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Thu, 17 Oct 2024 10:55:38 -0700 (PDT) MIME-Version: 1.0 References: <20241016201719.2449143-1-Liam.Howlett@oracle.com> <20241016201719.2449143-2-Liam.Howlett@oracle.com> In-Reply-To: <20241016201719.2449143-2-Liam.Howlett@oracle.com> From: Jeff Xu Date: Thu, 17 Oct 2024 10:55:27 -0700 Message-ID: Subject: Re: [PATCH 1/2] mm/mremap: Clean up vma_to_resize() To: "Liam R. Howlett" Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Lorenzo Stoakes , Jann Horn , David Hildenbrand , Qi Zheng , Kefeng Wang , Pedro Falcato Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: A3E7814001B X-Rspamd-Server: rspam01 X-Stat-Signature: h1duszk1j1ntcirxao9osudg1es9owrc X-HE-Tag: 1729187732-219912 X-HE-Meta: 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 82Z+LrZK sHHnsiKerzeo0AYPh0tX3QnRjU2aHh2w9IIyeljbrOG5G/qHdWBcakGLWg8DTfyMYhqoAnw35PpFvxCxzEcd65DD8St/sc51DFXHthVbTEDPIBto7YsT4Rl9r2qhUV5Zbg8F7KYkLcOTBGUaKX+A0mnDDRgGFYNRbWLGRyflrx+OeYrr7F88QNSGwBdVke1Otd9W1vR6Ez2XgeI9/kYiGLN5/ASjdQmsBsCN8QNK4wCjL2kBr6YR1zWOARtHud6xTinJTfFXJCI6WHr+WUMcsYK++9xQTBvRA+BS9y9Onj2/vHBXyi1tQDj1t+oepT1nwz3d2RnNRdKu7vIelHmNmTAEiWlmJVd7AovHjOA+lEF4+bbZZWWSKmqQGkg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Oct 16, 2024 at 1:17=E2=80=AFPM Liam R. Howlett wrote: > > From: "Liam R. Howlett" > > vma_to_resize() is used in two locations to find and validate the vma > for the mremap location. One of the two locations already has the vma, > which is then re-found to validate the same vma. > > This code can be simplified by moving the vma_lookup() from > vma_to_resize() to mremap_to() and changing the return type to an int > error. > > Since the function now just validates the vma, the function is renamed > to mremap_vma_check() to better reflect what it is doing. > > Signed-off-by: Liam R. Howlett > --- > mm/mremap.c | 39 +++++++++++++++++++-------------------- > 1 file changed, 19 insertions(+), 20 deletions(-) > > diff --git a/mm/mremap.c b/mm/mremap.c > index 5917feafe8cc..648c29f568af 100644 > --- a/mm/mremap.c > +++ b/mm/mremap.c > @@ -826,17 +826,12 @@ static unsigned long move_vma(struct vm_area_struct= *vma, > return new_addr; > } > > -static struct vm_area_struct *vma_to_resize(unsigned long addr, > +static int mremap_vma_check(struct vm_area_struct *vma, unsigned long ad= dr, The original function is vma_to_resize, and mremap_vma_check is missing this context. Maybe mremap_vma_check_resize is a better name ? > unsigned long old_len, unsigned long new_len, unsigned long flags= ) > { > struct mm_struct *mm =3D current->mm; > - struct vm_area_struct *vma; > unsigned long pgoff; > > - vma =3D vma_lookup(mm, addr); > - if (!vma) > - return ERR_PTR(-EFAULT); > - > /* > * !old_len is a special case where an attempt is made to 'duplic= ate' > * a mapping. This makes no sense for private mappings as it wil= l > @@ -847,37 +842,37 @@ static struct vm_area_struct *vma_to_resize(unsigne= d long addr, > */ > if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) { > pr_warn_once("%s (%d): attempted to duplicate a private m= apping with mremap. This is not supported.\n", current->comm, current->pid= ); > - return ERR_PTR(-EINVAL); > + return -EINVAL; > } > > if ((flags & MREMAP_DONTUNMAP) && > (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))) > - return ERR_PTR(-EINVAL); > + return -EINVAL; > > /* We can't remap across vm area boundaries */ > if (old_len > vma->vm_end - addr) > - return ERR_PTR(-EFAULT); > + return -EFAULT; > > if (new_len =3D=3D old_len) > - return vma; > + return 0; > > /* Need to be careful about a growing mapping */ > pgoff =3D (addr - vma->vm_start) >> PAGE_SHIFT; > pgoff +=3D vma->vm_pgoff; > if (pgoff + (new_len >> PAGE_SHIFT) < pgoff) > - return ERR_PTR(-EINVAL); > + return -EINVAL; > > if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) > - return ERR_PTR(-EFAULT); > + return -EFAULT; > > if (!mlock_future_ok(mm, vma->vm_flags, new_len - old_len)) > - return ERR_PTR(-EAGAIN); > + return -EAGAIN; > > if (!may_expand_vm(mm, vma->vm_flags, > (new_len - old_len) >> PAGE_SHIFT)) > - return ERR_PTR(-ENOMEM); > + return -ENOMEM; > > - return vma; > + return 0; > } > > static unsigned long mremap_to(unsigned long addr, unsigned long old_len= , > @@ -936,7 +931,13 @@ static unsigned long mremap_to(unsigned long addr, u= nsigned long old_len, > old_len =3D new_len; > } > > - vma =3D vma_to_resize(addr, old_len, new_len, flags); > + vma =3D vma_lookup(mm, addr); > + if (!vma) { > + ret =3D -EFAULT; > + goto out; > + } > + > + mremap_vma_check(vma, addr, old_len, new_len, flags); > if (IS_ERR(vma)) { > ret =3D PTR_ERR(vma); > goto out; > @@ -1114,11 +1115,9 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsig= ned long, old_len, > /* > * Ok, we need to grow.. > */ > - vma =3D vma_to_resize(addr, old_len, new_len, flags); > - if (IS_ERR(vma)) { > - ret =3D PTR_ERR(vma); > + ret =3D mremap_vma_check(vma, addr, old_len, new_len, flags); > + if (ret) > goto out; > - } > > /* old_len exactly to the end of the area.. > */ > -- > 2.43.0 >