Messages in this thread | | | From | Daniel Phillips <> | Subject | Re: Why side-effects on open(2) are evil. (was Re: [RFD w/info-PATCH]device arguments from lookup) | Date | Thu, 24 May 2001 19:25:23 +0200 |
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On Thursday 24 May 2001 02:23, Edgar Toernig wrote: > Daniel Phillips wrote: > > > > It's going to be marked 'd', it's a directory, not a file. > > > > > > Aha. So you lose the S_ISCHR/BLK attribute. > > > > Readdir fills in a directory type, so ls sees it as a directory and > > does the right thing. On the other hand, we know we're on a device > > filesystem so we will next open the name as a regular file, and > > find ISCHR or ISBLK: good. > > ??? The kernel may know it, but the app? Or do you really want to > give different stat data on stat(2) and fstat(2)? These flags are > currently used by archive/backup prgs. It's a hint that these files > are not regular files and shouldn't be opened for reading. > Having a 'd' would mean that they would really try to enter the > directory and save it's contents. Don't know what happens in this > case to your "special" files ;-)
I guess that's much like the question 'what happens in proc?'.
Recursively entering the device directory is ok as long as everything inside it is ok. I tried zipping /proc/bus -r and what I got is what I'd expect if I'd cat'ed every non-directory entry. This is what I expected. Maybe it's not right - zipping /proc/kcore is kind of interesting. Regardless, we are no worse than proc here. In fact, since we don't anticipate putting an elephant like kcore in as a device property, we're a little nicer to get along with.
Correct me if I'm wrong, but what we learn from the proc example is that tarring your whole source tree starting at / is not something you want to do. Just extend that idea to /dev - however, if you do it, it will produce pretty reasonable results.
What *won't* happen is, you won't get side effects from opening your serial ports (you'd have to open them without O_DIRECTORY to get that) so that seems like a little step forward.
I'm still thinking about some of your other comments.
-- Daniel
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