Re: 2.6.24-rc5-mm1 - wonky disk cache and CDROM behavior...

Dave Young
2007-12-18T02:33:20Z

On Mon, Dec 17, 2007 at 09:07:56PM -0500, Valdis.Kletnieks@vt.edu wrote:
> On Mon, 17 Dec 2007 14:56:44 PST, Andrew Morton said:
>
> (Adding Al Viro to the list, he's listed as "file systems" and MAINTAINERS
> doesn't list 'isofs' anyplace. Will Al or Andrew please vector to whoever
> actually does that code?)
>
> > > I try it again, and it reports it died at the same exact place, but in about
> > > 2 seconds flat, and reports 91M/sec transfer. OK, that's *weird*, I didn't
> > > think that blocks read from /dev/cdrom would get cached, but OK.
> >
> > It'll remain cached if something is holding the device open.
>
> Does it need to be "device open", or are there other things as well? If the
> drop_cache was hosed, that would result in the same symptoms, no?
>
> > Something's holding s_umount for writing I guess. Possibly busted error
> > handling somewhere totally different.
>
> Aha - found what was holding it - an attempt to loopback mount the truncated
> file (before I realized it was truncated) had failed - I had gotten a 'Killed'
> back from the mount, but I didn't realize it had pulled an actual oops:
>
> Dec 17 15:54:33 turing-police kernel: [14503.402385] attempt to access beyond end of device
> Dec 17 15:54:33 turing-police kernel: [14503.402391] loop1: rw=0, want=1284500, limit=314240
> Dec 17 15:54:33 turing-police kernel: [14503.402395] ISOFS: unable to read i-node block
> Dec 17 15:54:33 turing-police kernel: [14503.402428] Unable to handle kernel NULL pointer dereference at 000000000000010b RIP:
> Dec 17 15:54:33 turing-police kernel: [14503.402440] [<ffffffff802a096b>] iput+0x11/0x80
> ...
> Dec 17 15:54:33 turing-police kernel: [14503.403008] Call Trace:
> Dec 17 15:54:33 turing-police kernel: [14503.403026] [<ffffffff802ff73e>] isofs_fill_super+0x7e9/0xa6b
> Dec 17 15:54:33 turing-police kernel: [14503.403045] [<ffffffff80523d28>] __down_write_nested+0x3d/0xa1
> Dec 17 15:54:33 turing-police kernel: [14503.403061] [<ffffffff80523d97>] __down_write+0xb/0xd
> Dec 17 15:54:33 turing-police kernel: [14503.403076] [<ffffffff8028fb63>] sget+0x397/0x3a9
> Dec 17 15:54:33 turing-police kernel: [14503.403090] [<ffffffff8028f204>] set_bdev_super+0x0/0x14
> Dec 17 15:54:33 turing-police kernel: [14503.403106] [<ffffffff80290301>] get_sb_bdev+0x109/0x157
> Dec 17 15:54:33 turing-police kernel: [14503.403120] [<ffffffff802fef55>] isofs_fill_super+0x0/0xa6b
> Dec 17 15:54:33 turing-police kernel: [14503.403138] [<ffffffff802fe2e9>] isofs_get_sb+0x13/0x15
> Dec 17 15:54:33 turing-police kernel: [14503.403151] [<ffffffff80290075>] vfs_kern_mount+0x90/0x11a
> Dec 17 15:54:33 turing-police kernel: [14503.403167] [<ffffffff8029015c>] do_kern_mount+0x47/0xe3
> Dec 17 15:54:33 turing-police kernel: [14503.403183] [<ffffffff802a5012>] do_mount+0x717/0x78a
> Dec 17 15:54:33 turing-police kernel: [14503.403199] [<ffffffff805242fc>] _read_lock_irq+0x9/0xb
> Dec 17 15:54:33 turing-police kernel: [14503.403212] [<ffffffff8026cce0>] find_lock_page+0x8c/0x97
> Dec 17 15:54:33 turing-police kernel: [14503.403227] [<ffffffff8026ecb6>] filemap_fault+0x1fa/0x3c6
> Dec 17 15:54:33 turing-police kernel: [14503.403241] [<ffffffff8026cb6b>] unlock_page+0x2d/0x31
> Dec 17 15:54:33 turing-police kernel: [14503.403254] [<ffffffff8027925c>] __do_fault+0x38d/0x3c3
> Dec 17 15:54:33 turing-police kernel: [14503.403274] [<ffffffff8027ab68>] handle_mm_fault+0x36d/0x6e9
> Dec 17 15:54:33 turing-police kernel: [14503.403293] [<ffffffff80271903>] __alloc_pages+0x68/0x2f6
> Dec 17 15:54:33 turing-police kernel: [14503.403314] [<ffffffff802a510e>] sys_mount+0x89/0xcb
> Dec 17 15:54:33 turing-police kernel: [14503.403328] [<ffffffff80214f34>] syscall_trace_enter+0x97/0x9b
> Dec 17 15:54:33 turing-police kernel: [14503.403344] [<ffffffff8020c34c>] tracesys+0xdc/0xe1
> Dec 17 15:54:33 turing-police kernel: [14503.403359]
> Dec 17 15:54:33 turing-police kernel: [14503.403366]
> Dec 17 15:54:33 turing-police kernel: [14503.403367] Code: 48 8b 87 10 01 00 00 48 83 bf 38 02 00 00 40 48 8b 40 38 75
>
> I don't mind it failing the mount, but the oops seems excessive. I suspect
> that *somewhere* in that stack trace, we're wanting something like a
>
> if (!foo_ptr)
> return -EIO;
>
> but I admit not being competent enough to decide where that should be.
>

Hi,
Could you please try the below patch:

Signed-off-by: Dave Young <hidave.darkstar@gmail.com>

---
fs/isofs/inode.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff -upr linux/fs/isofs/inode.c linux.new/fs/isofs/inode.c
--- linux/fs/isofs/inode.c 2007-12-18 10:31:12.000000000 +0800
+++ linux.new/fs/isofs/inode.c 2007-12-18 10:31:56.000000000 +0800
@@ -1414,7 +1414,7 @@ struct inode *isofs_iget(struct super_bl
ret = isofs_read_inode(inode);
if (ret < 0) {
iget_failed(inode);
- inode = ERR_PTR(ret);
+ return NULL;
} else {
unlock_new_inode(inode);
}