Commit d748c623 authored by Matthew Wilcox's avatar Matthew Wilcox Committed by Niv Sardi
Browse files

[XFS] Convert l_flushsema to a sv_t 



The l_flushsema doesn't exactly have completion semantics, nor mutex
semantics. It's used as a list of tasks which are waiting to be notified
that a flush has completed. It was also being used in a way that was
potentially racy, depending on the semaphore implementation.

By using a sv_t instead of a semaphore we avoid the need for a separate
counter, since we know we just need to wake everything on the queue.

Original waitqueue implementation from Matthew Wilcox. Cleanup and
conversion to sv_t by Christoph Hellwig.

SGI-PV: 981507
SGI-Modid: xfs-linux-melb:xfs-kern:31059a

Signed-off-by: default avatarMatthew Wilcox <willy@linux.intel.com>
Signed-off-by: default avatarChristoph Hellwig <hch@infradead.org>
Signed-off-by: default avatarDavid Chinner <dgc@sgi.com>
Signed-off-by: default avatarLachlan McIlroy <lachlan@sgi.com>
parent d729eae8

fs/xfs/xfs_log.c

+13 −16
Original line number Diff line number Diff line
@@ -1232,7 +1232,7 @@ xlog_alloc_log(xfs_mount_t *mp, 


	spin_lock_init(&log->l_icloglock);

	spin_lock_init(&log->l_grant_lock);

	initnsema(&log->l_flushsema, 0, "ic-flush");

	sv_init(&log->l_flush_wait, 0, "flush_wait");



	/* log record size must be multiple of BBSIZE; see xlog_rec_header_t */

	ASSERT((XFS_BUF_SIZE(bp) & BBMASK) == 0);
@@ -1577,7 +1577,6 @@ xlog_dealloc_log(xlog_t *log) 
		kmem_free(iclog);

		iclog = next_iclog;

	}

	freesema(&log->l_flushsema);

	spinlock_destroy(&log->l_icloglock);

	spinlock_destroy(&log->l_grant_lock);
@@ -2101,6 +2100,7 @@ xlog_state_do_callback( 
	int		   funcdidcallbacks; /* flag: function did callbacks */

	int		   repeats;	/* for issuing console warnings if

					 * looping too many times */

	int		   wake = 0;



	spin_lock(&log->l_icloglock);

	first_iclog = iclog = log->l_iclog;
@@ -2282,15 +2282,13 @@ xlog_state_do_callback( 
	}

#endif



	flushcnt = 0;

	if (log->l_iclog->ic_state & (XLOG_STATE_ACTIVE|XLOG_STATE_IOERROR)) {

		flushcnt = log->l_flushcnt;

		log->l_flushcnt = 0;

	}

	if (log->l_iclog->ic_state & (XLOG_STATE_ACTIVE|XLOG_STATE_IOERROR))

		wake = 1;

	spin_unlock(&log->l_icloglock);

	while (flushcnt--)

		vsema(&log->l_flushsema);

}	/* xlog_state_do_callback */



	if (wake)

		sv_broadcast(&log->l_flush_wait);

}





/*
@@ -2388,16 +2386,15 @@ restart: 
	}



	iclog = log->l_iclog;

	if (! (iclog->ic_state == XLOG_STATE_ACTIVE)) {

		log->l_flushcnt++;

		spin_unlock(&log->l_icloglock);

	if (iclog->ic_state != XLOG_STATE_ACTIVE) {

		xlog_trace_iclog(iclog, XLOG_TRACE_SLEEP_FLUSH);

		XFS_STATS_INC(xs_log_noiclogs);

		/* Ensure that log writes happen */

		psema(&log->l_flushsema, PINOD);



		/* Wait for log writes to have flushed */

		sv_wait(&log->l_flush_wait, 0, &log->l_icloglock, 0);

		goto restart;

	}

	ASSERT(iclog->ic_state == XLOG_STATE_ACTIVE);



	head = &iclog->ic_header;



	atomic_inc(&iclog->ic_refcnt);	/* prevents sync */

fs/xfs/xfs_log_priv.h

+2 −4
Original line number Diff line number Diff line
@@ -423,10 +423,8 @@ typedef struct log { 
	int			l_logBBsize;    /* size of log in BB chunks */



	/* The following block of fields are changed while holding icloglock */

	sema_t			l_flushsema ____cacheline_aligned_in_smp;

						/* iclog flushing semaphore */

	int			l_flushcnt;	/* # of procs waiting on this

						 * sema */

	sv_t			l_flush_wait ____cacheline_aligned_in_smp;

						/* waiting for iclog flush */

	int			l_covered_state;/* state of "covering disk

						 * log entries" */

	xlog_in_core_t		*l_iclog;       /* head log queue	*/

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