the sem there, the
> caller must not hold the mmap_sem already.
>
> Link: http://lkml.kernel.org/r/20190207053740.26915-3-dave@stgolabs.net
> Fixes: e523f289fe4d ("MIPS: c-r4k: Fix sigtramp SMP call to use kmap")
> Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
> Cc: Ralf Baechle <ralf@linux-mips.org>
> Cc: Paul Burton <paul.burton@mips.com>
> Cc: James Hogan <jhogan@kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Whilst I don't object to you merging this too strongly, I thought I'd
point out again that as I already replied to Davidlohr [1] the code
being changed here is unused in mainline & all affected stable branches.
In mips-next it's entirely removed. As such this patch will have no
effect on the kernel's behaviour & cause a minor conflict with
mips-next.
Thanks,
Paul
[1] https://lore.kernel.org/linux-mips/20190207190007.jz4rz6e6qxwazxm7@pburton-laptop/
^ permalink raw reply [flat|nested] 2+ messages in thread