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| author | Uros Bizjak <ubizjak@gmail.com> | 2024-05-23 11:19:26 +0200 |
|---|---|---|
| committer | Kent Overstreet <kent.overstreet@linux.dev> | 2024-07-14 19:00:12 -0400 |
| commit | 68573b936d3fceda9cd5cce3a577e035d19ad426 (patch) | |
| tree | 872f291bf9b8d6f439c9d0a5bd372d42557e8e6b /fs/bcachefs/journal.c | |
| parent | e76a2b65b0565f55ea668ec46d54f6a00b8ea9fc (diff) | |
| download | lwn-68573b936d3fceda9cd5cce3a577e035d19ad426.tar.gz lwn-68573b936d3fceda9cd5cce3a577e035d19ad426.zip | |
bcachefs: Use try_cmpxchg() family of functions instead of cmpxchg()
Use try_cmpxchg() family of functions instead of
cmpxchg (*ptr, old, new) == old. x86 CMPXCHG instruction returns
success in ZF flag, so this change saves a compare after cmpxchg
(and related move instruction in front of cmpxchg).
Also, try_cmpxchg() implicitly assigns old *ptr value to "old" when
cmpxchg fails. There is no need to re-read the value in the loop.
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Brian Foster <bfoster@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Diffstat (limited to 'fs/bcachefs/journal.c')
| -rw-r--r-- | fs/bcachefs/journal.c | 17 |
1 files changed, 8 insertions, 9 deletions
diff --git a/fs/bcachefs/journal.c b/fs/bcachefs/journal.c index 10b19791ec98..649e3a01608a 100644 --- a/fs/bcachefs/journal.c +++ b/fs/bcachefs/journal.c @@ -230,7 +230,6 @@ static void __journal_entry_close(struct journal *j, unsigned closed_val, bool t struct bch_fs *c = container_of(j, struct bch_fs, journal); struct journal_buf *buf = journal_cur_buf(j); union journal_res_state old, new; - u64 v = atomic64_read(&j->reservations.counter); unsigned sectors; BUG_ON(closed_val != JOURNAL_ENTRY_CLOSED_VAL && @@ -238,15 +237,16 @@ static void __journal_entry_close(struct journal *j, unsigned closed_val, bool t lockdep_assert_held(&j->lock); + old.v = atomic64_read(&j->reservations.counter); do { - old.v = new.v = v; + new.v = old.v; new.cur_entry_offset = closed_val; if (old.cur_entry_offset == JOURNAL_ENTRY_ERROR_VAL || old.cur_entry_offset == new.cur_entry_offset) return; - } while ((v = atomic64_cmpxchg(&j->reservations.counter, - old.v, new.v)) != old.v); + } while (!atomic64_try_cmpxchg(&j->reservations.counter, + &old.v, new.v)); if (!__journal_entry_is_open(old)) return; @@ -353,7 +353,6 @@ static int journal_entry_open(struct journal *j) ((journal_cur_seq(j) + 1) & JOURNAL_BUF_MASK); union journal_res_state old, new; int u64s; - u64 v; lockdep_assert_held(&j->lock); BUG_ON(journal_entry_is_open(j)); @@ -432,9 +431,9 @@ static int journal_entry_open(struct journal *j) */ j->cur_entry_u64s = u64s; - v = atomic64_read(&j->reservations.counter); + old.v = atomic64_read(&j->reservations.counter); do { - old.v = new.v = v; + new.v = old.v; BUG_ON(old.cur_entry_offset == JOURNAL_ENTRY_ERROR_VAL); @@ -446,8 +445,8 @@ static int journal_entry_open(struct journal *j) /* Handle any already added entries */ new.cur_entry_offset = le32_to_cpu(buf->data->u64s); - } while ((v = atomic64_cmpxchg(&j->reservations.counter, - old.v, new.v)) != old.v); + } while (!atomic64_try_cmpxchg(&j->reservations.counter, + &old.v, new.v)); if (nr_unwritten_journal_entries(j) == 1) mod_delayed_work(j->wq, |