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linux/fs/bcachefs/rebalance.h
Kent Overstreet fb3f57bb11 bcachefs: rebalance_work
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>
2023-11-01 21:11:05 -04:00

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C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _BCACHEFS_REBALANCE_H
#define _BCACHEFS_REBALANCE_H
#include "rebalance_types.h"
int bch2_set_rebalance_needs_scan(struct bch_fs *, u64 inum);
int bch2_set_fs_needs_rebalance(struct bch_fs *);
static inline void rebalance_wakeup(struct bch_fs *c)
{
struct task_struct *p;
rcu_read_lock();
p = rcu_dereference(c->rebalance.thread);
if (p)
wake_up_process(p);
rcu_read_unlock();
}
void bch2_rebalance_status_to_text(struct printbuf *, struct bch_fs *);
void bch2_rebalance_stop(struct bch_fs *);
int bch2_rebalance_start(struct bch_fs *);
void bch2_fs_rebalance_init(struct bch_fs *);
#endif /* _BCACHEFS_REBALANCE_H */