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authorThomas Gleixner <tglx@linutronix.de>2019-08-09 14:42:32 +0200
committerTheodore Ts'o <tytso@mit.edu>2019-10-21 09:16:46 -0400
commit464170647b5648bb81f3615567485fcb9a685bed (patch)
treecb8bee9bf114c269de6c405bdb0fcdafbd65dd76 /fs/jbd2/commit.c
parent2e710ff03fc4599059eeda68c8de2383e65af825 (diff)
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 <jack@suse.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Jan Kara <jack@suse.cz> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: Mark Fasheh <mark@fasheh.com> Cc: Joseph Qi <joseph.qi@linux.alibaba.com> Cc: Joel Becker <jlbec@evilplan.org> Cc: Jan Kara <jack@suse.com> Cc: linux-ext4@vger.kernel.org Link: https://lore.kernel.org/r/20190809124233.13277-7-jack@suse.cz Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/jbd2/commit.c')
-rw-r--r--fs/jbd2/commit.c8
1 files changed, 4 insertions, 4 deletions
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)