1. 09 Jan, 2006 4 commits
  2. 17 Sep, 2005 1 commit
  3. 07 Sep, 2005 1 commit
    • Tom Zanussi's avatar
      [PATCH] relayfs · e82894f8
      Tom Zanussi authored
      Here's the latest version of relayfs, against linux-2.6.11-mm2.  I'm hoping
      you'll consider putting this version back into your tree - the previous
      rounds of comment seem to have shaken out all the API issues and the number
      of comments on the code itself have also steadily dwindled.
      This patch is essentially the same as the relayfs redux part 5 patch, with
      some minor changes based on reviewer comments.  Thanks again to Pekka
      Enberg for those.  The patch size without documentation is now a little
      smaller at just over 40k.  Here's a detailed list of the changes:
      - removed the attribute_flags in relay open and changed it to a
        boolean specifying either overwrite or no-overwrite mode, and removed
        everything referencing the attribute flags.
      - added a check for NULL names in relayfs_create_entry()
      - got rid of the unnecessary multiple labels in relay_create_buf()
      - some minor simplification of relay_alloc_buf() which got rid of a
        couple params
      - updated the Documentation
      In addition, this version (through code contained in the relay-apps tarball
      linked to below, not as part of the relayfs patch) tries to make it as easy
      as possible to create the cooperating kernel/user pieces of a typical and
      common type of logging application, one where kernel logging is kicked off
      when a user space data collection app starts and stops when the collection
      app exits, with the data being automatically logged to disk in between.  To
      create this type of application, you basically just include a header file
      (relay-app.h, included in the relay-apps tarball) in your kernel module,
      define a couple of callbacks and call an initialization function, and on
      the user side call a single function that sets up and continuously monitors
      the buffers, and writes data to files as it becomes available.  Channels
      are created when the collection app is started and destroyed when it exits,
      not when the kernel module is inserted, so different channel buffer sizes
      can be specified for each separate run via command-line options.  See the
      README in the relay-apps tarball for details.
      Also included in the relay-apps tarball are a couple examples
      demonstrating how you can use this to create quick and dirty kernel
      logging/debugging applications.  They are:
      - tprintk, short for 'tee printk', which temporarily puts a kprobe on
        printk() and writes a duplicate stream of printk output to a relayfs
        channel.  This could be used anywhere there's printk() debugging code
        in the kernel which you'd like to exercise, but would rather not have
        your system logs cluttered with debugging junk.  You'd probably want
        to kill klogd while you do this, otherwise there wouldn't be much
        point (since putting a kprobe on printk() doesn't change the output
        of printk()).  I've used this method to temporarily divert the packet
        logging output of the iptables LOG target from the system logs to
        relayfs files instead, for instance.
      - klog, which just provides a printk-like formatted logging function
        on top of relayfs.  Again, you can use this to keep stuff out of your
        system logs if used in place of printk.
      The example applications can be found here:
      From: Christoph Hellwig <hch@lst.de>
        avoid lookup_hash usage in relayfs
      Signed-off-by: default avatarTom Zanussi <zanussi@us.ibm.com>
      Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>