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/transaction.c | 100 ++++++++++++++++++++++++-------------------------- 1 file changed, 47 insertions(+), 53 deletions(-) (limited to 'fs/jbd2/transaction.c') diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c index f2af4afc690a..7c11afe60532 100644 --- a/fs/jbd2/transaction.c +++ b/fs/jbd2/transaction.c @@ -879,7 +879,7 @@ repeat: start_lock = jiffies; lock_buffer(bh); - jbd_lock_bh_state(bh); + spin_lock(&jh->b_state_lock); /* If it takes too long to lock the buffer, trace it */ time_lock = jbd2_time_diff(start_lock, jiffies); @@ -929,7 +929,7 @@ repeat: error = -EROFS; if (is_handle_aborted(handle)) { - jbd_unlock_bh_state(bh); + spin_unlock(&jh->b_state_lock); goto out; } error = 0; @@ -993,7 +993,7 @@ repeat: */ if (buffer_shadow(bh)) { JBUFFER_TRACE(jh, "on shadow: sleep"); - jbd_unlock_bh_state(bh); + spin_unlock(&jh->b_state_lock); wait_on_bit_io(&bh->b_state, BH_Shadow, TASK_UNINTERRUPTIBLE); goto repeat; } @@ -1014,7 +1014,7 @@ repeat: JBUFFER_TRACE(jh, "generate frozen data"); if (!frozen_buffer) { JBUFFER_TRACE(jh, "allocate memory for buffer"); - jbd_unlock_bh_state(bh); + spin_unlock(&jh->b_state_lock); frozen_buffer = jbd2_alloc(jh2bh(jh)->b_size, GFP_NOFS | __GFP_NOFAIL); goto repeat; @@ -1033,7 +1033,7 @@ attach_next: jh->b_next_transaction = transaction; done: - jbd_unlock_bh_state(bh); + spin_unlock(&jh->b_state_lock); /* * If we are about to journal a buffer, then any revoke pending on it is @@ -1172,7 +1172,7 @@ int jbd2_journal_get_create_access(handle_t *handle, struct buffer_head *bh) * that case: the transaction must have deleted the buffer for it to be * reused here. */ - jbd_lock_bh_state(bh); + spin_lock(&jh->b_state_lock); J_ASSERT_JH(jh, (jh->b_transaction == transaction || jh->b_transaction == NULL || (jh->b_transaction == journal->j_committing_transaction && @@ -1207,7 +1207,7 @@ int jbd2_journal_get_create_access(handle_t *handle, struct buffer_head *bh) jh->b_next_transaction = transaction; spin_unlock(&journal->j_list_lock); } - jbd_unlock_bh_state(bh); + spin_unlock(&jh->b_state_lock); /* * akpm: I added this. ext3_alloc_branch can pick up new indirect @@ -1275,13 +1275,13 @@ repeat: committed_data = jbd2_alloc(jh2bh(jh)->b_size, GFP_NOFS|__GFP_NOFAIL); - jbd_lock_bh_state(bh); + spin_lock(&jh->b_state_lock); if (!jh->b_committed_data) { /* Copy out the current buffer contents into the * preserved, committed copy. */ JBUFFER_TRACE(jh, "generate b_committed data"); if (!committed_data) { - jbd_unlock_bh_state(bh); + spin_unlock(&jh->b_state_lock); goto repeat; } @@ -1289,7 +1289,7 @@ repeat: committed_data = NULL; memcpy(jh->b_committed_data, bh->b_data, bh->b_size); } - jbd_unlock_bh_state(bh); + spin_unlock(&jh->b_state_lock); out: jbd2_journal_put_journal_head(jh); if (unlikely(committed_data)) @@ -1390,16 +1390,16 @@ int jbd2_journal_dirty_metadata(handle_t *handle, struct buffer_head *bh) */ if (jh->b_transaction != transaction && jh->b_next_transaction != transaction) { - jbd_lock_bh_state(bh); + spin_lock(&jh->b_state_lock); J_ASSERT_JH(jh, jh->b_transaction == transaction || jh->b_next_transaction == transaction); - jbd_unlock_bh_state(bh); + spin_unlock(&jh->b_state_lock); } if (jh->b_modified == 1) { /* If it's in our transaction it must be in BJ_Metadata list. */ if (jh->b_transaction == transaction && jh->b_jlist != BJ_Metadata) { - jbd_lock_bh_state(bh); + spin_lock(&jh->b_state_lock); if (jh->b_transaction == transaction && jh->b_jlist != BJ_Metadata) pr_err("JBD2: assertion failure: h_type=%u " @@ -1409,13 +1409,13 @@ int jbd2_journal_dirty_metadata(handle_t *handle, struct buffer_head *bh) jh->b_jlist); J_ASSERT_JH(jh, jh->b_transaction != transaction || jh->b_jlist == BJ_Metadata); - jbd_unlock_bh_state(bh); + spin_unlock(&jh->b_state_lock); } goto out; } journal = transaction->t_journal; - jbd_lock_bh_state(bh); + spin_lock(&jh->b_state_lock); if (jh->b_modified == 0) { /* @@ -1501,7 +1501,7 @@ int jbd2_journal_dirty_metadata(handle_t *handle, struct buffer_head *bh) __jbd2_journal_file_buffer(jh, transaction, BJ_Metadata); spin_unlock(&journal->j_list_lock); out_unlock_bh: - jbd_unlock_bh_state(bh); + spin_unlock(&jh->b_state_lock); out: JBUFFER_TRACE(jh, "exit"); return ret; @@ -1539,11 +1539,13 @@ int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh) BUFFER_TRACE(bh, "entry"); - jbd_lock_bh_state(bh); + jh = jbd2_journal_grab_journal_head(bh); + if (!jh) { + __bforget(bh); + return 0; + } - if (!buffer_jbd(bh)) - goto not_jbd; - jh = bh2jh(bh); + spin_lock(&jh->b_state_lock); /* Critical error: attempting to delete a bitmap buffer, maybe? * Don't do any jbd operations, and return an error. */ @@ -1664,18 +1666,14 @@ int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh) spin_unlock(&journal->j_list_lock); } drop: - jbd_unlock_bh_state(bh); __brelse(bh); + spin_unlock(&jh->b_state_lock); + jbd2_journal_put_journal_head(jh); if (drop_reserve) { /* no need to reserve log space for this block -bzzz */ handle->h_buffer_credits++; } return err; - -not_jbd: - jbd_unlock_bh_state(bh); - __bforget(bh); - goto drop; } /** @@ -1874,7 +1872,7 @@ free_and_exit: * * j_list_lock is held. * - * jbd_lock_bh_state(jh2bh(jh)) is held. + * jh->b_state_lock is held. */ static inline void @@ -1898,7 +1896,7 @@ __blist_add_buffer(struct journal_head **list, struct journal_head *jh) * * Called with j_list_lock held, and the journal may not be locked. * - * jbd_lock_bh_state(jh2bh(jh)) is held. + * jh->b_state_lock is held. */ static inline void @@ -1930,7 +1928,7 @@ static void __jbd2_journal_temp_unlink_buffer(struct journal_head *jh) transaction_t *transaction; struct buffer_head *bh = jh2bh(jh); - J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh)); + lockdep_assert_held(&jh->b_state_lock); transaction = jh->b_transaction; if (transaction) assert_spin_locked(&transaction->t_journal->j_list_lock); @@ -1984,11 +1982,11 @@ void jbd2_journal_unfile_buffer(journal_t *journal, struct journal_head *jh) /* Get reference so that buffer cannot be freed before we unlock it */ get_bh(bh); - jbd_lock_bh_state(bh); + spin_lock(&jh->b_state_lock); spin_lock(&journal->j_list_lock); __jbd2_journal_unfile_buffer(jh); spin_unlock(&journal->j_list_lock); - jbd_unlock_bh_state(bh); + spin_unlock(&jh->b_state_lock); jbd2_journal_put_journal_head(jh); __brelse(bh); } @@ -1996,7 +1994,7 @@ void jbd2_journal_unfile_buffer(journal_t *journal, struct journal_head *jh) /* * Called from jbd2_journal_try_to_free_buffers(). * - * Called under jbd_lock_bh_state(bh) + * Called under jh->b_state_lock */ static void __journal_try_to_free_buffer(journal_t *journal, struct buffer_head *bh) @@ -2083,10 +2081,10 @@ int jbd2_journal_try_to_free_buffers(journal_t *journal, if (!jh) continue; - jbd_lock_bh_state(bh); + spin_lock(&jh->b_state_lock); __journal_try_to_free_buffer(journal, bh); + spin_unlock(&jh->b_state_lock); jbd2_journal_put_journal_head(jh); - jbd_unlock_bh_state(bh); if (buffer_jbd(bh)) goto busy; } while ((bh = bh->b_this_page) != head); @@ -2107,7 +2105,7 @@ busy: * * Called under j_list_lock. * - * Called under jbd_lock_bh_state(bh). + * Called under jh->b_state_lock. */ static int __dispose_buffer(struct journal_head *jh, transaction_t *transaction) { @@ -2201,7 +2199,7 @@ static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh, /* OK, we have data buffer in journaled mode */ write_lock(&journal->j_state_lock); - jbd_lock_bh_state(bh); + spin_lock(&jh->b_state_lock); spin_lock(&journal->j_list_lock); /* @@ -2282,10 +2280,10 @@ static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh, * for commit and try again. */ if (partial_page) { - jbd2_journal_put_journal_head(jh); spin_unlock(&journal->j_list_lock); - jbd_unlock_bh_state(bh); + spin_unlock(&jh->b_state_lock); write_unlock(&journal->j_state_lock); + jbd2_journal_put_journal_head(jh); return -EBUSY; } /* @@ -2297,10 +2295,10 @@ static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh, set_buffer_freed(bh); if (journal->j_running_transaction && buffer_jbddirty(bh)) jh->b_next_transaction = journal->j_running_transaction; - jbd2_journal_put_journal_head(jh); spin_unlock(&journal->j_list_lock); - jbd_unlock_bh_state(bh); + spin_unlock(&jh->b_state_lock); write_unlock(&journal->j_state_lock); + jbd2_journal_put_journal_head(jh); return 0; } else { /* Good, the buffer belongs to the running transaction. @@ -2324,10 +2322,10 @@ zap_buffer: * here. */ jh->b_modified = 0; - jbd2_journal_put_journal_head(jh); spin_unlock(&journal->j_list_lock); - jbd_unlock_bh_state(bh); + spin_unlock(&jh->b_state_lock); write_unlock(&journal->j_state_lock); + jbd2_journal_put_journal_head(jh); zap_buffer_unlocked: clear_buffer_dirty(bh); J_ASSERT_BH(bh, !buffer_jbddirty(bh)); @@ -2414,7 +2412,7 @@ void __jbd2_journal_file_buffer(struct journal_head *jh, int was_dirty = 0; struct buffer_head *bh = jh2bh(jh); - J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh)); + lockdep_assert_held(&jh->b_state_lock); assert_spin_locked(&transaction->t_journal->j_list_lock); J_ASSERT_JH(jh, jh->b_jlist < BJ_Types); @@ -2476,11 +2474,11 @@ void __jbd2_journal_file_buffer(struct journal_head *jh, void jbd2_journal_file_buffer(struct journal_head *jh, transaction_t *transaction, int jlist) { - jbd_lock_bh_state(jh2bh(jh)); + spin_lock(&jh->b_state_lock); spin_lock(&transaction->t_journal->j_list_lock); __jbd2_journal_file_buffer(jh, transaction, jlist); spin_unlock(&transaction->t_journal->j_list_lock); - jbd_unlock_bh_state(jh2bh(jh)); + spin_unlock(&jh->b_state_lock); } /* @@ -2490,7 +2488,7 @@ void jbd2_journal_file_buffer(struct journal_head *jh, * buffer on that transaction's metadata list. * * Called under j_list_lock - * Called under jbd_lock_bh_state(jh2bh(jh)) + * Called under jh->b_state_lock * * When this function returns true, there's no next transaction to refile to * and the caller has to drop jh reference through @@ -2501,7 +2499,7 @@ bool __jbd2_journal_refile_buffer(struct journal_head *jh) int was_dirty, jlist; struct buffer_head *bh = jh2bh(jh); - J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh)); + lockdep_assert_held(&jh->b_state_lock); if (jh->b_transaction) assert_spin_locked(&jh->b_transaction->t_journal->j_list_lock); @@ -2547,17 +2545,13 @@ bool __jbd2_journal_refile_buffer(struct journal_head *jh) */ void jbd2_journal_refile_buffer(journal_t *journal, struct journal_head *jh) { - struct buffer_head *bh = jh2bh(jh); bool drop; - /* Get reference so that buffer cannot be freed before we unlock it */ - get_bh(bh); - jbd_lock_bh_state(bh); + spin_lock(&jh->b_state_lock); spin_lock(&journal->j_list_lock); drop = __jbd2_journal_refile_buffer(jh); - jbd_unlock_bh_state(bh); + spin_unlock(&jh->b_state_lock); spin_unlock(&journal->j_list_lock); - __brelse(bh); if (drop) jbd2_journal_put_journal_head(jh); } -- cgit v1.2.3-59-g8ed1b