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authorTejun Heo <tj@kernel.org>2014-07-01 16:41:03 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-07-02 09:32:09 -0700
commitecca47ce8294843045e7465d76fee84dbf07a004 (patch)
treefdd191b4517786683da541715670c08e77a3fb6a /include
parent4c834452aad01531db949414f94f817a86348d59 (diff)
kernfs: kernfs_notify() must be useable from non-sleepable contexts
d911d9874801 ("kernfs: make kernfs_notify() trigger inotify events too") added fsnotify triggering to kernfs_notify() which requires a sleepable context. There are already existing users of kernfs_notify() which invoke it from an atomic context and in general it's silly to require a sleepable context for triggering a notification. The following is an invalid context bug triggerd by md invoking sysfs_notify() from IO completion path. BUG: sleeping function called from invalid context at kernel/locking/mutex.c:586 in_atomic(): 1, irqs_disabled(): 1, pid: 0, name: swapper/1 2 locks held by swapper/1/0: #0: (&(&vblk->vq_lock)->rlock){-.-...}, at: [<ffffffffa0039042>] virtblk_done+0x42/0xe0 [virtio_blk] #1: (&(&bitmap->counts.lock)->rlock){-.....}, at: [<ffffffff81633718>] bitmap_endwrite+0x68/0x240 irq event stamp: 33518 hardirqs last enabled at (33515): [<ffffffff8102544f>] default_idle+0x1f/0x230 hardirqs last disabled at (33516): [<ffffffff818122ed>] common_interrupt+0x6d/0x72 softirqs last enabled at (33518): [<ffffffff810a1272>] _local_bh_enable+0x22/0x50 softirqs last disabled at (33517): [<ffffffff810a29e0>] irq_enter+0x60/0x80 CPU: 1 PID: 0 Comm: swapper/1 Not tainted 3.16.0-0.rc2.git2.1.fc21.x86_64 #1 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 0000000000000000 f90db13964f4ee05 ffff88007d403b80 ffffffff81807b4c 0000000000000000 ffff88007d403ba8 ffffffff810d4f14 0000000000000000 0000000000441800 ffff880078fa1780 ffff88007d403c38 ffffffff8180caf2 Call Trace: <IRQ> [<ffffffff81807b4c>] dump_stack+0x4d/0x66 [<ffffffff810d4f14>] __might_sleep+0x184/0x240 [<ffffffff8180caf2>] mutex_lock_nested+0x42/0x440 [<ffffffff812d76a0>] kernfs_notify+0x90/0x150 [<ffffffff8163377c>] bitmap_endwrite+0xcc/0x240 [<ffffffffa00de863>] close_write+0x93/0xb0 [raid1] [<ffffffffa00df029>] r1_bio_write_done+0x29/0x50 [raid1] [<ffffffffa00e0474>] raid1_end_write_request+0xe4/0x260 [raid1] [<ffffffff813acb8b>] bio_endio+0x6b/0xa0 [<ffffffff813b46c4>] blk_update_request+0x94/0x420 [<ffffffff813bf0ea>] blk_mq_end_io+0x1a/0x70 [<ffffffffa00392c2>] virtblk_request_done+0x32/0x80 [virtio_blk] [<ffffffff813c0648>] __blk_mq_complete_request+0x88/0x120 [<ffffffff813c070a>] blk_mq_complete_request+0x2a/0x30 [<ffffffffa0039066>] virtblk_done+0x66/0xe0 [virtio_blk] [<ffffffffa002535a>] vring_interrupt+0x3a/0xa0 [virtio_ring] [<ffffffff81116177>] handle_irq_event_percpu+0x77/0x340 [<ffffffff8111647d>] handle_irq_event+0x3d/0x60 [<ffffffff81119436>] handle_edge_irq+0x66/0x130 [<ffffffff8101c3e4>] handle_irq+0x84/0x150 [<ffffffff818146ad>] do_IRQ+0x4d/0xe0 [<ffffffff818122f2>] common_interrupt+0x72/0x72 <EOI> [<ffffffff8105f706>] ? native_safe_halt+0x6/0x10 [<ffffffff81025454>] default_idle+0x24/0x230 [<ffffffff81025f9f>] arch_cpu_idle+0xf/0x20 [<ffffffff810f5adc>] cpu_startup_entry+0x37c/0x7b0 [<ffffffff8104df1b>] start_secondary+0x25b/0x300 This patch fixes it by punting the notification delivery through a work item. This ends up adding an extra pointer to kernfs_elem_attr enlarging kernfs_node by a pointer, which is not ideal but not a very big deal either. If this turns out to be an actual issue, we can move kernfs_elem_attr->size to kernfs_node->iattr later. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Josh Boyer <jwboyer@fedoraproject.org> Cc: Jens Axboe <axboe@kernel.dk> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/kernfs.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 17aa1cce6f8e..145375ea0bd9 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -91,6 +91,7 @@ struct kernfs_elem_attr {
const struct kernfs_ops *ops;
struct kernfs_open_node *open;
loff_t size;
+ struct kernfs_node *notify_next; /* for kernfs_notify() */
};
/*

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