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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/journal.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/journal.c')
-rw-r--r--fs/jbd2/journal.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 1c58859aa592..5d4192f05879 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -363,7 +363,7 @@ int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
/* keep subsequent assertions sane */
atomic_set(&new_bh->b_count, 1);
- jbd_lock_bh_state(bh_in);
+ spin_lock(&jh_in->b_state_lock);
repeat:
/*
* If a new transaction has already done a buffer copy-out, then
@@ -405,13 +405,13 @@ repeat:
if (need_copy_out && !done_copy_out) {
char *tmp;
- jbd_unlock_bh_state(bh_in);
+ spin_unlock(&jh_in->b_state_lock);
tmp = jbd2_alloc(bh_in->b_size, GFP_NOFS);
if (!tmp) {
brelse(new_bh);
return -ENOMEM;
}
- jbd_lock_bh_state(bh_in);
+ spin_lock(&jh_in->b_state_lock);
if (jh_in->b_frozen_data) {
jbd2_free(tmp, bh_in->b_size);
goto repeat;
@@ -464,7 +464,7 @@ repeat:
__jbd2_journal_file_buffer(jh_in, transaction, BJ_Shadow);
spin_unlock(&journal->j_list_lock);
set_buffer_shadow(bh_in);
- jbd_unlock_bh_state(bh_in);
+ spin_unlock(&jh_in->b_state_lock);
return do_escape | (done_copy_out << 1);
}
@@ -2410,6 +2410,8 @@ static struct journal_head *journal_alloc_journal_head(void)
ret = kmem_cache_zalloc(jbd2_journal_head_cache,
GFP_NOFS | __GFP_NOFAIL);
}
+ if (ret)
+ spin_lock_init(&ret->b_state_lock);
return ret;
}