[PATCH 01/13] xfs: xfs_iflock is no longer a completion

[Dave Chinner <david@fromorbit.com>]

From: Dave Chinner <dchinner@redhat.com>

With the recent rework of the inode cluster flushing, we no longer
ever wait on the the inode flush "lock". It was never a lock in the
first place, just a completion to allow callers to wait for inode IO
to complete. We now never wait for flush completion as all inode
flushing is non-blocking. Hence we can get rid of all the iflock
infrastructure and instead just set and check a state flag.

Rename the XFS_IFLOCK flag to XFS_IFLUSHING, convert all the
xfs_iflock_nowait() test-and-set operations on that flag, and
replace all the xfs_ifunlock() calls to clear operations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
 fs/xfs/xfs_icache.c     | 17 ++++------
 fs/xfs/xfs_inode.c      | 73 +++++++++++++++--------------------------
 fs/xfs/xfs_inode.h      | 33 +------------------
 fs/xfs/xfs_inode_item.c | 15 ++++-----
 fs/xfs/xfs_inode_item.h |  4 +--
 fs/xfs/xfs_mount.c      | 11 ++++---
 fs/xfs/xfs_super.c      | 10 +++---
 7 files changed, 55 insertions(+), 108 deletions(-)

diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index 101028ebb571..aa6aad258670 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -52,7 +52,6 @@ xfs_inode_alloc(
 
 	XFS_STATS_INC(mp, vn_active);
 	ASSERT(atomic_read(&ip->i_pincount) == 0);
-	ASSERT(!xfs_isiflocked(ip));
 	ASSERT(ip->i_ino == 0);
 
 	/* initialise the xfs inode */
@@ -123,7 +122,7 @@ void
 xfs_inode_free(
 	struct xfs_inode	*ip)
 {
-	ASSERT(!xfs_isiflocked(ip));
+	ASSERT(!xfs_iflags_test(ip, XFS_IFLUSHING));
 
 	/*
 	 * Because we use RCU freeing we need to ensure the inode always
@@ -1035,23 +1034,21 @@ xfs_reclaim_inode(
 
 	if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL))
 		goto out;
-	if (!xfs_iflock_nowait(ip))
+	if (xfs_iflags_test_and_set(ip, XFS_IFLUSHING))
 		goto out_iunlock;
 
 	if (XFS_FORCED_SHUTDOWN(ip->i_mount)) {
 		xfs_iunpin_wait(ip);
-		/* xfs_iflush_abort() drops the flush lock */
 		xfs_iflush_abort(ip);
 		goto reclaim;
 	}
 	if (xfs_ipincount(ip))
-		goto out_ifunlock;
+		goto out_clear_flush;
 	if (!xfs_inode_clean(ip))
-		goto out_ifunlock;
+		goto out_clear_flush;
 
-	xfs_ifunlock(ip);
+	xfs_iflags_clear(ip, XFS_IFLUSHING);
 reclaim:
-	ASSERT(!xfs_isiflocked(ip));
 
 	/*
 	 * Because we use RCU freeing we need to ensure the inode always appears
@@ -1101,8 +1098,8 @@ xfs_reclaim_inode(
 	__xfs_inode_free(ip);
 	return;
 
-out_ifunlock:
-	xfs_ifunlock(ip);
+out_clear_flush:
+	xfs_iflags_clear(ip, XFS_IFLUSHING);
 out_iunlock:
 	xfs_iunlock(ip, XFS_ILOCK_EXCL);
 out:
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index c06129cffba9..2072bd25989a 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -598,22 +598,6 @@ xfs_lock_two_inodes(
 	}
 }
 
-void
-__xfs_iflock(
-	struct xfs_inode	*ip)
-{
-	wait_queue_head_t *wq = bit_waitqueue(&ip->i_flags, __XFS_IFLOCK_BIT);
-	DEFINE_WAIT_BIT(wait, &ip->i_flags, __XFS_IFLOCK_BIT);
-
-	do {
-		prepare_to_wait_exclusive(wq, &wait.wq_entry, TASK_UNINTERRUPTIBLE);
-		if (xfs_isiflocked(ip))
-			io_schedule();
-	} while (!xfs_iflock_nowait(ip));
-
-	finish_wait(wq, &wait.wq_entry);
-}
-
 STATIC uint
 _xfs_dic2xflags(
 	uint16_t		di_flags,
@@ -2531,11 +2515,8 @@ xfs_ifree_mark_inode_stale(
 	 * valid, the wrong inode or stale.
 	 */
 	spin_lock(&ip->i_flags_lock);
-	if (ip->i_ino != inum || __xfs_iflags_test(ip, XFS_ISTALE)) {
-		spin_unlock(&ip->i_flags_lock);
-		rcu_read_unlock();
-		return;
-	}
+	if (ip->i_ino != inum || __xfs_iflags_test(ip, XFS_ISTALE))
+		goto out_iflags_unlock;
 
 	/*
 	 * Don't try to lock/unlock the current inode, but we _cannot_ skip the
@@ -2552,16 +2533,14 @@ xfs_ifree_mark_inode_stale(
 		}
 	}
 	ip->i_flags |= XFS_ISTALE;
-	spin_unlock(&ip->i_flags_lock);
-	rcu_read_unlock();
 
 	/*
-	 * If we can't get the flush lock, the inode is already attached.  All
+	 * If the inode is flushing, it is already attached to the buffer.  All
 	 * we needed to do here is mark the inode stale so buffer IO completion
 	 * will remove it from the AIL.
 	 */
 	iip = ip->i_itemp;
-	if (!xfs_iflock_nowait(ip)) {
+	if (__xfs_iflags_test(ip, XFS_IFLUSHING)) {
 		ASSERT(!list_empty(&iip->ili_item.li_bio_list));
 		ASSERT(iip->ili_last_fields);
 		goto out_iunlock;
@@ -2573,10 +2552,12 @@ xfs_ifree_mark_inode_stale(
 	 * commit as the flock synchronises removal of the inode from the
 	 * cluster buffer against inode reclaim.
 	 */
-	if (!iip || list_empty(&iip->ili_item.li_bio_list)) {
-		xfs_ifunlock(ip);
+	if (!iip || list_empty(&iip->ili_item.li_bio_list))
 		goto out_iunlock;
-	}
+
+	__xfs_iflags_set(ip, XFS_IFLUSHING);
+	spin_unlock(&ip->i_flags_lock);
+	rcu_read_unlock();
 
 	/* we have a dirty inode in memory that has not yet been flushed. */
 	spin_lock(&iip->ili_lock);
@@ -2586,9 +2567,16 @@ xfs_ifree_mark_inode_stale(
 	spin_unlock(&iip->ili_lock);
 	ASSERT(iip->ili_last_fields);
 
+	if (ip != free_ip)
+		xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	return;
+
 out_iunlock:
 	if (ip != free_ip)
 		xfs_iunlock(ip, XFS_ILOCK_EXCL);
+out_iflags_unlock:
+	spin_unlock(&ip->i_flags_lock);
+	rcu_read_unlock();
 }
 
 /*
@@ -2631,8 +2619,9 @@ xfs_ifree_cluster(
 
 		/*
 		 * We obtain and lock the backing buffer first in the process
-		 * here, as we have to ensure that any dirty inode that we
-		 * can't get the flush lock on is attached to the buffer.
+		 * here to ensure dirty inodes attached to the buffer remain in
+		 * the flushing state while we mark them stale.
+		 *
 		 * If we scan the in-memory inodes first, then buffer IO can
 		 * complete before we get a lock on it, and hence we may fail
 		 * to mark all the active inodes on the buffer stale.
@@ -3443,7 +3432,7 @@ xfs_iflush(
 	int			error;
 
 	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_ILOCK_SHARED));
-	ASSERT(xfs_isiflocked(ip));
+	ASSERT(xfs_iflags_test(ip, XFS_IFLUSHING));
 	ASSERT(ip->i_df.if_format != XFS_DINODE_FMT_BTREE ||
 	       ip->i_df.if_nextents > XFS_IFORK_MAXEXT(ip, XFS_DATA_FORK));
 	ASSERT(iip->ili_item.li_buf == bp);
@@ -3613,7 +3602,7 @@ xfs_iflush_cluster(
 		/*
 		 * Quick and dirty check to avoid locks if possible.
 		 */
-		if (__xfs_iflags_test(ip, XFS_IRECLAIM | XFS_IFLOCK))
+		if (__xfs_iflags_test(ip, XFS_IRECLAIM | XFS_IFLUSHING))
 			continue;
 		if (xfs_ipincount(ip))
 			continue;
@@ -3627,7 +3616,7 @@ xfs_iflush_cluster(
 		 */
 		spin_lock(&ip->i_flags_lock);
 		ASSERT(!__xfs_iflags_test(ip, XFS_ISTALE));
-		if (__xfs_iflags_test(ip, XFS_IRECLAIM | XFS_IFLOCK)) {
+		if (__xfs_iflags_test(ip, XFS_IRECLAIM | XFS_IFLUSHING)) {
 			spin_unlock(&ip->i_flags_lock);
 			continue;
 		}
@@ -3635,23 +3624,16 @@ xfs_iflush_cluster(
 		/*
 		 * ILOCK will pin the inode against reclaim and prevent
 		 * concurrent transactions modifying the inode while we are
-		 * flushing the inode.
+		 * flushing the inode. If we get the lock, set the flushing
+		 * state before we drop the i_flags_lock.
 		 */
 		if (!xfs_ilock_nowait(ip, XFS_ILOCK_SHARED)) {
 			spin_unlock(&ip->i_flags_lock);
 			continue;
 		}
+		__xfs_iflags_set(ip, XFS_IFLUSHING);
 		spin_unlock(&ip->i_flags_lock);
 
-		/*
-		 * Skip inodes that are already flush locked as they have
-		 * already been written to the buffer.
-		 */
-		if (!xfs_iflock_nowait(ip)) {
-			xfs_iunlock(ip, XFS_ILOCK_SHARED);
-			continue;
-		}
-
 		/*
 		 * Abort flushing this inode if we are shut down because the
 		 * inode may not currently be in the AIL. This can occur when
@@ -3661,7 +3643,6 @@ xfs_iflush_cluster(
 		 */
 		if (XFS_FORCED_SHUTDOWN(mp)) {
 			xfs_iunpin_wait(ip);
-			/* xfs_iflush_abort() drops the flush lock */
 			xfs_iflush_abort(ip);
 			xfs_iunlock(ip, XFS_ILOCK_SHARED);
 			error = -EIO;
@@ -3670,7 +3651,7 @@ xfs_iflush_cluster(
 
 		/* don't block waiting on a log force to unpin dirty inodes */
 		if (xfs_ipincount(ip)) {
-			xfs_ifunlock(ip);
+			xfs_iflags_clear(ip, XFS_IFLUSHING);
 			xfs_iunlock(ip, XFS_ILOCK_SHARED);
 			continue;
 		}
@@ -3678,7 +3659,7 @@ xfs_iflush_cluster(
 		if (!xfs_inode_clean(ip))
 			error = xfs_iflush(ip, bp);
 		else
-			xfs_ifunlock(ip);
+			xfs_iflags_clear(ip, XFS_IFLUSHING);
 		xfs_iunlock(ip, XFS_ILOCK_SHARED);
 		if (error)
 			break;
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index e9a8bb184d1f..5ea962c6cf98 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -211,8 +211,7 @@ static inline bool xfs_inode_has_cow_data(struct xfs_inode *ip)
 #define XFS_INEW		(1 << __XFS_INEW_BIT)
 #define XFS_ITRUNCATED		(1 << 5) /* truncated down so flush-on-close */
 #define XFS_IDIRTY_RELEASE	(1 << 6) /* dirty release already seen */
-#define __XFS_IFLOCK_BIT	7	 /* inode is being flushed right now */
-#define XFS_IFLOCK		(1 << __XFS_IFLOCK_BIT)
+#define XFS_IFLUSHING		(1 << 7) /* inode is being flushed */
 #define __XFS_IPINNED_BIT	8	 /* wakeup key for zero pin count */
 #define XFS_IPINNED		(1 << __XFS_IPINNED_BIT)
 #define XFS_IEOFBLOCKS		(1 << 9) /* has the preallocblocks tag set */
@@ -233,36 +232,6 @@ static inline bool xfs_inode_has_cow_data(struct xfs_inode *ip)
 	(XFS_IRECLAIMABLE | XFS_IRECLAIM | \
 	 XFS_IDIRTY_RELEASE | XFS_ITRUNCATED)
 
-/*
- * Synchronize processes attempting to flush the in-core inode back to disk.
- */
-
-static inline int xfs_isiflocked(struct xfs_inode *ip)
-{
-	return xfs_iflags_test(ip, XFS_IFLOCK);
-}
-
-extern void __xfs_iflock(struct xfs_inode *ip);
-
-static inline int xfs_iflock_nowait(struct xfs_inode *ip)
-{
-	return !xfs_iflags_test_and_set(ip, XFS_IFLOCK);
-}
-
-static inline void xfs_iflock(struct xfs_inode *ip)
-{
-	if (!xfs_iflock_nowait(ip))
-		__xfs_iflock(ip);
-}
-
-static inline void xfs_ifunlock(struct xfs_inode *ip)
-{
-	ASSERT(xfs_isiflocked(ip));
-	xfs_iflags_clear(ip, XFS_IFLOCK);
-	smp_mb();
-	wake_up_bit(&ip->i_flags, __XFS_IFLOCK_BIT);
-}
-
 /*
  * Flags for inode locking.
  * Bit ranges:	1<<1  - 1<<16-1 -- iolock/ilock modes (bitfield)
diff --git a/fs/xfs/xfs_inode_item.c b/fs/xfs/xfs_inode_item.c
index 6c65938cee1c..099ae8ee7908 100644
--- a/fs/xfs/xfs_inode_item.c
+++ b/fs/xfs/xfs_inode_item.c
@@ -491,8 +491,7 @@ xfs_inode_item_push(
 	    (ip->i_flags & XFS_ISTALE))
 		return XFS_ITEM_PINNED;
 
-	/* If the inode is already flush locked, we're already flushing. */
-	if (xfs_isiflocked(ip))
+	if (xfs_iflags_test(ip, XFS_IFLUSHING))
 		return XFS_ITEM_FLUSHING;
 
 	if (!xfs_buf_trylock(bp))
@@ -703,7 +702,7 @@ xfs_iflush_finish(
 		iip->ili_last_fields = 0;
 		iip->ili_flush_lsn = 0;
 		spin_unlock(&iip->ili_lock);
-		xfs_ifunlock(iip->ili_inode);
+		xfs_iflags_clear(iip->ili_inode, XFS_IFLUSHING);
 		if (drop_buffer)
 			xfs_buf_rele(bp);
 	}
@@ -711,8 +710,8 @@ xfs_iflush_finish(
 
 /*
  * Inode buffer IO completion routine.  It is responsible for removing inodes
- * attached to the buffer from the AIL if they have not been re-logged, as well
- * as completing the flush and unlocking the inode.
+ * attached to the buffer from the AIL if they have not been re-logged and
+ * completing the inode flush.
  */
 void
 xfs_iflush_done(
@@ -755,10 +754,10 @@ xfs_iflush_done(
 }
 
 /*
- * This is the inode flushing abort routine.  It is called from xfs_iflush when
+ * This is the inode flushing abort routine.  It is called when
  * the filesystem is shutting down to clean up the inode state.  It is
  * responsible for removing the inode item from the AIL if it has not been
- * re-logged, and unlocking the inode's flush lock.
+ * re-logged and clearing the inode's flush state.
  */
 void
 xfs_iflush_abort(
@@ -790,7 +789,7 @@ xfs_iflush_abort(
 		list_del_init(&iip->ili_item.li_bio_list);
 		spin_unlock(&iip->ili_lock);
 	}
-	xfs_ifunlock(ip);
+	xfs_iflags_clear(ip, XFS_IFLUSHING);
 	if (bp)
 		xfs_buf_rele(bp);
 }
diff --git a/fs/xfs/xfs_inode_item.h b/fs/xfs/xfs_inode_item.h
index 048b5e7dee90..23a7b4928727 100644
--- a/fs/xfs/xfs_inode_item.h
+++ b/fs/xfs/xfs_inode_item.h
@@ -25,8 +25,8 @@ struct xfs_inode_log_item {
 	 *
 	 * We need atomic changes between inode dirtying, inode flushing and
 	 * inode completion, but these all hold different combinations of
-	 * ILOCK and iflock and hence we need some other method of serialising
-	 * updates to the flush state.
+	 * ILOCK and IFLUSHING and hence we need some other method of
+	 * serialising updates to the flush state.
 	 */
 	spinlock_t		ili_lock;	   /* flush state lock */
 	unsigned int		ili_last_fields;   /* fields when flushed */
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index c8ae49a1e99c..bbfd1d5b1c04 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -1059,11 +1059,12 @@ xfs_unmountfs(
 	 * We can potentially deadlock here if we have an inode cluster
 	 * that has been freed has its buffer still pinned in memory because
 	 * the transaction is still sitting in a iclog. The stale inodes
-	 * on that buffer will have their flush locks held until the
-	 * transaction hits the disk and the callbacks run. the inode
-	 * flush takes the flush lock unconditionally and with nothing to
-	 * push out the iclog we will never get that unlocked. hence we
-	 * need to force the log first.
+	 * on that buffer will be pinned to the buffer until the
+	 * transaction hits the disk and the callbacks run. Pushing the AIL will
+	 * skip the stale inodes and may never see the pinned buffer, so
+	 * nothing will push out the iclog and unpin the buffer. Hence we
+	 * need to force the log here to ensure all items are flushed into the
+	 * AIL before we go any further.
 	 */
 	xfs_log_force(mp, XFS_LOG_SYNC);
 
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 71ac6c1cdc36..68ec8db12cc7 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -654,11 +654,11 @@ xfs_fs_destroy_inode(
 	ASSERT_ALWAYS(!xfs_iflags_test(ip, XFS_IRECLAIM));
 
 	/*
-	 * We always use background reclaim here because even if the
-	 * inode is clean, it still may be under IO and hence we have
-	 * to take the flush lock. The background reclaim path handles
-	 * this more efficiently than we can here, so simply let background
-	 * reclaim tear down all inodes.
+	 * We always use background reclaim here because even if the inode is
+	 * clean, it still may be under IO and hence we have wait for IO
+	 * completion to occur before we can reclaim the inode. The background
+	 * reclaim path handles this more efficiently than we can here, so
+	 * simply let background reclaim tear down all inodes.
 	 */
 	xfs_inode_set_reclaim_tag(ip);
 }
-- 
2.26.2.761.g0e0b3e54be