Re: [zfs-discuss] Creating NFSv4/ZFS XATTR through dirfd through /proc not allowed?
On Fri, Jul 13, 2012 at 2:16 AM, ольга крыжановская
wrote:
> Can some one here explain why accessing a NFSv4/ZFS xattr directory
> through proc is forbidden?
>
[...]
> truss says the syscall fails with
> open("/proc/3988/fd/10/myxattr", O_WRONLY|O_CREAT|O_TRUNC, 0666) Err#13 EACCES
>
> Accessing files or directories through /proc/$$/fd/ from a shell
> otherwise works, only the xattr directories cause trouble. Native C
> code has the same problem.
>
> Olga
Does "runat" let you see those xattr files?
--
Gordon Ross
Nexenta Systems, Inc. www.nexenta.com
Enterprise class storage for everyone
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Re: [zfs-discuss] Creating NFSv4/ZFS XATTR through dirfd through /proc not allowed?
Yes, accessing the files through runat works.
I think /proc (and /dev/fd, which has the same trouble but only works
if the same process accesses the fds, for obvious reasons since
/dev/fd is per process and can not be shared between processes unlike
/proc/$pid/fd/) gets confused because the directories have no name.
pfiles gets confused in a similar way and some times crashes, but
without a predictable pattern or test case.
As interestingly side note, doing a cd to the /proc/$$/fd/$fd first works:
cut here
touch x4 ; cd -@ x4 ; redirect {n}<"." ; cd .. ;
(cd "/proc/$$/fd/$n" ; print "hello1" >"myxattr") ;
(cd -@ x4 ; cat "myxattr" ) ;
rm x4
stop cutting here
Accessing the file with the full path directly does not work:
cut here
touch x1 ; cd -@ x1 ; redirect {n}<"." ; cd .. ;
print "hello1" >"/proc/$$/fd/$n/myxattr1" ;
(cd -@ x1 ; cat "myxattr1" ) ;
rm x1
stop cutting here
Olga
On Fri, Jul 13, 2012 at 9:17 PM, Gordon Ross wrote:
> On Fri, Jul 13, 2012 at 2:16 AM, ольга крыжановская
> wrote:
>> Can some one here explain why accessing a NFSv4/ZFS xattr directory
>> through proc is forbidden?
>>
> [...]
>> truss says the syscall fails with
>> open("/proc/3988/fd/10/myxattr", O_WRONLY|O_CREAT|O_TRUNC, 0666) Err#13
>> EACCES
>>
>> Accessing files or directories through /proc/$$/fd/ from a shell
>> otherwise works, only the xattr directories cause trouble. Native C
>> code has the same problem.
>>
>> Olga
>
> Does "runat" let you see those xattr files?
>
> --
> Gordon Ross
> Nexenta Systems, Inc. www.nexenta.com
> Enterprise class storage for everyone
--
, __ ,
{ \/`o;-Olga Kryzhanovska -;o`\/ }
.'-/`-/ olga.kryzhanov...@gmail.com \-`\-'.
`'-..-| / http://twitter.com/fleyta \ |-..-'`
/\/\ Solaris/BSD//C/C++ programmer /\/\
`--` `--`
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Re: [zfs-discuss] [osol-discuss] Creating NFSv4/ZFS XATTR through dirfd through /proc not allowed?
I don't think that xattrs were ever intended or designed
for /proc content.
I could file an RFE for you if you wish.
Thanks,
Cindy
On 07/13/12 14:00, ольга крыжановская wrote:
Yes, accessing the files through runat works.
I think /proc (and /dev/fd, which has the same trouble but only works
if the same process accesses the fds, for obvious reasons since
/dev/fd is per process and can not be shared between processes unlike
/proc/$pid/fd/) gets confused because the directories have no name.
pfiles gets confused in a similar way and some times crashes, but
without a predictable pattern or test case.
As interestingly side note, doing a cd to the /proc/$$/fd/$fd first works:
cut here
touch x4 ; cd -@ x4 ; redirect {n}<"." ; cd .. ;
(cd "/proc/$$/fd/$n" ; print "hello1">"myxattr") ;
(cd -@ x4 ; cat "myxattr" ) ;
rm x4
stop cutting here
Accessing the file with the full path directly does not work:
cut here
touch x1 ; cd -@ x1 ; redirect {n}<"." ; cd .. ;
print "hello1">"/proc/$$/fd/$n/myxattr1" ;
(cd -@ x1 ; cat "myxattr1" ) ;
rm x1
stop cutting here
Olga
On Fri, Jul 13, 2012 at 9:17 PM, Gordon Ross wrote:
On Fri, Jul 13, 2012 at 2:16 AM, ольга крыжановская
wrote:
Can some one here explain why accessing a NFSv4/ZFS xattr directory
through proc is forbidden?
[...]
truss says the syscall fails with
open("/proc/3988/fd/10/myxattr", O_WRONLY|O_CREAT|O_TRUNC, 0666) Err#13 EACCES
Accessing files or directories through /proc/$$/fd/ from a shell
otherwise works, only the xattr directories cause trouble. Native C
code has the same problem.
Olga
Does "runat" let you see those xattr files?
--
Gordon Ross
Nexenta Systems, Inc. www.nexenta.com
Enterprise class storage for everyone
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Re: [zfs-discuss] [osol-discuss] Creating NFSv4/ZFS XATTR through dirfd through /proc not allowed?
Cindy, I was not trying to open a xattr for files in /proc.
1. Please read the openat() manual page
2. I opened a fd to the directory where the xattrs are in
3. My process, for example pid 123456, now has an open fd, for example
with the number 12, which points to this xattr directory
4. Now I want to use this directory fd to create a file. If I use
openat(12, ...) the code works correct. If I use
open("/proc/123456/fd/12/myxattr",...) the code does NOT work.
IMO this is a bug in the /proc file system, because using the openat()
code path works (to prove that I am not doing some thing impossible).
Olga
On Sat, Jul 14, 2012 at 2:33 AM, Cindy Swearingen
wrote:
> I don't think that xattrs were ever intended or designed
> for /proc content.
>
> I could file an RFE for you if you wish.
>
> Thanks,
>
> Cindy
>
>
> On 07/13/12 14:00, ольга крыжановская wrote:
>>
>> Yes, accessing the files through runat works.
>>
>> I think /proc (and /dev/fd, which has the same trouble but only works
>> if the same process accesses the fds, for obvious reasons since
>> /dev/fd is per process and can not be shared between processes unlike
>> /proc/$pid/fd/) gets confused because the directories have no name.
>> pfiles gets confused in a similar way and some times crashes, but
>> without a predictable pattern or test case.
>>
>> As interestingly side note, doing a cd to the /proc/$$/fd/$fd first works:
>> cut here
>> touch x4 ; cd -@ x4 ; redirect {n}<"." ; cd .. ;
>> (cd "/proc/$$/fd/$n" ; print "hello1">"myxattr") ;
>> (cd -@ x4 ; cat "myxattr" ) ;
>> rm x4
>> stop cutting here
>> Accessing the file with the full path directly does not work:
>> cut here
>> touch x1 ; cd -@ x1 ; redirect {n}<"." ; cd .. ;
>> print "hello1">"/proc/$$/fd/$n/myxattr1" ;
>> (cd -@ x1 ; cat "myxattr1" ) ;
>> rm x1
>> stop cutting here
>>
>> Olga
>>
>> On Fri, Jul 13, 2012 at 9:17 PM, Gordon Ross
>> wrote:
>>>
>>> On Fri, Jul 13, 2012 at 2:16 AM, ольга крыжановская
>>> wrote:
Can some one here explain why accessing a NFSv4/ZFS xattr directory
through proc is forbidden?
>>> [...]
truss says the syscall fails with
open("/proc/3988/fd/10/myxattr", O_WRONLY|O_CREAT|O_TRUNC, 0666) Err#13
EACCES
Accessing files or directories through /proc/$$/fd/ from a shell
otherwise works, only the xattr directories cause trouble. Native C
code has the same problem.
Olga
>>>
>>>
>>> Does "runat" let you see those xattr files?
>>>
>>> --
>>> Gordon Ross
>>> Nexenta Systems, Inc. www.nexenta.com
>>> Enterprise class storage for everyone
>>
>>
>>
>>
>
--
, __ ,
{ \/`o;-Olga Kryzhanovska -;o`\/ }
.'-/`-/ olga.kryzhanov...@gmail.com \-`\-'.
`'-..-| / http://twitter.com/fleyta \ |-..-'`
/\/\ Solaris/BSD//C/C++ programmer /\/\
`--` `--`
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