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Date: Tue, 11 Jun 2013 18:44:29 -0400
From: Paul Gortmaker <paul.gortmaker@...driver.com>
To: "Theodore Ts'o" <tytso@....edu>
CC: <linux-ext4@...r.kernel.org>, <linux-rt-users@...r.kernel.org>,
Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: [PATCH 5/6] jbd2: make jbd_debug that won't split printk statements
Since the jbd_debug() is implemented with two separate printk()
calls, it can lead to corrupted and misleading debug output like
the following (see lines marked with "*"):
[ 290.339362] (fs/jbd2/journal.c, 203): kjournald2: kjournald2 wakes
[ 290.339365] (fs/jbd2/journal.c, 155): kjournald2: commit_sequence=42103, commit_request=42104
[ 290.339369] (fs/jbd2/journal.c, 158): kjournald2: OK, requests differ
[* 290.339376] (fs/jbd2/journal.c, 648): jbd2_log_wait_commit:
[* 290.339379] (fs/jbd2/commit.c, 370): jbd2_journal_commit_transaction: JBD2: want 42104, j_commit_sequence=42103
[* 290.339382] JBD2: starting commit of transaction 42104
[ 290.339410] (fs/jbd2/revoke.c, 566): jbd2_journal_write_revoke_records: Wrote 0 revoke records
[ 290.376555] (fs/jbd2/commit.c, 1088): jbd2_journal_commit_transaction: JBD2: commit 42104 complete, head 42079
i.e. the debug output from log_wait_commit and journal_commit_transaction
have become interleaved. The output should have been:
(fs/jbd2/journal.c, 648): jbd2_log_wait_commit: JBD2: want 42104, j_commit_sequence=42103
(fs/jbd2/commit.c, 370): jbd2_journal_commit_transaction: JBD2: starting commit of transaction 42104
It is expected that this is not easy to replicate -- I was only able
to cause it on preempt-rt kernels, and even then only under heavy
I/O load.
Reported-by: Paul Gortmaker <paul.gortmaker@...driver.com>
Suggested-by: "Theodore Ts'o" <tytso@....edu>
Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
---
fs/jbd2/journal.c | 17 +++++++++++++++++
include/linux/jbd2.h | 14 +++++---------
2 files changed, 22 insertions(+), 9 deletions(-)
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 9545757..6aa196e 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -103,6 +103,23 @@ EXPORT_SYMBOL(jbd2_inode_cache);
static void __journal_abort_soft (journal_t *journal, int errno);
static int jbd2_journal_create_slab(size_t slab_size);
+#ifdef CONFIG_JBD2_DEBUG
+void __jbd2_debug(int level, const char *file, const char *func,
+ unsigned int line, const char *fmt, ...)
+{
+ struct va_format vaf;
+ va_list args;
+
+ if (level > jbd2_journal_enable_debug)
+ return;
+ va_start(args, fmt);
+ vaf.fmt = fmt;
+ vaf.va = &args;
+ printk(KERN_DEBUG "%s: (%s, %u): %pV\n", file, func, line, &vaf);
+ va_end(args);
+}
+#endif
+
/* Checksumming functions */
int jbd2_verify_csum_type(journal_t *j, journal_superblock_t *sb)
{
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 9986ab8..8d95314 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -56,17 +56,13 @@
*/
#define JBD2_EXPENSIVE_CHECKING
extern ushort jbd2_journal_enable_debug;
+void __jbd2_debug(int level, const char *file, const char *func,
+ unsigned int line, const char *fmt, ...);
-#define jbd_debug(n, f, a...) \
- do { \
- if ((n) <= jbd2_journal_enable_debug) { \
- printk (KERN_DEBUG "(%s, %d): %s: ", \
- __FILE__, __LINE__, __func__); \
- printk (f, ## a); \
- } \
- } while (0)
+#define jbd_debug(n, fmt, a...) \
+ __jbd2_debug((n), __FILE__, __func__, __LINE__, (fmt), ##a)
#else
-#define jbd_debug(f, a...) /**/
+#define jbd_debug(n, fmt, a...) /**/
#endif
extern void *jbd2_alloc(size_t size, gfp_t flags);
--
1.8.1.2
--
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