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

1 files changed, 2 insertions, 0 deletions

diff --git a/sbin/fsck_ffs/fsck.h b/sbin/fsck_ffs/fsck.h
index 342b95f..250fc1f 100644
--- a/sbin/fsck_ffs/fsck.h
+++ b/sbin/fsck_ffs/fsck.h
@@ -274,6 +274,7 @@ char	yflag;			/* assume a yes response */
 int	bkgrdflag;		/* use a snapshot to run on an active system */
 int	bflag;			/* location of alternate super block */
 int	debug;			/* output debugging info */
+int	Eflag;			/* zero out empty data blocks */
 int	inoopt;			/* trim out unused inodes */
 char	ckclean;		/* only do work if not cleanly unmounted */
 int	cvtlevel;		/* convert to newer file system format */
@@ -337,6 +338,7 @@ char	       *blockcheck(char *name);
 int		blread(int fd, char *buf, ufs2_daddr_t blk, long size);
 void		bufinit(void);
 void		blwrite(int fd, char *buf, ufs2_daddr_t blk, long size);
+void		blerase(int fd, ufs2_daddr_t blk, long size);
 void		cacheino(union dinode *dp, ino_t inumber);
 void		catch(int);
 void		catchquit(int);