| Message ID | 20241016201719.2449143-2-Liam.Howlett@oracle.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/mremap: Remove extra vma tree walk | expand |
On Wed, Oct 16, 2024 at 1:17 PM Liam R. Howlett <Liam.Howlett@oracle.com> wrote: > > From: "Liam R. Howlett" <Liam.Howlett@Oracle.com> > > 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 <Liam.Howlett@Oracle.com> > --- > 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 addr, 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 = current->mm; > - struct vm_area_struct *vma; > unsigned long pgoff; > > - vma = vma_lookup(mm, addr); > - if (!vma) > - return ERR_PTR(-EFAULT); > - > /* > * !old_len is a special case where an attempt is made to 'duplicate' > * a mapping. This makes no sense for private mappings as it will > @@ -847,37 +842,37 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr, > */ > if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) { > pr_warn_once("%s (%d): attempted to duplicate a private mapping 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 == old_len) > - return vma; > + return 0; > > /* Need to be careful about a growing mapping */ > pgoff = (addr - vma->vm_start) >> PAGE_SHIFT; > pgoff += 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, unsigned long old_len, > old_len = new_len; > } > > - vma = vma_to_resize(addr, old_len, new_len, flags); > + vma = vma_lookup(mm, addr); > + if (!vma) { > + ret = -EFAULT; > + goto out; > + } > + > + mremap_vma_check(vma, addr, old_len, new_len, flags); > if (IS_ERR(vma)) { > ret = PTR_ERR(vma); > goto out; > @@ -1114,11 +1115,9 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, > /* > * Ok, we need to grow.. > */ > - vma = vma_to_resize(addr, old_len, new_len, flags); > - if (IS_ERR(vma)) { > - ret = PTR_ERR(vma); > + ret = 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 >
* Jeff Xu <jeffxu@chromium.org> [241017 13:55]: > On Wed, Oct 16, 2024 at 1:17 PM Liam R. Howlett <Liam.Howlett@oracle.com> wrote: > > > > From: "Liam R. Howlett" <Liam.Howlett@Oracle.com> > > > > 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 <Liam.Howlett@Oracle.com> > > --- > > 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 addr, > The original function is vma_to_resize, and mremap_vma_check is > missing this context. > Maybe mremap_vma_check_resize is a better name ? Good point. That suggestion is long though. Perhaps vma_check_resize(), since this is a static function in the mremap.c file, it is fine to drop mremap from the name. ... Thanks, Liam
On Thu, Oct 17, 2024 at 11:07 AM Liam R. Howlett <Liam.Howlett@oracle.com> wrote: > > * Jeff Xu <jeffxu@chromium.org> [241017 13:55]: > > On Wed, Oct 16, 2024 at 1:17 PM Liam R. Howlett <Liam.Howlett@oracle.com> wrote: > > > > > > From: "Liam R. Howlett" <Liam.Howlett@Oracle.com> > > > > > > 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 <Liam.Howlett@Oracle.com> > > > --- > > > 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 addr, > > The original function is vma_to_resize, and mremap_vma_check is > > missing this context. > > Maybe mremap_vma_check_resize is a better name ? > > Good point. That suggestion is long though. Perhaps > vma_check_resize(), since this is a static function in the mremap.c > file, it is fine to drop mremap from the name. > I'm ok with that. > ... > > Thanks, > Liam
On Thu, 17 Oct 2024 11:15:20 -0700 Jeff Xu <jeffxu@chromium.org> wrote: > > > > -static struct vm_area_struct *vma_to_resize(unsigned long addr, > > > > +static int mremap_vma_check(struct vm_area_struct *vma, unsigned long addr, > > > The original function is vma_to_resize, and mremap_vma_check is > > > missing this context. > > > Maybe mremap_vma_check_resize is a better name ? > > > > Good point. That suggestion is long though. Perhaps > > vma_check_resize(), since this is a static function in the mremap.c > > file, it is fine to drop mremap from the name. > > > I'm ok with that. Any function with "check" in the name makes my teeth ache. "check" what? And the name doesn't carry any connotation of the return value's meaning. eg, "check_the_cheese()" versus "cheese_is_fresh()". The latter name tells you what is being checked and it tells you what a "true" return value means. Also, the dang function isn't documented. Also, why is mremap_to() calling mremap_vma_check() without testing its return value? mremap_vma_check() doesn't actually alter anything, does it? If it does then it's misnamed.
* Andrew Morton <akpm@linux-foundation.org> [241017 17:08]: > On Thu, 17 Oct 2024 11:15:20 -0700 Jeff Xu <jeffxu@chromium.org> wrote: > > > > > > -static struct vm_area_struct *vma_to_resize(unsigned long addr, > > > > > +static int mremap_vma_check(struct vm_area_struct *vma, unsigned long addr, > > > > The original function is vma_to_resize, and mremap_vma_check is > > > > missing this context. > > > > Maybe mremap_vma_check_resize is a better name ? > > > > > > Good point. That suggestion is long though. Perhaps > > > vma_check_resize(), since this is a static function in the mremap.c > > > file, it is fine to drop mremap from the name. > > > > > I'm ok with that. > > Any function with "check" in the name makes my teeth ache. "check" > what? And the name doesn't carry any connotation of the return value's > meaning. > > eg, "check_the_cheese()" versus "cheese_is_fresh()". The latter name > tells you what is being checked and it tells you what a "true" return > value means. Fair enough, how about resize_is_valid()? > > Also, the dang function isn't documented. I'll add that, thanks. > > Also, why is mremap_to() calling mremap_vma_check() without testing its > return value? mremap_vma_check() doesn't actually alter anything, does > it? If it does then it's misnamed. That's an issue, I'll fix it. Thanks, Liam
On Thu, 17 Oct 2024 19:53:10 -0400 "Liam R. Howlett" <Liam.Howlett@oracle.com> wrote: > > eg, "check_the_cheese()" versus "cheese_is_fresh()". The latter name > > tells you what is being checked and it tells you what a "true" return > > value means. > > Fair enough, how about resize_is_valid()? Sounds great. Although I do prefer cheese_is_fresh().
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 addr, unsigned long old_len, unsigned long new_len, unsigned long flags) { struct mm_struct *mm = current->mm; - struct vm_area_struct *vma; unsigned long pgoff; - vma = vma_lookup(mm, addr); - if (!vma) - return ERR_PTR(-EFAULT); - /* * !old_len is a special case where an attempt is made to 'duplicate' * a mapping. This makes no sense for private mappings as it will @@ -847,37 +842,37 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr, */ if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) { pr_warn_once("%s (%d): attempted to duplicate a private mapping 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 == old_len) - return vma; + return 0; /* Need to be careful about a growing mapping */ pgoff = (addr - vma->vm_start) >> PAGE_SHIFT; pgoff += 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, unsigned long old_len, old_len = new_len; } - vma = vma_to_resize(addr, old_len, new_len, flags); + vma = vma_lookup(mm, addr); + if (!vma) { + ret = -EFAULT; + goto out; + } + + mremap_vma_check(vma, addr, old_len, new_len, flags); if (IS_ERR(vma)) { ret = PTR_ERR(vma); goto out; @@ -1114,11 +1115,9 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, /* * Ok, we need to grow.. */ - vma = vma_to_resize(addr, old_len, new_len, flags); - if (IS_ERR(vma)) { - ret = PTR_ERR(vma); + ret = mremap_vma_check(vma, addr, old_len, new_len, flags); + if (ret) goto out; - } /* old_len exactly to the end of the area.. */