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    SubjectRe: [net PATCH v2 1/2] net: netprio: fix files lock and remove useless d_path bits
    On Mon, Aug 13, 2012 at 07:43:21PM -0700, John Fastabend wrote:
    > Add lock to prevent a race with a file closing and also remove
    > useless and ugly sscanf code. The extra code was never needed
    > and the case it supposedly protected against is in fact handled
    > correctly by sock_from_file as pointed out by Al Viro.
    >
    > CC: Neil Horman <nhorman@tuxdriver.com>
    > Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
    > Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
    > ---
    >
    > net/core/netprio_cgroup.c | 22 ++++------------------
    > 1 files changed, 4 insertions(+), 18 deletions(-)
    >
    > diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
    > index ed0c043..f65dba3 100644
    > --- a/net/core/netprio_cgroup.c
    > +++ b/net/core/netprio_cgroup.c
    > @@ -277,12 +277,6 @@ out_free_devname:
    > void net_prio_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
    > {
    > struct task_struct *p;
    > - char *tmp = kzalloc(sizeof(char) * PATH_MAX, GFP_KERNEL);
    > -
    > - if (!tmp) {
    > - pr_warn("Unable to attach cgrp due to alloc failure!\n");
    > - return;
    > - }
    >
    > cgroup_taskset_for_each(p, cgrp, tset) {
    > unsigned int fd;
    > @@ -296,32 +290,24 @@ void net_prio_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
    > continue;
    > }
    >
    > - rcu_read_lock();
    > + spin_lock(&files->file_lock);
    > fdt = files_fdtable(files);
    > for (fd = 0; fd < fdt->max_fds; fd++) {
    > - char *path;
    > struct file *file;
    > struct socket *sock;
    > - unsigned long s;
    > - int rv, err = 0;
    > + int err;
    >
    > file = fcheck_files(files, fd);
    > if (!file)
    > continue;
    >
    > - path = d_path(&file->f_path, tmp, PAGE_SIZE);
    > - rv = sscanf(path, "socket:[%lu]", &s);
    > - if (rv <= 0)
    > - continue;
    > -
    > sock = sock_from_file(file, &err);
    > - if (!err)
    > + if (sock)
    > sock_update_netprioidx(sock->sk, p);
    > }
    > - rcu_read_unlock();
    > + spin_unlock(&files->file_lock);
    > task_unlock(p);
    > }
    > - kfree(tmp);
    > }
    >
    > static struct cftype ss_files[] = {
    >
    This looks ok to me, but I've already shown my inability to review code that
    interfaces with VFS. Al, what do you think?

    Neil

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