Re: Reading from file in module fails

From: Libor Vanek (libor_at_conet.cz)
Date: 05/03/04

  • Next message: Sau Dan Lee: "[PATCH] modused: mark some modules as in use (Re: [PATCH] (fix:oops with rmmod i8042))" 
    Date:	Mon, 3 May 2004 13:43:16 +0200
To: Erik Mouw <erik@harddisk-recovery.com>

    > > I need to copy files (yes - I know that kernel shouldn't do this but
    > > I REALLY need).
    >
    > This is ugly, but it should do the trick:
    >
    > int rv;
    > char *argv[4] = {"/bin/cp", "/tmp/foo", "/tmp/bar", NULL};
    > char *envp[3] = {"HOME=/", "PATH=/sbin:/bin:/usr/sbin:/usr/bin", NULL};
    >
    > rv = call_usermodehelper(argv[0], argv, envp, 1);
    >
    > if(rv < 0) {
    > /* error handling */
    > }
    >
    > Called from kernel, done in userspace. And if you want to access an SQL
    > database from kernel tomorrow, it's just a matter of changing the
    > usermode helper.
    >
    > (BTW, if you need to copy files from kernel, it's usually a sign of bad
    > design)

    Geez - that's REALLY ugly :-) But for testing I can use it.

    It's not bad design - what I'm doing is writing snapshots for VFS as my diploma thesis. And I need to create copy of file before it's changed (copy-on-write). There is no other way how to do it in kernel-space (and user-space solutions like using LUFS are really slow)

    Thx,
    Libor

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  • Next message: Sau Dan Lee: "[PATCH] modused: mark some modules as in use (Re: [PATCH] (fix:oops with rmmod i8042))"

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