Re: [PATCH 02/10] linux: Simplify opendir buffer allocation

[Florian Weimer <fw@deneb.enyo.de>]

* Adhemerval Zanella via Libc-alpha:

> THe fallback allocation is removed, so the possible size constraint
> should be analized just once; __alloc_dir assumes that 'statp'
> argument is non-null, and the max_buffer_size move to close its
> used.

Type: analized

> +    return NULL;
> +
> +  /* The st_blksize value of the directory is used as a hint for the
> +     size of the buffer which receives struct dirent values from the
> +     kernel.  st_blksize is limited to max_buffer_size, in case the
> +     file system provides a bogus value.  */
> +  enum { max_buffer_size = 1U << 20 };
> +
> +  const size_t allocation_size = 4 * BUFSIZ;
> +  _Static_assert (allocation_size >= sizeof (struct dirent64),
> +		  "allocation_size < sizeof (struct dirent64)");
> +
>    /* Increase allocation if requested, but not if the value appears to
> +     be bogus.  It will be between 32Kb (for blocksizes smaller than BUFSIZ)
> +     up to 1Mb.  */
> +  size_t allocation = MIN (MAX ((size_t) statp->st_blksize, allocation_size),
> +			   max_buffer_size);
>  
>    DIR *dirp = (DIR *) malloc (sizeof (DIR) + allocation);
>    if (dirp == NULL)
>      {
> +      if (close_fd)
> +	__close_nocancel_nostatus (fd);
> +      return NULL;
>      }
>  
>    dirp->fd = fd;

This looks okay to me.  I wonder if we should just use 32 KiB
uncodintionally, though?