"Steven J. Magnani" <[email protected]> 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 <[email protected]> --- 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 <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
