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    SubjectRe: [PATCH/RFC 1/2] anon-inodes: Remove fd_install() from anon_inode_getfd()
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     > If we let the caller call fd_install(), then it may be messed up WRT 
    > cleanup (fd, file, inode).

    Yes, that is a tiny bit tricky (need to call put_unused_fd() if you
    don't install the fd).

    > How about removing the inode pointer handout altogether, and *doing*
    > fd_install() inside anon_inode_getfd() like:
    >
    > if (pfile != NULL) {
    > get_file(file);
    > *pfile = file;
    > }
    > fd_install(fd, file);
    >
    > In this way, if the caller want the file* back, he gets the reference
    > bumped before fd_install().

    I think that may be a bit cleaner than Al's approach, but it still
    leaves the same trap that create_vcpu_fd() falls into. The current
    code is:

    static int create_vcpu_fd(struct kvm_vcpu *vcpu)
    {
    int fd, r;
    struct inode *inode;
    struct file *file;

    r = anon_inode_getfd(&fd, &inode, &file,
    "kvm-vcpu", &kvm_vcpu_fops, vcpu);
    if (r)
    return r;
    atomic_inc(&vcpu->kvm->filp->f_count);
    return fd;
    }

    and with your proposal, the natural way to write that becomes:

    static int create_vcpu_fd(struct kvm_vcpu *vcpu)
    {
    int fd, r;

    r = anon_inode_getfd(&fd, NULL,
    "kvm-vcpu", &kvm_vcpu_fops, vcpu);
    if (r)
    return r;
    atomic_inc(&vcpu->kvm->filp->f_count);
    return fd;
    }

    which still has the same bug.

    Maybe a good way to handle this is just to make the get_file() not
    optional. I dunno... I feel like we've spent more discussion on this
    point than it deserves, so someone should just make a decision and
    I'll adapt the ib_uverbs code to work with whatever it is.

    - R.


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