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f92ee31e03
Current code assumes we have only one space_info for each block group type (DATA, METADATA, and SYSTEM). We sometime need multiple space infos to manage special block groups. One example is handling the data relocation block group for the zoned mode. That block group is dedicated for writing relocated data and we cannot allocate any regular extent from that block group, which is implemented in the zoned extent allocator. This block group still belongs to the normal data space_info. So, when all the normal data block groups are full and there is some free space in the dedicated block group, the space_info looks to have some free space, while it cannot allocate normal extent anymore. That results in a strange ENOSPC error. We need to have a space_info for the relocation data block group to represent the situation properly. Adds a basic infrastructure for having a "sub-group" of a space_info: creation and removing. A sub-group space_info belongs to one of the primary space_infos and has the same flags as its parent. This commit first introduces the relocation data sub-space_info, and the next commit will introduce tree-log sub-space_info. In the future, it could be useful to implement tiered storage for btrfs e.g. by implementing a sub-group space_info for block groups resides on a fast storage. Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com> Signed-off-by: David Sterba <dsterba@suse.com>
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.