This only seems to happen when the array isn't clean.
Last known good kernel: 33af79d12e0fa25545d49e86afc67ea8ad5f2f40
First bad kernel: e89970aa93b06d0605a488e74af3b0a2a80e03b5
[ 7.123394] md: md0 still in use.
[ 7.327984] md: bind<sdc3>
[ 7.328295] md: bind<sdb3>
[ 7.328435] md: md0: raid array is not clean -- starting background reconstruction
[ 7.328836] raid1: raid set md0 active with 2 out of 2 mirrors
[ 7.354117] md0: bitmap initialized from disk: read 15/15 pages, set 0 bits
[ 7.354238] created bitmap (233 pages) for device md0
[ 7.373700] md: resync of RAID array md0
[ 7.373703] md: minimum _guaranteed_ speed: 1000 KB/sec/disk.
[ 7.373707] md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for resync.
[ 7.373712] md: using 128k window, over a total of 975747840 blocks.
[ 7.421444] md: md0: resync done.
[ 7.506594] RAID1 conf printout:
[ 7.506713] --- wd:2 rd:2
[ 7.506829] disk 0, wo:0, o:1, dev:sdb3
[ 7.506945] disk 1, wo:0, o:1, dev:sdc3
[ 7.858561] EXT3-fs: INFO: recovery required on readonly filesystem.
[ 7.858691] EXT3-fs: write access will be enabled during recovery.
[ 8.735551] ------------[ cut here ]------------
[ 8.735667] WARNING: at include/linux/blkdev.h:447 blk_plug_device+0x5e/0x97()
[ 8.735877] Modules linked in:
[ 8.736011] Pid: 1403, comm: exe Not tainted 2.6.26 #06912-g8e053ca
[ 8.736130]
[ 8.736131] Call Trace:
[ 8.736353] [<ffffffff80231f34>] warn_on_slowpath+0x58/0x86
[ 8.736476] [<ffffffff8025f50f>] ? mempool_alloc_slab+0x11/0x13
[ 8.736596] [<ffffffff8025f5fd>] ? mempool_alloc+0x2c/0xe8
[ 8.736704] [<ffffffff8025f50f>] ? mempool_alloc_slab+0x11/0x13
[ 8.736835] [<ffffffff804c4368>] ? bitmap_get_counter+0x156/0x1fa
[ 8.736945] [<ffffffff80338b10>] blk_plug_device+0x5e/0x97
[ 8.737073] [<ffffffff804c4ecc>] bitmap_startwrite+0x12a/0x172
[ 8.737194] [<ffffffff802acf3c>] ? bio_alloc_bioset+0x4b/0x8f
[ 8.737315] [<ffffffff804b0835>] make_request+0x5c3/0x658
[ 8.737438] [<ffffffff80247c9b>] ? up_read+0x9/0xb
[ 8.737551] [<ffffffff8033808b>] generic_make_request+0x1e3/0x21a
[ 8.737677] [<ffffffff802acecb>] ? bvec_alloc_bs+0x81/0xa7
[ 8.737786] [<ffffffff8033964f>] submit_bio+0x111/0x11a
[ 8.737917] [<ffffffff802a8f79>] submit_bh+0xf0/0x114
[ 8.738025] [<ffffffff802aac0d>] __block_write_full_page+0x1c2/0x2ae
[ 8.738155] [<ffffffff802aee0f>] ? blkdev_get_block+0x0/0x4d
[ 8.738264] [<ffffffff802aee0f>] ? blkdev_get_block+0x0/0x4d
[ 8.738382] [<ffffffff802aadeb>] block_write_full_page+0xf2/0xfb
[ 8.738510] [<ffffffff802aea50>] blkdev_writepage+0x13/0x15
[ 8.738623] [<ffffffff8026340c>] __writepage+0x12/0x2b
[ 8.738742] [<ffffffff802638c1>] write_cache_pages+0x1ae/0x318
[ 8.738851] [<ffffffff802633fa>] ? __writepage+0x0/0x2b
[ 8.738969] [<ffffffff80263a4a>] generic_writepages+0x1f/0x25
[ 8.739087] [<ffffffff80263a78>] do_writepages+0x28/0x37
[ 8.739217] [<ffffffff8025d9fe>] __filemap_fdatawrite_range+0x55/0x60
[ 8.739337] [<ffffffff8025dba3>] filemap_fdatawrite+0x1a/0x1c
[ 8.739455] [<ffffffff8025dbbe>] filemap_write_and_wait+0x19/0x38
[ 8.739576] [<ffffffff802a9c35>] sync_blockdev+0x1b/0x1d
[ 8.739696] [<ffffffff802e46dc>] journal_recover+0x9b/0xab
[ 8.739815] [<ffffffff802e6baf>] journal_load+0x4d/0x89
[ 8.739933] [<ffffffff802dc143>] ext3_fill_super+0xec5/0x14c6
[ 8.740054] [<ffffffff805cf2c6>] ? __down_write+0xb/0xd
[ 8.740174] [<ffffffff8028a43a>] get_sb_bdev+0xfe/0x14d
[ 8.740289] [<ffffffff802db27e>] ? ext3_fill_super+0x0/0x14c6
[ 8.740418] [<ffffffff802d991f>] ext3_get_sb+0x13/0x15
[ 8.740536] [<ffffffff8028a1fc>] vfs_kern_mount+0x52/0x9a
[ 8.740654] [<ffffffff8028a2a1>] do_kern_mount+0x47/0xe2
[ 8.740773] [<ffffffff8029fc62>] do_new_mount+0x5f/0x92
[ 8.740890] [<ffffffff8029fe44>] do_mount+0x1af/0x1de
[ 8.746963] [<ffffffff805d4625>] ? bad_gs+0x10ab/0x2476
[ 8.747073] [<ffffffff8029fefc>] sys_mount+0x89/0xd5
[ 8.747209] [<ffffffff8020b4eb>] system_call_fastpath+0x16/0x1b
[ 8.747317]
[ 8.747431] ---[ end trace 2e59dd16bd35ee32 ]---
[ 9.027047] BUG: scheduling while atomic: md0_raid1/1379/0x00000002
[ 9.027182] Modules linked in:
[ 9.027327] Pid: 1379, comm: md0_raid1 Tainted: G W 2.6.26 #06912-g8e053ca
[ 9.027543]
[ 9.027544] Call Trace:
[ 9.027769] [<ffffffff80341aa2>] ? cfq_set_request+0x2b3/0x339
[ 9.027890] [<ffffffff8022de0c>] __schedule_bug+0x62/0x66
[ 9.028015] [<ffffffff805cd8b8>] schedule+0xab/0x5f1
[ 9.028135] [<ffffffff805ce02f>] io_schedule+0x28/0x33
[ 9.028254] [<ffffffff80339012>] get_request_wait+0x91/0xf1
[ 9.028375] [<ffffffff802449df>] ? autoremove_wake_function+0x0/0x38
[ 9.028485] [<ffffffff8033932c>] __make_request+0x2ba/0x359
[ 9.028623] [<ffffffff8025f50f>] ? mempool_alloc_slab+0x11/0x13
[ 9.028742] [<ffffffff8033808b>] generic_make_request+0x1e3/0x21a
[ 9.028866] [<ffffffff802acecb>] ? bvec_alloc_bs+0x81/0xa7
[ 9.028979] [<ffffffff8033964f>] submit_bio+0x111/0x11a
[ 9.029089] [<ffffffff802acfb8>] ? bio_clone+0x38/0x40
[ 9.029674] [<ffffffff804bc7fa>] md_super_write+0xb2/0xbe
[ 9.029801] [<ffffffff804c3fae>] write_page+0x198/0x305
[ 9.029926] [<ffffffff803365b1>] ? elv_rqhash_reposition+0x36/0x38
[ 9.030110] [<ffffffff8033663d>] ? elv_merged_request+0x39/0x46
[ 9.030246] [<ffffffff804c5007>] bitmap_unplug+0xb7/0x188
[ 9.030390] [<ffffffff804aeeb9>] flush_pending_writes+0x5d/0x97
[ 9.030539] [<ffffffff804af46f>] raid1d+0x74/0xd4c
[ 9.030685] [<ffffffff8023ae5e>] ? lock_timer_base+0x26/0x4a
[ 9.030814] [<ffffffff8023aed8>] ? try_to_del_timer_sync+0x56/0x62
[ 9.031048] [<ffffffff8023aef8>] ? del_timer_sync+0x14/0x20
[ 9.031196] [<ffffffff805ce11e>] ? schedule_timeout+0x98/0xb4
[ 9.031334] [<ffffffff8023ab0e>] ? process_timeout+0x0/0xb
[ 9.031480] [<ffffffff804c322f>] md_thread+0xd5/0xed
[ 9.031619] [<ffffffff802449df>] ? autoremove_wake_function+0x0/0x38
[ 9.031785] [<ffffffff804c315a>] ? md_thread+0x0/0xed
[ 9.031936] [<ffffffff802448ad>] kthread+0x49/0x78
[ 9.032089] [<ffffffff8020c409>] child_rip+0xa/0x11
[ 9.032245] [<ffffffff80244864>] ? kthread+0x0/0x78
[ 9.032390] [<ffffffff8020c3ff>] ? child_rip+0x0/0x11
[ 9.032524]
--
Simon Arlott