From 464170647b5648bb81f3615567485fcb9a685bed Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Fri, 9 Aug 2019 14:42:32 +0200 Subject: jbd2: Make state lock a spinlock Bit-spinlocks are problematic on PREEMPT_RT if functions which might sleep on RT, e.g. spin_lock(), alloc/free(), are invoked inside the lock held region because bit spinlocks disable preemption even on RT. A first attempt was to replace state lock with a spinlock placed in struct buffer_head and make the locking conditional on PREEMPT_RT and DEBUG_BIT_SPINLOCKS. Jan pointed out that there is a 4 byte hole in struct journal_head where a regular spinlock fits in and he would not object to convert the state lock to a spinlock unconditionally. Aside of solving the RT problem, this also gains lockdep coverage for the journal head state lock (bit-spinlocks are not covered by lockdep as it's hard to fit a lockdep map into a single bit). The trivial change would have been to convert the jbd_*lock_bh_state() inlines, but that comes with the downside that these functions take a buffer head pointer which needs to be converted to a journal head pointer which adds another level of indirection. As almost all functions which use this lock have a journal head pointer readily available, it makes more sense to remove the lock helper inlines and write out spin_*lock() at all call sites. Fixup all locking comments as well. Suggested-by: Jan Kara Signed-off-by: Thomas Gleixner Signed-off-by: Jan Kara Cc: "Theodore Ts'o" Cc: Mark Fasheh Cc: Joseph Qi Cc: Joel Becker Cc: Jan Kara Cc: linux-ext4@vger.kernel.org Link: https://lore.kernel.org/r/20190809124233.13277-7-jack@suse.cz Signed-off-by: Theodore Ts'o --- fs/jbd2/commit.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'fs/jbd2/commit.c') diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c index a0a191f3df77..8e1ff875de43 100644 --- a/fs/jbd2/commit.c +++ b/fs/jbd2/commit.c @@ -482,10 +482,10 @@ void jbd2_journal_commit_transaction(journal_t *journal) if (jh->b_committed_data) { struct buffer_head *bh = jh2bh(jh); - jbd_lock_bh_state(bh); + spin_lock(&jh->b_state_lock); jbd2_free(jh->b_committed_data, bh->b_size); jh->b_committed_data = NULL; - jbd_unlock_bh_state(bh); + spin_unlock(&jh->b_state_lock); } jbd2_journal_refile_buffer(journal, jh); } @@ -928,7 +928,7 @@ restart_loop: * done with it. */ get_bh(bh); - jbd_lock_bh_state(bh); + spin_lock(&jh->b_state_lock); J_ASSERT_JH(jh, jh->b_transaction == commit_transaction); /* @@ -1024,7 +1024,7 @@ restart_loop: } JBUFFER_TRACE(jh, "refile or unfile buffer"); drop_ref = __jbd2_journal_refile_buffer(jh); - jbd_unlock_bh_state(bh); + spin_unlock(&jh->b_state_lock); if (drop_ref) jbd2_journal_put_journal_head(jh); if (try_to_free) -- cgit