(lots of cc's added) On Wed, 3 Mar 2010 23:52:20 -0500 foo saa <foosaa@xxxxxxxxx> wrote: > 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. > OK, this is bad. Did you try running fsync() after a write(), check the return value? I doubt if this is a VFS bug. As O_DIRECT writes are also failing to report errors, I'd suspect that the driver or block layers really are failing to propagate the error back. Do the ata guys know of a way of deliberately injecting errors to test these codepaths? If we don't have that, something using the fault-injection code would be nice. As low-level as possible, preferably at interrupt time. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>