Re: [PATCH] fs/squashfs: use do_div function for math

["Pali Rohár" <pali@kernel.org>]

On Monday 09 May 2022 15:08:15 Miquel Raynal wrote:
> Hello,
> 
> trini@konsulko.com wrote on Thu, 5 May 2022 09:15:00 -0400:
> 
> > On Thu, May 05, 2022 at 11:26:37AM +0200, Sean Nyekjaer wrote:
> > 
> > > From: Sean Nyekjaer <sean.nyekjaer.ext@siemensgamesa.com>
> > > 
> > > When compling for x86:
> > > ld.bfd: fs/squashfs/sqfs.o: in function `sqfs_read':
> > > u-boot/fs/squashfs/sqfs.c:1443: undefined reference to `__udivmoddi4'
> > > ld.bfd: u-boot/fs/squashfs/sqfs.c:1521: undefined reference to `__udivmoddi4'
> > > 
> > > Signed-off-by: Sean Nyekjaer <sean.nyekjaer.ext@siemensgamesa.com>
> > > ---
> > >  fs/squashfs/sqfs.c | 5 +++--
> > >  1 file changed, 3 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/fs/squashfs/sqfs.c b/fs/squashfs/sqfs.c
> > > index 5d9c52af80..6405db4ff3 100644
> > > --- a/fs/squashfs/sqfs.c
> > > +++ b/fs/squashfs/sqfs.c
> > > @@ -8,6 +8,7 @@
> > >   */
> > >  
> > >  #include <asm/unaligned.h>
> > > +#include <div64.h>
> > >  #include <errno.h>
> > >  #include <fs.h>
> > >  #include <linux/types.h>
> > > @@ -1440,7 +1441,7 @@ int sqfs_read(const char *filename, void *buf, loff_t offset, loff_t len,
> > >  	}
> > >  
> > >  	for (j = 0; j < datablk_count; j++) {
> > > -		start = data_offset / ctxt.cur_dev->blksz;
> > > +		start = do_div(data_offset, ctxt.cur_dev->blksz);
> > >  		table_size = SQFS_BLOCK_SIZE(finfo.blk_sizes[j]);
> > >  		table_offset = data_offset - (start * ctxt.cur_dev->blksz);
> > >  		n_blks = DIV_ROUND_UP(table_size + table_offset,
> > > @@ -1516,7 +1517,7 @@ int sqfs_read(const char *filename, void *buf, loff_t offset, loff_t len,
> > >  		goto out;
> > >  	}
> > >  
> > > -	start = frag_entry.start / ctxt.cur_dev->blksz;
> > > +	start = do_div(frag_entry.start, ctxt.cur_dev->blksz);
> > >  	table_size = SQFS_BLOCK_SIZE(frag_entry.size);
> > >  	table_offset = frag_entry.start - (start * ctxt.cur_dev->blksz);
> > >  	n_blks = DIV_ROUND_UP(table_size + table_offset, ctxt.cur_dev->blksz);  
> > 
> > Adding maintainers...
> 
> I guess that's a correct fix, so
> 
> Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
> 
> Thanks,
> Miquèl

Hello! do_div() macro modifies its first argument. It is correct?
Because previous code did not modify anything.