xfs: convert log grant ticket queues to list heads

The grant write and reserve queues use a roll-your-own double linked
list, so convert it to a standard list_head structure and convert
all the list traversals to use list_for_each_entry(). We can also
get rid of the XLOG_TIC_IN_Q flag as we can use the list_empty()
check to tell if the ticket is in a list or not.

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

3 files changed, 53 insertions, 97 deletions

diff --git a/fs/xfs/linux-2.6/xfs_trace.h b/fs/xfs/linux-2.6/xfs_trace.h
index 83e8760159ef..69b9e1f1baaf 100644
--- a/fs/xfs/linux-2.6/xfs_trace.h
+++ b/fs/xfs/linux-2.6/xfs_trace.h
@@ -766,8 +766,8 @@ DECLARE_EVENT_CLASS(xfs_loggrant_class,
                 __field(int, curr_res)
                 __field(int, unit_res)
                 __field(unsigned int, flags)
-                __field(void *, reserve_headq)
-                __field(void *, write_headq)
+                __field(int, reserveq)
+                __field(int, writeq)
                 __field(int, grant_reserve_cycle)
                 __field(int, grant_reserve_bytes)
                 __field(int, grant_write_cycle)
@@ -784,8 +784,8 @@ DECLARE_EVENT_CLASS(xfs_loggrant_class,
                 __entry->curr_res = tic->t_curr_res;
                 __entry->unit_res = tic->t_unit_res;
                 __entry->flags = tic->t_flags;
-                __entry->reserve_headq = log->l_reserve_headq;
-                __entry->write_headq = log->l_write_headq;
+                __entry->reserveq = list_empty(&log->l_reserveq);
+                __entry->writeq = list_empty(&log->l_writeq);
                 __entry->grant_reserve_cycle = log->l_grant_reserve_cycle;
                 __entry->grant_reserve_bytes = log->l_grant_reserve_bytes;
                 __entry->grant_write_cycle = log->l_grant_write_cycle;
@@ -795,8 +795,8 @@ DECLARE_EVENT_CLASS(xfs_loggrant_class,
                 __entry->tail_lsn = log->l_tail_lsn;
         ),
         TP_printk("dev %d:%d type %s t_ocnt %u t_cnt %u t_curr_res %u "
-                  "t_unit_res %u t_flags %s reserve_headq 0x%p "
-                  "write_headq 0x%p grant_reserve_cycle %d "
+                  "t_unit_res %u t_flags %s reserveq %s "
+                  "writeq %s grant_reserve_cycle %d "
                   "grant_reserve_bytes %d grant_write_cycle %d "
                   "grant_write_bytes %d curr_cycle %d curr_block %d "
                   "tail_cycle %d tail_block %d",
@@ -807,8 +807,8 @@ DECLARE_EVENT_CLASS(xfs_loggrant_class,
                   __entry->curr_res,
                   __entry->unit_res,
                   __print_flags(__entry->flags, "|", XLOG_TIC_FLAGS),
-                  __entry->reserve_headq,
-                  __entry->write_headq,
+                  __entry->reserveq ? "empty" : "active",
+                  __entry->writeq ? "empty" : "active",
                   __entry->grant_reserve_cycle,
                   __entry->grant_reserve_bytes,
                   __entry->grant_write_cycle,
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index cee4ab9f8a9e..1b82735471ab 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -95,38 +95,6 @@ STATIC void	xlog_verify_tail_lsn(xlog_t *log, xlog_in_core_t *iclog,
 
 STATIC int      xlog_iclogs_empty(xlog_t *log);
 
-
-static void
-xlog_ins_ticketq(struct xlog_ticket **qp, struct xlog_ticket *tic)
-{
-        if (*qp) {
-                tic->t_next         = (*qp);
-                tic->t_prev         = (*qp)->t_prev;
-                (*qp)->t_prev->t_next = tic;
-                (*qp)->t_prev       = tic;
-        } else {
-                tic->t_prev = tic->t_next = tic;
-                *qp = tic;
-        }
-
-        tic->t_flags |= XLOG_TIC_IN_Q;
-}
-
-static void
-xlog_del_ticketq(struct xlog_ticket **qp, struct xlog_ticket *tic)
-{
-        if (tic == tic->t_next) {
-                *qp = NULL;
-        } else {
-                *qp = tic->t_next;
-                tic->t_next->t_prev = tic->t_prev;
-                tic->t_prev->t_next = tic->t_next;
-        }
-
-        tic->t_next = tic->t_prev = NULL;
-        tic->t_flags &= ~XLOG_TIC_IN_Q;
-}
-
 static void
 xlog_grant_sub_space(struct log *log, int bytes)
 {
@@ -724,7 +692,7 @@ xfs_log_move_tail(xfs_mount_t	*mp,
                 log->l_tail_lsn = tail_lsn;
         }
 
-        if ((tic = log->l_write_headq)) {
+        if (!list_empty(&log->l_writeq)) {
 #ifdef DEBUG
                 if (log->l_flags & XLOG_ACTIVE_RECOVERY)
                         panic("Recovery problem");
@@ -732,7 +700,7 @@ xfs_log_move_tail(xfs_mount_t	*mp,
                 cycle = log->l_grant_write_cycle;
                 bytes = log->l_grant_write_bytes;
                 free_bytes = xlog_space_left(log, cycle, bytes);
-                do {
+                list_for_each_entry(tic, &log->l_writeq, t_queue) {
                         ASSERT(tic->t_flags & XLOG_TIC_PERM_RESERV);
 
                         if (free_bytes < tic->t_unit_res && tail_lsn != 1)
@@ -740,10 +708,10 @@ xfs_log_move_tail(xfs_mount_t	*mp,
                         tail_lsn = 0;
                         free_bytes -= tic->t_unit_res;
                         sv_signal(&tic->t_wait);
-                        tic = tic->t_next;
-                } while (tic != log->l_write_headq);
+                }
         }
-        if ((tic = log->l_reserve_headq)) {
+
+        if (!list_empty(&log->l_reserveq)) {
 #ifdef DEBUG
                 if (log->l_flags & XLOG_ACTIVE_RECOVERY)
                         panic("Recovery problem");
@@ -751,7 +719,7 @@ xfs_log_move_tail(xfs_mount_t	*mp,
                 cycle = log->l_grant_reserve_cycle;
                 bytes = log->l_grant_reserve_bytes;
                 free_bytes = xlog_space_left(log, cycle, bytes);
-                do {
+                list_for_each_entry(tic, &log->l_reserveq, t_queue) {
                         if (tic->t_flags & XLOG_TIC_PERM_RESERV)
                                 need_bytes = tic->t_unit_res*tic->t_cnt;
                         else
@@ -761,8 +729,7 @@ xfs_log_move_tail(xfs_mount_t	*mp,
                         tail_lsn = 0;
                         free_bytes -= need_bytes;
                         sv_signal(&tic->t_wait);
-                        tic = tic->t_next;
-                } while (tic != log->l_reserve_headq);
+                }
         }
         spin_unlock(&log->l_grant_lock);
 }       /* xfs_log_move_tail */
@@ -1053,6 +1020,8 @@ xlog_alloc_log(xfs_mount_t	*mp,
         log->l_curr_cycle  = 1;     /* 0 is bad since this is initial value */
         log->l_grant_reserve_cycle = 1;
         log->l_grant_write_cycle = 1;
+        INIT_LIST_HEAD(&log->l_reserveq);
+        INIT_LIST_HEAD(&log->l_writeq);
 
         error = EFSCORRUPTED;
         if (xfs_sb_version_hassector(&mp->m_sb)) {
@@ -2550,8 +2519,8 @@ xlog_grant_log_space(xlog_t	   *log,
         trace_xfs_log_grant_enter(log, tic);
 
         /* something is already sleeping; insert new transaction at end */
-        if (log->l_reserve_headq) {
-                xlog_ins_ticketq(&log->l_reserve_headq, tic);
+        if (!list_empty(&log->l_reserveq)) {
+                list_add_tail(&tic->t_queue, &log->l_reserveq);
 
                 trace_xfs_log_grant_sleep1(log, tic);
 
@@ -2583,8 +2552,8 @@ redo:
         free_bytes = xlog_space_left(log, log->l_grant_reserve_cycle,
                                      log->l_grant_reserve_bytes);
         if (free_bytes < need_bytes) {
-                if ((tic->t_flags & XLOG_TIC_IN_Q) == 0)
-                        xlog_ins_ticketq(&log->l_reserve_headq, tic);
+                if (list_empty(&tic->t_queue))
+                        list_add_tail(&tic->t_queue, &log->l_reserveq);
 
                 trace_xfs_log_grant_sleep2(log, tic);
 
@@ -2602,8 +2571,9 @@ redo:
                 trace_xfs_log_grant_wake2(log, tic);
 
                 goto redo;
-        } else if (tic->t_flags & XLOG_TIC_IN_Q)
-                xlog_del_ticketq(&log->l_reserve_headq, tic);
+        }
+
+        list_del_init(&tic->t_queue);
 
         /* we've got enough space */
         xlog_grant_add_space(log, need_bytes);
@@ -2626,9 +2596,7 @@ redo:
         return 0;
 
  error_return:
-        if (tic->t_flags & XLOG_TIC_IN_Q)
-                xlog_del_ticketq(&log->l_reserve_headq, tic);
-
+        list_del_init(&tic->t_queue);
         trace_xfs_log_grant_error(log, tic);
 
         /*
@@ -2653,7 +2621,6 @@ xlog_regrant_write_log_space(xlog_t	   *log,
                              xlog_ticket_t *tic)
 {
         int             free_bytes, need_bytes;
-        xlog_ticket_t   *ntic;
 #ifdef DEBUG
         xfs_lsn_t       tail_lsn;
 #endif
@@ -2683,22 +2650,23 @@ xlog_regrant_write_log_space(xlog_t	   *log,
          * this transaction.
          */
         need_bytes = tic->t_unit_res;
-        if ((ntic = log->l_write_headq)) {
+        if (!list_empty(&log->l_writeq)) {
+                struct xlog_ticket *ntic;
                 free_bytes = xlog_space_left(log, log->l_grant_write_cycle,
                                              log->l_grant_write_bytes);
-                do {
+                list_for_each_entry(ntic, &log->l_writeq, t_queue) {
                         ASSERT(ntic->t_flags & XLOG_TIC_PERM_RESERV);
 
                         if (free_bytes < ntic->t_unit_res)
                                 break;
                         free_bytes -= ntic->t_unit_res;
                         sv_signal(&ntic->t_wait);
-                        ntic = ntic->t_next;
-                } while (ntic != log->l_write_headq);
+                }
 
-                if (ntic != log->l_write_headq) {
-                        if ((tic->t_flags & XLOG_TIC_IN_Q) == 0)
-                                xlog_ins_ticketq(&log->l_write_headq, tic);
+                if (ntic != list_first_entry(&log->l_writeq,
+                                                struct xlog_ticket, t_queue)) {
+                        if (list_empty(&tic->t_queue))
+                                list_add_tail(&tic->t_queue, &log->l_writeq);
 
                         trace_xfs_log_regrant_write_sleep1(log, tic);
 
@@ -2727,8 +2695,8 @@ redo:
         free_bytes = xlog_space_left(log, log->l_grant_write_cycle,
                                      log->l_grant_write_bytes);
         if (free_bytes < need_bytes) {
-                if ((tic->t_flags & XLOG_TIC_IN_Q) == 0)
-                        xlog_ins_ticketq(&log->l_write_headq, tic);
+                if (list_empty(&tic->t_queue))
+                        list_add_tail(&tic->t_queue, &log->l_writeq);
                 spin_unlock(&log->l_grant_lock);
                 xlog_grant_push_ail(log->l_mp, need_bytes);
                 spin_lock(&log->l_grant_lock);
@@ -2745,8 +2713,9 @@ redo:
 
                 trace_xfs_log_regrant_write_wake2(log, tic);
                 goto redo;
-        } else if (tic->t_flags & XLOG_TIC_IN_Q)
-                xlog_del_ticketq(&log->l_write_headq, tic);
+        }
+
+        list_del_init(&tic->t_queue);
 
         /* we've got enough space */
         xlog_grant_add_space_write(log, need_bytes);
@@ -2766,9 +2735,7 @@ redo:
 
 
  error_return:
-        if (tic->t_flags & XLOG_TIC_IN_Q)
-                xlog_del_ticketq(&log->l_reserve_headq, tic);
-
+        list_del_init(&tic->t_queue);
         trace_xfs_log_regrant_write_error(log, tic);
 
         /*
@@ -3435,6 +3402,7 @@ xlog_ticket_alloc(
         }
 
         atomic_set(&tic->t_ref, 1);
+        INIT_LIST_HEAD(&tic->t_queue);
         tic->t_unit_res         = unit_bytes;
         tic->t_curr_res         = unit_bytes;
         tic->t_cnt              = cnt;
@@ -3742,26 +3710,17 @@ xfs_log_force_umount(
         spin_unlock(&log->l_icloglock);
 
         /*
-         * We don't want anybody waiting for log reservations
-         * after this. That means we have to wake up everybody
-         * queued up on reserve_headq as well as write_headq.
-         * In addition, we make sure in xlog_{re}grant_log_space
-         * that we don't enqueue anything once the SHUTDOWN flag
-         * is set, and this action is protected by the GRANTLOCK.
+         * We don't want anybody waiting for log reservations after this. That
+         * means we have to wake up everybody queued up on reserveq as well as
+         * writeq.  In addition, we make sure in xlog_{re}grant_log_space that
+         * we don't enqueue anything once the SHUTDOWN flag is set, and this
+         * action is protected by the GRANTLOCK.
          */
-        if ((tic = log->l_reserve_headq)) {
-                do {
-                        sv_signal(&tic->t_wait);
-                        tic = tic->t_next;
-                } while (tic != log->l_reserve_headq);
-        }
+        list_for_each_entry(tic, &log->l_reserveq, t_queue)
+                sv_signal(&tic->t_wait);
 
-        if ((tic = log->l_write_headq)) {
-                do {
-                        sv_signal(&tic->t_wait);
-                        tic = tic->t_next;
-                } while (tic != log->l_write_headq);
-        }
+        list_for_each_entry(tic, &log->l_writeq, t_queue)
+                sv_signal(&tic->t_wait);
         spin_unlock(&log->l_grant_lock);
 
         if (!(log->l_iclog->ic_state & XLOG_STATE_IOERROR)) {
diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index c1ce505313e9..a5b3c021a406 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h
@@ -132,12 +132,10 @@ static inline uint xlog_get_client_id(__be32 i)
  */
 #define XLOG_TIC_INITED         0x1     /* has been initialized */
 #define XLOG_TIC_PERM_RESERV    0x2     /* permanent reservation */
-#define XLOG_TIC_IN_Q           0x4
 
 #define XLOG_TIC_FLAGS \
         { XLOG_TIC_INITED,      "XLOG_TIC_INITED" }, \
-        { XLOG_TIC_PERM_RESERV, "XLOG_TIC_PERM_RESERV" }, \
-        { XLOG_TIC_IN_Q,        "XLOG_TIC_IN_Q" }
+        { XLOG_TIC_PERM_RESERV, "XLOG_TIC_PERM_RESERV" }
 
 #endif  /* __KERNEL__ */
 
@@ -244,8 +242,7 @@ typedef struct xlog_res {
 
 typedef struct xlog_ticket {
         sv_t               t_wait;       /* ticket wait queue            : 20 */
-        struct xlog_ticket *t_next;      /*                              :4|8 */
-        struct xlog_ticket *t_prev;      /*                              :4|8 */
+        struct list_head   t_queue;      /* reserve/write queue */
         xlog_tid_t         t_tid;        /* transaction identifier       : 4  */
         atomic_t           t_ref;        /* ticket reference count       : 4  */
         int                t_curr_res;   /* current reservation in bytes : 4  */
@@ -519,8 +516,8 @@ typedef struct log {
 
         /* The following block of fields are changed while holding grant_lock */
         spinlock_t              l_grant_lock ____cacheline_aligned_in_smp;
-        xlog_ticket_t           *l_reserve_headq;
-        xlog_ticket_t           *l_write_headq;
+        struct list_head        l_reserveq;
+        struct list_head        l_writeq;
         int                     l_grant_reserve_cycle;
         int                     l_grant_reserve_bytes;
         int                     l_grant_write_cycle;