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Description of problem: When swapping on a zram device on a heavy loaded system, I received the following warning: Adding 1023992k swap on /dev/zram0. Priority:10 extents:1 across:1023992k SS ================================= [ INFO: inconsistent lock state ] 2.6.32-131.17.1.el6.x86_64.debug #1 --------------------------------- inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-R} usage. kswapd0/38 [HC0[0]:SC0[0]:HE1:SE1] takes: (&zram->init_lock){+++++-}, at: [<ffffffffa043803a>] zram_make_request+0x4a/0x250 [zram] {RECLAIM_FS-ON-W} state was registered at: [<ffffffff810abdd3>] mark_held_locks+0x73/0xa0 [<ffffffff810abea1>] lockdep_trace_alloc+0xa1/0xe0 [<ffffffff81174f17>] kmem_cache_alloc_notrace+0x37/0x260 [<ffffffffa04374b7>] zram_init_device+0x87/0x280 [zram] [<ffffffffa043822f>] zram_make_request+0x23f/0x250 [zram] [<ffffffff8126b011>] generic_make_request+0x321/0x630 [<ffffffff8126b3ad>] submit_bio+0x8d/0x120 [<ffffffff811c02c6>] submit_bh+0xf6/0x150 [<ffffffff811c2d3b>] block_read_full_page+0x28b/0x3f0 [<ffffffff811c7bb8>] blkdev_readpage+0x18/0x20 [<ffffffff81139515>] __do_page_cache_readahead+0x255/0x260 [<ffffffff811395c9>] force_page_cache_readahead+0x79/0xb0 [<ffffffff811399d3>] page_cache_sync_readahead+0x43/0x50 [<ffffffff81124698>] generic_file_aio_read+0x598/0x740 [<ffffffff8118ee5a>] do_sync_read+0xfa/0x140 [<ffffffff8118f885>] vfs_read+0xb5/0x1a0 [<ffffffff8118f9c1>] sys_read+0x51/0x90 [<ffffffff8100b132>] system_call_fastpath+0x16/0x1b irq event stamp: 37627129 hardirqs last enabled at (37627129): [<ffffffff8150e720>] _spin_unlock_irq+0x30/0x40 hardirqs last disabled at (37627128): [<ffffffff8150ea6f>] _spin_lock_irq+0x1f/0x80 softirqs last enabled at (37626488): [<ffffffff8107403a>] __do_softirq+0x14a/0x200 softirqs last disabled at (37626471): [<ffffffff8100c38c>] call_softirq+0x1c/0x30 other info that might help us debug this: no locks held by kswapd0/38. stack backtrace: Pid: 38, comm: kswapd0 Tainted: G C ---------------- 2.6.32-131.17.1.el6.x86_64.debug #1 Call Trace: [<ffffffff810aace7>] ? print_usage_bug+0x177/0x180 [<ffffffff810abc8d>] ? mark_lock+0x35d/0x430 [<ffffffff810acc77>] ? __lock_acquire+0x487/0x1590 [<ffffffff8109b705>] ? sched_clock_local+0x25/0x90 [<ffffffff81013673>] ? native_sched_clock+0x13/0x60 [<ffffffff81012b49>] ? sched_clock+0x9/0x10 [<ffffffff8109b828>] ? sched_clock_cpu+0xb8/0x110 [<ffffffff810a867d>] ? trace_hardirqs_off+0xd/0x10 [<ffffffff8109b96f>] ? cpu_clock+0x6f/0x80 [<ffffffff810ade24>] ? lock_acquire+0xa4/0x120 [<ffffffffa043803a>] ? zram_make_request+0x4a/0x250 [zram] [<ffffffff810ac12d>] ? trace_hardirqs_on+0xd/0x10 [<ffffffff8150d1e1>] ? down_read+0x51/0xa0 [<ffffffffa043803a>] ? zram_make_request+0x4a/0x250 [zram] [<ffffffff811728b3>] ? cache_alloc_debugcheck_after+0xf3/0x230 [<ffffffffa043803a>] ? zram_make_request+0x4a/0x250 [zram] [<ffffffff8126b011>] ? generic_make_request+0x321/0x630 [<ffffffff8109b828>] ? sched_clock_cpu+0xb8/0x110 [<ffffffff811464c8>] ? inc_zone_page_state+0x68/0xa0 [<ffffffff810ac0dd>] ? trace_hardirqs_on_caller+0x14d/0x190 [<ffffffff8126b3ad>] ? submit_bio+0x8d/0x120 [<ffffffff8115e344>] ? swap_writepage+0x94/0xe0 [<ffffffff8113d386>] ? pageout.clone.1+0x136/0x330 [<ffffffff8113db6f>] ? shrink_page_list.clone.0+0x40f/0x6a0 [<ffffffff8100bbd0>] ? restore_args+0x0/0x30 [<ffffffff8109b828>] ? sched_clock_cpu+0xb8/0x110 [<ffffffff810a867d>] ? trace_hardirqs_off+0xd/0x10 [<ffffffff8109b96f>] ? cpu_clock+0x6f/0x80 [<ffffffff810ab7dd>] ? lock_release_holdtime+0x3d/0x190 [<ffffffff8150e720>] ? _spin_unlock_irq+0x30/0x40 [<ffffffff8113e0f9>] ? shrink_inactive_list+0x2f9/0x750 [<ffffffff8109b828>] ? sched_clock_cpu+0xb8/0x110 [<ffffffff8109b96f>] ? cpu_clock+0x6f/0x80 [<ffffffff8113e8df>] ? shrink_zone+0x38f/0x510 [<ffffffff8113fe69>] ? balance_pgdat+0x709/0x800 [<ffffffff8113c430>] ? isolate_pages_global+0x0/0x3a0 [<ffffffff811400a6>] ? kswapd+0x146/0x3a0 [<ffffffff810ab7dd>] ? lock_release_holdtime+0x3d/0x190 [<ffffffff8150e770>] ? _spin_unlock_irqrestore+0x40/0x80 [<ffffffff81094130>] ? autoremove_wake_function+0x0/0x40 [<ffffffff8113ff60>] ? kswapd+0x0/0x3a0 [<ffffffff81093de6>] ? kthread+0x96/0xa0 [<ffffffff8100c28a>] ? child_rip+0xa/0x20 [<ffffffff8100bbd0>] ? restore_args+0x0/0x30 [<ffffffff81093d50>] ? kthread+0x0/0xa0 [<ffffffff8100c280>] ? child_rip+0x0/0x20 Version-Release number of selected component (if applicable): How reproducible: Not always. Steps to Reproduce: 1. Load a system memory so that swapout happens frequently 2. swapon a zram device 3. Actual results: See above. Expected results: No warning. Additional info: I believe the problem is related to memory allocation in zram_init_device(). We probably should use GFP_NOFS or GFP_NOIO there.
I know think this is a false positive: the reclaim can not happen with an uninitialized device. I've posted a patch upstream to prevent the warning to occur.
This request was not resolved in time for the current release. Red Hat invites you to ask your support representative to propose this request, if still desired, for consideration in the next release of Red Hat Enterprise Linux.