linux-kernel - [patch V2 5/7] fs/jbd2: Simplify journal_unmap

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Date:   Thu, 01 Aug 2019 03:01:31 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Sebastian Siewior <bigeasy@...utronix.de>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Julia Cartwright <julia@...com>, linux-ext4@...r.kernel.org,
        "Theodore Tso" <tytso@....edu>, Jan Kara <jack@...e.com>,
        Jan Kara <jack@...e.cz>, Matthew Wilcox <willy@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org, Mark Fasheh <mark@...heh.com>,
        Joseph Qi <joseph.qi@...ux.alibaba.com>,
        Joel Becker <jlbec@...lplan.org>
Subject: [patch V2 5/7] fs/jbd2: Simplify journal_unmap_buffer()

journal_unmap_buffer() checks first whether the buffer head is a journal.
If so it takes locks and then invokes jbd2_journal_grab_journal_head()
followed by another check whether this is journal head buffer.

The double checking is pointless.

Replace the initial check with jbd2_journal_grab_journal_head() which
alredy checks whether the buffer head is actually a journal.

Allows also early access to the journal head pointer for the upcoming
conversion of state lock to a regular spinlock.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-ext4@...r.kernel.org
Cc: "Theodore Ts'o" <tytso@....edu>
Cc: Jan Kara <jack@...e.com>
---
V2: New patch
---
 fs/jbd2/transaction.c |    8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -2196,7 +2196,8 @@ static int journal_unmap_buffer(journal_
 	 * holding the page lock. --sct
 	 */
 
-	if (!buffer_jbd(bh))
+	jh = jbd2_journal_grab_journal_head(bh);
+	if (!jh)
 		goto zap_buffer_unlocked;
 
 	/* OK, we have data buffer in journaled mode */
@@ -2204,10 +2205,6 @@ static int journal_unmap_buffer(journal_
 	jbd_lock_bh_state(bh);
 	spin_lock(&journal->j_list_lock);
 
-	jh = jbd2_journal_grab_journal_head(bh);
-	if (!jh)
-		goto zap_buffer_no_jh;
-
 	/*
 	 * We cannot remove the buffer from checkpoint lists until the
 	 * transaction adding inode to orphan list (let's call it T)
@@ -2329,7 +2326,6 @@ static int journal_unmap_buffer(journal_
 	 */
 	jh->b_modified = 0;
 	jbd2_journal_put_journal_head(jh);
-zap_buffer_no_jh:
 	spin_unlock(&journal->j_list_lock);
 	jbd_unlock_bh_state(bh);
 	write_unlock(&journal->j_state_lock);