From: Frederic Weisbecker Date: Thu, 7 May 2009 20:51:20 +0000 (+0200) Subject: kill-the-BKL/reiserfs: add reiserfs_cond_resched() X-Git-Tag: firefly_0821_release~9833^2~3455^2~40 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=e43d3f21c502dec786f2885a75e25859f18d6ffa;p=firefly-linux-kernel-4.4.55.git kill-the-BKL/reiserfs: add reiserfs_cond_resched() Usually, when we call cond_resched(), we want the write lock to be released and then reacquired once we return from scheduling. Not only does it follow the previous bkl based locking scheme, but it also let other waiters to get the lock. But if we aren't going to reschedule(), such as in !TIF_NEED_RESCHED case, it's useless to release the lock. Worse, if we release and reacquire the lock whereas it is not needed, we create useless contentions. Also if someone takes the lock while we are modifying or reading the tree, there are good chances we'll have to retry our operation, eg if the block we were seeeking has moved. So this patch introduces a helper which only unlock the write lock if we are going to schedule. [ Impact: prepare to inject less lock contention and less tree operation attempts ] Reported-by: Andi Kleen Cc: Jeff Mahoney Cc: Chris Mason Cc: Ingo Molnar Cc: Alexander Beregalov Signed-off-by: Frederic Weisbecker --- diff --git a/include/linux/reiserfs_fs.h b/include/linux/reiserfs_fs.h index fa5dbf307c40..27f4ecc28180 100644 --- a/include/linux/reiserfs_fs.h +++ b/include/linux/reiserfs_fs.h @@ -62,6 +62,19 @@ void reiserfs_write_unlock(struct super_block *s); int reiserfs_write_lock_once(struct super_block *s); void reiserfs_write_unlock_once(struct super_block *s, int lock_depth); +/* + * When we schedule, we usually want to also release the write lock, + * according to the previous bkl based locking scheme of reiserfs. + */ +static inline void reiserfs_cond_resched(struct super_block *s) +{ + if (need_resched()) { + reiserfs_write_unlock(s); + schedule(); + reiserfs_write_lock(s); + } +} + struct fid; /* in reading the #defines, it may help to understand that they employ