Ocfs2 devel - Sep 2008 - [PATCH] jbd2: Create proc entry with bdevname+i_ino.

jbd2 currently creates statistics files for each loaded journal in
/proc/fs/jbd2/<bdevname>.  ocfs2 loads multiple journals when recovering
other nodes, and the multiple journals on a given bdev collide in the
proc namespace.

This patch changes the location to /proc/fs/jbd2/<bdevname>-<i_ino>
as
proposed by Jan Kara.  ocfs2 can load multiple journals safely without
collision.  There are, to my knowledge, no programmatic users, so the
name change shouldn't (haha) cause any problems.

ocfs2 has 64bit inode numbers, so a collision could theoretically happen
with inodes above 32bits, but ocfs2 journals are generally created at
the front of the volume during mkfs(8).  In addition, ocfs2 restricts
inodes to 32bits unless the 'inode64' option is specified.

Signed-off-by: Joel Becker <joel.becker at oracle.com>
---
 fs/jbd2/journal.c |   12 ++++++++----
 1 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 8207a01..18d3063 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -901,9 +901,11 @@ static struct proc_dir_entry *proc_jbd2_stats;
 
 static void jbd2_stats_proc_init(journal_t *journal)
 {
-	char name[BDEVNAME_SIZE];
+	char dname[BDEVNAME_SIZE];
+	char name[NAME_MAX];
 
-	bdevname(journal->j_dev, name);
+	bdevname(journal->j_dev, dname);
+	snprintf(name, NAME_MAX, "%s-%lu", dname,
journal->j_inode->i_ino);
 	journal->j_proc_entry = proc_mkdir(name, proc_jbd2_stats);
 	if (journal->j_proc_entry) {
 		proc_create_data("history", S_IRUGO, journal->j_proc_entry,
@@ -915,9 +917,11 @@ static void jbd2_stats_proc_init(journal_t *journal)
 
 static void jbd2_stats_proc_exit(journal_t *journal)
 {
-	char name[BDEVNAME_SIZE];
+	char dname[BDEVNAME_SIZE];
+	char name[NAME_MAX];
 
-	bdevname(journal->j_dev, name);
+	bdevname(journal->j_dev, dname);
+	snprintf(name, NAME_MAX, "%s-%lu", dname,
journal->j_inode->i_ino);
 	remove_proc_entry("info", journal->j_proc_entry);
 	remove_proc_entry("history", journal->j_proc_entry);
 	remove_proc_entry(name, proc_jbd2_stats);
-- 
1.5.6.3


-- 

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Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker at oracle.com
Phone: (650) 506-8127

On Mon, Sep 08, 2008 at 04:31:14PM -0700, Joel Becker
wrote:
> jbd2 currently creates statistics files for each loaded journal in
> /proc/fs/jbd2/<bdevname>.  ocfs2 loads multiple journals when
recovering
> other nodes, and the multiple journals on a given bdev collide in the
> proc namespace.
Did this patch ever get reviewied? We'd really like it in so that Ocfs2 can
use JBD2...

Thanks,
	--Mark

--
Mark Fasheh