xfs: replace i_flock with a sleeping bitlock
We almost never block on i_flock, the exception is synchronous inode
flushing. Instead of bloating the inode with a 16/24-byte completion
that we abuse as a semaphore just implement it as a bitlock that uses
a bit waitqueue for the rare sleeping path. This primarily is a
tradeoff between a much smaller inode and a faster non-blocking
path vs faster wakeups, and we are much better off with the former.
A small downside is that we will lose lockdep checking for i_flock, but
given that it's always taken inside the ilock that should be acceptable.
Note that for example the inode writeback locking is implemented in a
very similar way.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index be8dc0c..960d2a8 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -237,7 +237,6 @@
struct xfs_inode_log_item *i_itemp; /* logging information */
mrlock_t i_lock; /* inode lock */
mrlock_t i_iolock; /* inode IO lock */
- struct completion i_flush; /* inode flush completion q */
atomic_t i_pincount; /* inode pin count */
wait_queue_head_t i_ipin_wait; /* inode pinning wait queue */
spinlock_t i_flags_lock; /* inode i_flags lock */
@@ -324,6 +323,19 @@
return ret;
}
+static inline int
+xfs_iflags_test_and_set(xfs_inode_t *ip, unsigned short flags)
+{
+ int ret;
+
+ spin_lock(&ip->i_flags_lock);
+ ret = ip->i_flags & flags;
+ if (!ret)
+ ip->i_flags |= flags;
+ spin_unlock(&ip->i_flags_lock);
+ return ret;
+}
+
/*
* Project quota id helpers (previously projid was 16bit only
* and using two 16bit values to hold new 32bit projid was chosen
@@ -344,35 +356,17 @@
}
/*
- * Manage the i_flush queue embedded in the inode. This completion
- * queue synchronizes processes attempting to flush the in-core
- * inode back to disk.
- */
-static inline void xfs_iflock(xfs_inode_t *ip)
-{
- wait_for_completion(&ip->i_flush);
-}
-
-static inline int xfs_iflock_nowait(xfs_inode_t *ip)
-{
- return try_wait_for_completion(&ip->i_flush);
-}
-
-static inline void xfs_ifunlock(xfs_inode_t *ip)
-{
- complete(&ip->i_flush);
-}
-
-/*
* In-core inode flags.
*/
-#define XFS_IRECLAIM 0x0001 /* started reclaiming this inode */
-#define XFS_ISTALE 0x0002 /* inode has been staled */
-#define XFS_IRECLAIMABLE 0x0004 /* inode can be reclaimed */
-#define XFS_INEW 0x0008 /* inode has just been allocated */
-#define XFS_IFILESTREAM 0x0010 /* inode is in a filestream directory */
-#define XFS_ITRUNCATED 0x0020 /* truncated down so flush-on-close */
-#define XFS_IDIRTY_RELEASE 0x0040 /* dirty release already seen */
+#define XFS_IRECLAIM (1 << 0) /* started reclaiming this inode */
+#define XFS_ISTALE (1 << 1) /* inode has been staled */
+#define XFS_IRECLAIMABLE (1 << 2) /* inode can be reclaimed */
+#define XFS_INEW (1 << 3) /* inode has just been allocated */
+#define XFS_IFILESTREAM (1 << 4) /* inode is in a filestream dir. */
+#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)
/*
* Per-lifetime flags need to be reset when re-using a reclaimable inode during
@@ -385,6 +379,34 @@
XFS_IFILESTREAM);
/*
+ * Synchronize processes attempting to flush the in-core inode back to disk.
+ */
+
+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)
+{
+ xfs_iflags_clear(ip, XFS_IFLOCK);
+ wake_up_bit(&ip->i_flags, __XFS_IFLOCK_BIT);
+}
+
+static inline int xfs_isiflocked(struct xfs_inode *ip)
+{
+ return xfs_iflags_test(ip, XFS_IFLOCK);
+}
+
+/*
* Flags for inode locking.
* Bit ranges: 1<<1 - 1<<16-1 -- iolock/ilock modes (bitfield)
* 1<<16 - 1<<32-1 -- lockdep annotation (integers)