jbd2: Reserve space for revoke descriptor blocks

Extend functions for starting, extending, and restarting transaction
handles to take number of revoke records handle must be able to
accommodate. These functions then make sure transaction has enough
credits to be able to store resulting revoke descriptor blocks. Also
revoke code tracks number of revoke records created by a handle to catch
situation where some place didn't reserve enough space for revoke
records. Similarly to standard transaction credits, space for unused
reserved revoke records is released when the handle is stopped.

On the ext4 side we currently take a simplistic approach of reserving
space for 1024 revoke records for any transaction. This grows amount of
credits reserved for each handle only by a few and is enough for any
normal workload so that we don't hit warnings in jbd2. We will refine
the logic in following commits.

Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20191105164437.32602-20-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 47 insertions, 7 deletions

diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index ba388da7e02b..1c121afbcf8f 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -101,6 +101,7 @@ static void jbd2_get_transaction(journal_t *journal,
 	atomic_set(&transaction->t_outstanding_credits,
 		   jbd2_descriptor_blocks_per_trans(journal) +
 		   atomic_read(&journal->j_reserved_credits));
+	atomic_set(&transaction->t_outstanding_revokes, 0);
 	atomic_set(&transaction->t_handle_count, 0);
 	INIT_LIST_HEAD(&transaction->t_inode_list);
 	INIT_LIST_HEAD(&transaction->t_private_list);
@@ -418,6 +419,7 @@ repeat:
 	update_t_max_wait(transaction, ts);
 	handle->h_transaction = transaction;
 	handle->h_requested_credits = blocks;
+	handle->h_revoke_credits_requested = handle->h_revoke_credits;
 	handle->h_start_jiffies = jiffies;
 	atomic_inc(&transaction->t_updates);
 	atomic_inc(&transaction->t_handle_count);
@@ -451,8 +453,8 @@ static handle_t *new_handle(int nblocks)
 }
 
 handle_t *jbd2__journal_start(journal_t *journal, int nblocks, int rsv_blocks,
-			      gfp_t gfp_mask, unsigned int type,
-			      unsigned int line_no)
+			      int revoke_records, gfp_t gfp_mask,
+			      unsigned int type, unsigned int line_no)
 {
 	handle_t *handle = journal_current_handle();
 	int err;
@@ -466,6 +468,8 @@ handle_t *jbd2__journal_start(journal_t *journal, int nblocks, int rsv_blocks,
 		return handle;
 	}
 
+	nblocks += DIV_ROUND_UP(revoke_records,
+				journal->j_revoke_records_per_block);
 	handle = new_handle(nblocks);
 	if (!handle)
 		return ERR_PTR(-ENOMEM);
@@ -481,6 +485,7 @@ handle_t *jbd2__journal_start(journal_t *journal, int nblocks, int rsv_blocks,
 		rsv_handle->h_journal = journal;
 		handle->h_rsv_handle = rsv_handle;
 	}
+	handle->h_revoke_credits = revoke_records;
 
 	err = start_this_handle(journal, handle, gfp_mask);
 	if (err < 0) {
@@ -521,7 +526,7 @@ EXPORT_SYMBOL(jbd2__journal_start);
  */
 handle_t *jbd2_journal_start(journal_t *journal, int nblocks)
 {
-	return jbd2__journal_start(journal, nblocks, 0, GFP_NOFS, 0, 0);
+	return jbd2__journal_start(journal, nblocks, 0, 0, GFP_NOFS, 0, 0);
 }
 EXPORT_SYMBOL(jbd2_journal_start);
 
@@ -598,6 +603,7 @@ EXPORT_SYMBOL(jbd2_journal_start_reserved);
  * int jbd2_journal_extend() - extend buffer credits.
  * @handle:  handle to 'extend'
  * @nblocks: nr blocks to try to extend by.
+ * @revoke_records: number of revoke records to try to extend by.
  *
  * Some transactions, such as large extends and truncates, can be done
  * atomically all at once or in several stages.  The operation requests
@@ -614,7 +620,7 @@ EXPORT_SYMBOL(jbd2_journal_start_reserved);
  * return code < 0 implies an error
  * return code > 0 implies normal transaction-full status.
  */
-int jbd2_journal_extend(handle_t *handle, int nblocks)
+int jbd2_journal_extend(handle_t *handle, int nblocks, int revoke_records)
 {
 	transaction_t *transaction = handle->h_transaction;
 	journal_t *journal;
@@ -636,6 +642,12 @@ int jbd2_journal_extend(handle_t *handle, int nblocks)
 		goto error_out;
 	}
 
+	nblocks += DIV_ROUND_UP(
+			handle->h_revoke_credits_requested + revoke_records,
+			journal->j_revoke_records_per_block) -
+		DIV_ROUND_UP(
+			handle->h_revoke_credits_requested,
+			journal->j_revoke_records_per_block);
 	spin_lock(&transaction->t_handle_lock);
 	wanted = atomic_add_return(nblocks,
 				   &transaction->t_outstanding_credits);
@@ -655,6 +667,8 @@ int jbd2_journal_extend(handle_t *handle, int nblocks)
 
 	handle->h_buffer_credits += nblocks;
 	handle->h_requested_credits += nblocks;
+	handle->h_revoke_credits += revoke_records;
+	handle->h_revoke_credits_requested += revoke_records;
 	result = 0;
 
 	jbd_debug(3, "extended handle %p by %d\n", handle, nblocks);
@@ -669,10 +683,31 @@ static void stop_this_handle(handle_t *handle)
 {
 	transaction_t *transaction = handle->h_transaction;
 	journal_t *journal = transaction->t_journal;
+	int revokes;
 
 	J_ASSERT(journal_current_handle() == handle);
 	J_ASSERT(atomic_read(&transaction->t_updates) > 0);
 	current->journal_info = NULL;
+	/*
+	 * Subtract necessary revoke descriptor blocks from handle credits. We
+	 * take care to account only for revoke descriptor blocks the
+	 * transaction will really need as large sequences of transactions with
+	 * small numbers of revokes are relatively common.
+	 */
+	revokes = handle->h_revoke_credits_requested - handle->h_revoke_credits;
+	if (revokes) {
+		int t_revokes, revoke_descriptors;
+		int rr_per_blk = journal->j_revoke_records_per_block;
+
+		WARN_ON_ONCE(DIV_ROUND_UP(revokes, rr_per_blk)
+				> handle->h_buffer_credits);
+		t_revokes = atomic_add_return(revokes,
+				&transaction->t_outstanding_revokes);
+		revoke_descriptors =
+			DIV_ROUND_UP(t_revokes, rr_per_blk) -
+			DIV_ROUND_UP(t_revokes - revokes, rr_per_blk);
+		handle->h_buffer_credits -= revoke_descriptors;
+	}
 	atomic_sub(handle->h_buffer_credits,
 		   &transaction->t_outstanding_credits);
 	if (handle->h_rsv_handle)
@@ -692,6 +727,7 @@ static void stop_this_handle(handle_t *handle)
  * int jbd2_journal_restart() - restart a handle .
  * @handle:  handle to restart
  * @nblocks: nr credits requested
+ * @revoke_records: number of revoke record credits requested
  * @gfp_mask: memory allocation flags (for start_this_handle)
  *
  * Restart a handle for a multi-transaction filesystem
@@ -704,7 +740,8 @@ static void stop_this_handle(handle_t *handle)
  * credits. We preserve reserved handle if there's any attached to the
  * passed in handle.
  */
-int jbd2__journal_restart(handle_t *handle, int nblocks, gfp_t gfp_mask)
+int jbd2__journal_restart(handle_t *handle, int nblocks, int revoke_records,
+			  gfp_t gfp_mask)
 {
 	transaction_t *transaction = handle->h_transaction;
 	journal_t *journal;
@@ -735,7 +772,10 @@ int jbd2__journal_restart(handle_t *handle, int nblocks, gfp_t gfp_mask)
 	read_unlock(&journal->j_state_lock);
 	if (need_to_start)
 		jbd2_log_start_commit(journal, tid);
-	handle->h_buffer_credits = nblocks;
+	handle->h_buffer_credits = nblocks +
+		DIV_ROUND_UP(revoke_records,
+			     journal->j_revoke_records_per_block);
+	handle->h_revoke_credits = revoke_records;
 	return start_this_handle(journal, handle, gfp_mask);
 }
 EXPORT_SYMBOL(jbd2__journal_restart);
@@ -743,7 +783,7 @@ EXPORT_SYMBOL(jbd2__journal_restart);
 
 int jbd2_journal_restart(handle_t *handle, int nblocks)
 {
-	return jbd2__journal_restart(handle, nblocks, GFP_NOFS);
+	return jbd2__journal_restart(handle, nblocks, 0, GFP_NOFS);
 }
 EXPORT_SYMBOL(jbd2_journal_restart);