> On Sep 2, 2015, at 17:11, Gregory Farnum <gfarnum@xxxxxxxxxx> wrote:
>
> Whoops, forgot to add Zheng.
>
> On Wed, Sep 2, 2015 at 10:11 AM, Gregory Farnum <gfarnum@xxxxxxxxxx> wrote:
>> On Wed, Sep 2, 2015 at 10:00 AM, Janusz Borkowski
>> <janusz.borkowski@xxxxxxxxxxxxxx> wrote:
>>> Hi!
>>>
>>> I mount cephfs using kernel client (3.10.0-229.11.1.el7.x86_64).
>>>
>>> The effect is the same when doing "echo >>" from another machine and from a
>>> machine keeping the file open.
>>>
>>> The file is opened with open( ..,
>>> O_WRONLY|O_LARGEFILE|O_APPEND|O_BINARY|O_CREAT)
>>>
>>> Shell ">>" is implemented as (from strace bash -c "echo '7789' >>
>>> /mnt/ceph/test):
>>>
>>> open("/mnt/ceph/test", O_WRONLY|O_CREAT|O_APPEND, 0666) = 3
>>>
>>> The test file had ~500KB size.
>>>
>>> Each subsequent "echo >>" writes to the start of the test file, first "echo"
>>> overwriting the original contents, next "echos" overwriting bytes written by
>>> the preceding "echo".
>>
>> Hmmm. The userspace (ie, ceph-fuse) implementation of this is a little
>> bit racy but ought to work. I'm not as familiar with the kernel code
>> but I'm not seeing any special behavior in the Ceph code — Zheng,
>> would you expect this to work? It looks like some of the linux
>> filesystems have their own O_APPEND handling and some don't, but I
>> can't find it in the VFS either.
>> -Greg
Yes, the kernel client does not handle the case that multiple clients do append write to the same file. I will fix it soon.
Regards
Yan, Zheng
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