2009-01-11 19:15:09

by Simon Holm Thøgersen

Subject: [PATCH] jbd2: fix wrong use of do_div

the following warning:

fs/jbd2/journal.c: In function ‘jbd2_seq_info_show’:
fs/jbd2/journal.c:850: warning: format ‘%lu’ expects type ‘long
unsigned int’, but argument 3 has type ‘uint32_t’

is caused by wrong usage of do_div that modifies the dividend in-place
and returns the quotient. So not only would an incorrect value be
displayed, but s->journal->j_average_commit_time would also be changed
to a wrong value! This patch fixes it.

Signed-off-by: Simon Holm Thøgersen <[email protected]>
---
fs/jbd2/journal.c | 8 ++++++--
1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 5667530..f9620e3 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -828,6 +828,7 @@ static void *jbd2_seq_info_next(struct seq_file *seq, void *v, loff_t *pos)
static int jbd2_seq_info_show(struct seq_file *seq, void *v)
{
struct jbd2_stats_proc_session *s = seq->private;
+ u64 n;

if (v != SEQ_START_TOKEN)
return 0;
@@ -846,8 +847,11 @@ static int jbd2_seq_info_show(struct seq_file *seq, void *v)
jiffies_to_msecs(s->stats->u.run.rs_flushing / s->stats->ts_tid));
seq_printf(seq, " %ums logging transaction\n",
jiffies_to_msecs(s->stats->u.run.rs_logging / s->stats->ts_tid));
- seq_printf(seq, " %luus average transaction commit time\n",
- do_div(s->journal->j_average_commit_time, 1000));
+
+ n = s->journal->j_average_commit_time;
+ do_div(n, 1000);
+ seq_printf(seq, " %llus average transaction commit time\n", n);
+
seq_printf(seq, " %lu handles per transaction\n",
s->stats->u.run.rs_handle_count / s->stats->ts_tid);
seq_printf(seq, " %lu blocks per transaction\n",
--
1.6.0.2.526.g5c283

2009-01-12 01:43:15

by Simon Holm Thøgersen

Subject: Re: [PATCH] jbd2: fix wrong use of do_div

[I got a simpler version 2 of the patch here]

the following warning:

fs/jbd2/journal.c: In function ‘jbd2_seq_info_show’:
fs/jbd2/journal.c:850: warning: format ‘%lu’ expects type ‘long
unsigned int’, but argument 3 has type ‘uint32_t’

is caused by wrong usage of do_div that modifies the dividend in-place
and returns the quotient. So not only would an incorrect value be
displayed, but s->journal->j_average_commit_time would also be changed
to a wrong value!

Fix it by using div_u64 instead.

Signed-off-by: Simon Holm Thøgersen <[email protected]>
---
fs/jbd2/journal.c | 6 +++---
1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 5667530..eb34300 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -37,10 +37,10 @@
#include <linux/proc_fs.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
+#include <linux/math64.h>

#include <asm/uaccess.h>
#include <asm/page.h>
-#include <asm/div64.h>

EXPORT_SYMBOL(jbd2_journal_start);
EXPORT_SYMBOL(jbd2_journal_restart);
@@ -846,8 +846,8 @@ static int jbd2_seq_info_show(struct seq_file *seq,
void *v)
jiffies_to_msecs(s->stats->u.run.rs_flushing / s->stats->ts_tid));
seq_printf(seq, " %ums logging transaction\n",
jiffies_to_msecs(s->stats->u.run.rs_logging / s->stats->ts_tid));
- seq_printf(seq, " %luus average transaction commit time\n",
- do_div(s->journal->j_average_commit_time, 1000));
+ seq_printf(seq, " %lluus average transaction commit time\n",
+ div_u64(s->journal->j_average_commit_time, 1000));
seq_printf(seq, " %lu handles per transaction\n",
s->stats->u.run.rs_handle_count / s->stats->ts_tid);
seq_printf(seq, " %lu blocks per transaction\n",
--
1.6.0.2.526.g5c283

2009-01-12 03:36:18

by Theodore Ts'o

Subject: Re: [PATCH] jbd2: fix wrong use of do_div

Thanks for the patch; I've queued it for testing and will push it to
Linus.

- Ted