Messages in this thread | | | Date | Wed, 3 Mar 2010 23:52:20 -0500 | Subject | Linux kernel - Libata bad block error handling to user mode program | From | foo saa <> |
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hi everyone,
I am in the process of writing a disk erasure application in C. The program does zerofill the drive (Good or Bad) before someone destroys it. During the erasure process, I need to record the number of bad sectors during the zerofill operation.
The method used to write to the hdd involves opening the appropriate /dev block device using open() call with O_WRONLY flag, start issuing write() calls to fill the sectors. A 512 byte buffer filled with zero's is used. All calls are of 64bit enabled. (I am using _LARGEFILE64_SOURCE define).
The problem is (mostly with the bad hdd's), when the write call encounters a bad sector, it takes a bit longer than usual and writes the sector without any errors. (dmesg shows a lot of error messages embedded in the LIBATA error handling code!). The call never fails for any reason.
I am using 2.6.27-7-generic and gcc version 4.3.2 on ubuntu 8.10. I have tried upto 2.6.30.10 and multiple distros with similar behavior.
Here is a summary of things I have attempted.
I know about the bad sector and it's location on the hdd, since it has been verified by using Windows based hex editor utilities, DOS based erasure applications, MHDD and many other HDD utilities.
I have tried using O_DIRECT with aligned buffers, but still could not identify the bad sectors during the writing process.
I have tried using fadvise, posix_fadvise functions to get of the caching, but still failed.
I have tried using SG_IO and SAT translation (direct ATA commands with device addressing) and it fails too. Raw devices is out of question now.
The libata is not letting / informing the user mode program (executing under root) about the media / write errors / bad blocks and failures, though it notifies the kernel and logs to syslog. It also tries to reallocate, softreset, hardreset the block device which is evident from the dmesg logs.
What has to be done for my program to identify / receive the bad block / sector information during the read / write process?
How can I receive the bad sector / physical and media write errors in my program? This is my only requirement and question.
I am currently out of options unless anyone from here can show some new direction!
My only option is to recompile the kernel with libata customization and changes according to my requirement. (Can I instruct to libata to skip the error handling process and pass certain errors to my program?).
Is this a good approach and recommended one? If not what should be done to achieve it? If yes, can somebody throw some light on it?
Please let me know if you have any queries in my above explanation.
Thank you for reading this rather long post!
Regards sponnusa
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