!1330 [sync] PR-1325: jbd2: fix several checkpoint

Merge Pull Request from: @openeuler-sync-bot 
 

Origin pull request: 
https://gitee.com/openeuler/kernel/pulls/1325 
 
PR sync from: Zhihao Cheng <chengzhihao1@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/QARA5X5OQUKRFUIORG2YVB6YE3V5CGQB/ 
Zhang Yi (4):
  jbd2: remove journal_clean_one_cp_list()
  jbd2: fix a race when checking checkpoint buffer busy
  jbd2: remove __journal_try_to_free_buffer()
  jbd2: fix checkpoint cleanup performance regression

Zhihao Cheng (1):
  jbd2: Fix wrongly judgement for buffer head removing while doing
    checkpoint


-- 
2.31.1
 
 
Link:https://gitee.com/openeuler/kernel/pulls/1330 

Reviewed-by: zhangyi (F) <yi.zhang@huawei.com> 
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com> 

fs/jbd2/checkpoint.c

@@ -204,20 +204,6 @@ int jbd2_log_do_checkpoint(journal_t *journal)
 		jh = transaction->t_checkpoint_list;
 		bh = jh2bh(jh);
 
-		/*
-		 * The buffer may be writing back, or flushing out in the
-		 * last couple of cycles, or re-adding into a new transaction,
-		 * need to check it again until it's unlocked.
-		 */
-		if (buffer_locked(bh)) {
-			get_bh(bh);
-			spin_unlock(&journal->j_list_lock);
-			wait_on_buffer(bh);
-			/* the journal_head may have gone by now */
-			BUFFER_TRACE(bh, "brelse");
-			__brelse(bh);
-			goto retry;
-		}
 		if (jh->b_transaction != NULL) {
 			transaction_t *t = jh->b_transaction;
 			tid_t tid = t->t_tid;
@@ -252,7 +238,22 @@ int jbd2_log_do_checkpoint(journal_t *journal)
 			spin_lock(&journal->j_list_lock);
 			goto restart;
 		}
-		if (!buffer_dirty(bh)) {
+		if (!trylock_buffer(bh)) {
+			/*
+			 * The buffer is locked, it may be writing back, or
+			 * flushing out in the last couple of cycles, or
+			 * re-adding into a new transaction, need to check
+			 * it again until it's unlocked.
+			 */
+			get_bh(bh);
+			spin_unlock(&journal->j_list_lock);
+			wait_on_buffer(bh);
+			/* the journal_head may have gone by now */
+			BUFFER_TRACE(bh, "brelse");
+			__brelse(bh);
+			goto retry;
+		} else if (!buffer_dirty(bh)) {
+			unlock_buffer(bh);
 			BUFFER_TRACE(bh, "remove from checkpoint");
 			/*
 			 * If the transaction was released or the checkpoint
@@ -262,6 +263,7 @@ int jbd2_log_do_checkpoint(journal_t *journal)
 			    !transaction->t_checkpoint_list)
 				goto out;
 		} else {
+			unlock_buffer(bh);
 			/*
 			 * We are about to write the buffer, it could be
 			 * raced by some other transaction shrink or buffer
@@ -347,50 +349,12 @@ int jbd2_cleanup_journal_tail(journal_t *journal)
 
 /* Checkpoint list management */
 
-/*
- * journal_clean_one_cp_list
- *
- * Find all the written-back checkpoint buffers in the given list and
- * release them. If 'destroy' is set, clean all buffers unconditionally.
- *
- * Called with j_list_lock held.
- * Returns 1 if we freed the transaction, 0 otherwise.
- */
-static int journal_clean_one_cp_list(struct journal_head *jh, bool destroy)
-{
-	struct journal_head *last_jh;
-	struct journal_head *next_jh = jh;
-
-	if (!jh)
-		return 0;
-
-	last_jh = jh->b_cpprev;
-	do {
-		jh = next_jh;
-		next_jh = jh->b_cpnext;
-
-		if (!destroy && __cp_buffer_busy(jh))
-			return 0;
-
-		if (__jbd2_journal_remove_checkpoint(jh))
-			return 1;
-		/*
-		 * This function only frees up some memory
-		 * if possible so we dont have an obligation
-		 * to finish processing. Bail out if preemption
-		 * requested:
-		 */
-		if (need_resched())
-			return 0;
-	} while (jh != last_jh);
-
-	return 0;
-}
+enum shrink_type {SHRINK_DESTROY, SHRINK_BUSY_STOP, SHRINK_BUSY_SKIP};
 
 /*
  * journal_shrink_one_cp_list
  *
- * Find 'nr_to_scan' written-back checkpoint buffers in the given list
+ * Find all the written-back checkpoint buffers in the given list
  * and try to release them. If the whole transaction is released, set
  * the 'released' parameter. Return the number of released checkpointed
  * buffers.
@@ -398,7 +362,7 @@ static int journal_clean_one_cp_list(struct journal_head *jh, bool destroy)
  * Called with j_list_lock held.
  */
 static unsigned long journal_shrink_one_cp_list(struct journal_head *jh,
-						unsigned long *nr_to_scan,
+						enum shrink_type type,
 						bool *released)
 {
 	struct journal_head *last_jh;
@@ -406,7 +370,8 @@ static unsigned long journal_shrink_one_cp_list(struct journal_head *jh,
 	unsigned long nr_freed = 0;
 	int ret;
 
-	if (!jh || *nr_to_scan == 0)
+	*released = false;
+	if (!jh)
 		return 0;
 
 	last_jh = jh->b_cpprev;
@@ -414,12 +379,18 @@ static unsigned long journal_shrink_one_cp_list(struct journal_head *jh,
 		jh = next_jh;
 		next_jh = jh->b_cpnext;
 
-		(*nr_to_scan)--;
-		if (__cp_buffer_busy(jh))
-			continue;
+		if (type == SHRINK_DESTROY) {
+			ret = __jbd2_journal_remove_checkpoint(jh);
+		} else {
+			ret = jbd2_journal_try_remove_checkpoint(jh);
+			if (ret < 0) {
+				if (type == SHRINK_BUSY_SKIP)
+					continue;
+				break;
+			}
+		}
 
 		nr_freed++;
-		ret = __jbd2_journal_remove_checkpoint(jh);
 		if (ret) {
 			*released = true;
 			break;
@@ -427,7 +398,7 @@ static unsigned long journal_shrink_one_cp_list(struct journal_head *jh,
 
 		if (need_resched())
 			break;
-	} while (jh != last_jh && *nr_to_scan);
+	} while (jh != last_jh);
 
 	return nr_freed;
 }
@@ -445,11 +416,11 @@ unsigned long jbd2_journal_shrink_checkpoint_list(journal_t *journal,
 						  unsigned long *nr_to_scan)
 {
 	transaction_t *transaction, *last_transaction, *next_transaction;
-	bool released;
+	bool __maybe_unused released;
 	tid_t first_tid = 0, last_tid = 0, next_tid = 0;
 	tid_t tid = 0;
 	unsigned long nr_freed = 0;
-	unsigned long nr_scanned = *nr_to_scan;
+	unsigned long freed;
 
 again:
 	spin_lock(&journal->j_list_lock);
@@ -478,10 +449,11 @@ unsigned long jbd2_journal_shrink_checkpoint_list(journal_t *journal,
 		transaction = next_transaction;
 		next_transaction = transaction->t_cpnext;
 		tid = transaction->t_tid;
-		released = false;
 
-		nr_freed += journal_shrink_one_cp_list(transaction->t_checkpoint_list,
-						       nr_to_scan, &released);
+		freed = journal_shrink_one_cp_list(transaction->t_checkpoint_list,
+						   SHRINK_BUSY_SKIP, &released);
+		nr_freed += freed;
+		(*nr_to_scan) -= min(*nr_to_scan, freed);
 		if (*nr_to_scan == 0)
 			break;
 		if (need_resched() || spin_needbreak(&journal->j_list_lock))
@@ -502,9 +474,8 @@ unsigned long jbd2_journal_shrink_checkpoint_list(journal_t *journal,
 	if (*nr_to_scan && next_tid)
 		goto again;
 out:
-	nr_scanned -= *nr_to_scan;
 	trace_jbd2_shrink_checkpoint_list(journal, first_tid, tid, last_tid,
-					  nr_freed, nr_scanned, next_tid);
+					  nr_freed, next_tid);
 
 	return nr_freed;
 }
@@ -520,19 +491,21 @@ unsigned long jbd2_journal_shrink_checkpoint_list(journal_t *journal,
 void __jbd2_journal_clean_checkpoint_list(journal_t *journal, bool destroy)
 {
 	transaction_t *transaction, *last_transaction, *next_transaction;
-	int ret;
+	enum shrink_type type;
+	bool released;
 
 	transaction = journal->j_checkpoint_transactions;
 	if (!transaction)
 		return;
 
+	type = destroy ? SHRINK_DESTROY : SHRINK_BUSY_STOP;
 	last_transaction = transaction->t_cpprev;
 	next_transaction = transaction;
 	do {
 		transaction = next_transaction;
 		next_transaction = transaction->t_cpnext;
-		ret = journal_clean_one_cp_list(transaction->t_checkpoint_list,
-						destroy);
+		journal_shrink_one_cp_list(transaction->t_checkpoint_list,
+					   type, &released);
 		/*
 		 * This function only frees up some memory if possible so we
 		 * dont have an obligation to finish processing. Bail out if
@@ -545,7 +518,7 @@ void __jbd2_journal_clean_checkpoint_list(journal_t *journal, bool destroy)
 		 * avoids pointless scanning of transactions which still
 		 * weren't checkpointed.
 		 */
-		if (!ret)
+		if (!released)
 			return;
 	} while (transaction != last_transaction);
 }
@@ -655,6 +628,34 @@ int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
 	return 1;
 }
 
+/*
+ * Check the checkpoint buffer and try to remove it from the checkpoint
+ * list if it's clean. Returns -EBUSY if it is not clean, returns 1 if
+ * it frees the transaction, 0 otherwise.
+ *
+ * This function is called with j_list_lock held.
+ */
+int jbd2_journal_try_remove_checkpoint(struct journal_head *jh)
+{
+	struct buffer_head *bh = jh2bh(jh);
+
+	if (!trylock_buffer(bh))
+		return -EBUSY;
+	if (buffer_dirty(bh)) {
+		unlock_buffer(bh);
+		return -EBUSY;
+	}
+	unlock_buffer(bh);
+
+	/*
+	 * Buffer is clean and the IO has finished (we held the buffer
+	 * lock) so the checkpoint is done. We can safely remove the
+	 * buffer from this transaction.
+	 */
+	JBUFFER_TRACE(jh, "remove from checkpoint list");
+	return __jbd2_journal_remove_checkpoint(jh);
+}
+
 /*
  * journal_insert_checkpoint: put a committed buffer onto a checkpoint
  * list so that we know when it is safe to clean the transaction out of

fs/jbd2/transaction.c

@@ -1758,8 +1758,7 @@ int jbd2_journal_forget(handle_t *handle, struct buffer_head *bh)
 		 * Otherwise, if the buffer has been written to disk,
 		 * it is safe to remove the checkpoint and drop it.
 		 */
-		if (!buffer_dirty(bh)) {
-			__jbd2_journal_remove_checkpoint(jh);
+		if (jbd2_journal_try_remove_checkpoint(jh) >= 0) {
 			spin_unlock(&journal->j_list_lock);
 			goto drop;
 		}
@@ -2074,35 +2073,6 @@ void jbd2_journal_unfile_buffer(journal_t *journal, struct journal_head *jh)
 	__brelse(bh);
 }
 
-/*
- * Called from jbd2_journal_try_to_free_buffers().
- *
- * Called under jh->b_state_lock
- */
-static void
-__journal_try_to_free_buffer(journal_t *journal, struct buffer_head *bh)
-{
-	struct journal_head *jh;
-
-	jh = bh2jh(bh);
-
-	if (buffer_locked(bh) || buffer_dirty(bh))
-		goto out;
-
-	if (jh->b_next_transaction != NULL || jh->b_transaction != NULL)
-		goto out;
-
-	spin_lock(&journal->j_list_lock);
-	if (jh->b_cp_transaction != NULL) {
-		/* written-back checkpointed metadata buffer */
-		JBUFFER_TRACE(jh, "remove from checkpoint list");
-		__jbd2_journal_remove_checkpoint(jh);
-	}
-	spin_unlock(&journal->j_list_lock);
-out:
-	return;
-}
-
 /**
  * jbd2_journal_try_to_free_buffers() - try to free page buffers.
  * @journal: journal for operation
@@ -2160,7 +2130,13 @@ int jbd2_journal_try_to_free_buffers(journal_t *journal, struct page *page)
 			continue;
 
 		spin_lock(&jh->b_state_lock);
-		__journal_try_to_free_buffer(journal, bh);
+		if (!jh->b_transaction && !jh->b_next_transaction) {
+			spin_lock(&journal->j_list_lock);
+			/* Remove written-back checkpointed metadata buffer */
+			if (jh->b_cp_transaction != NULL)
+				jbd2_journal_try_remove_checkpoint(jh);
+			spin_unlock(&journal->j_list_lock);
+		}
 		spin_unlock(&jh->b_state_lock);
 		jbd2_journal_put_journal_head(jh);
 		if (buffer_jbd(bh))

include/linux/jbd2.h

@@ -1439,6 +1439,7 @@ extern void jbd2_journal_commit_transaction(journal_t *);
 void __jbd2_journal_clean_checkpoint_list(journal_t *journal, bool destroy);
 unsigned long jbd2_journal_shrink_checkpoint_list(journal_t *journal, unsigned long *nr_to_scan);
 int __jbd2_journal_remove_checkpoint(struct journal_head *);
+int jbd2_journal_try_remove_checkpoint(struct journal_head *jh);
 void jbd2_journal_destroy_checkpoint(journal_t *journal);
 void __jbd2_journal_insert_checkpoint(struct journal_head *, transaction_t *);
 

include/trace/events/jbd2.h

@@ -462,11 +462,9 @@ TRACE_EVENT(jbd2_shrink_scan_exit,
 TRACE_EVENT(jbd2_shrink_checkpoint_list,
 
 	TP_PROTO(journal_t *journal, tid_t first_tid, tid_t tid, tid_t last_tid,
-		 unsigned long nr_freed, unsigned long nr_scanned,
-		 tid_t next_tid),
+		 unsigned long nr_freed, tid_t next_tid),
 
-	TP_ARGS(journal, first_tid, tid, last_tid, nr_freed,
-		nr_scanned, next_tid),
+	TP_ARGS(journal, first_tid, tid, last_tid, nr_freed, next_tid),
 
 	TP_STRUCT__entry(
 		__field(dev_t, dev)
@@ -474,7 +472,6 @@ TRACE_EVENT(jbd2_shrink_checkpoint_list,
 		__field(tid_t, tid)
 		__field(tid_t, last_tid)
 		__field(unsigned long, nr_freed)
-		__field(unsigned long, nr_scanned)
 		__field(tid_t, next_tid)
 	),
 
@@ -484,15 +481,14 @@ TRACE_EVENT(jbd2_shrink_checkpoint_list,
 		__entry->tid		= tid;
 		__entry->last_tid	= last_tid;
 		__entry->nr_freed	= nr_freed;
-		__entry->nr_scanned	= nr_scanned;
 		__entry->next_tid	= next_tid;
 	),
 
 	TP_printk("dev %d,%d shrink transaction %u-%u(%u) freed %lu "
-		  "scanned %lu next transaction %u",
+		  "next transaction %u",
 		  MAJOR(__entry->dev), MINOR(__entry->dev),
 		  __entry->first_tid, __entry->tid, __entry->last_tid,
-		  __entry->nr_freed, __entry->nr_scanned, __entry->next_tid)
+		  __entry->nr_freed, __entry->next_tid)
 );
 
 #endif /* _TRACE_JBD2_H */