[XFS] replace dquot flush semaphore with a completion

Use the new completion flush code to implement the dquot flush lock.
Removes one of the final users of semaphores in the XFS code base.

SGI-PV: 981498

SGI-Modid: xfs-linux-melb:xfs-kern:31822a

Signed-off-by: David Chinner <david@fromorbit.com>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>

4 files changed, 38 insertions, 41 deletions

diff --git a/fs/xfs/quota/xfs_dquot.c b/fs/xfs/quota/xfs_dquot.c
index 9de42d031745..32290578c661 100644
--- a/fs/xfs/quota/xfs_dquot.c
+++ b/fs/xfs/quota/xfs_dquot.c
@@ -101,9 +101,16 @@ xfs_qm_dqinit(
         if (brandnewdquot) {
                 dqp->dq_flnext = dqp->dq_flprev = dqp;
                 mutex_init(&dqp->q_qlock);
-                initnsema(&dqp->q_flock, 1, "fdq");
                 sv_init(&dqp->q_pinwait, SV_DEFAULT, "pdq");
 
+                /*
+                 * 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(&dqp->q_flush);
+                complete(&dqp->q_flush);
+
 #ifdef XFS_DQUOT_TRACE
                 dqp->q_trace = ktrace_alloc(DQUOT_TRACE_SIZE, KM_SLEEP);
                 xfs_dqtrace_entry(dqp, "DQINIT");
@@ -150,7 +157,6 @@ xfs_qm_dqdestroy(
         ASSERT(! XFS_DQ_IS_ON_FREELIST(dqp));
 
         mutex_destroy(&dqp->q_qlock);
-        freesema(&dqp->q_flock);
         sv_destroy(&dqp->q_pinwait);
 
 #ifdef XFS_DQUOT_TRACE
@@ -1211,7 +1217,7 @@ xfs_qm_dqflush(
         int                     error;
 
         ASSERT(XFS_DQ_IS_LOCKED(dqp));
-        ASSERT(XFS_DQ_IS_FLUSH_LOCKED(dqp));
+        ASSERT(!completion_done(&dqp->q_flush));
         xfs_dqtrace_entry(dqp, "DQFLUSH");
 
         /*
@@ -1348,34 +1354,18 @@ xfs_qm_dqflush_done(
         xfs_dqfunlock(dqp);
 }
 
-
-int
-xfs_qm_dqflock_nowait(
-        xfs_dquot_t *dqp)
-{
-        int locked;
-
-        locked = cpsema(&((dqp)->q_flock));
-
-        /* XXX ifdef these out */
-        if (locked)
-                (dqp)->dq_flags |= XFS_DQ_FLOCKED;
-        return (locked);
-}
-
-
 int
 xfs_qm_dqlock_nowait(
         xfs_dquot_t *dqp)
 {
-        return (mutex_trylock(&((dqp)->q_qlock)));
+        return mutex_trylock(&dqp->q_qlock);
 }
 
 void
 xfs_dqlock(
         xfs_dquot_t *dqp)
 {
-        mutex_lock(&(dqp->q_qlock));
+        mutex_lock(&dqp->q_qlock);
 }
 
 void
@@ -1468,7 +1458,7 @@ xfs_qm_dqpurge(
          * if we're turning off quotas. Basically, we need this flush
          * lock, and are willing to block on it.
          */
-        if (! xfs_qm_dqflock_nowait(dqp)) {
+        if (!xfs_dqflock_nowait(dqp)) {
                 /*
                  * Block on the flush lock after nudging dquot buffer,
                  * if it is incore.
diff --git a/fs/xfs/quota/xfs_dquot.h b/fs/xfs/quota/xfs_dquot.h
index f7393bba4e95..8958d0faf8d3 100644
--- a/fs/xfs/quota/xfs_dquot.h
+++ b/fs/xfs/quota/xfs_dquot.h
@@ -82,7 +82,7 @@ typedef struct xfs_dquot {
         xfs_qcnt_t       q_res_icount;  /* total inos allocd+reserved */
         xfs_qcnt_t       q_res_rtbcount;/* total realtime blks used+reserved */
         mutex_t          q_qlock;       /* quota lock */
-        sema_t           q_flock;       /* flush lock */
+        struct completion q_flush;      /* flush completion queue */
         uint             q_pincount;    /* pin count for this dquot */
         sv_t             q_pinwait;     /* sync var for pinning */
 #ifdef XFS_DQUOT_TRACE
@@ -113,17 +113,25 @@ XFS_DQ_IS_LOCKED(xfs_dquot_t *dqp)
 
 
 /*
- * The following three routines simply manage the q_flock
- * semaphore embedded in the dquot.  This semaphore synchronizes
- * processes attempting to flush the in-core dquot back to disk.
+ * Manage the q_flush completion queue embedded in the dquot.  This completion
+ * queue synchronizes processes attempting to flush the in-core dquot back to
+ * disk.
  */
-#define xfs_dqflock(dqp)         { psema(&((dqp)->q_flock), PINOD | PRECALC);\
-                                   (dqp)->dq_flags |= XFS_DQ_FLOCKED; }
-#define xfs_dqfunlock(dqp)       { ASSERT(issemalocked(&((dqp)->q_flock))); \
-                                   vsema(&((dqp)->q_flock)); \
-                                   (dqp)->dq_flags &= ~(XFS_DQ_FLOCKED); }
+static inline void xfs_dqflock(xfs_dquot_t *dqp)
+{
+        wait_for_completion(&dqp->q_flush);
+}
+
+static inline int xfs_dqflock_nowait(xfs_dquot_t *dqp)
+{
+        return try_wait_for_completion(&dqp->q_flush);
+}
+
+static inline void xfs_dqfunlock(xfs_dquot_t *dqp)
+{
+        complete(&dqp->q_flush);
+}
 
-#define XFS_DQ_IS_FLUSH_LOCKED(dqp) (issemalocked(&((dqp)->q_flock)))
 #define XFS_DQ_IS_ON_FREELIST(dqp)  ((dqp)->dq_flnext != (dqp))
 #define XFS_DQ_IS_DIRTY(dqp)    ((dqp)->dq_flags & XFS_DQ_DIRTY)
 #define XFS_QM_ISUDQ(dqp)       ((dqp)->dq_flags & XFS_DQ_USER)
@@ -167,7 +175,6 @@ extern int		xfs_qm_dqflush(xfs_dquot_t *, uint);
 extern int              xfs_qm_dqpurge(xfs_dquot_t *);
 extern void             xfs_qm_dqunpin_wait(xfs_dquot_t *);
 extern int              xfs_qm_dqlock_nowait(xfs_dquot_t *);
-extern int              xfs_qm_dqflock_nowait(xfs_dquot_t *);
 extern void             xfs_qm_dqflock_pushbuf_wait(xfs_dquot_t *dqp);
 extern void             xfs_qm_adjust_dqtimers(xfs_mount_t *,
                                         xfs_disk_dquot_t *);
diff --git a/fs/xfs/quota/xfs_dquot_item.c b/fs/xfs/quota/xfs_dquot_item.c
index 08d2fc89e6a1..f028644caa5e 100644
--- a/fs/xfs/quota/xfs_dquot_item.c
+++ b/fs/xfs/quota/xfs_dquot_item.c
@@ -151,7 +151,7 @@ xfs_qm_dquot_logitem_push(
         dqp = logitem->qli_dquot;
 
         ASSERT(XFS_DQ_IS_LOCKED(dqp));
-        ASSERT(XFS_DQ_IS_FLUSH_LOCKED(dqp));
+        ASSERT(!completion_done(&dqp->q_flush));
 
         /*
          * Since we were able to lock the dquot's flush lock and
@@ -245,7 +245,7 @@ xfs_qm_dquot_logitem_pushbuf(
          * inode flush completed and the inode was taken off the AIL.
          * So, just get out.
          */
-        if (!issemalocked(&(dqp->q_flock))  ||
+        if (completion_done(&dqp->q_flush)  ||
             ((qip->qli_item.li_flags & XFS_LI_IN_AIL) == 0)) {
                 qip->qli_pushbuf_flag = 0;
                 xfs_dqunlock(dqp);
@@ -258,7 +258,7 @@ xfs_qm_dquot_logitem_pushbuf(
         if (bp != NULL) {
                 if (XFS_BUF_ISDELAYWRITE(bp)) {
                         dopush = ((qip->qli_item.li_flags & XFS_LI_IN_AIL) &&
-                                  issemalocked(&(dqp->q_flock)));
+                                  !completion_done(&dqp->q_flush));
                         qip->qli_pushbuf_flag = 0;
                         xfs_dqunlock(dqp);
 
@@ -317,7 +317,7 @@ xfs_qm_dquot_logitem_trylock(
                 return (XFS_ITEM_LOCKED);
 
         retval = XFS_ITEM_SUCCESS;
-        if (! xfs_qm_dqflock_nowait(dqp)) {
+        if (!xfs_dqflock_nowait(dqp)) {
                 /*
                  * The dquot is already being flushed.  It may have been
                  * flushed delayed write, however, and we don't want to
diff --git a/fs/xfs/quota/xfs_qm.c b/fs/xfs/quota/xfs_qm.c
index 021934a3d456..3825d7484079 100644
--- a/fs/xfs/quota/xfs_qm.c
+++ b/fs/xfs/quota/xfs_qm.c
@@ -484,7 +484,7 @@ again:
                 xfs_dqtrace_entry(dqp, "FLUSHALL: DQDIRTY");
                 /* XXX a sentinel would be better */
                 recl = XFS_QI_MPLRECLAIMS(mp);
-                if (! xfs_qm_dqflock_nowait(dqp)) {
+                if (!xfs_dqflock_nowait(dqp)) {
                         /*
                          * If we can't grab the flush lock then check
                          * to see if the dquot has been flushed delayed
@@ -1062,7 +1062,7 @@ xfs_qm_sync(
 
                 /* XXX a sentinel would be better */
                 recl = XFS_QI_MPLRECLAIMS(mp);
-                if (! xfs_qm_dqflock_nowait(dqp)) {
+                if (!xfs_dqflock_nowait(dqp)) {
                         if (nowait) {
                                 xfs_dqunlock(dqp);
                                 continue;
@@ -2079,7 +2079,7 @@ xfs_qm_shake_freelist(
                  * Try to grab the flush lock. If this dquot is in the process of
                  * getting flushed to disk, we don't want to reclaim it.
                  */
-                if (! xfs_qm_dqflock_nowait(dqp)) {
+                if (!xfs_dqflock_nowait(dqp)) {
                         xfs_dqunlock(dqp);
                         dqp = dqp->dq_flnext;
                         continue;
@@ -2257,7 +2257,7 @@ xfs_qm_dqreclaim_one(void)
                  * Try to grab the flush lock. If this dquot is in the process of
                  * getting flushed to disk, we don't want to reclaim it.
                  */
-                if (! xfs_qm_dqflock_nowait(dqp)) {
+                if (!xfs_dqflock_nowait(dqp)) {
                         xfs_dqunlock(dqp);
                         continue;
                 }