Re: Your CVS fix 1.109 to union_vnops.c

From: Takanori Watanabe (takawata_at_init-main.com)
Date: 10/04/04

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    To: Uwe Doering <gemini@geminix.org>
Date: Mon, 04 Oct 2004 18:12:14 +0900

    In message <4160FBD9.10603@geminix.org>, Uwe Doering wrote:
    >takawata@jp.freebsd.org wrote:
    >> In message <4160ED06.6070603@geminix.org>, Uwe Doering wrote:
    >>
    >>>Takanori Watanabe wrote:
    >>>[...]
    >>>>Ok, the issue Uwe says is when underlying filesystem and
    >>>>wrapping filesystem are diffent and if there are two files
    >>>>with same identifier exists.
    >>>>And the issue I want to fix is when underlying filesystem and
    >>>>wrapping filesystem are same so getcwd routine failed to distinguish
    >>>>the mount point.
    >>>>
    >>>>So it can be solved by translating fsid if the fsid of a file is same as
    >>>>that of mountpoint. True?
    >>>
    >>>Correct. In this case the inode number is guaranteed to be unique.
    >>>This might be okay as a local patch, but it is IMHO not a fix suited for
    >>>FreeBSD in general.
    >>
    >> Ok. How about this?
    >
    >This wouldn't be correct, either. Unionfs can be stacked, that is, you
    >can't even be sure for a single layer that the passed up va_fsid will
    >always be the same. The underlying unionfs can be comprised of two
    >layers on two different file systems as well, and so on. You can
    >override va_fsid only if the original file system id is guaranteed to be
    >the same for all files in that layer (single file system case).

    Ok, whats next?

    Index: union.h
    ===================================================================
    RCS file: /home/ncvs/src/sys/fs/unionfs/union.h,v
    retrieving revision 1.28
    diff -u -r1.28 union.h
    --- union.h 7 Apr 2004 20:46:03 -0000 1.28
    +++ union.h 4 Oct 2004 09:03:26 -0000
    @@ -44,6 +44,7 @@
             struct ucred *um_cred; /* Credentials of user calling mount */
             int um_cmode; /* cmask from mount process */
             int um_op; /* Operation mode */
    + dev_t um_upperdev; /* Upper root node fsid[0]*/
     };
     
     #ifdef _KERNEL
    Index: union_vfsops.c
    ===================================================================
    RCS file: /home/ncvs/src/sys/fs/unionfs/union_vfsops.c,v
    retrieving revision 1.67
    diff -u -r1.67 union_vfsops.c
    --- union_vfsops.c 30 Jul 2004 22:08:51 -0000 1.67
    +++ union_vfsops.c 4 Oct 2004 09:03:26 -0000
    @@ -72,6 +72,7 @@
             struct vnode *lowerrootvp = NULLVP;
             struct vnode *upperrootvp = NULLVP;
             struct union_mount *um = 0;
    + struct vattr va;
             struct ucred *cred = 0;
             char *cp = 0, *target;
             int op;
    @@ -190,6 +191,12 @@
                                     M_UNIONFSMNT, M_WAITOK | M_ZERO);
     
             um->um_op = op;
    +
    + error = VOP_GETATTR(upperrootvp, &va, td->td_ucred, td);
    + if(error)
    + goto bad;
    +
    + um->um_upperdev = va.va_fsid;
     
             switch (um->um_op) {
             case UNMNT_ABOVE:
    Index: union_vnops.c
    ===================================================================
    RCS file: /home/ncvs/src/sys/fs/unionfs/union_vnops.c,v
    retrieving revision 1.109
    diff -u -r1.109 union_vnops.c
    --- union_vnops.c 2 Oct 2004 17:17:04 -0000 1.109
    +++ union_vnops.c 4 Oct 2004 09:03:27 -0000
    @@ -932,6 +932,7 @@
     {
             int error;
             struct union_node *un = VTOUNION(ap->a_vp);
    + struct union_mount *um = MOUNTTOUNIONMOUNT(ap->a_vp->v_mount);
             struct vnode *vp;
             struct vattr *vap;
             struct vattr va;
    @@ -972,7 +973,8 @@
                     union_newsize(ap->a_vp, VNOVAL, vap->va_size);
             }
     
    - ap->a_vap->va_fsid = ap->a_vp->v_mount->mnt_stat.f_fsid.val[0];
    + if(vap->va_fsid == um->um_upperdev)
    + vap->va_fsid = ap->a_vp->v_mount->mnt_stat.f_fsid.val[0];
     
             if ((vap != ap->a_vap) && (vap->va_type == VDIR))
                     ap->a_vap->va_nlink += vap->va_nlink;

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