svn commit: r221233 - head/sbin/fsck_ffs

[Alexander Motin]

Dag-Erling Smorgrav wrote:
> Author: des
> Date: Fri Apr 29 23:00:23 2011
> New Revision: 221233
> URL: http://svn.freebsd.org/changeset/base/221233
> 
> Log:
>   Add an -E option to mirror newfs's.  The idea is that if you have a system
>   that was built before ffs grew support for TRIM, your filesystem will have
>   plenty of free blocks that the flash chip doesn't know are free, so it
>   can't take advantage of them for wear leveling.  Once you've upgraded your
>   kernel, you enable TRIM on the filesystem (tunefs -t enable), then run
>   fsck_ffs -E on it before mounting it.
>   
>   I tested this patch by half-filling an mdconfig'ed filesystem image,
>   running fsck_ffs -E on it, then verifying that the contents were not
>   damaged by comparing them to a pristine copy using rsync's checksum
>   functionality.  There is no reliable way to test it on real hardware.
>   
>   Many thanks to mckusick@, who provided the tricky parts of this patch and
>   reviewed the final version.
>   
>   Reviewed by:	mckusick@
>   MFC after:	3 weeks

Thank you!

Not exactly scientific test, but my laptop survived it fine with 10% and
50% of free space. And it indeed restored the write speed, respecting
that I had no kernel TRIM support enabled there before. For additional
check of the drive's block remapper behavior I've written all free space
with file of zeroes and deleted it -- after reboot I am still here. :)

-- 
Alexander Motin