David, I ran into another issue that caused one my machines to hang on a bunch of tasks and then hard lock. Here's the backtrace of the hang: INFO: task kworker/1:2:4214 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/1:2 D ffff880443513fc0 0 4214 2 0x00000000 Workqueue: ceph-msgr con_work [libceph] ffff88042b093868 0000000000000246 ffff88042b8e5bc0 ffffffff81569fc6 ffff88042c51dbc0 ffff88042b093fd8 ffff88042b093fd8 ffff88042b093fd8 ffff88042c518000 ffff88042c51dbc0 ffff8804266b8d10 ffff8804439d7188 Call Trace: [<ffffffff81569fc6>] ? _raw_spin_unlock_irqrestore+0x16/0x20 [<ffffffffa0016570>] ? fscache_wait_bit_interruptible+0x30/0x30 [fscache] [<ffffffff81568d09>] schedule+0x29/0x70 [<ffffffffa001657e>] fscache_wait_atomic_t+0xe/0x20 [fscache] [<ffffffff815665cf>] out_of_line_wait_on_atomic_t+0x9f/0xe0 [<ffffffff81083560>] ? autoremove_wake_function+0x40/0x40 [<ffffffffa0015a9c>] __fscache_relinquish_cookie+0x15c/0x310 [fscache] [<ffffffffa00a4fae>] ceph_fscache_unregister_inode_cookie+0x3e/0x50 [ceph] [<ffffffffa007e373>] ceph_destroy_inode+0x33/0x200 [ceph] [<ffffffff811c13ae>] ? __fsnotify_inode_delete+0xe/0x10 [<ffffffff8119ba1c>] destroy_inode+0x3c/0x70 [<ffffffff8119bb69>] evict+0x119/0x1b0 [<ffffffff8119c3f3>] iput+0x103/0x190 [<ffffffffa009aaed>] iterate_session_caps+0x7d/0x240 [ceph] [<ffffffffa009b170>] ? remove_session_caps_cb+0x270/0x270 [ceph] [<ffffffffa00a1fc5>] dispatch+0x725/0x1b40 [ceph] [<ffffffff81459466>] ? kernel_recvmsg+0x46/0x60 [<ffffffffa002c0e8>] ? ceph_tcp_recvmsg+0x48/0x60 [libceph] [<ffffffffa002ecbe>] try_read+0xc1e/0x1e70 [libceph] [<ffffffffa0030015>] con_work+0x105/0x1920 [libceph] [<ffffffff8100349e>] ? xen_end_context_switch+0x1e/0x30 [<ffffffff8108dbca>] ? finish_task_switch+0x5a/0xc0 [<ffffffff8107aa59>] process_one_work+0x179/0x490 [<ffffffff8107bf5b>] worker_thread+0x11b/0x370 [<ffffffff8107be40>] ? manage_workers.isra.21+0x2e0/0x2e0 [<ffffffff81082a80>] kthread+0xc0/0xd0 [<ffffffff81010000>] ? perf_trace_xen_mmu_set_pud+0xd0/0xd0 [<ffffffff810829c0>] ? flush_kthread_worker+0xb0/0xb0 [<ffffffff81572cec>] ret_from_fork+0x7c/0xb0 [<ffffffff810829c0>] ? flush_kthread_worker+0xb0/0xb0 It looks like it's waiting for the the cookie's n_active to drop down to 0 ... but it isn't. After spending a bunch of hours reading the code, then having a some beers (it is Saturday night after all), then looking at code again... I think that the __fscache_check_consistency() function increments the n_active counter but never lowers it. I think the solution to this is the bellow diff but I'm not a 100% sure. Can you let me know if I'm on the right track... of it's beer googles? diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c index 318e843..b2a86e3 100644 --- a/fs/fscache/cookie.c +++ b/fs/fscache/cookie.c @@ -586,7 +586,8 @@ int __fscache_check_consistency(struct fscache_cookie *cookie) fscache_operation_init(op, NULL, NULL); op->flags = FSCACHE_OP_MYTHREAD | - (1 << FSCACHE_OP_WAITING); + (1 << FSCACHE_OP_WAITING) | + (1 << FSCACHE_OP_UNUSE_COOKIE); spin_lock(&cookie->lock); Thanks, - Milosz On Fri, Sep 6, 2013 at 4:03 PM, Sage Weil <sage@xxxxxxxxxxx> wrote: > On Fri, 6 Sep 2013, Milosz Tanski wrote: >> Sage, >> >> I've taken David's latest changes and per his request merged his >> 'fscache-fixes-for-ceph' tag then applied my changes on top of that. >> In addition to the pervious changes I also added a fix for the >> warnings the linux-next build bot found. >> >> I've given the results a quick test to make sure it builds, boots and >> runs okay. The code is located in my repository: >> >> https://adfin@xxxxxxxxxxxxx/adfin/linux-fs.git in the wip-fscache-v2 branch >> >> I hope that this is the final go for now and thanks for everyone's patience. > > Looks good; I'll send this to Linus along with the other ceph patches > shortly. > > Thanks, everyone! > sage > > >> >> - Milosz >> >> On Fri, Sep 6, 2013 at 11:59 AM, David Howells <dhowells@xxxxxxxxxx> wrote: >> > Milosz Tanski <milosz@xxxxxxxxx> wrote: >> > >> >> After running this for a day on some loaded machines I ran into what >> >> looks like an old issue with the new code. I remember you saw an issue >> >> that manifested it self in a similar way a while back. >> >> >> >> [13837253.462779] FS-Cache: Assertion failed >> >> [13837253.462782] 3 == 5 is false >> >> [13837253.462807] ------------[ cut here ]------------ >> >> [13837253.462811] kernel BUG at fs/fscache/operation.c:414! >> > >> > Bah. >> > >> > I forgot to call fscache_op_complete(). Patch updated and repushed. >> > >> > Btw, I've reordered the patches to put the CIFS patch last. Can you merge the >> > patches prior to the CIFS commit from my branch rather than cherry picking >> > them so that if they go via two different routes, GIT will handle the merge >> > correctly? I've stuck a tag on it (fscache-fixes-for-ceph) to make that >> > easier for you. >> > >> > I've also asked another RH engineer to try doing some basic testing on the >> > CIFS stuff - which may validate the fscache_readpages_cancel patch. >> > >> > David >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> >> -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html