On Wed, Dec 11, 2024 at 3:28 PM Kalesh Singh <kaleshsingh@xxxxxxxxxx> wrote:
>
> Consolidate the hint searches from both directions (topdown and
> bottomup) into generic_mmap_hint().
>
> No functional change is introduced.
>
> Signed-off-by: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
> ---
>
> Changes in v2:
> - MAP_FIXED case is also handled in arch_mmap_hint() since this is just a
> special case of the hint addr being "enforced", per Yang Shi.
> - Consolidate error handling in arch_mmap_hint().
Reviewed-by: Yang Shi <shy828301@xxxxxxxxx>
>
> include/linux/sched/mm.h | 4 +++
> mm/mmap.c | 76 ++++++++++++++++++++++++----------------
> 2 files changed, 50 insertions(+), 30 deletions(-)
>
> diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
> index 928a626725e6..edeec19d1708 100644
> --- a/include/linux/sched/mm.h
> +++ b/include/linux/sched/mm.h
> @@ -201,6 +201,10 @@ unsigned long mm_get_unmapped_area_vmflags(struct mm_struct *mm,
> unsigned long flags,
> vm_flags_t vm_flags);
>
> +unsigned long generic_mmap_hint(struct file *filp, unsigned long addr,
> + unsigned long len, unsigned long pgoff,
> + unsigned long flags);
> +
> unsigned long
> generic_get_unmapped_area(struct file *filp, unsigned long addr,
> unsigned long len, unsigned long pgoff,
> diff --git a/mm/mmap.c b/mm/mmap.c
> index df9154b15ef9..382b4eac5406 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -620,6 +620,47 @@ unsigned long vm_unmapped_area(struct vm_unmapped_area_info *info)
> return addr;
> }
>
> +/*
> + * Look up unmapped area at the requested hint addr
> + *
> + * NOTE: MAP_FIXED is also handled here since it's a special case of
> + * enforcing the hint address.
> + *
> + * Returns:
> + * ERR_VALUE: If the requested mapping is not valid
> + * 0: If there isn't a sufficiently large hole at the hint addr.
> + * addr: If sufficient VA space is available at the hint address;
> + * or MAP_FIXED was specified.
> + */
> +unsigned long generic_mmap_hint(struct file *filp, unsigned long addr,
> + unsigned long len, unsigned long pgoff,
> + unsigned long flags)
> +{
> + struct mm_struct *mm = current->mm;
> + struct vm_area_struct *vma, *prev;
> + const unsigned long mmap_end = arch_get_mmap_end(addr, len, flags);
> +
> + /* requested length too big for entire address space */
> + if (len > mmap_end - mmap_min_addr)
> + return -ENOMEM;
> +
> + if (flags & MAP_FIXED)
> + return addr;
> +
> + if (!addr)
> + return 0;
> +
> + addr = PAGE_ALIGN(addr);
> + vma = find_vma_prev(mm, addr, &prev);
> + if (mmap_end - len >= addr && addr >= mmap_min_addr &&
> + (!vma || addr + len <= vm_start_gap(vma)) &&
> + (!prev || addr >= vm_end_gap(prev)))
> + return addr;
> +
> + /* Fallback to VA space search */
> + return 0;
> +}
> +
> /* Get an address range which is currently unmapped.
> * For shmat() with addr=0.
> *
> @@ -637,25 +678,13 @@ generic_get_unmapped_area(struct file *filp, unsigned long addr,
> unsigned long flags, vm_flags_t vm_flags)
> {
> struct mm_struct *mm = current->mm;
> - struct vm_area_struct *vma, *prev;
> struct vm_unmapped_area_info info = {};
> const unsigned long mmap_end = arch_get_mmap_end(addr, len, flags);
>
> - if (len > mmap_end - mmap_min_addr)
> - return -ENOMEM;
> -
> - if (flags & MAP_FIXED)
> + addr = generic_mmap_hint(filp, addr, len, pgoff, flags);
> + if (addr)
> return addr;
>
> - if (addr) {
> - addr = PAGE_ALIGN(addr);
> - vma = find_vma_prev(mm, addr, &prev);
> - if (mmap_end - len >= addr && addr >= mmap_min_addr &&
> - (!vma || addr + len <= vm_start_gap(vma)) &&
> - (!prev || addr >= vm_end_gap(prev)))
> - return addr;
> - }
> -
> info.length = len;
> info.low_limit = mm->mmap_base;
> info.high_limit = mmap_end;
> @@ -685,27 +714,14 @@ generic_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
> unsigned long len, unsigned long pgoff,
> unsigned long flags, vm_flags_t vm_flags)
> {
> - struct vm_area_struct *vma, *prev;
> struct mm_struct *mm = current->mm;
> struct vm_unmapped_area_info info = {};
> const unsigned long mmap_end = arch_get_mmap_end(addr, len, flags);
>
> - /* requested length too big for entire address space */
> - if (len > mmap_end - mmap_min_addr)
> - return -ENOMEM;
> -
> - if (flags & MAP_FIXED)
> - return addr;
> -
> /* requesting a specific address */
> - if (addr) {
> - addr = PAGE_ALIGN(addr);
> - vma = find_vma_prev(mm, addr, &prev);
> - if (mmap_end - len >= addr && addr >= mmap_min_addr &&
> - (!vma || addr + len <= vm_start_gap(vma)) &&
> - (!prev || addr >= vm_end_gap(prev)))
> - return addr;
> - }
> + addr = generic_mmap_hint(filp, addr, len, pgoff, flags);
> + if (addr)
> + return addr;
>
> info.flags = VM_UNMAPPED_AREA_TOPDOWN;
> info.length = len;
> --
> 2.47.0.338.g60cca15819-goog
>
>
