fb3f57bb11
This adds a new btree, rebalance_work, to eliminate scanning required for finding extents that need work done on them in the background - i.e. for the background_target and background_compression options. rebalance_work is a bitset btree, where a KEY_TYPE_set corresponds to an extent in the extents or reflink btree at the same pos. A new extent field is added, bch_extent_rebalance, which indicates that this extent has work that needs to be done in the background - and which options to use. This allows per-inode options to be propagated to indirect extents - at least in some circumstances. In this patch, changing IO options on a file will not propagate the new options to indirect extents pointed to by that file. Updating (setting/clearing) the rebalance_work btree is done by the extent trigger, which looks at the bch_extent_rebalance field. Scanning is still requrired after changing IO path options - either just for a given inode, or for the whole filesystem. We indicate that scanning is required by adding a KEY_TYPE_cookie key to the rebalance_work btree: the cookie counter is so that we can detect that scanning is still required when an option has been flipped mid-way through an existing scan. Future possible work: - Propagate options to indirect extents when being changed - Add other IO path options - nr_replicas, ec, to rebalance_work so they can be applied in the background when they change - Add a counter, for bcachefs fs usage output, showing the pending amount of rebalance work: we'll probably want to do this after the disk space accounting rewrite (moving it to a new btree) 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 Restructured Text 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.