linux-ext4 - Re: [PATCH 1/4] jbd2/journal_commit_transaction: relocate state lock to incorporate all users

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Date:	Mon, 10 Jun 2013 22:12:30 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Paul Gortmaker <paul.gortmaker@...driver.com>
Cc:	linux-ext4@...r.kernel.org, linux-rt-users@...r.kernel.org
Subject: Re: [PATCH 1/4] jbd2/journal_commit_transaction: relocate state lock
 to incorporate all users

On Mon, Jun 10, 2013 at 03:32:00PM -0400, Paul Gortmaker wrote:
> The state lock is taken after we are doing an assert on the state
> value, not before.  It is also taken after the jbd_debug() call.
> Noting that 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 "*"):

This is only a cosmetic fix, but instead of trying to fix it by moving
a lock --- which would only fix this issue, but there are probably
others cases where this might be an issue, I'd suggest fixing it with
something like this:

/* in fs/jbd2/journal.c */
void __jbd2_debug(int level, 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, "jbd2: (%s, %u): %pV\n", func, line, &vaf);
	va_end(args);
}

/* in jbd2.h */

#define jbd_debug(n, fmt, a...) __jbd2_debug((n), __func__, __LINE__, (fmt), ##a)

Could you give this approach a try?

Thanks,

							- Ted
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