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[PATCH 4/6] Replace inode flush semaphore with a completion

To: xfs@xxxxxxxxxxx
Subject: [PATCH 4/6] Replace inode flush semaphore with a completion
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Fri, 27 Jun 2008 18:44:42 +1000
Cc: linux-kernel@xxxxxxxxxxxxxxx, matthew@xxxxxx, dwalker@xxxxxxxxxx, Dave Chinner <david@xxxxxxxxxxxxx>
In-reply-to: <1214556284-4160-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1214556284-4160-1-git-send-email-david@xxxxxxxxxxxxx>
Sender: xfs-bounce@xxxxxxxxxxx
Use the new completion flush code to implement the inode
flush lock. Removes one of the final users of semaphores
in the XFS code base.

Version 2:
o make flock functions static inlines
o use new completion interfaces

Signed-off-by: Dave Chinner <david@xxxxxxxxxxxxx>
---
 fs/xfs/xfs_iget.c       |   32 ++++++++------------------------
 fs/xfs/xfs_inode.c      |   11 +++++------
 fs/xfs/xfs_inode.h      |   25 +++++++++++++++++++++----
 fs/xfs/xfs_inode_item.c |   11 +++++------
 4 files changed, 39 insertions(+), 40 deletions(-)

diff --git a/fs/xfs/xfs_iget.c b/fs/xfs/xfs_iget.c
index b07604b..eb4db18 100644
--- a/fs/xfs/xfs_iget.c
+++ b/fs/xfs/xfs_iget.c
@@ -216,7 +216,14 @@ finish_inode:
        mrlock_init(&ip->i_iolock, MRLOCK_BARRIER, "xfsio", ip->i_ino);
        init_waitqueue_head(&ip->i_ipin_wait);
        atomic_set(&ip->i_pincount, 0);
-       initnsema(&ip->i_flock, 1, "xfsfino");
+
+       /*
+        * Because we want to use a counting completion, complete
+        * the flush completion once to allow a single access to
+        * the flush completion without blocking.
+        */
+       init_completion(&ip->i_flush);
+       complete(&ip->i_flush);
 
        if (lock_flags)
                xfs_ilock(ip, lock_flags);
@@ -775,26 +782,3 @@ xfs_isilocked(
 }
 #endif
 
-/*
- * The following three routines simply manage the i_flock
- * semaphore embedded in the inode.  This semaphore synchronizes
- * processes attempting to flush the in-core inode back to disk.
- */
-void
-xfs_iflock(xfs_inode_t *ip)
-{
-       psema(&(ip->i_flock), PINOD|PLTWAIT);
-}
-
-int
-xfs_iflock_nowait(xfs_inode_t *ip)
-{
-       return (cpsema(&(ip->i_flock)));
-}
-
-void
-xfs_ifunlock(xfs_inode_t *ip)
-{
-       ASSERT(issemalocked(&(ip->i_flock)));
-       vsema(&(ip->i_flock));
-}
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index bedc661..1047bdc 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -2630,7 +2630,6 @@ xfs_idestroy(
                xfs_idestroy_fork(ip, XFS_ATTR_FORK);
        mrfree(&ip->i_lock);
        mrfree(&ip->i_iolock);
-       freesema(&ip->i_flock);
 
 #ifdef XFS_INODE_TRACE
        ktrace_free(ip->i_trace);
@@ -3048,10 +3047,10 @@ cluster_corrupt_out:
 /*
  * xfs_iflush() will write a modified inode's changes out to the
  * inode's on disk home.  The caller must have the inode lock held
- * in at least shared mode and the inode flush semaphore must be
- * held as well.  The inode lock will still be held upon return from
+ * in at least shared mode and the inode flush completion must be
+ * active as well.  The inode lock will still be held upon return from
  * the call and the caller is free to unlock it.
- * The inode flush lock will be unlocked when the inode reaches the disk.
+ * The inode flush will be completed when the inode reaches the disk.
  * The flags indicate how the inode's buffer should be written out.
  */
 int
@@ -3070,7 +3069,7 @@ xfs_iflush(
        XFS_STATS_INC(xs_iflush_count);
 
        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_ILOCK_SHARED));
-       ASSERT(issemalocked(&(ip->i_flock)));
+       ASSERT(!completion_done(&ip->i_flush));
        ASSERT(ip->i_d.di_format != XFS_DINODE_FMT_BTREE ||
               ip->i_d.di_nextents > ip->i_df.if_ext_max);
 
@@ -3233,7 +3232,7 @@ xfs_iflush_int(
 #endif
 
        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_ILOCK_SHARED));
-       ASSERT(issemalocked(&(ip->i_flock)));
+       ASSERT(!completion_done(&ip->i_flush));
        ASSERT(ip->i_d.di_format != XFS_DINODE_FMT_BTREE ||
               ip->i_d.di_nextents > ip->i_df.if_ext_max);
 
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index 17a04b6..086282d 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -223,7 +223,7 @@ typedef struct xfs_inode {
        struct xfs_inode_log_item *i_itemp;     /* logging information */
        mrlock_t                i_lock;         /* inode lock */
        mrlock_t                i_iolock;       /* inode IO lock */
-       sema_t                  i_flock;        /* inode flush 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 */
@@ -473,11 +473,8 @@ int                xfs_ilock_nowait(xfs_inode_t *, uint);
 void           xfs_iunlock(xfs_inode_t *, uint);
 void           xfs_ilock_demote(xfs_inode_t *, uint);
 int            xfs_isilocked(xfs_inode_t *, uint);
-void           xfs_iflock(xfs_inode_t *);
-int            xfs_iflock_nowait(xfs_inode_t *);
 uint           xfs_ilock_map_shared(xfs_inode_t *);
 void           xfs_iunlock_map_shared(xfs_inode_t *, uint);
-void           xfs_ifunlock(xfs_inode_t *);
 void           xfs_ireclaim(xfs_inode_t *);
 int            xfs_finish_reclaim(xfs_inode_t *, int, int);
 int            xfs_finish_reclaim_all(struct xfs_mount *, int);
@@ -570,6 +567,26 @@ extern struct kmem_zone    *xfs_ifork_zone;
 extern struct kmem_zone        *xfs_inode_zone;
 extern struct kmem_zone        *xfs_ili_zone;
 
+/*
+ * 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);
+}
+
 #endif /* __KERNEL__ */
 
 #endif /* __XFS_INODE_H__ */
diff --git a/fs/xfs/xfs_inode_item.c b/fs/xfs/xfs_inode_item.c
index 0eee08a..97c7452 100644
--- a/fs/xfs/xfs_inode_item.c
+++ b/fs/xfs/xfs_inode_item.c
@@ -779,11 +779,10 @@ xfs_inode_item_pushbuf(
        ASSERT(iip->ili_push_owner == current_pid());
 
        /*
-        * If flushlock isn't locked anymore, chances are that the
-        * inode flush completed and the inode was taken off the AIL.
-        * So, just get out.
+        * If a flush is not in progress anymore, chances are that the
+        * inode was taken off the AIL. So, just get out.
         */
-       if (!issemalocked(&(ip->i_flock)) ||
+       if (completion_done(&ip->i_flush) ||
            ((iip->ili_item.li_flags & XFS_LI_IN_AIL) == 0)) {
                iip->ili_pushbuf_flag = 0;
                xfs_iunlock(ip, XFS_ILOCK_SHARED);
@@ -805,7 +804,7 @@ xfs_inode_item_pushbuf(
                         * If not, we can flush it async.
                         */
                        dopush = ((iip->ili_item.li_flags & XFS_LI_IN_AIL) &&
-                                 issemalocked(&(ip->i_flock)));
+                                 !completion_done(&ip->i_flush));
                        iip->ili_pushbuf_flag = 0;
                        xfs_iunlock(ip, XFS_ILOCK_SHARED);
                        xfs_buftrace("INODE ITEM PUSH", bp);
@@ -858,7 +857,7 @@ xfs_inode_item_push(
        ip = iip->ili_inode;
 
        ASSERT(xfs_isilocked(ip, XFS_ILOCK_SHARED));
-       ASSERT(issemalocked(&(ip->i_flock)));
+       ASSERT(!completion_done(&ip->i_flush));
        /*
         * Since we were able to lock the inode's flush lock and
         * we found it on the AIL, the inode must be dirty.  This
-- 
1.5.5.4


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