On Sat 09-08-14 07:00:00, Matthew Wilcox wrote:
> On Wed, Jul 30, 2014 at 11:52:29AM +0200, Jan Kara wrote:
> > I see the problem now. How about an attached patch? Do you see other
> > lockdep warnings with it?
>
> Hit another one :-( Same inversion between i_mmap_mutex and jbd2_handle:
>
> -> #1 (&mapping->i_mmap_mutex){+.+...}:
> [<ffffffff810cfa12>] lock_acquire+0xb2/0x1f0
> [<ffffffff815cb5e5>] mutex_lock_nested+0x75/0x420
> [<ffffffff811bc0ff>] rmap_walk+0x6f/0x390
> [<ffffffff811bc5a9>] page_mkclean+0x69/0x90
> [<ffffffff81189c10>] clear_page_dirty_for_io+0x60/0x120
> [<ffffffffa01d1017>] mpage_submit_page+0x47/0x80 [ext4]
> [<ffffffffa01d1160>] mpage_process_page_bufs+0x110/0x120 [ext4]
> [<ffffffffa01d16f0>] mpage_prepare_extent_to_map+0x1f0/0x2f0 [ext4]
> [<ffffffffa01d6e57>] ext4_writepages+0x427/0x1060 [ext4]
> [<ffffffff8118c211>] do_writepages+0x21/0x40
> [<ffffffff8117e909>] __filemap_fdatawrite_range+0x59/0x60
> [<ffffffff8117ea0d>] filemap_write_and_wait_range+0x2d/0x70
> [<ffffffffa01cd7d8>] ext4_sync_file+0x118/0x490 [ext4]
> [<ffffffff8122dd2b>] vfs_fsync_range+0x1b/0x30
> [<ffffffff811b99ad>] SyS_msync+0x1ed/0x250
>
> (ext4_writepages starts a transaction before calling
> mpage_prepare_extent_to_map)
Hum, yes, this is difficult. Getting rid of
clear_page_dirty_for_io() when the transaction is started isn't easily
possible :(. So I'm afraid we'll have to find some other way to synchronize
page faults and truncate / punch hole in DAX.
Honza
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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