>
> +unsigned long shmem_get_unmapped_area(struct file *file,
> + unsigned long uaddr, unsigned long len,
> + unsigned long pgoff, unsigned long flags)
> +{
> + unsigned long (*get_area)(struct file *,
> + unsigned long, unsigned long, unsigned long, unsigned long);
> + unsigned long addr;
> + unsigned long offset;
> + unsigned long inflated_len;
> + unsigned long inflated_addr;
> + unsigned long inflated_offset;
> +
> + if (len > TASK_SIZE)
> + return -ENOMEM;
> +
> + get_area = current->mm->get_unmapped_area;
> + addr = get_area(file, uaddr, len, pgoff, flags);
> +
> + if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
> + return addr;
> + if (IS_ERR_VALUE(addr))
> + return addr;
> + if (addr & ~PAGE_MASK)
> + return addr;
> + if (addr > TASK_SIZE - len)
> + return addr;
> +
> + if (shmem_huge == SHMEM_HUGE_DENY)
> + return addr;
> + if (len < HPAGE_PMD_SIZE)
> + return addr;
> + if (flags & MAP_FIXED)
> + return addr;
> + /*
> + * Our priority is to support MAP_SHARED mapped hugely;
> + * and support MAP_PRIVATE mapped hugely too, until it is COWed.
> + * But if caller specified an address hint, respect that as before.
> + */
> + if (uaddr)
> + return addr;
> +
> + if (shmem_huge != SHMEM_HUGE_FORCE) {
> + struct super_block *sb;
> +
> + if (file) {
> + VM_BUG_ON(file->f_op != &shmem_file_operations);
> + sb = file_inode(file)->i_sb;
> + } else {
> + /*
> + * Called directly from mm/mmap.c, or drivers/char/mem.c
> + * for "/dev/zero", to create a shared anonymous object.
> + */
> + if (IS_ERR(shm_mnt))
> + return addr;
> + sb = shm_mnt->mnt_sb;
> + }
> + if (SHMEM_SB(sb)->huge != SHMEM_HUGE_NEVER)
> + return addr;
Try to ask for a larger arena if huge page is not disabled for
the mount(s/!=/==/)?
> + }
> +
> + offset = (pgoff << PAGE_SHIFT) & (HPAGE_PMD_SIZE-1);
> + if (offset && offset + len < 2 * HPAGE_PMD_SIZE)
> + return addr;
> + if ((addr & (HPAGE_PMD_SIZE-1)) == offset)
> + return addr;
> +
> + inflated_len = len + HPAGE_PMD_SIZE - PAGE_SIZE;
> + if (inflated_len > TASK_SIZE)
> + return addr;
> + if (inflated_len < len)
> + return addr;
> +
> + inflated_addr = get_area(NULL, 0, inflated_len, 0, flags);
> + if (IS_ERR_VALUE(inflated_addr))
> + return addr;
> + if (inflated_addr & ~PAGE_MASK)
> + return addr;
> +
> + inflated_offset = inflated_addr & (HPAGE_PMD_SIZE-1);
> + inflated_addr += offset - inflated_offset;
> + if (inflated_offset > offset)
> + inflated_addr += HPAGE_PMD_SIZE;
> +
> + if (inflated_addr > TASK_SIZE - len)
> + return addr;
> + return inflated_addr;
> +}
> +
>
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