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a36d8f0e0e
We've been getting away from feature bits: they don't have any kind of ordering, and thus it's possible for people to enable weird combinations of features that were never tested or intended to be run. Much better to just give every new feature, compatible or incompatible, a version number. Additionally, we probably won't ever rev the major version number: major version numbers represent incompatible versions, but that doesn't really fit with how we actually roll out incompatible features - we need a better way of rolling out incompatible features. So, this patch adds two new superblock fields: - BCH_SB_VERSION_INCOMPAT - BCH_SB_VERSION_INCOMPAT_ALLOWED BCH_SB_VERSION_INCOMPAT_ALLOWED indicates that incompatible features up to version number x are allowed to be used without user prompting, but it does not by itself deny old versions from mounting. BCH_SB_VERSION_INCOMPAT does deny old versions from mounting, and must be <= BCH_SB_VERSION_INCOMPAT_ALLOWED. BCH_SB_VERSION_INCOMPAT will only be set when a codepath attempts to use an incompatible feature, so as to not unnecessarily break compatibility with old versions. bch2_request_incompat_feature() is the new interface to check if an incompatible feature may be used. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.