[PATCH 07/11] xfs: replace i_pin_wait with a bit waitqueue

Christoph Hellwig
2011-12-18T20:01:34Z

[-- Attachment #1: xfs-kill-i_ipin_wait --]
[-- Type: text/plain, Size: 4132 bytes --]

Replace i_pin_wait, which is only used during synchronous inode flushing
with a bit waitqueue. This trades off a much smaller inode against
slightly slower wakeup performance, and saves 12 (32-bit) or 20 (64-bit)
bytes in the XFS inode.

Reviewed-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

---
fs/xfs/xfs_inode.c | 27 +++++++++++++++++++++------
fs/xfs/xfs_inode.h | 3 ++-
fs/xfs/xfs_inode_item.c | 2 +-
fs/xfs/xfs_super.c | 1 -
4 files changed, 24 insertions(+), 9 deletions(-)

Index: xfs/fs/xfs/xfs_inode.c
===================================================================
--- xfs.orig/fs/xfs/xfs_inode.c 2011-11-30 12:59:08.843047205 +0100
+++ xfs/fs/xfs/xfs_inode.c 2011-11-30 12:59:10.296372665 +0100
@@ -2037,7 +2037,7 @@ xfs_idestroy_fork(
* once someone is waiting for it to be unpinned.
*/
static void
-xfs_iunpin_nowait(
+xfs_iunpin(
struct xfs_inode *ip)
{
ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_ILOCK_SHARED));
@@ -2049,14 +2049,29 @@ xfs_iunpin_nowait(

}

+static void
+__xfs_iunpin_wait(
+ struct xfs_inode *ip)
+{
+ wait_queue_head_t *wq = bit_waitqueue(&ip->i_flags, __XFS_IPINNED_BIT);
+ DEFINE_WAIT_BIT(wait, &ip->i_flags, __XFS_IPINNED_BIT);
+
+ xfs_iunpin(ip);
+
+ do {
+ prepare_to_wait(wq, &wait.wait, TASK_UNINTERRUPTIBLE);
+ if (xfs_ipincount(ip))
+ io_schedule();
+ } while (xfs_ipincount(ip));
+ finish_wait(wq, &wait.wait);
+}
+
void
xfs_iunpin_wait(
struct xfs_inode *ip)
{
- if (xfs_ipincount(ip)) {
- xfs_iunpin_nowait(ip);
- wait_event(ip->i_ipin_wait, (xfs_ipincount(ip) == 0));
- }
+ if (xfs_ipincount(ip))
+ __xfs_iunpin_wait(ip);
}

/*
@@ -2415,7 +2430,7 @@ xfs_iflush(
* out for us if they occur after the log force completes.
*/
if (!(flags & SYNC_WAIT) && xfs_ipincount(ip)) {
- xfs_iunpin_nowait(ip);
+ xfs_iunpin(ip);
xfs_ifunlock(ip);
return EAGAIN;
}
Index: xfs/fs/xfs/xfs_inode.h
===================================================================
--- xfs.orig/fs/xfs/xfs_inode.h 2011-11-30 12:59:08.846380520 +0100
+++ xfs/fs/xfs/xfs_inode.h 2011-11-30 12:59:10.296372665 +0100
@@ -238,7 +238,6 @@ typedef struct xfs_inode {
mrlock_t i_lock; /* inode lock */
mrlock_t i_iolock; /* inode IO lock */
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 */
/* Miscellaneous state. */
unsigned long i_flags; /* see defined flags below */
@@ -367,6 +366,8 @@ xfs_set_projid(struct xfs_inode *ip,
#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_IPINNED_BIT 8 /* wakeup key for zero pin count */
+#define XFS_IPINNED (1 << __XFS_IPINNED_BIT)

/*
* Per-lifetime flags need to be reset when re-using a reclaimable inode during
Index: xfs/fs/xfs/xfs_inode_item.c
===================================================================
--- xfs.orig/fs/xfs/xfs_inode_item.c 2011-11-30 12:59:08.846380520 +0100
+++ xfs/fs/xfs/xfs_inode_item.c 2011-11-30 12:59:10.296372665 +0100
@@ -555,7 +555,7 @@ xfs_inode_item_unpin(
trace_xfs_inode_unpin(ip, _RET_IP_);
ASSERT(atomic_read(&ip->i_pincount) > 0);
if (atomic_dec_and_test(&ip->i_pincount))
- wake_up(&ip->i_ipin_wait);
+ wake_up_bit(&ip->i_flags, __XFS_IPINNED_BIT);
}

/*
Index: xfs/fs/xfs/xfs_super.c
===================================================================
--- xfs.orig/fs/xfs/xfs_super.c 2011-11-30 12:59:08.846380520 +0100
+++ xfs/fs/xfs/xfs_super.c 2011-11-30 12:59:10.296372665 +0100
@@ -828,7 +828,6 @@ xfs_fs_inode_init_once(
/* xfs inode */
atomic_set(&ip->i_pincount, 0);
spin_lock_init(&ip->i_flags_lock);
- init_waitqueue_head(&ip->i_ipin_wait);

mrlock_init(&ip->i_lock, MRLOCK_ALLOW_EQUAL_PRI|MRLOCK_BARRIER,
"xfsino", ip->i_ino);