diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2019-08-09 14:42:32 +0200 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2019-10-21 09:16:46 -0400 |
| commit | 464170647b5648bb81f3615567485fcb9a685bed (patch) | |
| tree | cb8bee9bf114c269de6c405bdb0fcdafbd65dd76 /include/linux/jbd2.h | |
| parent | 2e710ff03fc4599059eeda68c8de2383e65af825 (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 'include/linux/jbd2.h')
| -rw-r--r-- | include/linux/jbd2.h | 20 |
1 files changed, 2 insertions, 18 deletions
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h index d0c77478d49d..9cafbc9a76d9 100644 --- a/include/linux/jbd2.h +++ b/include/linux/jbd2.h @@ -313,7 +313,6 @@ enum jbd_state_bits { BH_Revoked, /* Has been revoked from the log */ BH_RevokeValid, /* Revoked flag is valid */ BH_JBDDirty, /* Is dirty but journaled */ - BH_State, /* Pins most journal_head state */ BH_JournalHead, /* Pins bh->b_private and jh->b_bh */ BH_Shadow, /* IO on shadow buffer is running */ BH_Verified, /* Metadata block has been verified ok */ @@ -342,21 +341,6 @@ static inline struct journal_head *bh2jh(struct buffer_head *bh) return bh->b_private; } -static inline void jbd_lock_bh_state(struct buffer_head *bh) -{ - bit_spin_lock(BH_State, &bh->b_state); -} - -static inline int jbd_is_locked_bh_state(struct buffer_head *bh) -{ - return bit_spin_is_locked(BH_State, &bh->b_state); -} - -static inline void jbd_unlock_bh_state(struct buffer_head *bh) -{ - bit_spin_unlock(BH_State, &bh->b_state); -} - static inline void jbd_lock_bh_journal_head(struct buffer_head *bh) { bit_spin_lock(BH_JournalHead, &bh->b_state); @@ -551,9 +535,9 @@ struct transaction_chp_stats_s { * ->jbd_lock_bh_journal_head() (This is "innermost") * * j_state_lock - * ->jbd_lock_bh_state() + * ->b_state_lock * - * jbd_lock_bh_state() + * b_state_lock * ->j_list_lock * * j_state_lock |