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kill-the-bkl/reiserfs: use mutex_lock in reiserfs_mutex_lock_safe

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reiserfs_mutex_lock_safe() is a hack to avoid any dependency between
an internal reiserfs mutex and the write lock, it has been proposed
to follow the old bkl logic.

The code does the following:

while (!mutex_trylock(m)) {
	reiserfs_write_unlock(s);
	schedule();
	reiserfs_write_lock(s);
}

It then imitate the implicit behaviour of the lock when it was
a Bkl and hadn't such dependency:

mutex_lock(m) {
	if (fastpath)
		let's go
	else {
		wait_for_mutex() {
			schedule() {
				unlock_kernel()
				reacquire_lock_kernel()
			}
		}
	}
}

The problem is that by using such explicit schedule(), we don't
benefit of the adaptive mutex spinning on owner.

The logic in use now is:

reiserfs_write_unlock(s);
mutex_lock(m); // -> possible adaptive spinning
reiserfs_write_lock(s);

[ Impact: restore the use of adaptive spinning mutexes in reiserfs ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
This commit is contained in:
Frederic Weisbecker
2009-05-08 20:01:09 +02:00
parent d6f5b0aa08
commit c63e3c0b24
1 changed files with 3 additions and 5 deletions
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8
fs/reiserfs/journal.c
View File

@@ -566,11 +566,9 @@ static inline void insert_journal_hash(struct reiserfs_journal_cnode **table,
static inline void reiserfs_mutex_lock_safe(struct mutex *m, static inline void reiserfs_mutex_lock_safe(struct mutex *m,
struct super_block *s) struct super_block *s)
{ {
while (!mutex_trylock(m)) { reiserfs_write_unlock(s);
reiserfs_write_unlock(s); mutex_lock(m);
schedule(); reiserfs_write_lock(s);
reiserfs_write_lock(s);
}
} }
/* lock the current transaction */ /* lock the current transaction */