diff options
author | Kent Overstreet <kent.overstreet@linux.dev> | 2022-11-02 17:12:00 -0400 |
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committer | Kent Overstreet <kent.overstreet@linux.dev> | 2023-10-22 17:09:51 -0400 |
commit | a8b3a677e786fa869d220a6a78b5532a36dc2f4d (patch) | |
tree | 3fdbdbb71945ae42dab8dc94971e1c78286eaa63 /fs/bcachefs/nocow_locking.c | |
parent | 4dcd1cae72912ab08d313ee5a730608022b211d4 (diff) |
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/nocow_locking.c')
-rw-r--r-- | fs/bcachefs/nocow_locking.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/fs/bcachefs/nocow_locking.c b/fs/bcachefs/nocow_locking.c new file mode 100644 index 000000000000..8f06e08370a2 --- /dev/null +++ b/fs/bcachefs/nocow_locking.c @@ -0,0 +1,15 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include "bcachefs.h" +#include "nocow_locking.h" +#include "util.h" + +void __bch2_bucket_nocow_lock(struct bucket_nocow_lock_table *t, + two_state_lock_t *l, int flags) +{ + struct bch_fs *c = container_of(t, struct bch_fs, nocow_locks); + u64 start_time = local_clock(); + + bch2_two_state_lock(l, flags & BUCKET_NOCOW_LOCK_UPDATE); + bch2_time_stats_update(&c->times[BCH_TIME_nocow_lock_contended], start_time); +} |