On Fri 13-07-12 04:21:44, OGAWA Hirofumi wrote: > "Steven J. Magnani" <st...@digidescorp.com> writes: > > > 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... > > It looks like the bug of __getblk_slow(). If requested block was beyond > end of device, __find_get_block() will find buffer_mapped()'s buffer, > but block >= end_block is unmapped. So, it can be loop. > > The following patch fixes it? If it fix, there are some options to check > it. > > a) Check it like this patch and warn. > b) (a), but without warn. > c) Check it in init_page_buffers() and return -EIO or such > > Well, anyway, Cc to Jens. > > Signed-off-by: OGAWA Hirofumi <hirof...@mail.parknet.co.jp> I think Jeff Moyer has sent a similar fix recently. It may even be already queued in Jens' tree. Jeff?
Honza > --- > > fs/buffer.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff -puN fs/buffer.c~debug fs/buffer.c > --- tux3fs/fs/buffer.c~debug 2012-07-13 04:10:40.000000000 +0900 > +++ tux3fs-hirofumi/fs/buffer.c 2012-07-13 04:11:50.000000000 +0900 > @@ -1055,6 +1055,13 @@ __getblk_slow(struct block_device *bdev, > dump_stack(); > return NULL; > } > + if (block >= blkdev_max_block(I_BDEV(bdev->bd_inode))) { > + printk(KERN_ERR "getblk(): block %llu, end_block %llu\n", > + (unsigned long long)block, > + (unsigned long > long)blkdev_max_block(I_BDEV(bdev->bd_inode))); > + dump_stack(); > + return NULL; > + } > > for (;;) { > struct buffer_head * bh; > _ > > -- > OGAWA Hirofumi <hirof...@mail.parknet.co.jp> > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Jan Kara <j...@suse.cz> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/