I'm experiencing a kernel panic while using fuse related to SPLICE_F_MOVE. Some stack traces [ 52.864466] CPU: 1 PID: 10619 Comm: cp Not tainted 5.15.0-upstream-DEV #7 [ 52.879137] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 52.888490] RIP: 0010:__list_del_entry_valid+0x69/0x80 [ 52.893907] Code: 7f 12 84 31 c0 e8 2d 42 55 00 0f 0b 48 c7 c7 37 8e 10 84 31 c0 e8 1d 42 55 00 0f 0b 48 c7 c7 19 52 19 84 31 c0 e8 0d 42 55 00 <0f> 0b 48 c7 c7 8e e7 15 84 31 c0 e8 fd 41 55 00 0f 0b 00 00 00 cc [ 52.980251] RSP: 0018:ffff8938ea093978 EFLAGS: 00010046 [ 52.994508] RAX: 0000000000000054 RBX: ffffd8d7c5914ec0 RCX: 45fe15c1d0642d00 [ 53.001774] RDX: ffff893939d230b8 RSI: ffff893939d17510 RDI: ffff893939d17510 [ 53.009039] RBP: ffff8938ea093978 R08: 0000000000000000 R09: ffffffff8492dbf0 [ 53.016312] R10: 00000000ffff7fff R11: 0000000000000000 R12: ffff8938ea093a98 [ 53.023575] R13: ffff8938ced23400 R14: 000000000000000d R15: ffff8938ced23400 [ 53.030843] FS: 00007f8bd4b1d740(0000) GS:ffff893939d00000(0000) knlGS:0000000000000000 [ 53.039064] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 53.044939] CR2: 000000000020c86e CR3: 0000000164572003 CR4: 00000000003706e0 [ 53.087945] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 53.105377] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 53.119206] Call Trace: [ 53.121786] release_pages+0x1d0/0x490 [ 53.125856] __pagevec_release+0x4f/0x60 [ 53.129914] invalidate_inode_pages2_range+0x5c4/0x600 [ 53.135186] ? kmem_cache_free+0x7c/0x100 [ 53.139330] invalidate_inode_pages2+0x17/0x20 [ 53.143907] fuse_finish_open+0x75/0x150 [ 53.147976] fuse_open_common+0x113/0x120 [ 53.152117] fuse_open+0x10/0x20 [ 53.155487] do_dentry_open+0x263/0x360 [ 53.167370] vfs_open+0x2d/0x30 [ 53.173633] path_openat+0xa0f/0xd90 [ 53.177353] ? mntput+0x23/0x40 [ 53.180635] ? path_put+0x1e/0x30 [ 53.184104] do_filp_open+0xc7/0x170 [ 53.187933] do_sys_openat2+0x91/0x170 [ 53.195012] __x64_sys_openat+0x7e/0xa0 [ 53.198989] do_syscall_64+0x44/0xa0 [ 53.202714] ? exc_page_fault+0x71/0x160 [ 53.211294] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 53.219256] RIP: 0033:0x7f8bd4c4bec2 [ 53.231375] Code: 8d 48 08 48 89 4d d8 8b 18 48 8b 05 90 8d 07 00 83 38 00 75 30 b8 01 01 00 00 41 89 da bf 9c ff ff ff 4c 89 f6 44 89 fa 0f 05 <48> 89 c3 48 3d 00 f0 ff ff 77 42 89 d8 48 81 c4 c8 00 00 00 5b 41 [ 53.261026] RSP: 002b:00007ffd4ae55570 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 [ 53.268738] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f8bd4c4bec2 [ 53.284714] RDX: 0000000000000000 RSI: 00007ffd4ae57bbc RDI: 00000000ffffff9c [ 53.305198] RBP: 00007ffd4ae55650 R08: 0000000000000000 R09: 00007ffd4ae55baf [ 53.312469] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 [ 53.319736] R13: 00000000000081a4 R14: 00007ffd4ae57bbc R15: 0000000000000000 [ 53.327003] Modules linked in: 9p 9pnet_virtio 9pnet vfat fat virtio_net net_failover failover [ 53.335755] ---[ end trace 086000a6a6747ea3 ]--- With CONFIG_DEBUG_VM it looks like we are trying to add a page to the lru that is already on the lru. [ 133.194168] invalid opcode: 0000 [#1] SMP PTI [ 133.197918] CPU: 1 PID: 10035 Comm: fusexmp Not tainted 5.15.0-dbg-DEV #5 [ 133.213134] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 [ 133.213134] RIP: 0010:lru_cache_add+0x1be/0x1f0 [ 133.213134] Code: c7 c6 1c 6c 01 8c e8 41 8d 03 00 0f 0b 48 c7 c6 1c 6c 01 8c e8 33 8d 03 00 0f 0b 48 89 df 48 c7 c6 60 12 fe 8b e8 22 8d 03 00 <0f> 0b 48 c7 c6 d8 6b ff 8b e8 14 8d 03 00 0f 0b 48 c7 c6 1c 6c 01 [ 133.213134] RSP: 0018:ffff9eb7c319fb88 EFLAGS: 00010296 [ 133.213134] RAX: bbc197b826b34400 RBX: ffffeb5405464e80 RCX: bbc197b826b34400 [ 133.213134] RDX: c0000000ffff7fff RSI: 0000000000000004 RDI: ffff8e52b9d17868 [ 133.213134] RBP: ffff9eb7c319fb90 R08: 0000000000000000 R09: ffffffff8c73ef80 [ 133.213134] R10: 00000000ffff7fff R11: 0000000000000000 R12: 0000000000000000 [ 133.303035] R13: ffffeb5405464e80 R14: ffff9eb7c319fd70 R15: 0000000000001000 [ 133.303035] FS: 00007fe9b5aef700(0000) GS:ffff8e52b9d00000(0000) knlGS:0000000000000000 [ 133.303035] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 133.303035] CR2: 000000000020c86e CR3: 0000000106ab2006 CR4: 00000000003706e0 [ 133.303035] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 133.303035] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 133.303035] Call Trace: [ 133.303035] fuse_copy_page+0x60e/0xa80 [ 133.303035] fuse_copy_args+0xd1/0x1e0 [ 133.303035] fuse_dev_do_write+0x14f6/0x1b20 [ 133.303035] ? __kmalloc_node+0x3c/0x50 [ 133.303035] ? __mutex_unlock_slowpath+0x3d/0x230 [ 133.303035] fuse_dev_splice_write+0x364/0x410 [ 133.303035] do_splice+0x551/0x870 [ 133.303035] ? rcu_lock_release+0x10/0x20 [ 133.303035] ? __fget_files+0x15a/0x170 [ 133.303035] __se_sys_splice+0x15e/0x210 [ 133.303035] __x64_sys_splice+0x29/0x30 [ 133.303035] do_syscall_64+0x44/0xa0 [ 133.303035] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 133.303035] RIP: 0033:0x7fe9bab60953 [ 133.303035] Code: 49 89 ca b8 13 01 00 00 0f 05 48 3d 01 f0 ff ff 73 34 c3 48 83 ec 08 e8 0b 0b 00 00 48 89 04 24 49 89 ca b8 13 01 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 51 0b 00 00 48 89 d0 48 83 c4 08 48 3d 01 [ 133.553661] RSP: 002b:00007fe9b5aee8c0 EFLAGS: 00000297 ORIG_RAX: 0000000000000113 [ 133.553661] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fe9bab60953 [ 133.553661] RDX: 0000000000000003 RSI: 0000000000000000 RDI: 00000000000000cd [ 133.553661] RBP: 00007fe9b5aee9d0 R08: 0000000000040010 R09: 0000000000000001 [ 133.553661] R10: 0000000000000000 R11: 0000000000000297 R12: 0000000000040010 [ 133.553661] R13: 00007fe9b5aee9e0 R14: 00007fe9b5aeea00 R15: 00000624ffc22440 [ 133.553661] Modules linked in: 9p 9pnet_virtio 9pnet vfat fat virtio_net net_failover failover [ 133.625460] ---[ end trace bef475c49a5ebe99 ]--- The following reproduces the panic. In libfuse modify and build example/passthrough.c: $ git clone https://github.com/libfuse/libfuse $ cd libfuse # Enable FUSE_CAP_SLICE_WRITE and FUSE_CAP_SPLICE_MOVE in xmp_init. $ sed -i 's/(void) conn;/conn->want |= FUSE_CAP_SPLICE_WRITE | FUSE_CAP_SPLICE_MOVE;/' example/passthrough.c $ mkdir build; cd build; meson ..; ninja $ mkdir /tmp/fuse $ example/passthrough /tmp/fuse $ dd if=/dev/zero of=/tmp/zeros bs=1M count=100 $ while true; do /tmp/fuse/bin/cp /tmp/fuse/tmp/zeros /dev/null & done --- https://github.com/libfuse/libfuse/commit/3b17db6f7417d5396230bfd56a64cae4e1e2a47c changed libfuse to use vmsplice for malloced pages. Reverting this commit makes the splices and kernel panics go away.
