[Toybox] [NEW TOYS] hardware rescan tool, FIFREEZE/FITHAW wrapper...(possibly out of scope?)

[Isaac Dunham]

I've written a couple of new toys that might well be out of scope, but
might be interesting or useful "for parts".

I'll describe the commands and the use cases.

1-hwrs: 
This was originally intended as a SUID helper cludge for my Acer 
Aspire One, which has a PCI-bus based SD card reader that only
shows up when the SD card is inserted. Kernel PCI hotplug does not work
properly, with the card reader frequently failing to show up, dmesg
getting spammed when I enable it, and the wireless card sporadically
failing for reasons that seem to be related.
However, it works to manually trigger a PCI bus rescan.
Additionally, neither mdev nor udev (as configured in Debian Squeeze) 
probe for partitions on slow external media, which makes configuring a 
user mount in /etc/fstab pointless.

I didn't want to have to log in as root every time I plugged in an SD
card, so I wrote this. It simply triggers a PCI bus rescan (hwrs -p),
then walks /dev opening every block device so as to make the kernel look
for partitions (hwrs -b).
Default behavior is the same as hwrs -pb.
The sole reason I wrote it as a new toy was that was the quickest way
to get it done.

If you think that this isn't in scope but the probe for partitions
sounds interesting for mdev, I'd be happy to write that.
(Coincidentally, I've thought of a way to make mdev handle hotplugging
with minimal code changes: use the environment to find the right uevent
file.)


2. xfs_freeze:
This is only a wrapper for the FIFREEZE/FITHAW ioctls.
FIFREEZE makes all writes to a filesystem (specified as a mountpoint!)
block until FITHAW is called.
The point here is to allow a filesystem to be put in a state that's
consistent enough for filesystem backup, checking, or repair, without
preventing reads or killing/waiting for programs that had open files on 
the filesystem.

The name is a historical artefact; this is a clone of the xfs_freeze
utility from xfsprogs.  These ioctls derive from and replace the 
XFS-specific XFS_IOC_FREEZE/XFS_IOC_THAW ioctls, which did exactly the
same thing.  But currently, at least xfs, ext*, jfs, gfs2, nilfs2, and
reiserfs support this ioctl.

I mainly wrote this because I hadn't done much with ioctls.


Thanks,
Isaac Dunham

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/* hwrs - rescan hardware
 *
 * Copyright 2014 Isaac Dunham
USE_HWRS(NEWTOY(hwrs, "bp", TOYFLAG_NEEDROOT|TOYFLAG_STAYROOT|TOYFLAG_USR|TOYFLAG_BIN))

config HWRS
  bool "hwrs"
  default n
  help
    usage: hwrs [-bp]

    rescan hardware
    -b scan block devices for partitions
    -p scan PCI busses for new hardware
*/

#define FOR_hwrs
#include "toys.h"

int blockopen(struct dirtree *node)
{
  int pfd = dirtree_parentfd(node);

  if S_ISBLK(node->st.st_mode) {
    close(openat(pfd, node->name, O_RDONLY));
  }
  return dirtree_notdotdot(node) & DIRTREE_RECURSE;
}

void hwrs_main(void)
{
  if (!toys.optflags) toys.optflags = (FLAG_b|FLAG_p);
  if (toys.optflags & FLAG_p) {
    int fd = xopen("/sys/bus/pci/rescan", O_WRONLY | O_TRUNC);
    write(fd, "1", 2);
    close(fd);
  }
  if (toys.optflags & FLAG_b) {
    dirtree_read("/dev/", blockopen);
  }
}
-------------- next part --------------
/* xfs_freeze.c - freeze or thaw filesystem
 *

USE_XFS_FREEZE(NEWTOY(xfs_freeze, "<1>1f|u|[!fu]", TOYFLAG_USR|TOYFLAG_SBIN))


config XFS_FREEZE
  bool "xfs_freeze"
  default n
  help
    usage: xfs_freeze {-f  | -u} /PATH/TO/MOUNT
    Freeze or unfreeze a filesystem.
    -f  freeze
    -u  unfreeze
    
*/

#define FOR_xfs_freeze
#include "toys.h"
#include <linux/fs.h>


void xfs_freeze_main(void)
{
  long p = 1;
  int io_call = toys.optflags & FLAG_f ? FIFREEZE : FITHAW;
  toys.exitval = ioctl(xopen(*toys.optargs,O_RDONLY), io_call, &p);
}