| Message ID | 20230301022720.1380780-1-surenb@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [1/2] mm/mmap: remove unnecessary vp->vma check in vma_prepare | expand |
On 01.03.23 03:27, Suren Baghdasaryan wrote: > vp->vma in vma_prepare() is always non-NULL, therefore checking it is > not necessary. Remove the extra check. > > Fixes: e8f071350ea5 ("mm/mmap: write-lock VMAs in vma_prepare before modifying them") > Reported-by: kernel test robot <lkp@intel.com> > Reported-by: Dan Carpenter <error27@gmail.com> It would be great to mention that this simply silences a smatch warning. Otherwise, one might be mislead that this commit fixes an actual BUG ;) > Link: https://lore.kernel.org/r/202302281802.J93Nma7q-lkp@intel.com/ > Signed-off-by: Suren Baghdasaryan <surenb@google.com> > --- > Fix cleanly apply over mm-unstable, SHA in "Fixes" is from that tree. > > mm/mmap.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index 0cd3714c2182..0759d53b470c 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -505,8 +505,7 @@ static inline void init_vma_prep(struct vma_prepare *vp, > */ > static inline void vma_prepare(struct vma_prepare *vp) > { > - if (vp->vma) > - vma_start_write(vp->vma); > + vma_start_write(vp->vma); > if (vp->adj_next) > vma_start_write(vp->adj_next); > /* vp->insert is always a newly created VMA, no need for locking */ Yes, that looks correct. Reviewed-by: David Hildenbrand <david@redhat.com>
* Suren Baghdasaryan <surenb@google.com> [230228 21:27]: > vp->vma in vma_prepare() is always non-NULL, therefore checking it is > not necessary. Remove the extra check. > > Fixes: e8f071350ea5 ("mm/mmap: write-lock VMAs in vma_prepare before modifying them") > Reported-by: kernel test robot <lkp@intel.com> > Reported-by: Dan Carpenter <error27@gmail.com> > Link: https://lore.kernel.org/r/202302281802.J93Nma7q-lkp@intel.com/ > Signed-off-by: Suren Baghdasaryan <surenb@google.com> > --- > Fix cleanly apply over mm-unstable, SHA in "Fixes" is from that tree. > > mm/mmap.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index 0cd3714c2182..0759d53b470c 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -505,8 +505,7 @@ static inline void init_vma_prep(struct vma_prepare *vp, > */ > static inline void vma_prepare(struct vma_prepare *vp) > { > - if (vp->vma) > - vma_start_write(vp->vma); > + vma_start_write(vp->vma); Would a WARN_ON_ONCE() be worth it? Maybe not since it will be detected rather quickly once we dereference it below, but it might make it more clear as to what happened? I'm happy either way. Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com> > if (vp->adj_next) > vma_start_write(vp->adj_next); > /* vp->insert is always a newly created VMA, no need for locking */ > -- > 2.39.2.722.g9855ee24e9-goog >
On Wed, Mar 1, 2023 at 6:10 AM Liam R. Howlett <Liam.Howlett@oracle.com> wrote: > > * Suren Baghdasaryan <surenb@google.com> [230228 21:27]: > > vp->vma in vma_prepare() is always non-NULL, therefore checking it is > > not necessary. Remove the extra check. > > > > Fixes: e8f071350ea5 ("mm/mmap: write-lock VMAs in vma_prepare before modifying them") > > Reported-by: kernel test robot <lkp@intel.com> > > Reported-by: Dan Carpenter <error27@gmail.com> > > Link: https://lore.kernel.org/r/202302281802.J93Nma7q-lkp@intel.com/ > > Signed-off-by: Suren Baghdasaryan <surenb@google.com> > > --- > > Fix cleanly apply over mm-unstable, SHA in "Fixes" is from that tree. > > > > mm/mmap.c | 3 +-- > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > diff --git a/mm/mmap.c b/mm/mmap.c > > index 0cd3714c2182..0759d53b470c 100644 > > --- a/mm/mmap.c > > +++ b/mm/mmap.c > > @@ -505,8 +505,7 @@ static inline void init_vma_prep(struct vma_prepare *vp, > > */ > > static inline void vma_prepare(struct vma_prepare *vp) > > { > > - if (vp->vma) > > - vma_start_write(vp->vma); > > + vma_start_write(vp->vma); > > Would a WARN_ON_ONCE() be worth it? Maybe not since it will be detected > rather quickly once we dereference it below, but it might make it more > clear as to what happened? WARN_ON_ONCE() seems like an overkill to me. It always follows after init_multi_vma_prep()/init_vma_prep() both of which set the VMA. Risk should be minimal here and as you said, misuse is easily discoverable. > > I'm happy either way. > > Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com> > > > if (vp->adj_next) > > vma_start_write(vp->adj_next); > > /* vp->insert is always a newly created VMA, no need for locking */ > > -- > > 2.39.2.722.g9855ee24e9-goog > >
diff --git a/mm/mmap.c b/mm/mmap.c index 0cd3714c2182..0759d53b470c 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -505,8 +505,7 @@ static inline void init_vma_prep(struct vma_prepare *vp, */ static inline void vma_prepare(struct vma_prepare *vp) { - if (vp->vma) - vma_start_write(vp->vma); + vma_start_write(vp->vma); if (vp->adj_next) vma_start_write(vp->adj_next); /* vp->insert is always a newly created VMA, no need for locking */
vp->vma in vma_prepare() is always non-NULL, therefore checking it is not necessary. Remove the extra check. Fixes: e8f071350ea5 ("mm/mmap: write-lock VMAs in vma_prepare before modifying them") Reported-by: kernel test robot <lkp@intel.com> Reported-by: Dan Carpenter <error27@gmail.com> Link: https://lore.kernel.org/r/202302281802.J93Nma7q-lkp@intel.com/ Signed-off-by: Suren Baghdasaryan <surenb@google.com> --- Fix cleanly apply over mm-unstable, SHA in "Fixes" is from that tree. mm/mmap.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)