[1/1] Updated locking documentation for struct journal_t
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Message ID 20190308150605.98405-1-alexander.lochmann@tu-dortmund.de
State New
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  • [1/1] Updated locking documentation for struct journal_t
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Commit Message

Alexander Lochmann March 8, 2019, 3:06 p.m. UTC
We used LockDoc to derive locking rules for each member
of struct journal_t. Based on those results, we extended
the existing documentation by more members
of struct inode, and updated the existing documentation.

Signed-off-by: Alexander Lochmann <alexander.lochmann@tu-dortmund.de>
Signed-off-by: Horst Schirmeier <horst.schirmeier@tu-dortmund.de>
---
 include/linux/jbd2.h | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

Comments

Jan Kara March 11, 2019, 4:15 p.m. UTC | #1
On Fri 08-03-19 16:06:05, Alexander Lochmann wrote:
> We used LockDoc to derive locking rules for each member
> of struct journal_t. Based on those results, we extended
> the existing documentation by more members
> of struct inode, and updated the existing documentation.
> 
> Signed-off-by: Alexander Lochmann <alexander.lochmann@tu-dortmund.de>
> Signed-off-by: Horst Schirmeier <horst.schirmeier@tu-dortmund.de>
> ---
>  include/linux/jbd2.h | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)

Thanks for the patch! Some comments below.

> diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
> index 0f919d5fe84f..c1ba44ca515a 100644
> --- a/include/linux/jbd2.h
> +++ b/include/linux/jbd2.h
> @@ -585,7 +585,8 @@ struct transaction_s
>  	}			t_state;
>  
>  	/*
> -	 * Where in the log does this transaction's commit start? [no locking]
> +	 * Where in the log does this transaction's commit start?
> +	 * [journal_t->j_state_lock]
>  	 */
>  	unsigned long		t_log_start;
>  
> @@ -647,17 +648,17 @@ struct transaction_s
>  	unsigned long		t_max_wait;
>  
>  	/*
> -	 * When transaction started
> +	 * When transaction started [j_state_lock]
>  	 */
>  	unsigned long		t_start;
>  
>  	/*
> -	 * When commit was requested
> +	 * When commit was requested [j_state_lock]
>  	 */
>  	unsigned long		t_requested;
>  
>  	/*
> -	 * Checkpointing stats [j_checkpoint_sem]
> +	 * Checkpointing stats [j_list_lock]
>  	 */
>  	struct transaction_chp_stats_s t_chp_stats;
>  

These look correct to me.

> @@ -762,6 +764,7 @@ struct journal_s
>  
>  	/**
>  	 * @j_sb_buffer: The first part of the superblock buffer.
> +	 * [j_checkpoint_mutex]
>  	 */
>  	struct buffer_head	*j_sb_buffer;

This isn't true. j_sb_buffer is just initialized in journal_init_common()
and never changed. So there's no lock protecting it.


> @@ -1015,6 +1018,7 @@ struct journal_s
>  	 * @j_commit_interval:
>  	 *
>  	 * What is the maximum transaction lifetime before we begin a commit?
> +	 * [super_block->s_umount]
>  	 */
>  	unsigned long		j_commit_interval;

Ditto here.

> @@ -1032,7 +1036,7 @@ struct journal_s
>  	 * @j_revoke:
>  	 *
>  	 * The revoke table - maintains the list of revoked blocks in the
> -	 * current transaction.
> +	 * current transaction. [j_state_lock]
>  	 */
>  	struct jbd2_revoke_table_s *j_revoke;
>  

This is also not true. The contents of the revoke table itself is protected
by j_revoke_lock. The pointer to current revoke table (i.e. j_revoke
itself) is changed only when the currently running transation is in
T_SWITCH state - a special state where no updates can be happening anymore
and new transaction cannot be running yet either.

								Honza

Patch
diff mbox series

diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 0f919d5fe84f..c1ba44ca515a 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -585,7 +585,8 @@  struct transaction_s
 	}			t_state;
 
 	/*
-	 * Where in the log does this transaction's commit start? [no locking]
+	 * Where in the log does this transaction's commit start?
+	 * [journal_t->j_state_lock]
 	 */
 	unsigned long		t_log_start;
 
@@ -647,17 +648,17 @@  struct transaction_s
 	unsigned long		t_max_wait;
 
 	/*
-	 * When transaction started
+	 * When transaction started [j_state_lock]
 	 */
 	unsigned long		t_start;
 
 	/*
-	 * When commit was requested
+	 * When commit was requested [j_state_lock]
 	 */
 	unsigned long		t_requested;
 
 	/*
-	 * Checkpointing stats [j_checkpoint_sem]
+	 * Checkpointing stats [j_list_lock]
 	 */
 	struct transaction_chp_stats_s t_chp_stats;
 
@@ -744,6 +745,7 @@  jbd2_time_diff(unsigned long start, unsigned long end)
 /**
  * struct journal_s - The journal_s type is the concrete type associated with
  *     journal_t.
+ * (Locking Documentation improved by LockDoc)
  */
 struct journal_s
 {
@@ -762,6 +764,7 @@  struct journal_s
 
 	/**
 	 * @j_sb_buffer: The first part of the superblock buffer.
+	 * [j_checkpoint_mutex]
 	 */
 	struct buffer_head	*j_sb_buffer;
 
@@ -1015,6 +1018,7 @@  struct journal_s
 	 * @j_commit_interval:
 	 *
 	 * What is the maximum transaction lifetime before we begin a commit?
+	 * [super_block->s_umount]
 	 */
 	unsigned long		j_commit_interval;
 
@@ -1032,7 +1036,7 @@  struct journal_s
 	 * @j_revoke:
 	 *
 	 * The revoke table - maintains the list of revoked blocks in the
-	 * current transaction.
+	 * current transaction. [j_state_lock]
 	 */
 	struct jbd2_revoke_table_s *j_revoke;