On Fri, 2007-03-16 at 09:36 -0400, Ming Zhang wrote: > On Thu, 2007-03-15 at 20:21 -0700, Randy Dunlap wrote: > > On Mon, 12 Mar 2007 13:23:07 -0400 Ming Zhang wrote: > > > > > Hi All > > > > > > I know sometime we need ERR_PTR and PTR_ERR, but why we need to write > > > code like this line 356 in quotactl_block() > > > > > > 353 bdev = lookup_bdev(tmp); > > > 354 putname(tmp); > > > 355 if (IS_ERR(bdev)) > > > 356 return ERR_PTR(PTR_ERR(bdev)) > > > > > > instead of > > > > > > return bdev > > > > > > it convert a PTR to ERR and then back to PTR. any idea why? > > > > Did you test what happens when you change that return line to be only > > return bdev; > > ? Please do so. > > sorry i should be more accurate. > > ERR_PTR(PTR_ERR(bdev)) is like to > > return (void *)(long)bdev; > > then what is the difference between this and > > return (void *)bdev; > > > from speed, this 2 should have no difference. then any other > consideration? This is a very good question, and I am curious about the answer. I was hoping that you would get an answer. Can you do Randy's suggestion, and change "ERR_PTR(PTR_ERR(bdev))" to "bdev", and see if it breaks? Thanks, Avishay -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
