Comment 0 for bug 1382333

It was brought to my attention the following situation:

http://tracker.ceph.com/issues/6301

Precise kernel does not have XFS fix for kmem_alloc deadlock and users are facing this problem.

Output example:

"""
NFO: task ceph-osd:17047 blocked for more than 120 seconds.
[153972.073476] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[153972.076322] ceph-osd D ffff880869a28a60 0 17047 5423 0x00000000
[153972.076324] ffff880869a28750 0000000000000002 ffff880867788ee8 ffff8807e4e47500
[153972.079259] ffff880517addfd8 ffff880517addfd8 ffff880517addfd8 ffff880869a28750
[153972.082244] 0000000000000004 ffff880517addd48 ffff880517addd50 7fffffffffffffff
[153972.085278] Call Trace:
[153972.088310] [<ffffffff81410f4a>] ? schedule_timeout+0x1ca/0x270
[153972.091371] [<ffffffff8100abf1>] ? native_sched_clock+0x11/0x70
[153972.094386] [<ffffffff81070cda>] ? try_to_wake_up+0x1ea/0x270
[153972.097358] [<ffffffff81412623>] ? wait_for_completion+0xa3/0x120
[153972.100322] [<ffffffff81070d60>] ? try_to_wake_up+0x270/0x270
[153972.103292] [<ffffffff811a3702>] ? do_coredump+0x1b2/0xee0
[153972.106212] [<ffffffff811a3899>] ? do_coredump+0x349/0xee0
[153972.109085] [<ffffffff8134e0c4>] ? skb_queue_tail+0x24/0x60
[153972.111954] [<ffffffff813eb73a>] ? unix_dgram_sendmsg+0x5aa/0x640
[153972.114839] [<ffffffff81053049>] ? get_signal_to_deliver+0x199/0x5a0
[153972.117743] [<ffffffff81002353>] ? do_signal+0x63/0x8c0
[153972.120632] [<ffffffff81052030>] ? do_send_sig_info+0x60/0x90
[153972.123521] [<ffffffff81002c38>] ? do_notify_resume+0x88/0xa0
[153972.126400] [<ffffffff81414d6a>] ? int_signal+0x12/0x17
[153972.299643] XFS: possible memory allocation deadlock in kmem_alloc (mode:0x250)
[153972.868782] XFS: possible memory allocation deadlock in kmem_alloc (mode:0x250)
[153973.038189] XFS: possible memory allocation deadlock in kmem_alloc (mode:0x250)
[153974.309978] XFS: possible memory allocation deadlock in kmem_alloc (mode:0x250)
"""

Fix, already included in Utopic, is upstream commit: b3f03bac8132207a20286d5602eda64500c19724

Author: Dave Chinner <email address hidden>
Date: Tue Dec 3 23:50:57 2013 +1100

    xfs: xfs_dir2_block_to_sf temp buffer allocation fails

    If we are using a large directory block size, and memory becomes
    fragmented, we can get memory allocation failures trying to
    kmem_alloc(64k) for a temporary buffer. However, there is not need
    for a directory buffer sized allocation, as the end result ends up
    in the inode literal area. This is, at most, slightly less than 2k
    of space, and hence we don't need an allocation larger than that
    fora temporary buffer.

    Signed-off-by: Dave Chinner <email address hidden>
    Reviewed-by: Ben Myers <email address hidden>
    Signed-off-by: Ben Myers <email address hidden>