xfs: share code for grant head availability checks

Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

1 files changed, 60 insertions, 73 deletions

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 685997548fb8..c6a29a05c60a 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -245,6 +245,60 @@ shutdown:
         return XFS_ERROR(EIO);
 }
 
+/*
+ * Atomically get the log space required for a log ticket.
+ *
+ * Once a ticket gets put onto head->waiters, it will only return after the
+ * needed reservation is satisfied.
+ *
+ * This function is structured so that it has a lock free fast path. This is
+ * necessary because every new transaction reservation will come through this
+ * path. Hence any lock will be globally hot if we take it unconditionally on
+ * every pass.
+ *
+ * As tickets are only ever moved on and off head->waiters under head->lock, we
+ * only need to take that lock if we are going to add the ticket to the queue
+ * and sleep. We can avoid taking the lock if the ticket was never added to
+ * head->waiters because the t_queue list head will be empty and we hold the
+ * only reference to it so it can safely be checked unlocked.
+ */
+STATIC int
+xlog_grant_head_check(
+        struct log              *log,
+        struct xlog_grant_head  *head,
+        struct xlog_ticket      *tic,
+        int                     *need_bytes)
+{
+        int                     free_bytes;
+        int                     error = 0;
+
+        ASSERT(!(log->l_flags & XLOG_ACTIVE_RECOVERY));
+
+        /*
+         * If there are other waiters on the queue then give them a chance at
+         * logspace before us.  Wake up the first waiters, if we do not wake
+         * up all the waiters then go to sleep waiting for more free space,
+         * otherwise try to get some space for this transaction.
+         */
+        *need_bytes = xlog_ticket_reservation(log, head, tic);
+        free_bytes = xlog_space_left(log, &head->grant);
+        if (!list_empty_careful(&head->waiters)) {
+                spin_lock(&head->lock);
+                if (!xlog_grant_head_wake(log, head, &free_bytes) ||
+                    free_bytes < *need_bytes) {
+                        error = xlog_grant_head_wait(log, head, tic,
+                                                     *need_bytes);
+                }
+                spin_unlock(&head->lock);
+        } else if (free_bytes < *need_bytes) {
+                spin_lock(&head->lock);
+                error = xlog_grant_head_wait(log, head, tic, *need_bytes);
+                spin_unlock(&head->lock);
+        }
+
+        return error;
+}
+
 static void
 xlog_tic_reset_res(xlog_ticket_t *tic)
 {
@@ -2511,59 +2565,18 @@ restart:
         return 0;
 }       /* xlog_state_get_iclog_space */
 
-/*
- * Atomically get the log space required for a log ticket.
- *
- * Once a ticket gets put onto the reserveq, it will only return after the
- * needed reservation is satisfied.
- *
- * This function is structured so that it has a lock free fast path. This is
- * necessary because every new transaction reservation will come through this
- * path. Hence any lock will be globally hot if we take it unconditionally on
- * every pass.
- *
- * As tickets are only ever moved on and off the l_reserve.waiters under the
- * l_reserve.lock, we only need to take that lock if we are going to add
- * the ticket to the queue and sleep. We can avoid taking the lock if the ticket
- * was never added to the reserveq because the t_queue list head will be empty
- * and we hold the only reference to it so it can safely be checked unlocked.
- */
 STATIC int
 xlog_grant_log_space(
         struct log              *log,
         struct xlog_ticket      *tic)
 {
-        int                     free_bytes, need_bytes;
+        int                     need_bytes;
         int                     error = 0;
 
-        ASSERT(!(log->l_flags & XLOG_ACTIVE_RECOVERY));
-
         trace_xfs_log_grant_enter(log, tic);
 
-        /*
-         * If there are other waiters on the queue then give them a chance at
-         * logspace before us.  Wake up the first waiters, if we do not wake
-         * up all the waiters then go to sleep waiting for more free space,
-         * otherwise try to get some space for this transaction.
-         */
-        need_bytes = tic->t_unit_res;
-        if (tic->t_flags & XFS_LOG_PERM_RESERV)
-                need_bytes *= tic->t_ocnt;
-        free_bytes = xlog_space_left(log, &log->l_reserve_head.grant);
-        if (!list_empty_careful(&log->l_reserve_head.waiters)) {
-                spin_lock(&log->l_reserve_head.lock);
-                if (!xlog_grant_head_wake(log, &log->l_reserve_head, &free_bytes) ||
-                    free_bytes < need_bytes) {
-                        error = xlog_grant_head_wait(log, &log->l_reserve_head,
-                                                     tic, need_bytes);
-                }
-                spin_unlock(&log->l_reserve_head.lock);
-        } else if (free_bytes < need_bytes) {
-                spin_lock(&log->l_reserve_head.lock);
-                error = xlog_grant_head_wait(log, &log->l_reserve_head, tic,
-                                             need_bytes);
-                spin_unlock(&log->l_reserve_head.lock);
-        }
+        error = xlog_grant_head_check(log, &log->l_reserve_head, tic,
+                                      &need_bytes);
         if (error)
                 return error;
 
@@ -2576,16 +2589,13 @@ xlog_grant_log_space(
 
 /*
  * Replenish the byte reservation required by moving the grant write head.
- *
- * Similar to xlog_grant_log_space, the function is structured to have a lock
- * free fast path.
  */
 STATIC int
 xlog_regrant_write_log_space(
         struct log              *log,
         struct xlog_ticket      *tic)
 {
-        int                     free_bytes, need_bytes;
+        int                     need_bytes;
         int                     error = 0;
 
         tic->t_curr_res = tic->t_unit_res;
@@ -2594,33 +2604,10 @@ xlog_regrant_write_log_space(
         if (tic->t_cnt > 0)
                 return 0;
 
-        ASSERT(!(log->l_flags & XLOG_ACTIVE_RECOVERY));
-
         trace_xfs_log_regrant_write_enter(log, tic);
 
-        /*
-         * If there are other waiters on the queue then give them a chance at
-         * logspace before us.  Wake up the first waiters, if we do not wake
-         * up all the waiters then go to sleep waiting for more free space,
-         * otherwise try to get some space for this transaction.
-         */
-        need_bytes = tic->t_unit_res;
-        free_bytes = xlog_space_left(log, &log->l_write_head.grant);
-        if (!list_empty_careful(&log->l_write_head.waiters)) {
-                spin_lock(&log->l_write_head.lock);
-                if (!xlog_grant_head_wake(log, &log->l_write_head, &free_bytes) ||
-                    free_bytes < need_bytes) {
-                        error = xlog_grant_head_wait(log, &log->l_write_head,
-                                                     tic, need_bytes);
-                }
-                spin_unlock(&log->l_write_head.lock);
-        } else if (free_bytes < need_bytes) {
-                spin_lock(&log->l_write_head.lock);
-                error = xlog_grant_head_wait(log, &log->l_write_head, tic,
-                                             need_bytes);
-                spin_unlock(&log->l_write_head.lock);
-        }
-
+        error = xlog_grant_head_check(log, &log->l_write_head, tic,
+                                      &need_bytes);
         if (error)
                 return error;