[bug #30221] Disk cache is not working properly

[Ales Nesrsta]

URL:
  <http://savannah.gnu.org/bugs/?30221>

                 Summary: Disk cache is not working properly
                 Project: GNU GRUB
            Submitted by: starous
            Submitted on: Tue 22 Jun 2010 07:43:33 PM GMT
                Category: Disk &amp; Partition
                Severity: Major
                Priority: 5 - Normal
              Item Group: Software Error
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: starous
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 
                 Release: Bazaar - trunk
         Reproducibility: Intermittent
         Planned Release: None

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Details:

Hi,

when I made some experiments with more USB devices connected at one time, I
found some disk cache related problem.

Behavior is:

If I connect more than one USB disk (or multi-LUN device), then very often
happens following error after first time use of "ls (usbx,y)/" command,
specially if x>0:
grub> insmod uhci
grub> insmod usbms
grub> ls
(usb0) (usb0, msdos1) (usb1) (usb1, msdos1) ...

grub> ls (usb1,1)/
error: unknown filesystem

If I try the same command second time, it is working normally.

>From USB side is not indicated any error.

I tried to disable cache via simple stupid change in disk.c in function
grub_disk_read:
...
      /* Fetch the cache.  */
      /* data = grub_disk_cache_fetch (disk->dev->id, disk->id,
start_sector); */
      data = NULL;
      if (data)
...
and in this case "ls" is working normally every time (but, of course, 
slowly...).

So, it looks like in disk cache is some bug.
(It probably appears only if more disks with more partitions are used, I
think it is not related to USB disks only.)

I found this problem in experimental branch "usb" but "trunk" has the same
behavior (official release 1.98 I did not test).

Best regards
Ales




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