On Sun, Jan 16, 2005 at 12:35:30AM +0100, Mario Holbe wrote: > Hello, > > mounting an ext2 (ext3 as well) filesystem seems to modify the > block device's EOF behaviour: before the mount the device returned > EOF, after the mount it doesn't anymore: > > [on a fresh booted system] > [EMAIL PROTECTED]:~# uname -a > Linux darkside 2.4.27 #1 Sat Jan 15 17:07:20 CET 2005 i686 GNU/Linux > [EMAIL PROTECTED]:~# dd if=/dev/hdg7 of=/dev/null > 9992366+0 records in > 9992366+0 records out > 5116091392 bytes transferred in 87,157394 seconds (58699453 bytes/sec) > [EMAIL PROTECTED]:~# mke2fs /dev/hdg7 > ... > Block size=4096 (log=2) > Fragment size=4096 (log=2) > 625248 inodes, 1249045 blocks > ... > [EMAIL PROTECTED]:~# dd if=/dev/hdg7 of=/dev/null > 9992366+0 records in > 9992366+0 records out > 5116091392 bytes transferred in 87,439332 seconds (58510184 bytes/sec) > [EMAIL PROTECTED]:~# mount -t ext2 -o ro /dev/hdg7 /mnt > [EMAIL PROTECTED]:~# umount /dev/hdg7 > [EMAIL PROTECTED]:~# dd if=/dev/hdg7 of=/dev/null > attempt to access beyond end of device > 22:07: rw=0, want=4996184, limit=4996183 > dd: reading `/dev/hdg7': Input/output error > 9992360+0 records in > 9992360+0 records out > 5116088320 bytes transferred in 87,145443 seconds (58707468 bytes/sec) > [EMAIL PROTECTED]:~# bc > 1249045 * 4 > 4996180 > 1249045 * 4 * 2 > 9992360 > > Could somebody please explain this to me? Is this intentional?
No > I could partly imagine the ext2 mount shrinking the block device's > boundaries to the filesystem boundaries - for security reasons perhaps, > even if I personally think this isn't the best idea at all, since it > would violate layers encapsulation. > However, I have no idea why a) if so, this is not reverted at least > on umount and why b) the EOF behaviour of the block device changes - > before there were an EOF sent to the application (dd) while after there > isn't, but an I/O error instead. Its indeed strange. > Kernel is Debian's kernel-source-2.4.27 + kernel-patch-2.4-i2c + > kernel-patch-2.4-lm-sensors. > > It seems there were already some mails regarding this issue suggesting > this could have shown up between 2.4.24 and 2.4.25, but it seems they > were misunderstood, for example: > > From: "ProNIC Solutions" <[EMAIL PROTECTED]> > Subject: 2.4.25: attempt to access beyond end of device > Date: Tue, 16 Mar 2004 09:06:31 -0500 > Message-ID: <[EMAIL PROTECTED]> > > From: "Peter S. Mazinger" <[EMAIL PROTECTED]> > Subject: BUG in 2.4.25-rc1: attempt to access beyond end of device > Date: Fri, 6 Feb 2004 13:53:40 +0100 (CET) > Message-ID: <[EMAIL PROTECTED]> Actually these were fixed during v2.4.26-pre. Can you please turn readahead off (hdparm -a 0 /dev/hdg) and repeat the tests? The kernel is trying to read one block after EOD. > attempt to access beyond end of device > 22:07: rw=0, want=4996184, limit=4996183 So maybe an off-by-one read-ahead? Also I suggest a dump_stack() to see where the read is coming from. Any other ideas? - 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/
