Re: [PATCH 4/5] mm/hmm: hmm_vma_fault() doesn't always call hmm_range_unregister()

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 





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@xxxxxxxxxx> wrote:

From: Ralph Campbell <rcampbell@xxxxxxxxxx>

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@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Balbir Singh <bsingharora@xxxxxxxxx>
Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Souptick Joarder <jrdr.linux@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
   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.




[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Bugtraq]     [Linux OMAP]     [Linux MIPS]     [eCos]     [Asterisk Internet PBX]     [Linux API]

  Powered by Linux