[PATCH] mk2fs lazy_journal_init option

[Andreas Dilger <adilger@xxxxxxx>]

Attached is a patch to skip zeroing of the journal if the "-E  
lazy_journal_init" option is given to mke2fs (named to complement the  
"-E lazy_itable_init" option).  This can speed up format time  
significantly for large journal devices.  There is only a short-term  
risk of problems with the uninitialized journal, until such a time  
that the journal has been overwritten once.

To have any kind of problem with the uninitialized journal, the  
filesystem would have to have been newly reformatted twice nearly in a  
row, and then the node crashes before filling the journal even once,  
and the previously-written content would have to line up precisely on  
disk and also have the same transaction ID.

Patch has been lightly tested, showing mke2fs times steady at 14s for  
a 40GB filesystem, regardless of journal size, while previously it  
took up to 45s for an internal 2GB journal.

Signed-off-by: Andreas Dilger <adilger@xxxxxxx>

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

Attachment: e2fsprogs-lazy_journal_init.patch
Description: Binary data