Re: VOP_CREATE hanging

[Adam Burkepile <sadpoti%gmail.com@localhost>]

On Aug 12, 2008, at 8:59 AM, David Holland wrote:
> On Tue, Aug 12, 2008 at 06:02:21PM +0300, Antti Kantee wrote:
> > On Tue Aug 12 2008 at 07:40:05 -0700, Adam Burkepile wrote:
> > > For my subfile project I am creating a directory and not attaching  
> > > it
> > > to a parent directory, but rather storing the inode number of the
> > > directory and retrieving it using VGET.
>
> What does '..' point to in such a directory? Isn't that going to make
> fsck angry?


Yeah, the plan was to make . and .. point to the subfile directory.  
fsck is throwing a hissy fit right now but another part of the plan  
was to make fsck realize that it should treat nodes that were these  
special subfile directories differently, which is another problem that  
I will have to tackle.

On Aug 12, 2008, at 8:02 AM, Antti Kantee wrote:

> >                /* lock subfile directory */
> >                if(VOP_ISLOCKED(sdvp) == 0){
> >                        printf("sdvp is unlocked, now locking\n");
> >                        vn_lock(sdvp, LK_EXCLUSIVE | LK_RETRY);
> >                }
>
> Please don't write code which does locking like this, it's just  
> begging
> for trouble.  Your code should always know if it has a node locked  
> or not.

I have taken out the unnecessary locks/unlocks, it was just easier at  
the time.

> It is not legal to call VOP_CREATE() without calling namei (ultimately
> VOP_LOOKUP()), since this call sets up a lot of state in the file  
> system
> to prepare for the actual creation operation.

Ok, I have made the changes you mentioned (I think), but I'm still  
having the hanging problem.

                printf("subfile not found, needs to be created\n");
                NDINIT(&sfnd, CREATE, FOLLOW | TRYEMULROOT,  
UIO_USERSPACE, SCARG(uap, sub_path));

                /* set namedata with namei */
                error = namei(&sfnd);
                printf("namei error = %d\n",error);

                sfnd.ni_cnd.cn_nameiop = CREATE;
                sfnd.ni_cnd.cn_flags |= LOCKPARENT | LOCKLEAF;
                if ((SCARG(uap, flags) & O_EXCL) == 0 &&
                                ((SCARG(uap, flags) & O_NOFOLLOW) ==  
0))
                        sfnd.ni_cnd.cn_flags |= FOLLOW;

                //lock subfile directory
                vn_lock(sdvp, LK_EXCLUSIVE | LK_RETRY);

                /* set the attr of the new file */
                VATTR_NULL(&sfva);
                sfva.va_type = VREG;
                sfva.va_rdev = VNOVAL;
                sfva.va_mode = (bva.va_mode & ALLPERMS) &~ p->p_cwdi- 
>cwdi_cmask;
                if (SCARG(uap, flags) & O_EXCL)
                        sfva.va_vaflags |= VA_EXCLUSIVE;

                error = VOP_LOOKUP(sdvp,&sfvp,&(sfnd.ni_cnd));
                printf("VOP_LOOKUP error = %d\n",error);

                error = VOP_CREATE(sdvp,&sfvp,&(sfnd.ni_cnd),&sfva);
                printf("VOP_CREATE error = %d\n",error);

                if (error == 0)
                        vput(sfvp);
                goto out;


If it helps, from what I've been able to tell this is the functions it  
goes through before it hangs:
sys_subfile_open()
VOP_CREATE()
ufs_makeinode()
ufs_direnter()
UFS_BALLOC()


I had a few other questions:
1. Is VERIEXEC_PATH_GET / VERIEXEC_PATH_PUT necessary for VOP_CREATE?
2. When you said "calling ... ultimately VOP_LOOKUP()", did you mean  
me calling it (like I am trying to do).
3.
> Or, if you're working just with ffs, you could hack
> lookup into pieces so you can call the parts involved with the  
> necessary
> setup for create.

If VOP_LOOKUP is returning but ultimately messing up, could this be  
causing the problems that I'm having with VOP_CREATE? I ask because I  
am having a problem with VOP_LOOKUP not releasing some sort of lock on  
the fs. It is not letting me umount my test fs and manifest a some  
other weird errors (not being able to find files). The deadline is  
coming up so I was inclined to skip the problem and come back to it  
since it didn't seem like it was hanging the rest of the program and I  
want to have some functionality to show.