[REGRESSION] nfs client: Read-only file system (2.6.19-rc1,2)

[REGRESSION] nfs client: Read-only file system (2.6.19-rc1,2)

[Jiri Slaby]

Hi!

I can't write on mounted nfs filesystem since 2.6.19-rc1 (nfs client):
touch: cannot touch `aaa': Read-only file system

strace says:
open("aaa", O_WRONLY|O_NONBLOCK|O_CREAT|O_NOCTTY|O_LARGEFILE, 0666) = -1 EROFS 
(Read-only file system)

2.6.18 behaves correctly. Settings are the same, does anybody have any clue?

regards,
-- 
http://www.fi.muni.cz/~xslaby/            Jiri Slaby
faculty of informatics, masaryk university, brno, cz
e-mail: jirislaby gmail com, gpg pubkey fingerprint:
B674 9967 0407 CE62 ACC8  22A0 32CC 55C3 39D4 7A7E

Re: [REGRESSION] nfs client: Read-only file system (2.6.19-rc1,2)

[Trond Myklebust]

On Tue, 2006-10-17 at 17:24 +0200, Jiri Slaby wrote:
> Hi!
> 
> I can't write on mounted nfs filesystem since 2.6.19-rc1 (nfs client):
> touch: cannot touch `aaa': Read-only file system
> 
> strace says:
> open("aaa", O_WRONLY|O_NONBLOCK|O_CREAT|O_NOCTTY|O_LARGEFILE, 0666) = -1 EROFS 
> (Read-only file system)
> 
> 2.6.18 behaves correctly. Settings are the same, does anybody have any clue?
> 
> regards,

What does "cat /proc/mounts" say?

Re: [REGRESSION] nfs client: Read-only file system (2.6.19-rc1,2)

[Sven Hoexter]

Trond Myklebust wrote:
> On Tue, 2006-10-17 at 17:24 +0200, Jiri Slaby wrote:

Hi,

>> I can't write on mounted nfs filesystem since 2.6.19-rc1 (nfs client):
>> touch: cannot touch `aaa': Read-only file system
>> 
>> strace says:
>> open("aaa", O_WRONLY|O_NONBLOCK|O_CREAT|O_NOCTTY|O_LARGEFILE, 0666) = -1
>> EROFS (Read-only file system)
>> 
>> 2.6.18 behaves correctly. Settings are the same, does anybody have any
>> clue?
>
> What does "cat /proc/mounts" say?
Ok I'm not the OP but I can confirm the problem.

>From /proc/mounts:
arthur:/mnt/disk2/mp3 /mnt/mp3 nfs ro,nosuid,nodev,noexec,vers=3,rsize=8192,wsize=8192,hard,proto=tcp,timeo=600,retrans=2,sec=sys,addr=arthur 0 0

Reports ro here while mount still reports rw:
arthur:/mnt/disk2/mp3 on /mnt/mp3 type nfs (rw,noexec,nosuid,nodev,addr=192.168.88.80)

Sven

Re: [REGRESSION] nfs client: Read-only file system (2.6.19-rc1,2)

[Jiri Slaby]

Do not remove CCs.
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: Jiri Slaby <jirislaby@gmail.com>

Sven Hoexter wrote:
> Trond Myklebust wrote:
>> On Tue, 2006-10-17 at 17:24 +0200, Jiri Slaby wrote:
> 
> Hi,
> 
>>> I can't write on mounted nfs filesystem since 2.6.19-rc1 (nfs client):
>>> touch: cannot touch `aaa': Read-only file system
>>>
>>> strace says:
>>> open("aaa", O_WRONLY|O_NONBLOCK|O_CREAT|O_NOCTTY|O_LARGEFILE, 0666) = -1
>>> EROFS (Read-only file system)
>>>
>>> 2.6.18 behaves correctly. Settings are the same, does anybody have any
>>> clue?
>> What does "cat /proc/mounts" say?
> Ok I'm not the OP but I can confirm the problem.
> 
>>From /proc/mounts:
> arthur:/mnt/disk2/mp3 /mnt/mp3 nfs ro,nosuid,nodev,noexec,vers=3,rsize=8192,wsize=8192,hard,proto=tcp,timeo=600,retrans=2,sec=sys,addr=arthur 0 0
> 
> Reports ro here while mount still reports rw:
> arthur:/mnt/disk2/mp3 on /mnt/mp3 type nfs (rw,noexec,nosuid,nodev,addr=192.168.88.80)

I will post my output in some hours, if still needed.

regards,
-- 
http://www.fi.muni.cz/~xslaby/            Jiri Slaby
faculty of informatics, masaryk university, brno, cz
e-mail: jirislaby gmail com, gpg pubkey fingerprint:
B674 9967 0407 CE62 ACC8  22A0 32CC 55C3 39D4 7A7E

Re: [REGRESSION] nfs client: Read-only file system (2.6.19-rc1,2)

[Jiri Slaby]

Jiri Slaby wrote:
> Do not remove CCs.
> Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
> Cc: Jiri Slaby <jirislaby@gmail.com>
> 
> Sven Hoexter wrote:
>> Trond Myklebust wrote:
>>> On Tue, 2006-10-17 at 17:24 +0200, Jiri Slaby wrote:
>>
>> Hi,
>>
>>>> I can't write on mounted nfs filesystem since 2.6.19-rc1 (nfs client):
>>>> touch: cannot touch `aaa': Read-only file system
>>>>
>>>> strace says:
>>>> open("aaa", O_WRONLY|O_NONBLOCK|O_CREAT|O_NOCTTY|O_LARGEFILE, 0666) 
>>>> = -1
>>>> EROFS (Read-only file system)
>>>>
>>>> 2.6.18 behaves correctly. Settings are the same, does anybody have any
>>>> clue?
>>> What does "cat /proc/mounts" say?
>> Ok I'm not the OP but I can confirm the problem.
>>
>>> From /proc/mounts:
>> arthur:/mnt/disk2/mp3 /mnt/mp3 nfs 
>> ro,nosuid,nodev,noexec,vers=3,rsize=8192,wsize=8192,hard,proto=tcp,timeo=600,retrans=2,sec=sys,addr=arthur 
>> 0 0
>>
>> Reports ro here while mount still reports rw:
>> arthur:/mnt/disk2/mp3 on /mnt/mp3 type nfs 
>> (rw,noexec,nosuid,nodev,addr=192.168.88.80)
> 
> I will post my output in some hours, if still needed.

The very same thing. /etc/mtab still reports rw, while /proc/mounts says ro, weird.

regards,
-- 
http://www.fi.muni.cz/~xslaby/            Jiri Slaby
faculty of informatics, masaryk university, brno, cz
e-mail: jirislaby gmail com, gpg pubkey fingerprint:
B674 9967 0407 CE62 ACC8  22A0 32CC 55C3 39D4 7A7E

Re: [REGRESSION] nfs client: Read-only file system (2.6.19-rc1,2)

[Trond Myklebust]

On Wed, 2006-10-18 at 17:46 +0200, Jiri Slaby wrote:
> Jiri Slaby wrote:
> > Do not remove CCs.
> > Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
> > Cc: Jiri Slaby <jirislaby@gmail.com>
> > 
> > Sven Hoexter wrote:
> >> Trond Myklebust wrote:
> >>> On Tue, 2006-10-17 at 17:24 +0200, Jiri Slaby wrote:
> >>
> >> Hi,
> >>
> >>>> I can't write on mounted nfs filesystem since 2.6.19-rc1 (nfs client):
> >>>> touch: cannot touch `aaa': Read-only file system
> >>>>
> >>>> strace says:
> >>>> open("aaa", O_WRONLY|O_NONBLOCK|O_CREAT|O_NOCTTY|O_LARGEFILE, 0666) 
> >>>> = -1
> >>>> EROFS (Read-only file system)
> >>>>
> >>>> 2.6.18 behaves correctly. Settings are the same, does anybody have any
> >>>> clue?
> >>> What does "cat /proc/mounts" say?
> >> Ok I'm not the OP but I can confirm the problem.
> >>
> >>> From /proc/mounts:
> >> arthur:/mnt/disk2/mp3 /mnt/mp3 nfs 
> >> ro,nosuid,nodev,noexec,vers=3,rsize=8192,wsize=8192,hard,proto=tcp,timeo=600,retrans=2,sec=sys,addr=arthur 
> >> 0 0
> >>
> >> Reports ro here while mount still reports rw:
> >> arthur:/mnt/disk2/mp3 on /mnt/mp3 type nfs 
> >> (rw,noexec,nosuid,nodev,addr=192.168.88.80)
> > 
> > I will post my output in some hours, if still needed.
> 
> The very same thing. /etc/mtab still reports rw, while /proc/mounts says ro, weird.

I'll bet that you have always had a subdirectory of the exact same
filesystem mounted somewhere else ro, right?

The new NFS mount code will put those in the same superblock, and
whichever directory gets mounted first will determine whether or not the
superblock is marked as read-only.
Basically, NFS is now doing the exact same thing that local filesystems
have been doing all the time: if it is on the same disk, then it is all
represented by the same superblock. OTOH, if your server is exporting
more than one partition, then different partitions will be represented
by different superblocks.
We need to do this for the same reason that local filesystems do it: it
is the only way to ensure cache consistency. Otherwise, if you make
changes to a file that happens to be mounted in more than one place,
then you will see inconsistent results on the other mountpoints.

Per-mountpoint control over the 'ro' flag (i.e. to allow you to do
'mount --bind -oro /foo /bar') is a separate issue that needs further
work at the VFS level.

Cheers,
  Trond

Re: [REGRESSION] nfs client: Read-only file system (2.6.19-rc1,2)

[Jiri Slaby]

Trond Myklebust wrote:
> I'll bet that you have always had a subdirectory of the exact same
> filesystem mounted somewhere else ro, right?

Yup, exactly: /usr -ro and /home -rw on the same (hda3) partition.

> The new NFS mount code will put those in the same superblock, and
> whichever directory gets mounted first will determine whether or not the
> superblock is marked as read-only.
> Basically, NFS is now doing the exact same thing that local filesystems
> have been doing all the time: if it is on the same disk, then it is all
> represented by the same superblock. OTOH, if your server is exporting
> more than one partition, then different partitions will be represented
> by different superblocks.
> We need to do this for the same reason that local filesystems do it: it
> is the only way to ensure cache consistency. Otherwise, if you make
> changes to a file that happens to be mounted in more than one place,
> then you will see inconsistent results on the other mountpoints.

thanks for clarification,
-- 
http://www.fi.muni.cz/~xslaby/            Jiri Slaby
faculty of informatics, masaryk university, brno, cz
e-mail: jirislaby gmail com, gpg pubkey fingerprint:
B674 9967 0407 CE62 ACC8  22A0 32CC 55C3 39D4 7A7E

Re: [REGRESSION] nfs client: Read-only file system (2.6.19-rc1,2)

[J. Bruce Fields]

On Wed, Oct 18, 2006 at 07:44:17PM +0200, Jiri Slaby wrote:
> Trond Myklebust wrote:
> >I'll bet that you have always had a subdirectory of the exact same
> >filesystem mounted somewhere else ro, right?
> 
> Yup, exactly: /usr -ro and /home -rw on the same (hda3) partition.

Just out of curiosity--why are you doing that?

On the linux server, at least, that doesn't really prevent writing to
/usr unless you've also turned on subtree checking.  And subtree
checking causes other problems.

--b.

Re: [REGRESSION] nfs client: Read-only file system (2.6.19-rc1,2)

[Jiri Slaby]

J. Bruce Fields wrote:
> On Wed, Oct 18, 2006 at 07:44:17PM +0200, Jiri Slaby wrote:
>> Trond Myklebust wrote:
>>> I'll bet that you have always had a subdirectory of the exact same
>>> filesystem mounted somewhere else ro, right?
>> Yup, exactly: /usr -ro and /home -rw on the same (hda3) partition.
> 
> Just out of curiosity--why are you doing that?

Not me :). I do not admin that machine.

> On the linux server, at least, that doesn't really prevent writing to
> /usr unless you've also turned on subtree checking.  And subtree
> checking causes other problems.

thanks,
-- 
http://www.fi.muni.cz/~xslaby/            Jiri Slaby
faculty of informatics, masaryk university, brno, cz
e-mail: jirislaby gmail com, gpg pubkey fingerprint:
B674 9967 0407 CE62 ACC8  22A0 32CC 55C3 39D4 7A7E