>>>>> Ryusuke Konishi writes: >>>>> On Thu, 14 Jun 2012 11:22:17 +0700, Ivan Shmakov wrote: >>>>> Ryusuke Konishi writes: […] >>> Implementing Off-line resizing is a bit tough task because it >>> requires a user space library to read internal meta data of the >>> nilfs file system and append updated blocks to it. … I guess that a user-level toolkit akin to e2fsprogs would be handy anyway. (Shouldn't there be an fsck(8) for NILFS, BTW?) Other than resizing, there could be a feature to “split” a filesystem — take one or more “snapshot” checkpoints and make a copy of the parts of the filesystem “reachable” from these checkpoints on a distinct block device (perhaps of a differing size), which seems like one more way to do backups. >>> This is almost equivalent to implementing kernel functions of nilfs >>> in user land. […] >> I wonder, how complicated this task would be? In particular, do I >> need to alter all the segments to resize filesystem, or only >> specific ones? Also, are these internal metadata records just “a >> bunch of C structs”, or something more complex? > This needs at least the following tasks: > 1) Update two super blocks to increase/decrease the number of total > segments and the device size. (easy) > 2) Update segment usage information to adjust free segment count of > nilfs_sufile_header struct (sh_ncleansegs) which is written in > the segment usage file. (Sadly not easy) > 3) If truncating in-use segments, relocating blocks and updating disk > address translation information are also needed. (very hard) ACK. (Fortunately, I'm not that interested in shrinking filesystems right now.) > For reference, a discussion on this topic is found in the archives of > the list: > http://marc.info/?t=128419843600003&r=1&w=2 ACK, thanks! I hope to take a closer look at this problem within two weeks or so. (JFTR: those reading via Gmane may access the thread via either of [1, 2]; the first message in the thread is [3].) [1] http://comments.gmane.org/gmane.comp.file-systems.nilfs.user/397 [2] http://thread.gmane.org/gmane.comp.file-systems.nilfs.user/397/focus=1686 [3] news:BAEFA5609CC3AB4BAE1625CAD4C27E5C02986E1D@xxxxxxxxxxxxxxxxxxxxxxxxxx -- FSF associate member #7257 -- To unsubscribe from this list: send the line "unsubscribe linux-nilfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
