Yes, it's another issue of 'Nix uses experimental options long before they are fully baked and causes trouble after years in which they seemed to work perfectly fine'. So I tried to double the size of one of my ext4 filesystems just now, using x86-64 Linux 3.8.3. Like almost all my filesystems, it's ext4 atop LVM atop hardware RAID (on the same machine that experienced the infamous journal_async_commit and reboot-during-unmount corruption bug last year, as it happens). I did an online resize because the filesystem is NFS-exported so unmounting it is a bit of a pain. The resize never terminated, and most (but not all) I/O to ext4 filesystems locked up: looks like we grabbed a lock and never let it go. And, indeed, we had oopses. On reboot, the thing journal-replayed and did an unmounted resize fine: I took an e2image beforehand (but after it had been mounted by the system on boot, and umounted by me). I'm using a few-day-old resize2fs, from the maint branch of e2fsprogs, commit 871ad94. The filesystem is bind-mounted in two places, with the following mount options (for fs features and other tune2fs output, see the bottom of this email): rw,nosuid,nodev,relatime,nobarrier,quota,usrquota,grpquota,commit=30,stripe=16,data=ordered,usrquota,grpquota (hm, why are 'usrquota, grpquota' repeated? not important...) This is not by any means the first time I've done an online resize of a flexbg ext4 filesystem on this box. The last such was on April 17th 2012, using kernel 3.2.10 and e2fsprogs 1.42.1, and it worked fine. (I'm aware this is such a large gap in time as to be basically useless for problem resolution, but still.) I'm quite glad not all ext4 I/O hung: this is also my loghost, so the oopses were being logged to one of the afflicted filesystems! Here they are: info: [191093.449107] EXT4-fs (dm-6): resizing filesystem from 13107200 to 26214400 blocks info: [191093.451269] EXT4-fs (dm-6): resizing filesystem from 16777216 to 26214400 blocks info: [191093.451687] EXT4-fs (dm-6): Converting file system to meta_bg info: [191093.474152] EXT4-fs (dm-6): resizing filesystem from 16777216 to 26214400 blocks warning: [191093.474594] ------------[ cut here ]------------ crit: [191093.474821] kernel BUG at fs/ext4/resize.c:404! warning: [191093.475048] invalid opcode: 0000 [#1] SMP warning: [191093.475341] Modules linked in: firewire_ohci firewire_core [last unloaded: microcode] warning: [191093.475891] CPU 0 warning: [191093.475934] Pid: 23548, comm: resize2fs Not tainted 3.8.3-dirty #1 empty empty/S7010 warning: [191093.476556] RIP: 0010:[<ffffffff811af44f>] [<ffffffff811af44f>] set_flexbg_block_bitmap+0x8f/0x149 warning: [191093.477008] RSP: 0018:ffff88052327bb58 EFLAGS: 00010216 warning: [191093.477237] RAX: ffff8805bb4cd300 RBX: 0000000000000081 RCX: 0000000001008000 warning: [191093.477648] RDX: 0000000000000001 RSI: ffff8806113aa000 RDI: ffff88062234cc00 warning: [191093.478056] RBP: ffff88052327bbb8 R08: ffff88052327bb84 R09: 0000000000000000 warning: [191093.478466] R10: 00000000000001a7 R11: 0000000000000000 R12: ffff88062234c800 warning: [191093.478876] R13: ffff88013212e068 R14: ffff880523022040 R15: 0000000001008000 warning: [191093.479286] FS: 00007f73c45e0740(0000) GS:ffff88063fc00000(0000) knlGS:0000000000000000 warning: [191093.479698] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b warning: [191093.479929] CR2: 00007ff3f4364000 CR3: 000000039e119000 CR4: 00000000000027f0 warning: [191093.480345] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 warning: [191093.480756] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 warning: [191093.490624] Process resize2fs (pid: 23548, threadinfo ffff88052327a000, task ffff8805bb770000) warning: [191093.491038] Stack: warning: [191093.491254] ffff88013212e068 01008000816386e0 ffff880623fe07b0 0000008101008000 warning: [191093.491802] ffff88052327bbb8 00000001811b7782 ffff88052327bbb8 0000000000000008 warning: [191093.492352] 0000000000000040 0000000000000200 ffff88062234c800 0000000000000000 warning: [191093.492900] Call Trace: warning: [191093.493120] [<ffffffff811afa9e>] ext4_flex_group_add+0x595/0x1456 warning: [191093.493353] [<ffffffff811b199f>] ext4_resize_fs+0x8ca/0xba7 warning: [191093.493585] [<ffffffff8113bd16>] ? __mnt_want_write+0x48/0x4f warning: [191093.493819] [<ffffffff81193a36>] ext4_ioctl+0x83e/0x967 warning: [191093.494049] [<ffffffff811300b8>] ? do_filp_open+0x38/0x86 warning: [191093.494280] [<ffffffff8113158a>] vfs_ioctl+0x26/0x39 warning: [191093.494508] [<ffffffff81131e02>] do_vfs_ioctl+0x3ba/0x3fd warning: [191093.494738] [<ffffffff8111bd1c>] ? kmem_cache_free+0x5d/0x105 warning: [191093.494969] [<ffffffff8112c91b>] ? final_putname+0x35/0x3a warning: [191093.495198] [<ffffffff81131e9c>] sys_ioctl+0x57/0x87 warning: [191093.495428] [<ffffffff8151bd12>] system_call_fastpath+0x16/0x1b warning: [191093.495657] Code: 49 8b 44 24 18 89 4d b8 8d 04 c1 44 29 f8 39 d8 0f 47 c3 89 45 bc 49 8b 46 08 f6 04 50 02 74 0d 41 83 7e 10 01 0f 86 98 00 00 00 <0f> 0b 48 8b 7d b0 e8 1c ff ff ff 85 c0 0f 85 98 00 00 00 8b 45 alert: [191093.498529] RIP [<ffffffff811af44f>] set_flexbg_block_bitmap+0x8f/0x149 warning: [191093.498796] RSP <ffff88052327bb58> warning: [191093.499035] ---[ end trace 2931a3907f03d739 ]--- warning: [191093.499362] ------------[ cut here ]------------ crit: [191093.499588] kernel BUG at fs/jbd2/transaction.c:364! warning: [191093.499814] invalid opcode: 0000 [#2] SMP warning: [191093.500106] Modules linked in: firewire_ohci firewire_core [last unloaded: microcode] warning: [191093.500713] CPU 0 warning: [191093.500756] Pid: 23548, comm: resize2fs Tainted: G D 3.8.3-dirty #1 empty empty/S7010 warning: [191093.501377] RIP: 0010:[<ffffffff811c9d29>] [<ffffffff811c9d29>] jbd2__journal_start+0x3e/0xdb warning: [191093.501825] RSP: 0018:ffff88052327b3f8 EFLAGS: 00010206 warning: [191093.502053] RAX: ffff88060f069300 RBX: ffff880623fe07b0 RCX: 0000000000000018 warning: [191093.502461] RDX: 0000000000000050 RSI: 0000000000000002 RDI: ffff880622380800 warning: [191093.502870] RBP: ffff88052327b428 R08: 0000000000000040 R09: ffff88052327b868 warning: [191093.503277] R10: 0000000000000000 R11: 0000000000000001 R12: ffff8805bb770000 warning: [191093.503687] R13: ffff880622380800 R14: ffffffff811921cf R15: 0000000000000000 warning: [191093.504096] FS: 00007f73c45e0740(0000) GS:ffff88063fc00000(0000) knlGS:0000000000000000 warning: [191093.504508] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b warning: [191093.504738] CR2: 00007ff3f4364000 CR3: 0000000001a0b000 CR4: 00000000000027f0 warning: [191093.505147] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 warning: [191093.505555] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 warning: [191093.505963] Process resize2fs (pid: 23548, threadinfo ffff88052327a000, task ffff8805bb770000) warning: [191093.506375] Stack: warning: [191093.506593] 78302b6874617074 00623178302f3631 ffff880093532400 ffff880624246800 warning: [191093.507143] 0000000000000002 ffffffff811921cf ffff88052327b438 ffffffff811c9dd9 warning: [191093.507690] ffff88052327b468 ffffffff811ab104 ffff880093532400 ffff880093532400 warning: [191093.508237] Call Trace: warning: [191093.508457] [<ffffffff811921cf>] ? ext4_dirty_inode+0x1d/0x4c warning: [191093.508688] [<ffffffff811c9dd9>] jbd2_journal_start+0x13/0x15 warning: [191093.508921] [<ffffffff811ab104>] ext4_journal_start_sb+0xca/0xf3 warning: [191093.509153] [<ffffffff811921cf>] ext4_dirty_inode+0x1d/0x4c warning: [191093.509385] [<ffffffff811441ad>] __mark_inode_dirty+0x32/0x1e8 warning: [191093.509617] [<ffffffff81137a0d>] update_time+0x9e/0xa7 warning: [191093.509846] [<ffffffff8113b13c>] ? mnt_clone_write+0x12/0x2a warning: [191093.510077] [<ffffffff81137ab7>] file_update_time+0xa1/0xc2 warning: [191093.510313] [<ffffffff810e46ae>] __generic_file_aio_write+0x1c2/0x2d7 warning: [191093.510546] [<ffffffff8112537d>] ? __sb_start_write+0xc2/0xf6 warning: [191093.510776] [<ffffffff810e4835>] generic_file_aio_write+0x72/0xd3 warning: [191093.511008] [<ffffffff81189463>] ext4_file_write+0x37b/0x3b0 warning: [191093.511239] [<ffffffff8112357c>] do_sync_write+0x96/0xd6 warning: [191093.511470] [<ffffffff810ab73a>] do_acct_process.isra.4+0x2af/0x2e2 warning: [191093.511703] [<ffffffff810abcf8>] acct_process+0x6b/0x8b warning: [191093.511933] [<ffffffff810684e0>] do_exit+0x31e/0x87c warning: [191093.512161] [<ffffffff8103ab58>] oops_end+0x82/0x87 warning: [191093.512387] [<ffffffff8103ac93>] die+0x5a/0x63 warning: [191093.512611] [<ffffffff8103834d>] do_trap+0x6e/0x13a warning: [191093.512841] [<ffffffff81084313>] ? __atomic_notifier_call_chain+0x12/0x14 warning: [191093.513073] [<ffffffff8103861c>] do_invalid_op+0x96/0x9f warning: [191093.513302] [<ffffffff811af44f>] ? set_flexbg_block_bitmap+0x8f/0x149 warning: [191093.513535] [<ffffffff811caeee>] ? do_get_write_access+0x37e/0x3ba warning: [191093.513769] [<ffffffff8151cc78>] invalid_op+0x18/0x20 warning: [191093.513998] [<ffffffff811af44f>] ? set_flexbg_block_bitmap+0x8f/0x149 warning: [191093.514232] [<ffffffff811af3fc>] ? set_flexbg_block_bitmap+0x3c/0x149 warning: [191093.514464] [<ffffffff811afa9e>] ext4_flex_group_add+0x595/0x1456 warning: [191093.514697] [<ffffffff811b199f>] ext4_resize_fs+0x8ca/0xba7 warning: [191093.514926] [<ffffffff8113bd16>] ? __mnt_want_write+0x48/0x4f warning: [191093.515157] [<ffffffff81193a36>] ext4_ioctl+0x83e/0x967 warning: [191093.515387] [<ffffffff811300b8>] ? do_filp_open+0x38/0x86 warning: [191093.515618] [<ffffffff8113158a>] vfs_ioctl+0x26/0x39 warning: [191093.515846] [<ffffffff81131e02>] do_vfs_ioctl+0x3ba/0x3fd warning: [191093.516076] [<ffffffff8111bd1c>] ? kmem_cache_free+0x5d/0x105 warning: [191093.516307] [<ffffffff8112c91b>] ? final_putname+0x35/0x3a warning: [191093.516537] [<ffffffff81131e9c>] sys_ioctl+0x57/0x87 warning: [191093.516765] [<ffffffff8151bd12>] system_call_fastpath+0x16/0x1b warning: [191093.516994] Code: 48 83 ec 10 65 4c 8b 24 25 80 b8 00 00 48 85 ff 49 8b 9c 24 f0 05 00 00 0f 84 8a 00 00 00 48 85 db 74 12 48 8b 03 48 39 38 74 02 <0f> 0b ff 43 0c e9 83 00 00 00 48 8b 3d 5e ac af 00 41 89 f6 be alert: [191093.519855] RIP [<ffffffff811c9d29>] jbd2__journal_start+0x3e/0xdb warning: [191093.520124] RSP <ffff88052327b3f8> warning: [191093.520353] ---[ end trace 2931a3907f03d73a ]--- alert: [191093.520580] Fixing recursive fault but reboot is needed! ("reboot is needed", like I can reboot when everything blocks. Big red switch was needed :) ) tune2fs output of the e2image of the filesystem (which is 3.5Mb as an lzipped qcow e2image, if anyone wants it, just ask): tune2fs 1.42.7 (21-Jan-2013) Filesystem volume name: non-free Last mounted on: /pkg/non-free Filesystem UUID: 07799ff5-baef-4492-875d-c73730d6149e Filesystem magic number: 0xEF53 Filesystem revision #: 1 (dynamic) Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize Filesystem flags: signed_directory_hash Default mount options: (none) Filesystem state: clean Errors behavior: Continue Filesystem OS type: Linux Inode count: 3276800 Block count: 13107200 Reserved block count: 655360 Free blocks: 2095428 Free inodes: 3184251 First block: 0 Block size: 4096 Fragment size: 4096 Blocks per group: 32768 Fragments per group: 32768 Inodes per group: 8192 Inode blocks per group: 512 RAID stripe width: 16 Flex block group size: 64 Filesystem created: Tue May 26 21:33:29 2009 Last mount time: Tue Mar 19 19:47:26 2013 Last write time: Tue Mar 19 19:51:08 2013 Mount count: 10 Maximum mount count: 33 Last checked: Sun Oct 28 13:25:54 2012 Check interval: 15552000 (6 months) Next check after: Fri Apr 26 14:25:54 2013 Lifetime writes: 49 GB Reserved blocks uid: 0 (user root) Reserved blocks gid: 0 (group root) First inode: 11 Inode size: 256 Required extra isize: 28 Desired extra isize: 28 Journal inode: 8 Default directory hash: half_md4 Directory Hash Seed: 04d4f165-9ba9-40be-bdb4-c321cb0d6215 Journal backup: inode blocks -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html