lkml.org 
[lkml]   [2007]   [Aug]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] Send quota messages via netlink
    On Tue, 28 Aug 2007 16:13:18 +0200 Jan Kara <jack@suse.cz> wrote:

    > Hello,
    >
    > I'm sending rediffed patch implementing sending of quota messages via netlink
    > interface (some rationale in patch description). I've already posted it to
    > LKML some time ago and there were no objections, so I guess it's fine to put
    > it to -mm. Andrew, would you be so kind? Thanks.
    > Userspace deamon reading the messages from the kernel and sending them to
    > dbus and/or user console is also written (it's part of quota-tools). The
    > only remaining problem is there are a few changes needed to libnl needed for
    > the userspace daemon. They were basically acked by the maintainer but it
    > seems he has not merged the patches yet. So this will take a bit more time.
    >

    So it's a new kernel->userspace interface.

    But we have no description of the interface :(

    > +/* Send warning to userspace about user which exceeded quota */
    > +static void send_warning(const struct dquot *dquot, const char warntype)
    > +{
    > + static unsigned long seq;
    > + struct sk_buff *skb;
    > + void *msg_head;
    > + int ret;
    > +
    > + skb = genlmsg_new(QUOTA_NL_MSG_SIZE, GFP_NOFS);
    > + if (!skb) {
    > + printk(KERN_ERR
    > + "VFS: Not enough memory to send quota warning.\n");
    > + return;
    > + }
    > + msg_head = genlmsg_put(skb, 0, seq++, &quota_genl_family, 0, QUOTA_NL_C_WARNING);
    > + if (!msg_head) {
    > + printk(KERN_ERR
    > + "VFS: Cannot store netlink header in quota warning.\n");
    > + goto err_out;
    > + }
    > + ret = nla_put_u32(skb, QUOTA_NL_A_QTYPE, dquot->dq_type);
    > + if (ret)
    > + goto attr_err_out;
    > + ret = nla_put_u64(skb, QUOTA_NL_A_EXCESS_ID, dquot->dq_id);
    > + if (ret)
    > + goto attr_err_out;
    > + ret = nla_put_u32(skb, QUOTA_NL_A_WARNING, warntype);
    > + if (ret)
    > + goto attr_err_out;
    > + ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MAJOR,
    > + MAJOR(dquot->dq_sb->s_dev));
    > + if (ret)
    > + goto attr_err_out;
    > + ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MINOR,
    > + MINOR(dquot->dq_sb->s_dev));
    > + if (ret)
    > + goto attr_err_out;
    > + ret = nla_put_u64(skb, QUOTA_NL_A_CAUSED_ID, current->user->uid);
    > + if (ret)
    > + goto attr_err_out;
    > + genlmsg_end(skb, msg_head);
    > +
    > + ret = genlmsg_multicast(skb, 0, quota_genl_family.id, GFP_NOFS);
    > + if (ret < 0 && ret != -ESRCH)
    > + printk(KERN_ERR
    > + "VFS: Failed to send notification message: %d\n", ret);
    > + return;
    > +attr_err_out:
    > + printk(KERN_ERR "VFS: Failed to compose quota message: %d\n", ret);
    > +err_out:
    > + kfree_skb(skb);
    > +}
    > +#endif

    This is it. Normally netlink payloads are represented as a struct. How
    come this one is built-by-hand?

    It doesn't appear to be versioned. Should it be?

    Does it have (or need) reserved-set-to-zero space for expansion? Again,
    hard to tell..

    I guess it's OK to send a major and minor out of the kernel like this.
    What's it for? To represent a filesytem? I wonder if there's a more
    modern and useful way of describing the fs. Path to mountpoint or
    something?

    I suspect the namespace virtualisation guys would be interested in a new
    interface which is sending current->user->uid up to userspace. uids are
    per-namespace now. What are the implications? (cc's added)

    Is it worth adding a comment explaining why GFP_NOFS is used here?


    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2007-08-29 06:17    [W:2.344 / U:0.052 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site