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authorOlof Johansson <olof@lixom.net>2012-08-01 12:17:27 +0200
committerJens Axboe <axboe@kernel.dk>2012-08-01 12:17:27 +0200
commit4638a83e8615de9c16c39dfed234951d0f468cf1 (patch)
tree226161011e05735e8d4faa225040814746eb6536 /block/blk-ioc.c
parentfe86cdcef73ba19a2246a124f0ddbd19b14fb549 (diff)
downloadlinux-linaro-stable-4638a83e8615de9c16c39dfed234951d0f468cf1.tar.gz
block: uninitialized ioc->nr_tasks triggers WARN_ON
Hi, I'm using the old-fashioned 'dump' backup tool, and I noticed that it spews the below warning as of 3.5-rc1 and later (3.4 is fine): [ 10.886893] ------------[ cut here ]------------ [ 10.886904] WARNING: at include/linux/iocontext.h:140 copy_process+0x1488/0x1560() [ 10.886905] Hardware name: Bochs [ 10.886906] Modules linked in: [ 10.886908] Pid: 2430, comm: dump Not tainted 3.5.0-rc7+ #27 [ 10.886908] Call Trace: [ 10.886911] [<ffffffff8107ce8a>] warn_slowpath_common+0x7a/0xb0 [ 10.886912] [<ffffffff8107ced5>] warn_slowpath_null+0x15/0x20 [ 10.886913] [<ffffffff8107c088>] copy_process+0x1488/0x1560 [ 10.886914] [<ffffffff8107c244>] do_fork+0xb4/0x340 [ 10.886918] [<ffffffff8108effa>] ? recalc_sigpending+0x1a/0x50 [ 10.886919] [<ffffffff8108f6b2>] ? __set_task_blocked+0x32/0x80 [ 10.886920] [<ffffffff81091afa>] ? __set_current_blocked+0x3a/0x60 [ 10.886923] [<ffffffff81051db3>] sys_clone+0x23/0x30 [ 10.886925] [<ffffffff8179bd73>] stub_clone+0x13/0x20 [ 10.886927] [<ffffffff8179baa2>] ? system_call_fastpath+0x16/0x1b [ 10.886928] ---[ end trace 32a14af7ee6a590b ]--- Reproducing is easy, I can hit it on a KVM system with a very basic config (x86_64 make defconfig + enable the drivers needed). To hit it, just install dump (on debian/ubuntu, not sure what the package might be called on Fedora), and: dump -o -f /tmp/foo / You'll see the warning in dmesg once it forks off the I/O process and starts dumping filesystem contents. I bisected it down to the following commit: commit f6e8d01bee036460e03bd4f6a79d014f98ba712e Author: Tejun Heo <tj@kernel.org> Date: Mon Mar 5 13:15:26 2012 -0800 block: add io_context->active_ref Currently ioc->nr_tasks is used to decide two things - whether an ioc is done issuing IOs and whether it's shared by multiple tasks. This patch separate out the first into ioc->active_ref, which is acquired and released using {get|put}_io_context_active() respectively. This will be used to associate bio's with a given task. This patch doesn't introduce any visible behavior change. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> It seems like the init of ioc->nr_tasks was removed in that patch, so it starts out at 0 instead of 1. Tejun, is the right thing here to add back the init, or should something else be done? The below patch removes the warning, but I haven't done any more extensive testing on it. Signed-off-by: Olof Johansson <olof@lixom.net> Acked-by: Tejun Heo <tj@kernel.org> Cc: stable@kernel.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-ioc.c')
-rw-r--r--block/blk-ioc.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index 893b8007c657..fab4cdd3f7bb 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -244,6 +244,7 @@ int create_task_io_context(struct task_struct *task, gfp_t gfp_flags, int node)
/* initialize */
atomic_long_set(&ioc->refcount, 1);
+ atomic_set(&ioc->nr_tasks, 1);
atomic_set(&ioc->active_ref, 1);
spin_lock_init(&ioc->lock);
INIT_RADIX_TREE(&ioc->icq_tree, GFP_ATOMIC | __GFP_HIGH);