Messages in this thread | | | Subject | Re: [PATCH 4/5] mm/hmm: hmm_vma_fault() doesn't always call hmm_range_unregister() | From | Ralph Campbell <> | Date | Mon, 13 May 2019 10:23:27 -0700 |
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On 5/12/19 8:07 AM, Jerome Glisse wrote: > On Tue, May 07, 2019 at 11:12:14AM -0700, Ralph Campbell wrote: >> >> On 5/7/19 6:15 AM, Souptick Joarder wrote: >>> On Tue, May 7, 2019 at 5:00 AM <rcampbell@nvidia.com> wrote: >>>> >>>> From: Ralph Campbell <rcampbell@nvidia.com> >>>> >>>> The helper function hmm_vma_fault() calls hmm_range_register() but is >>>> missing a call to hmm_range_unregister() in one of the error paths. >>>> This leads to a reference count leak and ultimately a memory leak on >>>> struct hmm. >>>> >>>> Always call hmm_range_unregister() if hmm_range_register() succeeded. >>> >>> How about * Call hmm_range_unregister() in error path if >>> hmm_range_register() succeeded* ? >> >> Sure, sounds good. >> I'll include that in v2. > > NAK for the patch see below why > >> >>>> >>>> Signed-off-by: Ralph Campbell <rcampbell@nvidia.com> >>>> Cc: John Hubbard <jhubbard@nvidia.com> >>>> Cc: Ira Weiny <ira.weiny@intel.com> >>>> Cc: Dan Williams <dan.j.williams@intel.com> >>>> Cc: Arnd Bergmann <arnd@arndb.de> >>>> Cc: Balbir Singh <bsingharora@gmail.com> >>>> Cc: Dan Carpenter <dan.carpenter@oracle.com> >>>> Cc: Matthew Wilcox <willy@infradead.org> >>>> Cc: Souptick Joarder <jrdr.linux@gmail.com> >>>> Cc: Andrew Morton <akpm@linux-foundation.org> >>>> --- >>>> include/linux/hmm.h | 3 ++- >>>> 1 file changed, 2 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/include/linux/hmm.h b/include/linux/hmm.h >>>> index 35a429621e1e..fa0671d67269 100644 >>>> --- a/include/linux/hmm.h >>>> +++ b/include/linux/hmm.h >>>> @@ -559,6 +559,7 @@ static inline int hmm_vma_fault(struct hmm_range *range, bool block) >>>> return (int)ret; >>>> >>>> if (!hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT)) { >>>> + hmm_range_unregister(range); >>>> /* >>>> * The mmap_sem was taken by driver we release it here and >>>> * returns -EAGAIN which correspond to mmap_sem have been >>>> @@ -570,13 +571,13 @@ static inline int hmm_vma_fault(struct hmm_range *range, bool block) >>>> >>>> ret = hmm_range_fault(range, block); >>>> if (ret <= 0) { >>>> + hmm_range_unregister(range); >>> >>> what is the reason to moved it up ? >> >> I moved it up because the normal calling pattern is: >> down_read(&mm->mmap_sem) >> hmm_vma_fault() >> hmm_range_register() >> hmm_range_fault() >> hmm_range_unregister() >> up_read(&mm->mmap_sem) >> >> I don't think it is a bug to unlock mmap_sem and then unregister, >> it is just more consistent nesting. > > So this is not the usage pattern with HMM usage pattern is: > > hmm_range_register() > hmm_range_fault() > hmm_range_unregister() > > The hmm_vma_fault() is gonne so this patch here break thing. > > See https://cgit.freedesktop.org/~glisse/linux/log/?h=hmm-5.2-v3
The patch series is on top of v5.1-rc6-mmotm-2019-04-25-16-30. hmm_vma_fault() is defined there and in your hmm-5.2-v3 branch as a backward compatibility transition function in include/linux/hmm.h. So I agree the new API is to use hmm_range_register(), etc. This is intended to cover the transition period. Note that hmm_vma_fault() is being called from drivers/gpu/drm/nouveau/nouveau_svm.c in both trees.
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