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

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 21/04/2020 07:28, Florian Weimer wrote:
> * 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?

Do you mean instead of '4 * BUFSIZ'?