[ceph-users] CephFS: clients hanging on write with ceph-fuse

Andras Pataki apataki at flatironinstitute.org
Thu Nov 2 16:58:22 PDT 2017

I'm planning to test the newer ceph-fuse tomorrow.  Would it be better 
to stay with the Jewel 10.2.10 client, or would the 12.2.1 Luminous 
client be better (even though the back-end is Jewel for now)?


On 11/02/2017 05:54 PM, Gregory Farnum wrote:
> Have you tested on the new ceph-fuse? This does sound vaguely familiar 
> and is an issue I'd generally expect to have the fix backported for, 
> once it was identified.
> On Thu, Nov 2, 2017 at 11:40 AM Andras Pataki 
> <apataki at flatironinstitute.org <mailto:apataki at flatironinstitute.org>> 
> wrote:
>     We've been running into a strange problem with Ceph using
>     ceph-fuse and
>     the filesystem. All the back end nodes are on 10.2.10, the fuse
>     clients
>     are on 10.2.7.
>     After some hours of runs, some processes get stuck waiting for
>     fuse like:
>     [root at worker1144 ~]# cat /proc/58193/stack
>     [<ffffffffa08cd241>] wait_answer_interruptible+0x91/0xe0 [fuse]
>     [<ffffffffa08cd653>] __fuse_request_send+0x253/0x2c0 [fuse]
>     [<ffffffffa08cd6d2>] fuse_request_send+0x12/0x20 [fuse]
>     [<ffffffffa08d69d6>] fuse_send_write+0xd6/0x110 [fuse]
>     [<ffffffffa08d84d5>] fuse_perform_write+0x2f5/0x5a0 [fuse]
>     [<ffffffffa08d8a21>] fuse_file_aio_write+0x2a1/0x340 [fuse]
>     [<ffffffff811fdfbd>] do_sync_write+0x8d/0xd0
>     [<ffffffff811fe82d>] vfs_write+0xbd/0x1e0
>     [<ffffffff811ff34f>] SyS_write+0x7f/0xe0
>     [<ffffffff816975c9>] system_call_fastpath+0x16/0x1b
>     [<ffffffffffffffff>] 0xffffffffffffffff
>     The cluster is healthy (all OSDs up, no slow requests, etc.). More
>     details of my investigation efforts are in the bug report I just
>     submitted:
>     http://tracker.ceph.com/issues/22008
>     It looks like the fuse client is asking for some caps that it never
>     thinks it receives from the MDS, so the thread waiting for those
>     caps on
>     behalf of the writing client never wakes up.  The restart of the MDS
>     fixes the problem (since ceph-fuse re-negotiates caps).
>     Any ideas/suggestions?
>     Andras
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