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    SubjectRe: mount -o loop with truncated dosdisk.img uses 100% cpu and can't be killed
    On Thu, 2012-07-12 at 16:28 +0200, Stevie Trujillo wrote: 
    > Hello,
    > I was trying to create a bootdisk to update my BIOS, and accidentially
    > made a 512byte image with only the FreeDOS header in it.
    > ( Linux 3.4.4 )
    > # mount -o loop dosdisk.img /tmp
    > ^C^C^C
    > It uses 100% CPU and doesn't listen to me when I do ^C, kill -9 etc. I
    > think this means it's stuck in the kernel?

    Here is the stack trace I get for the mount process:

    [root@telezart smagnani]# cat /proc/1334/stack
    [<ffffffff81077a5a>] __cond_resched+0x2a/0x40
    [<ffffffff8110c4bb>] find_lock_page+0x3b/0x80
    [<ffffffff8110cbaf>] find_or_create_page+0x3f/0xb0
    [<ffffffff8119a692>] __getblk+0xf2/0x2a0
    [<ffffffff8119a893>] __bread+0x13/0xb0
    [<ffffffffa00fd1fe>] fat__get_entry+0x14e/0x220 [fat]
    [<ffffffffa00fd596>] fat_get_short_entry+0x66/0xc0 [fat]
    [<ffffffffa00ff765>] fat_subdirs+0x55/0x80 [fat]
    [<ffffffffa0103d30>] fat_fill_super+0x810/0xa80 [fat]
    [<ffffffffa00e821a>] vfat_fill_super+0x1a/0x20 [vfat]
    [<ffffffff8116d61b>] mount_bdev+0x1cb/0x210
    [<ffffffffa00e81f5>] vfat_mount+0x15/0x20 [vfat]
    [<ffffffff8116e410>] mount_fs+0x20/0xd0
    [<ffffffff81186e4f>] vfs_kern_mount+0x6f/0x100
    [<ffffffff81187804>] do_kern_mount+0x54/0x110
    [<ffffffff811891d6>] do_mount+0x306/0x8b0
    [<ffffffff811898cd>] sys_mount+0x8d/0xe0
    [<ffffffff81583629>] system_call_fastpath+0x16/0x1b
    [<ffffffffffffffff>] 0xffffffffffffffff

    I would think this is more likely a bug in the loopback driver than the
    FAT filesystem...
    Steven J. Magnani "I claim this network for MARS! Earthling, return my space modulator!"

    #include <standard.disclaimer>

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