Message-ID: <50AD1829.7050709@vflare.org>
Date:	Wed, 21 Nov 2012 10:06:33 -0800
From:	Nitin Gupta <ngupta@...are.org>
To:	Minchan Kim <minchan@...nel.org>
CC:	Seth Jennings <sjenning@...ux.vnet.ibm.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Pekka Enberg <penberg@...helsinki.fi>,
	Konrad Rzeszutek Wilk <konrad@...nok.org>,
	Dan Magenheimer <dan.magenheimer@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: Lockdep complain for zram

On 11/21/2012 12:37 AM, Minchan Kim wrote:
> Hi alls,
>
> Today, I saw below complain of lockdep.
> As a matter of fact, I knew it long time ago but forgot that.
> The reason lockdep complains is that now zram uses GFP_KERNEL
> in reclaim path(ex, __zram_make_request) :(
> I can fix it via replacing GFP_KERNEL with GFP_NOIO.
> But more big problem is vzalloc in zram_init_device which calls GFP_KERNEL.
> Of course, I can change it with __vmalloc which can receive gfp_t.
> But still we have a problem. Althoug __vmalloc can handle gfp_t, it calls
> allocation of GFP_KERNEL. That's why I sent the patch.
> https://lkml.org/lkml/2012/4/23/77
> Since then, I forgot it, saw the bug today and poped the question again.
>
> Yes. Fundamental problem is utter crap API vmalloc.
> If we can fix it, everyone would be happy. But life isn't simple like seeing
> my thread of the patch.
>
> So next option is to move zram_init_device into setting disksize time.
> But it makes unnecessary metadata waste until zram is used really(That's why
> Nitin move zram_init_device from disksize setting time to make_request) and
> it makes user should set the disksize before using, which are behavior change.
>
> I would like to clean up this issue before promoting because it might change
> usage behavior.
>
> Do you have any idea?
>

Maybe we can alloc_vm_area() right on device creation in create_device() 
assuming the default disksize. If user explicitly sets the disksize, 
this vm area is deallocated and a new one is allocated based on the new 
disksize.  When the device is reset, we should only free physical pages 
allocated for the table and the virtual area should be set back as if 
disksize is set to the default.

At the device init time, all the pages can be allocated with GFP_NOIO | 
__GPF_HIGHMEM and since the VM area is preallocated, map_vm_area() will 
not hit any of those page-table allocations with GFP_KERNEL.

Other allocations made directly from zram, for instance in the partial 
I/O case, should also be changed to GFP_NOIO | __GFP_HIGHMEM.

Thanks,
Nitin

> ============ 8< ==============
>
>
> [  335.772277] =================================
> [  335.772615] [ INFO: inconsistent lock state ]
> [  335.772955] 3.7.0-rc6 #162 Tainted: G         C
> [  335.773320] ---------------------------------
> [  335.773663] inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-R} usage.
> [  335.774170] kswapd0/23 [HC0[0]:SC0[0]:HE1:SE1] takes:
> [  335.774564]  (&zram->init_lock){+++++-}, at: [<ffffffffa0009d0a>] zram_make_request+0x4a/0x260 [zram]
> [  335.775321] {RECLAIM_FS-ON-W} state was registered at:
> [  335.775716]   [<ffffffff81099532>] mark_held_locks+0x82/0x130
> [  335.776009]   [<ffffffff81099c47>] lockdep_trace_alloc+0x67/0xc0
> [  335.776009]   [<ffffffff811189d4>] __alloc_pages_nodemask+0x94/0xa00
> [  335.776009]   [<ffffffff81152806>] alloc_pages_current+0xb6/0x120
> [  335.776009]   [<ffffffff811143d4>] __get_free_pages+0x14/0x50
> [  335.776009]   [<ffffffff81157dff>] kmalloc_order_trace+0x3f/0xf0
> [  335.776009]   [<ffffffffa0009b1b>] zram_init_device+0x7b/0x220 [zram]
> [  335.776009]   [<ffffffffa0009f0a>] zram_make_request+0x24a/0x260 [zram]
> [  335.776009]   [<ffffffff81299d8a>] generic_make_request+0xca/0x100
> [  335.776009]   [<ffffffff81299e3b>] submit_bio+0x7b/0x160
> [  335.776009]   [<ffffffff81197b92>] submit_bh+0xf2/0x120
> [  335.776009]   [<ffffffff8119b855>] block_read_full_page+0x235/0x3a0
> [  335.776009]   [<ffffffff8119efc8>] blkdev_readpage+0x18/0x20
> [  335.776009]   [<ffffffff8111c107>] __do_page_cache_readahead+0x2c7/0x2d0
> [  335.776009]   [<ffffffff8111c249>] force_page_cache_readahead+0x79/0xb0
> [  335.776009]   [<ffffffff8111c683>] page_cache_sync_readahead+0x43/0x50
> [  335.776009]   [<ffffffff81111490>] generic_file_aio_read+0x4f0/0x760
> [  335.776009]   [<ffffffff8119ffbb>] blkdev_aio_read+0xbb/0xf0
> [  335.776009]   [<ffffffff811661f3>] do_sync_read+0xa3/0xe0
> [  335.776009]   [<ffffffff81166910>] vfs_read+0xb0/0x180
> [  335.776009]   [<ffffffff81166a32>] sys_read+0x52/0xa0
> [  335.776009]   [<ffffffff8155a982>] system_call_fastpath+0x16/0x1b
> [  335.776009] irq event stamp: 97589
> [  335.776009] hardirqs last  enabled at (97589): [<ffffffff812b3374>] throtl_update_dispatch_stats+0x94/0xf0
> [  335.776009] hardirqs last disabled at (97588): [<ffffffff812b332d>] throtl_update_dispatch_stats+0x4d/0xf0
> [  335.776009] softirqs last  enabled at (67416): [<ffffffff81046c59>] __do_softirq+0x139/0x280
> [  335.776009] softirqs last disabled at (67395): [<ffffffff8155bb0c>] call_softirq+0x1c/0x30
> [  335.776009]
> [  335.776009] other info that might help us debug this:
> [  335.776009]  Possible unsafe locking scenario:
> [  335.776009]
> [  335.776009]        CPU0
> [  335.776009]        ----
> [  335.776009]   lock(&zram->init_lock);
> [  335.776009]   <Interrupt>
> [  335.776009]     lock(&zram->init_lock);
> [  335.776009]
> [  335.776009]  *** DEADLOCK ***
> [  335.776009]
> [  335.776009] no locks held by kswapd0/23.
> [  335.776009]
> [  335.776009] stack backtrace:
> [  335.776009] Pid: 23, comm: kswapd0 Tainted: G         C   3.7.0-rc6 #162
> [  335.776009] Call Trace:
> [  335.776009]  [<ffffffff81547ff7>] print_usage_bug+0x1f5/0x206
> [  335.776009]  [<ffffffff8100f90f>] ? save_stack_trace+0x2f/0x50
> [  335.776009]  [<ffffffff81096a65>] mark_lock+0x295/0x2f0
> [  335.776009]  [<ffffffff81095e90>] ? print_irq_inversion_bug.part.37+0x1f0/0x1f0
> [  335.776009]  [<ffffffff812b4af8>] ? blk_throtl_bio+0x88/0x630
> [  335.776009]  [<ffffffff81097024>] __lock_acquire+0x564/0x1c00
> [  335.776009]  [<ffffffff810996e5>] ? trace_hardirqs_on_caller+0x105/0x190
> [  335.776009]  [<ffffffff812b4e32>] ? blk_throtl_bio+0x3c2/0x630
> [  335.776009]  [<ffffffff812b4af8>] ? blk_throtl_bio+0x88/0x630
> [  335.776009]  [<ffffffff812a101c>] ? create_task_io_context+0xdc/0x150
> [  335.776009]  [<ffffffff812a101c>] ? create_task_io_context+0xdc/0x150
> [  335.776009]  [<ffffffffa0009d0a>] ? zram_make_request+0x4a/0x260 [zram]
> [  335.776009]  [<ffffffff81098c85>] lock_acquire+0x85/0x130
> [  335.776009]  [<ffffffffa0009d0a>] ? zram_make_request+0x4a/0x260 [zram]
> [  335.776009]  [<ffffffff8154f87c>] down_read+0x4c/0x61
> [  335.776009]  [<ffffffffa0009d0a>] ? zram_make_request+0x4a/0x260 [zram]
> [  335.776009]  [<ffffffff81299ac2>] ? generic_make_request_checks+0x222/0x420
> [  335.776009]  [<ffffffff8111a4fe>] ? test_set_page_writeback+0x6e/0x1a0
> [  335.776009]  [<ffffffffa0009d0a>] zram_make_request+0x4a/0x260 [zram]
> [  335.776009]  [<ffffffff81299d8a>] generic_make_request+0xca/0x100
> [  335.776009]  [<ffffffff81299e3b>] submit_bio+0x7b/0x160
> [  335.776009]  [<ffffffff81119423>] ? account_page_writeback+0x13/0x20
> [  335.776009]  [<ffffffff8111a585>] ? test_set_page_writeback+0xf5/0x1a0
> [  335.776009]  [<ffffffff81148aa9>] swap_writepage+0x1b9/0x240
> [  335.776009]  [<ffffffff81149bf5>] ? __swap_duplicate+0x65/0x170
> [  335.776009]  [<ffffffff8112715a>] ? shmem_writepage+0x17a/0x2f0
> [  335.776009]  [<ffffffff8112715a>] ? shmem_writepage+0x17a/0x2f0
> [  335.776009]  [<ffffffff8154f411>] ? __mutex_unlock_slowpath+0xd1/0x160
> [  335.776009]  [<ffffffff810996e5>] ? trace_hardirqs_on_caller+0x105/0x190
> [  335.776009]  [<ffffffff8109977d>] ? trace_hardirqs_on+0xd/0x10
> [  335.776009]  [<ffffffff81127195>] shmem_writepage+0x1b5/0x2f0
> [  335.776009]  [<ffffffff81122b96>] shrink_page_list+0x516/0x9a0
> [  335.776009]  [<ffffffff8111ca20>] ? __activate_page+0x150/0x150
> [  335.776009]  [<ffffffff811235c7>] shrink_inactive_list+0x1f7/0x3f0
> [  335.776009]  [<ffffffff81123f05>] shrink_lruvec+0x435/0x540
> [  335.776009]  [<ffffffff81065050>] ? __init_waitqueue_head+0x60/0x60
> [  335.776009]  [<ffffffff81125093>] kswapd+0x703/0xc80
> [  335.776009]  [<ffffffff81551dd0>] ? _raw_spin_unlock_irq+0x30/0x50
> [  335.776009]  [<ffffffff81065050>] ? __init_waitqueue_head+0x60/0x60
> [  335.776009]  [<ffffffff81124990>] ? try_to_free_pages+0x6f0/0x6f0
> [  335.776009]  [<ffffffff810646ea>] kthread+0xea/0xf0
> [  335.776009]  [<ffffffff81064600>] ? flush_kthread_work+0x1a0/0x1a0
> [  335.776009]  [<ffffffff8155a8dc>] ret_from_fork+0x7c/0xb0
> [  335.776009]  [<ffffffff81064600>] ? flush_kthread_work+0x1a0/0x1a0
>
>

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