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. ------------------------------------------------------------------------------ Mobile security can be enabling, not merely restricting. Employees who bring their own devices (BYOD) to work are irked by the imposition of MDM restrictions. Mobile Device Manager Plus allows you to control only the apps on BYO-devices by containerizing them, leaving personal data untouched! https://ad.doubleclick.net/ddm/clk/304595813;131938128;j _______________________________________________ Linux-f2fs-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
