From a8b3a677e786fa869d220a6a78b5532a36dc2f4d Mon Sep 17 00:00:00 2001 From: Kent Overstreet Date: Wed, 2 Nov 2022 17:12:00 -0400 Subject: bcachefs: Nocow support This adds support for nocow mode, where we do writes in-place when possible. Patch components: - New boolean filesystem and inode option, nocow: note that when nocow is enabled, data checksumming and compression are implicitly disabled - To prevent in-place writes from racing with data moves (data_update.c) or bucket reuse (i.e. a bucket being reused and re-allocated while a nocow write is in flight, we have a new locking mechanism. Buckets can be locked for either data update or data move, using a fixed size hash table of two_state_shared locks. We don't have any chaining, meaning updates and moves to different buckets that hash to the same lock will wait unnecessarily - we'll want to watch for this becoming an issue. - The allocator path also needs to check for in-place writes in flight to a given bucket before giving it out: thus we add another counter to bucket_alloc_state so we can track this. - Fsync now may need to issue cache flushes to block devices instead of flushing the journal. We add a device bitmask to bch_inode_info, ei_devs_need_flush, which tracks devices that need to have flushes issued - note that this will lead to unnecessary flushes when other codepaths have already issued flushes, we may want to replace this with a sequence number. - New nocow write path: look up extents, and if they're writable write to them - otherwise fall back to the normal COW write path. XXX: switch to sequence numbers instead of bitmask for devs needing journal flush XXX: ei_quota_lock being a mutex means bch2_nocow_write_done() needs to run in process context - see if we can improve this Signed-off-by: Kent Overstreet --- fs/bcachefs/data_update.c | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'fs/bcachefs/data_update.c') diff --git a/fs/bcachefs/data_update.c b/fs/bcachefs/data_update.c index 82d7e13e61a5..c3f12b3adb14 100644 --- a/fs/bcachefs/data_update.c +++ b/fs/bcachefs/data_update.c @@ -303,6 +303,13 @@ void bch2_data_update_read_done(struct data_update *m, void bch2_data_update_exit(struct data_update *update) { struct bch_fs *c = update->op.c; + struct bkey_ptrs_c ptrs = + bch2_bkey_ptrs_c(bkey_i_to_s_c(update->k.k)); + const struct bch_extent_ptr *ptr; + + bkey_for_each_ptr(ptrs, ptr) + bch2_bucket_nocow_unlock(&c->nocow_locks, + PTR_BUCKET_POS(c, ptr), 0); bch2_bkey_buf_exit(&update->k, c); bch2_disk_reservation_put(c, &update->op.res); @@ -451,6 +458,9 @@ int bch2_data_update_init(struct bch_fs *c, struct data_update *m, m->op.incompressible = true; i++; + + bch2_bucket_nocow_lock(&c->nocow_locks, + PTR_BUCKET_POS(c, &p.ptr), 0); } if (reserve_sectors) { -- cgit v1.2.3