[T-Mobile Samsung Galaxy S II SGH-T989] eris170:
The same thing seems to be happening with TWRP 2.6.0.4. It never finishes backing up. The twirly bar at the bottom just keeps going and going.. dmesg has similar errors as I was getting with CWM:

<6>[ 338.231903] zcache: created ephemeral tmem pool, id=1, client=65535
<6>[ 338.237457] EXT4-fs (mmcblk0p21): mounted filesystem with ordered data mode. Opts: (null)
<7>[ 338.245483] SELinux: initialized (dev mmcblk0p21, type ext4), uses xattr
<6>[ 338.266418] zcache: destroyed pool id=1, cli_id=65535
<6>[ 338.312561] zcache: created ephemeral tmem pool, id=1, client=65535
<6>[ 338.318054] EXT4-fs (mmcblk0p25): mounted filesystem with ordered data mode. Opts: (null)
<7>[ 338.337127] SELinux: initialized (dev mmcblk0p25, type ext4), uses xattr
<6>[ 338.343261] zcache: destroyed pool id=1, cli_id=65535
<4>[ 338.400177] EXT4-fs (mmcblk0p24): warning: mounting fs with errors, running e2fsck is recommended
<6>[ 338.413269] zcache: created ephemeral tmem pool, id=1, client=65535
<6>[ 338.418823] EXT4-fs (mmcblk0p24): mounted filesystem with ordered data mode. Opts: (null)
<7>[ 338.426849] SELinux: initialized (dev mmcblk0p24, type ext4), uses xattr
<6>[ 338.447357] zcache: destroyed pool id=1, cli_id=65535
<6>[ 338.498107] zcache: created ephemeral tmem pool, id=1, client=65535
<6>[ 338.503784] EXT4-fs (mmcblk0p27): mounted filesystem with ordered data mode. Opts: (null)
<7>[ 338.512145] SELinux: initialized (dev mmcblk0p27, type ext4), uses xattr
<6>[ 338.518615] zcache: destroyed pool id=1, cli_id=65535
<6>[ 339.817138] zcache: created ephemeral tmem pool, id=1, client=65535
<6>[ 339.822662] EXT4-fs (mmcblk0p25): mounted filesystem with ordered data mode. Opts: (null)
<7>[ 339.847167] SELinux: initialized (dev mmcblk0p25, type ext4), uses xattr
<4>[ 349.649108] EXT4-fs (mmcblk0p24): warning: mounting fs with errors, running e2fsck is recommended
<6>[ 349.682159] zcache: created ephemeral tmem pool, id=2, client=65535
<6>[ 349.687835] EXT4-fs (mmcblk0p24): mounted filesystem with ordered data mode. Opts: (null)
<7>[ 349.695648] SELinux: initialized (dev mmcblk0p24, type ext4), uses xattr
<2>[ 353.107177] EXT4-fs error (device mmcblk0p24): ext4_init_inode_table:1296: comm ext4lazyinit: Something is wrong with group 0
<2>[ 353.107238] Used itable blocks: 479itable unused count: 0
<2>[ 353.107269]
<3>[ 353.655029] Aborting journal on device mmcblk0p24-8.
<2>[ 353.696502] EXT4-fs (mmcblk0p24): Remounting filesystem read-only
<3>[ 362.501586] [TSP] Calibration End!!!!!!
<3>[ 362.504302] [TSP] Clearing unused slots
<3>[ 362.509887] [TSP] Calibration!!!!!!
<3>[ 362.515777] [TSP] Calibration End!!!!!!
<3>[ 362.518707] [TSP] Clearing unused slots
<6>[ 370.498046] max17040_set_property: charger full state!
<6>[ 410.588012] max17040_set_property: charger full state!
<6>[ 450.668121] max17040_set_property: charger full state!
<6>[ 450.672363] max17040_adjust_fullsoc : full_soc = 9641
<6>[ 456.575805] zcache: created ephemeral tmem pool, id=3, client=65535
<6>[ 456.581359] EXT4-fs (mmcblk0p21): mounted filesystem with ordered data mode. Opts: (null)
<7>[ 456.607147] SELinux: initialized (dev mmcblk0p21, type ext4), uses xattr
<6>[ 456.613250] zcache: destroyed pool id=3, cli_id=65535
<6>[ 456.689239] zcache: created ephemeral tmem pool, id=3, client=65535
<6>[ 456.694732] EXT4-fs (mmcblk0p27): mounted filesystem with ordered data mode. Opts: (null)
<7>[ 456.710479] SELinux: initialized (dev mmcblk0p27, type ext4), uses xattr
<6>[ 456.716491] zcache: destroyed pool id=3, cli_id=65535
<6>[ 456.817138] zcache: destroyed pool id=2, cli_id=65535
<3>[ 480.577301] INFO: task jbd2/mmcblk0p24:205 blocked for more than 120 seconds.
<3>[ 480.583831] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
<6>[ 480.607147] jbd2/mmcblk0p24 D c07b1dc8 0 205 2 0x00000000
<4>[ 480.612762] [<c07b1dc8>] (__schedule+0x5cc/0x788) from [<c02d9c10>] (jbd2_journal_commit_transaction+0x1e0/0x1484)
<4>[ 480.637969] [<c02d9c10>] (jbd2_journal_commit_transaction+0x1e0/0x1484) from [<c02de7dc>] (kjournald2+0xa4/0x204)
<4>[ 480.657165] [<c02de7dc>] (kjournald2+0xa4/0x204) from [<c01a8234>] (kthread+0x7c/0x88)
<4>[ 480.664306] [<c01a8234>] (kthread+0x7c/0x88) from [<c0105e80>] (kernel_thread_exit+0x0/0x8)
<6>[ 490.748779] max17040_set_property: charger full state!
<6>[ 530.879364] max17040_set_property: charger full state!
<6>[ 530.883728] max17040_adjust_fullsoc : full_soc = 9630
<6>[ 570.908752] max17040_set_property: charger full state!

Something seems messed up with the filesystem or underlying media on mmcblk0p24. Any other ideas?

UPDATE: Thought I'd make a tar file of the contents of p24 so if I format it, I can untar everything back to the partition. tar failed with an error on file csc/sales_code.dat so I added a --exclude for that file and it seems to work. That's no guarantee the contents of all the files aren't screwed up but it's better than nothing. Question is, how to I format the partition? It mounts as ext4 but there is no mkfs.ext4 utility in the recovery boot. I could format the partition and try to flash CM-10x but not sure if that makes sense.