Hi all, While fuzzing with trinity inside KVM tools guest running latest -next kernel I've stumbled on the following spew. This is a result of a failed allocation in alloc_extent_state_atomic() which triggers a BUG_ON when the return value is NULL. It's a bit weird that it BUGs on failed allocations, since it's obviously not a critical failure. [ 447.705167] kernel BUG at fs/btrfs/extent_io.c:676! [ 447.706201] invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC [ 447.707732] Dumping ftrace buffer: [ 447.708473] (ftrace buffer empty) [ 447.709684] Modules linked in: [ 447.710246] CPU: 17 PID: 4195 Comm: kswapd17 Tainted: G W 3.14.0-rc7-next-20140321-sasha-00018-g0516fe6-dirty #265 [ 447.710253] task: ffff88066be9b000 ti: ffff88066be82000 task.ti: ffff88066be82000 [ 447.710253] RIP: clear_extent_bit (fs/btrfs/extent_io.c:676) [ 447.710253] RSP: 0000:ffff88066be83768 EFLAGS: 00010246 [ 447.710253] RAX: 0000000000000000 RBX: 0000000000d00fff RCX: 0000000000000006 [ 447.710253] RDX: 00000000000058e0 RSI: ffff88066be9bd60 RDI: 0000000000000286 [ 447.710253] RBP: ffff88066be837e8 R08: 0000000000000000 R09: 0000000000000000 [ 447.710253] R10: 0000000000000001 R11: 454a4e495f544c55 R12: 0000000001ffffff [ 447.710253] R13: 0000000000000000 R14: ffff88007b89fd08 R15: 0000000000d00000 [ 447.710253] FS: 0000000000000000(0000) GS:ffff8804acc00000(0000) knlGS:0000000000000000 [ 447.710253] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b [ 447.710253] CR2: 0000000002aec968 CR3: 0000000005e29000 CR4: 00000000000006a0 [ 447.710253] DR0: 0000000000698000 DR1: 0000000000698000 DR2: 0000000000000000 [ 447.710253] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 [ 447.710253] Stack: [ 447.710253] ffff88066be83788 ffffffff844fc4d5 0000000000000000 ffff8804ab4800e8 [ 447.710253] 0000000000000000 0000000000000001 ffff8804ab4800c8 fffffffffffffbf7 [ 447.710253] ffff88066be837c8 0000000000000000 0000000000000006 ffffea0007aaf340 [ 447.710253] Call Trace: [ 447.710253] ? _raw_spin_unlock (arch/x86/include/asm/preempt.h:98 include/linux/spinlock_api_smp.h:152 kernel/locking/spinlock.c:183) [ 447.710253] try_release_extent_mapping (fs/btrfs/extent_io.c:3998 fs/btrfs/extent_io.c:4058) [ 447.710253] __btrfs_releasepage (fs/btrfs/inode.c:7521) [ 447.710253] btrfs_releasepage (fs/btrfs/inode.c:7534) [ 447.710253] try_to_release_page (mm/filemap.c:2984) [ 447.710253] invalidate_inode_page (mm/truncate.c:165 mm/truncate.c:215) [ 447.710253] invalidate_mapping_pages (mm/truncate.c:517) [ 447.710253] inode_lru_isolate (arch/x86/include/asm/current.h:14 include/linux/swap.h:33 fs/inode.c:724) [ 447.710253] ? insert_inode_locked (fs/inode.c:687) [ 447.710253] list_lru_walk_node (mm/list_lru.c:89) [ 447.710253] prune_icache_sb (fs/inode.c:759) [ 447.710253] super_cache_scan (fs/super.c:96) [ 447.710253] shrink_slab_node (mm/vmscan.c:306) [ 447.710253] shrink_slab (mm/vmscan.c:381) [ 447.710253] kswapd_shrink_zone (mm/vmscan.c:2909) [ 447.710253] kswapd (mm/vmscan.c:3090 mm/vmscan.c:3296) [ 447.710253] ? mem_cgroup_shrink_node_zone (mm/vmscan.c:3213) [ 447.710253] kthread (kernel/kthread.c:219) [ 447.710253] ? __tick_nohz_task_switch (arch/x86/include/asm/paravirt.h:809 kernel/time/tick-sched.c:272) [ 447.710253] ? kthread_create_on_node (kernel/kthread.c:185) [ 447.710253] ret_from_fork (arch/x86/kernel/entry_64.S:555) [ 447.710253] ? kthread_create_on_node (kernel/kthread.c:185) [ 447.710253] Code: e9 a9 00 00 00 0f 1f 00 48 39 c3 0f 82 87 00 00 00 4c 39 e3 0f 83 7e 00 00 00 48 8b 7d a0 e8 45 ef ff ff 48 85 c0 49 89 c5 75 05 <0f> 0b 0f 1f 00 48 8b 7d b0 48 8d 4b 01 48 89 c2 4c 89 f6 e8 c5 [ 447.710253] RIP clear_extent_bit (fs/btrfs/extent_io.c:676) [ 447.710253] RSP <ffff88066be83768> Thanks, Sasha