Re: [PATCH 1/3] fsx: factor out a file size update helper

["Darrick J. Wong" <djwong@kernel.org>]

On Thu, Aug 22, 2024 at 10:44:20AM -0400, Brian Foster wrote:
> In preparation for support for eof page pollution, factor out a file
> size update helper. This updates the internally tracked file size
> based on the upcoming operation and zeroes the appropriate range in
> the good buffer for extending operations.
> 
> Note that a handful of callers currently make these updates after
> performing the associated operation. Order is not important to
> current behavior, but it will be for a follow on patch, so make
> those calls a bit earlier as well.
> 
> Signed-off-by: Brian Foster <bfoster@redhat.com>
> ---
>  ltp/fsx.c | 57 +++++++++++++++++++++++++------------------------------
>  1 file changed, 26 insertions(+), 31 deletions(-)
> 
> diff --git a/ltp/fsx.c b/ltp/fsx.c
> index 2dc59b06..1389c51d 100644
> --- a/ltp/fsx.c
> +++ b/ltp/fsx.c
> @@ -983,6 +983,17 @@ gendata(char *original_buf, char *good_buf, unsigned offset, unsigned size)
>  	}
>  }
>  
> +/*
> + * Helper to update the tracked file size. If the offset begins beyond current
> + * EOF, zero the range from EOF to offset in the good buffer.
> + */
> +void
> +update_file_size(unsigned offset, unsigned size)
> +{
> +	if (offset > file_size)
> +		memset(good_buf + file_size, '\0', offset - file_size);
> +	file_size = offset + size;
> +}
>  
>  void
>  dowrite(unsigned offset, unsigned size)
> @@ -1003,10 +1014,8 @@ dowrite(unsigned offset, unsigned size)
>  	log4(OP_WRITE, offset, size, FL_NONE);
>  
>  	gendata(original_buf, good_buf, offset, size);
> -	if (file_size < offset + size) {
> -		if (file_size < offset)
> -			memset(good_buf + file_size, '\0', offset - file_size);
> -		file_size = offset + size;
> +	if (offset + size > file_size) {
> +		update_file_size(offset, size);
>  		if (lite) {
>  			warn("Lite file size bug in fsx!");
>  			report_failure(149);
> @@ -1070,10 +1079,8 @@ domapwrite(unsigned offset, unsigned size)
>  	log4(OP_MAPWRITE, offset, size, FL_NONE);
>  
>  	gendata(original_buf, good_buf, offset, size);
> -	if (file_size < offset + size) {
> -		if (file_size < offset)
> -			memset(good_buf + file_size, '\0', offset - file_size);
> -		file_size = offset + size;
> +	if (offset + size > file_size) {
> +		update_file_size(offset, size);
>  		if (lite) {
>  			warn("Lite file size bug in fsx!");
>  			report_failure(200);
> @@ -1136,9 +1143,7 @@ dotruncate(unsigned size)
>  
>  	log4(OP_TRUNCATE, 0, size, FL_NONE);
>  
> -	if (size > file_size)
> -		memset(good_buf + file_size, '\0', size - file_size);
> -	file_size = size;
> +	update_file_size(size, 0);
>  
>  	if (testcalls <= simulatedopcount)
>  		return;
> @@ -1247,6 +1252,9 @@ do_zero_range(unsigned offset, unsigned length, int keep_size)
>  	log4(OP_ZERO_RANGE, offset, length,
>  	     keep_size ? FL_KEEP_SIZE : FL_NONE);
>  
> +	if (end_offset > file_size)
> +		update_file_size(offset, length);
> +
>  	if (testcalls <= simulatedopcount)
>  		return;

Don't we only want to do the goodbuf zeroing if we don't bail out due to
the (testcalls <= simulatedopcount) logic?  Same question for
do_clone_range and do_copy_range.

/me reads the second patch but doesn't quite get it. :/

Are you doing this to mirror what the kernel does?  A comment here to
explain why we're doing this differently would help me.

--D

>  
> @@ -1263,17 +1271,6 @@ do_zero_range(unsigned offset, unsigned length, int keep_size)
>  	}
>  
>  	memset(good_buf + offset, '\0', length);
> -
> -	if (!keep_size && end_offset > file_size) {
> -		/*
> -		 * If there's a gap between the old file size and the offset of
> -		 * the zero range operation, fill the gap with zeroes.
> -		 */
> -		if (offset > file_size)
> -			memset(good_buf + file_size, '\0', offset - file_size);
> -
> -		file_size = end_offset;
> -	}
>  }
>  
>  #else
> @@ -1538,6 +1535,9 @@ do_clone_range(unsigned offset, unsigned length, unsigned dest)
>  
>  	log5(OP_CLONE_RANGE, offset, length, dest, FL_NONE);
>  
> +	if (dest + length > file_size)
> +		update_file_size(dest, length);
> +
>  	if (testcalls <= simulatedopcount)
>  		return;
>  
> @@ -1556,10 +1556,6 @@ do_clone_range(unsigned offset, unsigned length, unsigned dest)
>  	}
>  
>  	memcpy(good_buf + dest, good_buf + offset, length);
> -	if (dest > file_size)
> -		memset(good_buf + file_size, '\0', dest - file_size);
> -	if (dest + length > file_size)
> -		file_size = dest + length;
>  }
>  
>  #else
> @@ -1756,6 +1752,9 @@ do_copy_range(unsigned offset, unsigned length, unsigned dest)
>  
>  	log5(OP_COPY_RANGE, offset, length, dest, FL_NONE);
>  
> +	if (dest + length > file_size)
> +		update_file_size(dest, length);
> +
>  	if (testcalls <= simulatedopcount)
>  		return;
>  
> @@ -1792,10 +1791,6 @@ do_copy_range(unsigned offset, unsigned length, unsigned dest)
>  	}
>  
>  	memcpy(good_buf + dest, good_buf + offset, length);
> -	if (dest > file_size)
> -		memset(good_buf + file_size, '\0', dest - file_size);
> -	if (dest + length > file_size)
> -		file_size = dest + length;
>  }
>  
>  #else
> @@ -1846,7 +1841,7 @@ do_preallocate(unsigned offset, unsigned length, int keep_size)
>  
>  	if (end_offset > file_size) {
>  		memset(good_buf + file_size, '\0', end_offset - file_size);
> -		file_size = end_offset;
> +		update_file_size(offset, length);
>  	}
>  
>  	if (testcalls <= simulatedopcount)
> -- 
> 2.45.0
> 
>