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

Ben Myers
2012-01-13T22:42:56Z

On Sun, Dec 18, 2011 at 03:00:10PM -0500, Christoph Hellwig wrote:
> 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>

Looks good.

Reviewed-by: Ben Myers <bpm@sgi.com>

>
> ---
> 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);
>
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