On Tue, 2016-05-24 at 01:52 -0700, Christoph Hellwig wrote: > On Mon, May 23, 2016 at 01:08:05PM -0700, Viacheslav Dubeyko wrote: > > I think that it's some confusion. I didn't introduce any new fields in > > struct f2fs_super_block. The "major_ver" and "minor_ver" fields exist in > > F2FS superblock from the beginning of this file system implementation. > > The content of these two fields are defined during mkfs phase. The > > f2fs_format.c contains such code in f2fs_prepare_super_block(): > > They exists, but the kernel so far never checked them, and despite > that the feature checking works fine worth other f2fs features. > > > Current version in VERSION file is 1.6.1. So, historically F2FS is using > > version of on-disk layout. The suggested patch simply introduces the > > threshold value F2FS_MAX_SUPP_MAJOR_VERSION with the purpose to refuse > > the mount operation for the case of unsupported version of on-disk > > layout. > > While I've never seen an actual piece of documentation for the fields it > seems so far they just document the version of mkfs used to create > the file system. Suddenly overloading them with semantics is just > going to create problems. > The best way not to create a problem is to do nothing. The F2FS superblock has "major_ver" and "minor_ver" fields. This metadata structure is stored into F2FS volume. So, this two fields define the on-disk layout's version. We are trying to change the on-disk layout. It means that we need to increase the on-disk layout's version number and to check the version number, namely. What's wrong with my logic? > > First of all, it needs to distinguish two different points. First point, > > we need to increase the on-disk layout version because we are going to > > change on-disk layout in the way that old (current) driver will not > > support. > > That's exactly what most file systems use feature flags for. Frankly speaking, support of 16TB+ volumes is not a "feature" but simple bug fix. Because this issue was created during metadata structure definitions. And we are trying to fix this issue right now. And this issue is on-disk layout related issue. So, the key point here is not a feature flag but the on-disk layout's version, from my point of view. Thanks, Vyacheslav Dubeyko. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
