| Message ID | 1465441168-17738-1-git-send-email-tahsin@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Jun 08, 2016 at 07:59:28PM -0700, Tahsin Erdogan wrote: > Asynchronous wb switching of inodes takes an additional ref count on an > inode to make sure inode remains valid until switchover is completed. > > However, it is possible that inode->i_count has already reached zero > while inode is in writeback queue: > > ------------[ cut here ]------------ > WARNING: CPU: 1 PID: 917 at fs/inode.c:397 ihold+0x2b/0x30 > CPU: 1 PID: 917 Comm: kworker/u4:5 Not tainted 4.7.0-rc2+ #49 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs > 01/01/2011 > Workqueue: writeback wb_workfn (flush-8:16) > 0000000000000000 ffff88007ca0fb58 ffffffff805990af 0000000000000000 > 0000000000000000 ffff88007ca0fb98 ffffffff80268702 0000018d000004e2 > ffff88007cef40e8 ffff88007c9b89a8 ffff880079e3a740 0000000000000003 > Call Trace: > [<ffffffff805990af>] dump_stack+0x4d/0x6e > [<ffffffff80268702>] __warn+0xc2/0xe0 > [<ffffffff802687d8>] warn_slowpath_null+0x18/0x20 > [<ffffffff8035b4ab>] ihold+0x2b/0x30 > [<ffffffff80367ecc>] inode_switch_wbs+0x11c/0x180 > [<ffffffff80369110>] wbc_detach_inode+0x170/0x1a0 > [<ffffffff80369abc>] writeback_sb_inodes+0x21c/0x530 > [<ffffffff80369f7e>] wb_writeback+0xee/0x1e0 > [<ffffffff8036a147>] wb_workfn+0xd7/0x280 > [<ffffffff80287531>] ? try_to_wake_up+0x1b1/0x2b0 > [<ffffffff8027bb09>] process_one_work+0x129/0x300 > [<ffffffff8027be06>] worker_thread+0x126/0x480 > [<ffffffff8098cde7>] ? __schedule+0x1c7/0x561 > [<ffffffff8027bce0>] ? process_one_work+0x300/0x300 > [<ffffffff80280ff4>] kthread+0xc4/0xe0 > [<ffffffff80335578>] ? kfree+0xc8/0x100 > [<ffffffff809903cf>] ret_from_fork+0x1f/0x40 > [<ffffffff80280f30>] ? __kthread_parkme+0x70/0x70 > ---[ end trace aaefd2fd9f306bc4 ]--- > > Signed-off-by: Tahsin Erdogan <tahsin@google.com> Acked-by: Tejun Heo <tj@kernel.org> Can you please repost the patch to Jens Axboe <axboe@kernel.dk> with acked-by added? Please also cc Jan Kara <jack@suse.com>. Thanks.
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 989a2ce..b44ede0 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -478,14 +478,15 @@ static void inode_switch_wbs(struct inode *inode, int new_wb_id) spin_lock(&inode->i_lock); if (!(inode->i_sb->s_flags & MS_ACTIVE) || inode->i_state & (I_WB_SWITCH | I_FREEING) || + atomic_read(&inode->i_count) == 0 || inode_to_wb(inode) == isw->new_wb) { spin_unlock(&inode->i_lock); goto out_free; } inode->i_state |= I_WB_SWITCH; + ihold(inode); spin_unlock(&inode->i_lock); - ihold(inode); isw->inode = inode; atomic_inc(&isw_nr_in_flight);
Asynchronous wb switching of inodes takes an additional ref count on an inode to make sure inode remains valid until switchover is completed. However, it is possible that inode->i_count has already reached zero while inode is in writeback queue: ------------[ cut here ]------------ WARNING: CPU: 1 PID: 917 at fs/inode.c:397 ihold+0x2b/0x30 CPU: 1 PID: 917 Comm: kworker/u4:5 Not tainted 4.7.0-rc2+ #49 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Workqueue: writeback wb_workfn (flush-8:16) 0000000000000000 ffff88007ca0fb58 ffffffff805990af 0000000000000000 0000000000000000 ffff88007ca0fb98 ffffffff80268702 0000018d000004e2 ffff88007cef40e8 ffff88007c9b89a8 ffff880079e3a740 0000000000000003 Call Trace: [<ffffffff805990af>] dump_stack+0x4d/0x6e [<ffffffff80268702>] __warn+0xc2/0xe0 [<ffffffff802687d8>] warn_slowpath_null+0x18/0x20 [<ffffffff8035b4ab>] ihold+0x2b/0x30 [<ffffffff80367ecc>] inode_switch_wbs+0x11c/0x180 [<ffffffff80369110>] wbc_detach_inode+0x170/0x1a0 [<ffffffff80369abc>] writeback_sb_inodes+0x21c/0x530 [<ffffffff80369f7e>] wb_writeback+0xee/0x1e0 [<ffffffff8036a147>] wb_workfn+0xd7/0x280 [<ffffffff80287531>] ? try_to_wake_up+0x1b1/0x2b0 [<ffffffff8027bb09>] process_one_work+0x129/0x300 [<ffffffff8027be06>] worker_thread+0x126/0x480 [<ffffffff8098cde7>] ? __schedule+0x1c7/0x561 [<ffffffff8027bce0>] ? process_one_work+0x300/0x300 [<ffffffff80280ff4>] kthread+0xc4/0xe0 [<ffffffff80335578>] ? kfree+0xc8/0x100 [<ffffffff809903cf>] ret_from_fork+0x1f/0x40 [<ffffffff80280f30>] ? __kthread_parkme+0x70/0x70 ---[ end trace aaefd2fd9f306bc4 ]--- Signed-off-by: Tahsin Erdogan <tahsin@google.com> --- fs/fs-writeback.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)