Problem trying to find out which files could be affected by bad sectors
 

I regularly check my Linux partitions under Windows with HD Sentinel. It found some bad sectors on my ext4 / partition (/dev/sdf5) and now I am trying to find out which files could be affected to assess the damage.

I found the block size of the ext4 file system:

tune2fs -l /dev/sdf5 | grep Block

which returned 4096.

I checked for bad blocks:

badblocks -b 4096 /dev/sdf5

It found 3 bad blocks, one of them being block number 1692288.

Now to find the affected files I ran:

debugfs
open /dev/sdf5
testb 1692288
icheck 1692288

testb returns 'Block 1692288 marked in use', but icheck (to find the inode) returns '<block not found>'.

What does this mean? Is the filesystem corrupt? e2fsck -f /dev/sdf5 shows the filesystem is OK.

Regards,
Gijsbert

I would think so. If a block is marked as being in use, there should be a referencing inode. Even a block inside the journal itself should not return "block not found".

Very strange. Do you get any errors if you try to mount the file system? Anything suspicious in the logs?

I can mount the filesystem and I do not get any errors in the logs. Meanwhile I found the reason why icheck returns '<block not found>': the blocks are reserved as bad:

# dumpe2fs -b /dev/sdf5
dumpe2fs 1.41.12 (17-May-2010)
1692288
1692318
1692320

Regards,
Gijsbert

I guess they must have been detected by a previous fsck run. You should check with smartctl -a /dev/sdf before and after writing to these blocks to confirm that the drive reallocates properly. Pay special attention to the Reallocated_Sector_Ct and Current_Pending_Sector values.

If you're not already monitoring the drive with smartd, that may also be worth considering.

Bad blocks are a sign that the HDD may fail, so make sure to backup your data.