| Message ID | 20241018174114.2871880-2-Liam.Howlett@oracle.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/mremap: Remove extra vma tree walk | expand |
On Fri, Oct 18, 2024 at 01:41:13PM -0400, Liam R. Howlett 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 resize_is_valid() to better reflect what it is doing. > > This commit also adds documentation about the function. > > Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com> git-icdiff helped here a lot :) This LGTM, Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Generally a really nice clean up in any case, thanks for doing this! > --- > mm/mremap.c | 53 +++++++++++++++++++++++++++++++---------------------- > 1 file changed, 31 insertions(+), 22 deletions(-) > > diff --git a/mm/mremap.c b/mm/mremap.c > index 5917feafe8cc..e781ec4573ca 100644 > --- a/mm/mremap.c > +++ b/mm/mremap.c > @@ -826,17 +826,24 @@ static unsigned long move_vma(struct vm_area_struct *vma, > return new_addr; > } > > -static struct vm_area_struct *vma_to_resize(unsigned long addr, > +/* > + * resize_is_valid() - Ensure the vma can be resized to the new length at the give > + * address. > + * > + * @vma: The vma to resize > + * @addr: The old address > + * @old_len: The current size > + * @new_len: The desired size > + * @flags: The vma flags > + * > + * Return 0 on success, error otherwise. > + */ > +static int resize_is_valid(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 +854,37 @@ 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, > @@ -936,12 +943,16 @@ 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); > - if (IS_ERR(vma)) { > - ret = PTR_ERR(vma); > + vma = vma_lookup(mm, addr); > + if (!vma) { > + ret = -EFAULT; > goto out; > } > > + ret = resize_is_valid(vma, addr, old_len, new_len, flags); > + if (ret) > + goto out; > + > /* MREMAP_DONTUNMAP expands by old_len since old_len == new_len */ > if (flags & MREMAP_DONTUNMAP && > !may_expand_vm(mm, vma->vm_flags, old_len >> PAGE_SHIFT)) { > @@ -1114,11 +1125,9 @@ 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 = resize_is_valid(vma, addr, old_len, new_len, flags); > + if (ret) > goto out; > - } > > /* old_len exactly to the end of the area.. > */ > -- > 2.43.0 >
On Fri, Oct 18, 2024 at 6:41 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 resize_is_valid() to better reflect what it is doing. Small nit: Could we pick a stable naming scheme? I understand the kernel has historically had plenty of ways to name functions, including do_stuff is_stuff stuff_do stuff_is I thought we were starting to converge into vma_/vmi_/vms_ :( I would personally prefer vma_resize_is_valid/vma_resize_valid (even if it's a static function, so it doesn't matter _too_ much). Anyway, enough bikeshedding... > > This commit also adds documentation about the function. > > Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com> Reviewed-by: Pedro Falcato <pedro.falcato@gmail.com> This patch made me realize there's a couple of small improvements we can still do (maybe with a vmi) to clean up and speed up mremap (at least!). I'll look into those if I find some time.
* Pedro Falcato <pedro.falcato@gmail.com> [241022 18:08]: > On Fri, Oct 18, 2024 at 6:41 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 resize_is_valid() to better reflect what it is doing. > > Small nit: Could we pick a stable naming scheme? > I understand the kernel has historically had plenty of ways to name > functions, including > do_stuff > is_stuff > stuff_do > stuff_is > > I thought we were starting to converge into vma_/vmi_/vms_ :( > I would personally prefer vma_resize_is_valid/vma_resize_valid (even > if it's a static function, so it doesn't matter _too_ much). > Anyway, enough bikeshedding... Right. Usually the vma_/vmi_/vms_ stuff indicates the first argument to the functions exposed to other files. Yes, vma_ would work here, and I don't really mind that it's static and has the vma_ name. I'd suggest relocating it to vma.c or vma.h, but then we'd have to put mremap in the name and that would be rather long - I don't think we do anything like this elsewhere. > > > > > This commit also adds documentation about the function. > > > > Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com> > > Reviewed-by: Pedro Falcato <pedro.falcato@gmail.com> Thanks! > > This patch made me realize there's a couple of small improvements we > can still do (maybe with a vmi) to clean up and speed up mremap (at > least!). I'll look into those if I find some time. Agreed. If you do get to doing more clean up, I'd be fine with a rename of this function. Regards, Liam
diff --git a/mm/mremap.c b/mm/mremap.c index 5917feafe8cc..e781ec4573ca 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -826,17 +826,24 @@ static unsigned long move_vma(struct vm_area_struct *vma, return new_addr; } -static struct vm_area_struct *vma_to_resize(unsigned long addr, +/* + * resize_is_valid() - Ensure the vma can be resized to the new length at the give + * address. + * + * @vma: The vma to resize + * @addr: The old address + * @old_len: The current size + * @new_len: The desired size + * @flags: The vma flags + * + * Return 0 on success, error otherwise. + */ +static int resize_is_valid(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 +854,37 @@ 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, @@ -936,12 +943,16 @@ 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); - if (IS_ERR(vma)) { - ret = PTR_ERR(vma); + vma = vma_lookup(mm, addr); + if (!vma) { + ret = -EFAULT; goto out; } + ret = resize_is_valid(vma, addr, old_len, new_len, flags); + if (ret) + goto out; + /* MREMAP_DONTUNMAP expands by old_len since old_len == new_len */ if (flags & MREMAP_DONTUNMAP && !may_expand_vm(mm, vma->vm_flags, old_len >> PAGE_SHIFT)) { @@ -1114,11 +1125,9 @@ 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 = resize_is_valid(vma, addr, old_len, new_len, flags); + if (ret) goto out; - } /* old_len exactly to the end of the area.. */