Re: [PATCH] ltp/fsx: avoid infinite loop while finding offset2 in clone/dedupe/copy range ops

[Eryu Guan <guaneryu@gmail.com>]

On Fri, Aug 23, 2019 at 07:33:54AM -0700, Darrick J. Wong wrote:
> On Fri, Aug 23, 2019 at 03:22:59PM +0800, Eryu Guan wrote:
> > In CLONE/DEDUPE/COPY RANGE operations, we pick a "offset" and "size"
> > first, then find a suitable "offset2" by looping if there's overlap
> > (|offset2-offset| < size) or final file size is greater than max file
> > size (offset2 + size > maxfilelen).
> > 
> > But it's possible that there's no such suitable offset2 and we loop
> > forever. e.g. block_size = 4096, offset = 0, size = 4096 and maxfilelen
> > is a value smaller than 8212 (which could be set via '-l' option).
> > 
> > Fix it by making sure maxfilelen/file_size is big enough to hold 'size'
> > bytes from 'offset2', and just skip this operation if not.
> > 
> > Signed-off-by: Eryu Guan <eguan@linux.alibaba.com>
> > ---
> >  ltp/fsx.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> > 
> > diff --git a/ltp/fsx.c b/ltp/fsx.c
> > index 06d08e4e93f3..f6eb3308e8bc 100644
> > --- a/ltp/fsx.c
> > +++ b/ltp/fsx.c
> > @@ -1825,6 +1825,14 @@ do {						\
> >  	TRIM_LEN(off, len, size);		\
> >  } while (0)
> >  
> > +#define CHECK_RANGE(off, len, size)		\
> > +do {						\
> > +	if ((off + len * 2) > size) {		\
> > +		log5(op, offset, size, -1, FL_SKIPPED); \
> > +		goto out;			\
> > +	}					\
> > +} while (0)
> 
> Eww, macros.
> 
> Worse, macros that don't parenthesize the arguments.
> 
> Worse^2, macros that require variables to be defined in the caller's
> scope that aren't passed as explicit parameters.
> 
> Worse^3, macros with gotos.

Yeah, these are ugly :) I was meant to define this macro in the context
where it's used, and undefine it when it's out of scope.

> 
> Why not:
> 
> static inline bool CHECK_RANGE(...)
> {
> 	bool ret = ((off + len * 2) <= size);
> 
> 	if (!ret)
> 		log5(...);
> 	return ret;
> }
> 
> and then
> 
> if (!CHECK_RANGE(offset, size, maxfilelen))
> 	goto out;

Looks good, will rework. Thanks for the review!

Eryu
> 
> --D
> 
> }
> > +
> >  void
> >  cleanup(int sig)
> >  {
> > @@ -1989,6 +1997,7 @@ test(void)
> >  		TRIM_OFF_LEN(offset, size, file_size);
> >  		offset = offset & ~(block_size - 1);
> >  		size = size & ~(block_size - 1);
> > +		CHECK_RANGE(offset, size, maxfilelen);
> >  		do {
> >  			offset2 = random();
> >  			TRIM_OFF(offset2, maxfilelen);
> > @@ -2003,6 +2012,7 @@ test(void)
> >  			TRIM_OFF_LEN(offset, size, file_size);
> >  			offset = offset & ~(block_size - 1);
> >  			size = size & ~(block_size - 1);
> > +			CHECK_RANGE(offset, size, file_size);
> >  			do {
> >  				if (tries++ >= 30) {
> >  					size = 0;
> > @@ -2020,6 +2030,7 @@ test(void)
> >  		offset -= offset % readbdy;
> >  		if (o_direct)
> >  			size -= size % readbdy;
> > +		CHECK_RANGE(offset, size, maxfilelen);
> >  		do {
> >  			offset2 = random();
> >  			TRIM_OFF(offset2, maxfilelen);
> > -- 
> > 2.14.4.44.g2045bb6
> >