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reiserfs, kill-the-BKL: fix unsafe j_flush_mutex lock 

Impact: fix a deadlock

The j_flush_mutex is acquired safely in journal.c:
if we can't take it, we free the reiserfs per superblock lock
and wait a bit.

But we have a remaining place in kupdate_transactions() where
j_flush_mutex is still acquired traditionnaly. Thus the following
scenario (warned by lockdep) can happen:

A						B

mutex_lock(&write_lock)			mutex_lock(&write_lock)
	mutex_lock(&j_flush_mutex)	mutex_lock(&j_flush_mutex) //block
	mutex_unlock(&write_lock)
	sleep...
	mutex_lock(&write_lock) //deadlock

Fix this by using reiserfs_mutex_lock_safe() in kupdate_transactions().

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@texware.it>
Cc: Jeff Mahoney <jeffm@suse.com>
LKML-Reference: <1239660635-12940-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Frederic Weisbecker 2009-04-14 00:10:35 +02:00
parent 8ebc423238
commit a412f9efdd
1 changed files with 1 additions and 1 deletions
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2
fs/reiserfs/journal.c
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@ -1826,7 +1826,7 @@ static int kupdate_transactions(struct super_block *s,
struct reiserfs_journal *journal = SB_JOURNAL(s);
chunk.nr = 0;
mutex_lock(&journal->j_flush_mutex);
reiserfs_mutex_lock_safe(&journal->j_flush_mutex, s);
if (!journal_list_still_alive(s, orig_trans_id)) {
goto done;
}