jbd2: split updating of journal superblock and marking journal empty

There are three case of updating journal superblock. In the first case, we want
to mark journal as empty (setting s_sequence to 0), in the second case we want
to update log tail, in the third case we want to update s_errno. Split these
cases into separate functions. It makes the code slightly more straightforward
and later patches will make the distinction even more important.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
index 253e918..19dcd0b 100644 (file)
--- a/fs/jbd2/checkpoint.c
+++ b/fs/jbd2/checkpoint.c
@@ -550,7 +550,7 @@ int jbd2_cleanup_journal_tail(journal_t *journal)
            (journal->j_flags & JBD2_BARRIER))
                blkdev_issue_flush(journal->j_fs_dev, GFP_KERNEL, NULL);
        if (!(journal->j_flags & JBD2_ABORT))
-               jbd2_journal_update_superblock(journal, 1);
+               jbd2_journal_update_sb_log_tail(journal);
        return 0;
 }
 

diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index 8adc5d4..19371a8 100644 (file)
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -340,7 +340,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
        /* Do we need to erase the effects of a prior jbd2_journal_flush? */
        if (journal->j_flags & JBD2_FLUSHED) {
                jbd_debug(3, "super block updated\n");
-               jbd2_journal_update_superblock(journal, 1);
+               jbd2_journal_update_sb_log_tail(journal);
        } else {
                jbd_debug(3, "superblock not updated\n");
        }

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index cfb36d9..6e75fbd 100644 (file)
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -1110,40 +1110,30 @@ static int journal_reset(journal_t *journal)
 
        journal->j_max_transaction_buffers = journal->j_maxlen / 4;
 
-       /* Add the dynamic fields and write it to disk. */
-       jbd2_journal_update_superblock(journal, 1);
-       return jbd2_journal_start_thread(journal);
-}
-
-/**
- * void jbd2_journal_update_superblock() - Update journal sb on disk.
- * @journal: The journal to update.
- * @wait: Set to '0' if you don't want to wait for IO completion.
- *
- * Update a journal's dynamic superblock fields and write it to disk,
- * optionally waiting for the IO to complete.
- */
-void jbd2_journal_update_superblock(journal_t *journal, int wait)
-{
-       journal_superblock_t *sb = journal->j_superblock;
-       struct buffer_head *bh = journal->j_sb_buffer;
-
        /*
         * As a special case, if the on-disk copy is already marked as needing
-        * no recovery (s_start == 0) and there are no outstanding transactions
-        * in the filesystem, then we can safely defer the superblock update
-        * until the next commit by setting JBD2_FLUSHED.  This avoids
+        * no recovery (s_start == 0), then we can safely defer the superblock
+        * update until the next commit by setting JBD2_FLUSHED.  This avoids
         * attempting a write to a potential-readonly device.
         */
-       if (sb->s_start == 0 && journal->j_tail_sequence ==
-                               journal->j_transaction_sequence) {
+       if (sb->s_start == 0) {
                jbd_debug(1, "JBD2: Skipping superblock update on recovered sb "
                        "(start %ld, seq %d, errno %d)\n",
                        journal->j_tail, journal->j_tail_sequence,
                        journal->j_errno);
-               goto out;
+               journal->j_flags |= JBD2_FLUSHED;
+       } else {
+               /* Add the dynamic fields and write it to disk. */
+               jbd2_journal_update_sb_log_tail(journal);
        }
+       return jbd2_journal_start_thread(journal);
+}
 
+static void jbd2_write_superblock(journal_t *journal)
+{
+       struct buffer_head *bh = journal->j_sb_buffer;
+
+       trace_jbd2_write_superblock(journal);
        if (buffer_write_io_error(bh)) {
                /*
                 * Oh, dear.  A previous attempt to write the journal
@@ -1160,49 +1150,98 @@ void jbd2_journal_update_superblock(journal_t *journal, int wait)
                set_buffer_uptodate(bh);
        }
 
+       BUFFER_TRACE(bh, "marking dirty");
+       mark_buffer_dirty(bh);
+       sync_dirty_buffer(bh);
+       if (buffer_write_io_error(bh)) {
+               printk(KERN_ERR "JBD2: I/O error detected "
+                      "when updating journal superblock for %s.\n",
+                      journal->j_devname);
+               clear_buffer_write_io_error(bh);
+               set_buffer_uptodate(bh);
+       }
+}
+
+/**
+ * jbd2_journal_update_sb_log_tail() - Update log tail in journal sb on disk.
+ * @journal: The journal to update.
+ *
+ * Update a journal's superblock information about log tail and write it to
+ * disk, waiting for the IO to complete.
+ */
+void jbd2_journal_update_sb_log_tail(journal_t *journal)
+{
+       journal_superblock_t *sb = journal->j_superblock;
+
        read_lock(&journal->j_state_lock);
-       jbd_debug(1, "JBD2: updating superblock (start %ld, seq %d, errno %d)\n",
-                 journal->j_tail, journal->j_tail_sequence, journal->j_errno);
+       jbd_debug(1, "JBD2: updating superblock (start %ld, seq %d)\n",
+                 journal->j_tail, journal->j_tail_sequence);
 
        sb->s_sequence = cpu_to_be32(journal->j_tail_sequence);
        sb->s_start    = cpu_to_be32(journal->j_tail);
-       sb->s_errno    = cpu_to_be32(journal->j_errno);
        read_unlock(&journal->j_state_lock);
 
-       BUFFER_TRACE(bh, "marking dirty");
-       mark_buffer_dirty(bh);
-       if (wait) {
-               sync_dirty_buffer(bh);
-               if (buffer_write_io_error(bh)) {
-                       printk(KERN_ERR "JBD2: I/O error detected "
-                              "when updating journal superblock for %s.\n",
-                              journal->j_devname);
-                       clear_buffer_write_io_error(bh);
-                       set_buffer_uptodate(bh);
-               }
-       } else
-               write_dirty_buffer(bh, WRITE);
+       jbd2_write_superblock(journal);
 
-       trace_jbd2_update_superblock_end(journal, wait);
+       /* Log is no longer empty */
+       write_lock(&journal->j_state_lock);
+       WARN_ON(!sb->s_sequence);
+       journal->j_flags &= ~JBD2_FLUSHED;
+       write_unlock(&journal->j_state_lock);
+}
 
-out:
-       /* If we have just flushed the log (by marking s_start==0), then
-        * any future commit will have to be careful to update the
-        * superblock again to re-record the true start of the log. */
+/**
+ * jbd2_mark_journal_empty() - Mark on disk journal as empty.
+ * @journal: The journal to update.
+ *
+ * Update a journal's dynamic superblock fields to show that journal is empty.
+ * Write updated superblock to disk waiting for IO to complete.
+ */
+static void jbd2_mark_journal_empty(journal_t *journal)
+{
+       journal_superblock_t *sb = journal->j_superblock;
+
+       read_lock(&journal->j_state_lock);
+       jbd_debug(1, "JBD2: Marking journal as empty (seq %d)\n",
+                 journal->j_tail_sequence);
+
+       sb->s_sequence = cpu_to_be32(journal->j_tail_sequence);
+       sb->s_start    = cpu_to_be32(0);
+       read_unlock(&journal->j_state_lock);
+
+       jbd2_write_superblock(journal);
 
+       /* Log is no longer empty */
        write_lock(&journal->j_state_lock);
-       if (sb->s_start)
-               journal->j_flags &= ~JBD2_FLUSHED;
-       else
-               journal->j_flags |= JBD2_FLUSHED;
+       journal->j_flags |= JBD2_FLUSHED;
        write_unlock(&journal->j_state_lock);
 }
 
+
+/**
+ * jbd2_journal_update_sb_errno() - Update error in the journal.
+ * @journal: The journal to update.
+ *
+ * Update a journal's errno.  Write updated superblock to disk waiting for IO
+ * to complete.
+ */
+static void jbd2_journal_update_sb_errno(journal_t *journal)
+{
+       journal_superblock_t *sb = journal->j_superblock;
+
+       read_lock(&journal->j_state_lock);
+       jbd_debug(1, "JBD2: updating superblock error (errno %d)\n",
+                 journal->j_errno);
+       sb->s_errno    = cpu_to_be32(journal->j_errno);
+       read_unlock(&journal->j_state_lock);
+
+       jbd2_write_superblock(journal);
+}
+
 /*
  * Read the superblock for a given journal, performing initial
  * validation of the format.
  */
-
 static int journal_get_superblock(journal_t *journal)
 {
        struct buffer_head *bh;
@@ -1395,15 +1434,10 @@ int jbd2_journal_destroy(journal_t *journal)
        spin_unlock(&journal->j_list_lock);
 
        if (journal->j_sb_buffer) {
-               if (!is_journal_aborted(journal)) {
-                       /* We can now mark the journal as empty. */
-                       journal->j_tail = 0;
-                       journal->j_tail_sequence =
-                               ++journal->j_transaction_sequence;
-                       jbd2_journal_update_superblock(journal, 1);
-               } else {
+               if (!is_journal_aborted(journal))
+                       jbd2_mark_journal_empty(journal);
+               else
                        err = -EIO;
-               }
                brelse(journal->j_sb_buffer);
        }
 
@@ -1562,7 +1596,6 @@ int jbd2_journal_flush(journal_t *journal)
 {
        int err = 0;
        transaction_t *transaction = NULL;
-       unsigned long old_tail;
 
        write_lock(&journal->j_state_lock);
 
@@ -1604,14 +1637,8 @@ int jbd2_journal_flush(journal_t *journal)
         * the magic code for a fully-recovered superblock.  Any future
         * commits of data to the journal will restore the current
         * s_start value. */
+       jbd2_mark_journal_empty(journal);
        write_lock(&journal->j_state_lock);
-       old_tail = journal->j_tail;
-       journal->j_tail = 0;
-       write_unlock(&journal->j_state_lock);
-       jbd2_journal_update_superblock(journal, 1);
-       write_lock(&journal->j_state_lock);
-       journal->j_tail = old_tail;
-
        J_ASSERT(!journal->j_running_transaction);
        J_ASSERT(!journal->j_committing_transaction);
        J_ASSERT(!journal->j_checkpoint_transactions);
@@ -1652,7 +1679,7 @@ int jbd2_journal_wipe(journal_t *journal, int write)
 
        err = jbd2_journal_skip_recovery(journal);
        if (write)
-               jbd2_journal_update_superblock(journal, 1);
+               jbd2_mark_journal_empty(journal);
 
  no_recovery:
        return err;
@@ -1702,7 +1729,7 @@ static void __journal_abort_soft (journal_t *journal, int errno)
        __jbd2_journal_abort_hard(journal);
 
        if (errno)
-               jbd2_journal_update_superblock(journal, 1);
+               jbd2_journal_update_sb_errno(journal);
 }
 
 /**

diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 46eef77..5f05c77 100644 (file)
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -1087,7 +1087,7 @@ extern int           jbd2_journal_destroy    (journal_t *);
 extern int        jbd2_journal_recover    (journal_t *journal);
 extern int        jbd2_journal_wipe       (journal_t *, int);
 extern int        jbd2_journal_skip_recovery   (journal_t *);
-extern void       jbd2_journal_update_superblock       (journal_t *, int);
+extern void       jbd2_journal_update_sb_log_tail      (journal_t *);
 extern void       __jbd2_journal_abort_hard    (journal_t *);
 extern void       jbd2_journal_abort      (journal_t *, int);
 extern int        jbd2_journal_errno      (journal_t *);

diff --git a/include/trace/events/jbd2.h b/include/trace/events/jbd2.h
index ae59bc2..e05a362 100644 (file)
--- a/include/trace/events/jbd2.h
+++ b/include/trace/events/jbd2.h
@@ -236,25 +236,21 @@ TRACE_EVENT(jbd2_cleanup_journal_tail,
                  __entry->block_nr, __entry->freed)
 );
 
-TRACE_EVENT(jbd2_update_superblock_end,
+TRACE_EVENT(jbd2_write_superblock,
 
-       TP_PROTO(journal_t *journal, int wait),
+       TP_PROTO(journal_t *journal),
 
-       TP_ARGS(journal, wait),
+       TP_ARGS(journal),
 
        TP_STRUCT__entry(
                __field(        dev_t,  dev                     )
-               __field(        int,    wait                    )
        ),
 
        TP_fast_assign(
                __entry->dev            = journal->j_fs_dev->bd_dev;
-               __entry->wait           = wait;
        ),
 
-       TP_printk("dev %d,%d wait %d",
-                 MAJOR(__entry->dev), MINOR(__entry->dev),
-                 __entry->wait)
+       TP_printk("dev %d,%d", MAJOR(__entry->dev), MINOR(__entry->dev))
 );
 
 #endif /* _TRACE_JBD2_H */