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
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