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author | Kent Overstreet <kent.overstreet@linux.dev> | 2022-11-03 00:12:00 +0300 |
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committer | Kent Overstreet <kent.overstreet@linux.dev> | 2023-10-23 00:09:51 +0300 |
commit | a8b3a677e786fa869d220a6a78b5532a36dc2f4d (patch) | |
tree | 3fdbdbb71945ae42dab8dc94971e1c78286eaa63 /fs/bcachefs/move.c | |
parent | 4dcd1cae72912ab08d313ee5a730608022b211d4 (diff) | |
download | linux-a8b3a677e786fa869d220a6a78b5532a36dc2f4d.tar.xz |
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 <kent.overstreet@linux.dev>
Diffstat (limited to 'fs/bcachefs/move.c')
-rw-r--r-- | fs/bcachefs/move.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/fs/bcachefs/move.c b/fs/bcachefs/move.c index 52f126a0bb73..9e453b8495e8 100644 --- a/fs/bcachefs/move.c +++ b/fs/bcachefs/move.c @@ -260,6 +260,12 @@ static int bch2_move_extent(struct btree_trans *trans, if (!bch2_write_ref_tryget(c, BCH_WRITE_REF_move)) return -BCH_ERR_erofs_no_writes; + /* + * Before memory allocations & taking nocow locks in + * bch2_data_update_init(): + */ + bch2_trans_unlock(trans); + /* write path might have to decompress data: */ bkey_for_each_ptr_decode(k.k, ptrs, p, entry) sectors = max_t(unsigned, sectors, p.crc.uncompressed_size); @@ -506,6 +512,7 @@ static int __bch2_move_data(struct moving_context *ctxt, */ bch2_bkey_buf_reassemble(&sk, c, k); k = bkey_i_to_s_c(sk.k); + bch2_trans_unlock(&trans); ret2 = bch2_move_extent(&trans, &iter, ctxt, io_opts, btree_id, k, data_opts); |