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, 33 insertions, 10 deletions

diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 1dd2703a8e26..2a3d5f50e7a1 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -478,6 +478,7 @@ struct jbd2_revoke_table_s;
  * @h_journal: Which journal handle belongs to - used iff h_reserved set.
  * @h_rsv_handle: Handle reserved for finishing the logical operation.
  * @h_buffer_credits: Number of remaining buffers we are allowed to dirty.
+ * @h_revoke_credits: Number of remaining revoke records available for handle
  * @h_ref: Reference count on this handle.
  * @h_err: Field for caller's use to track errors through large fs operations.
  * @h_sync: Flag for sync-on-close.
@@ -488,6 +489,7 @@ struct jbd2_revoke_table_s;
  * @h_line_no: For handle statistics.
  * @h_start_jiffies: Handle Start time.
  * @h_requested_credits: Holds @h_buffer_credits after handle is started.
+ * @h_revoke_credits_requested: Holds @h_revoke_credits after handle is started.
  * @saved_alloc_context: Saved context while transaction is open.
  **/
 
@@ -505,6 +507,8 @@ struct jbd2_journal_handle
 
 	handle_t		*h_rsv_handle;
 	int			h_buffer_credits;
+	int			h_revoke_credits;
+	int			h_revoke_credits_requested;
 	int			h_ref;
 	int			h_err;
 
@@ -689,6 +693,17 @@ struct transaction_s
 	atomic_t		t_outstanding_credits;
 
 	/*
+	 * Number of revoke records for this transaction added by already
+	 * stopped handles. [none]
+	 */
+	atomic_t		t_outstanding_revokes;
+
+	/*
+	 * How many handles used this transaction? [none]
+	 */
+	atomic_t		t_handle_count;
+
+	/*
 	 * Forward and backward links for the circular list of all transactions
 	 * awaiting checkpoint. [j_list_lock]
 	 */
@@ -706,11 +721,6 @@ struct transaction_s
 	ktime_t			t_start_time;
 
 	/*
-	 * How many handles used this transaction? [none]
-	 */
-	atomic_t		t_handle_count;
-
-	/*
 	 * This transaction is being forced and some process is
 	 * waiting for it to finish.
 	 */
@@ -1027,6 +1037,13 @@ struct journal_s
 	int			j_max_transaction_buffers;
 
 	/**
+	 * @j_revoke_records_per_block:
+	 *
+	 * Number of revoke records that fit in one descriptor block.
+	 */
+	int			j_revoke_records_per_block;
+
+	/**
 	 * @j_commit_interval:
 	 *
 	 * What is the maximum transaction lifetime before we begin a commit?
@@ -1360,14 +1377,16 @@ static inline handle_t *journal_current_handle(void)
 
 extern handle_t *jbd2_journal_start(journal_t *, int nblocks);
 extern handle_t *jbd2__journal_start(journal_t *, int blocks, 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);
 extern int	 jbd2_journal_restart(handle_t *, int nblocks);
-extern int	 jbd2__journal_restart(handle_t *, int nblocks, gfp_t gfp_mask);
+extern int	 jbd2__journal_restart(handle_t *, int nblocks,
+				       int revoke_records, gfp_t gfp_mask);
 extern int	 jbd2_journal_start_reserved(handle_t *handle,
 				unsigned int type, unsigned int line_no);
 extern void	 jbd2_journal_free_reserved(handle_t *handle);
-extern int	 jbd2_journal_extend (handle_t *, int nblocks);
+extern int	 jbd2_journal_extend(handle_t *handle, int nblocks,
+				     int revoke_records);
 extern int	 jbd2_journal_get_write_access(handle_t *, struct buffer_head *);
 extern int	 jbd2_journal_get_create_access (handle_t *, struct buffer_head *);
 extern int	 jbd2_journal_get_undo_access(handle_t *, struct buffer_head *);
@@ -1631,7 +1650,11 @@ static inline tid_t  jbd2_get_latest_transaction(journal_t *journal)
 
 static inline int jbd2_handle_buffer_credits(handle_t *handle)
 {
-	return handle->h_buffer_credits;
+	journal_t *journal = handle->h_transaction->t_journal;
+
+	return handle->h_buffer_credits -
+		DIV_ROUND_UP(handle->h_revoke_credits_requested,
+			     journal->j_revoke_records_per_block);
 }
 
 #ifdef __KERNEL__