4 files changed, 63 insertions, 46 deletions

diff --git a/fs/xfs/linux-2.6/xfs_trace.h b/fs/xfs/linux-2.6/xfs_trace.h
index 3ff6b35f920..b180e1bf825 100644
--- a/fs/xfs/linux-2.6/xfs_trace.h
+++ b/fs/xfs/linux-2.6/xfs_trace.h
@@ -794,7 +794,7 @@ DECLARE_EVENT_CLASS(xfs_loggrant_class,
                                 &__entry->grant_write_bytes);
                 __entry->curr_cycle = log->l_curr_cycle;
                 __entry->curr_block = log->l_curr_block;
-                __entry->tail_lsn = log->l_tail_lsn;
+                __entry->tail_lsn = atomic64_read(&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 reserveq %s "
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 70790eb4833..d118bf80448 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -678,15 +678,11 @@ xfs_log_move_tail(xfs_mount_t	*mp,
         if (tail_lsn == 0)
                 tail_lsn = atomic64_read(&log->l_last_sync_lsn);
 
-        spin_lock(&log->l_grant_lock);
-
-        /* Also an invalid lsn.  1 implies that we aren't passing in a valid
-         * tail_lsn.
-         */
-        if (tail_lsn != 1) {
-                log->l_tail_lsn = tail_lsn;
-        }
+        /* tail_lsn == 1 implies that we weren't passed a valid value.  */
+        if (tail_lsn != 1)
+                atomic64_set(&log->l_tail_lsn, tail_lsn);
 
+        spin_lock(&log->l_grant_lock);
         if (!list_empty(&log->l_writeq)) {
 #ifdef DEBUG
                 if (log->l_flags & XLOG_ACTIVE_RECOVERY)
@@ -789,21 +785,19 @@ xfs_log_need_covered(xfs_mount_t *mp)
  * We may be holding the log iclog lock upon entering this routine.
  */
 xfs_lsn_t
-xlog_assign_tail_lsn(xfs_mount_t *mp)
+xlog_assign_tail_lsn(
+        struct xfs_mount        *mp)
 {
-        xfs_lsn_t tail_lsn;
-        xlog_t    *log = mp->m_log;
+        xfs_lsn_t               tail_lsn;
+        struct log              *log = mp->m_log;
 
         tail_lsn = xfs_trans_ail_tail(mp->m_ail);
-        spin_lock(&log->l_grant_lock);
         if (!tail_lsn)
                 tail_lsn = atomic64_read(&log->l_last_sync_lsn);
-        log->l_tail_lsn = tail_lsn;
-        spin_unlock(&log->l_grant_lock);
 
+        atomic64_set(&log->l_tail_lsn, tail_lsn);
         return tail_lsn;
-}       /* xlog_assign_tail_lsn */
-
+}
 
 /*
  * Return the space in the log between the tail and the head.  The head
@@ -831,8 +825,8 @@ xlog_space_left(
         int             head_bytes;
 
         xlog_crack_grant_head(head, &head_cycle, &head_bytes);
-        tail_bytes = BBTOB(BLOCK_LSN(log->l_tail_lsn));
-        tail_cycle = CYCLE_LSN(log->l_tail_lsn);
+        xlog_crack_atomic_lsn(&log->l_tail_lsn, &tail_cycle, &tail_bytes);
+        tail_bytes = BBTOB(tail_bytes);
         if (tail_cycle == head_cycle && head_bytes >= tail_bytes)
                 free_bytes = log->l_logsize - (head_bytes - tail_bytes);
         else if (tail_cycle + 1 < head_cycle)
@@ -1009,8 +1003,8 @@ xlog_alloc_log(xfs_mount_t	*mp,
 
         log->l_prev_block  = -1;
         /* log->l_tail_lsn = 0x100000000LL; cycle = 1; current block = 0 */
-        log->l_tail_lsn    = xlog_assign_lsn(1, 0);
-        atomic64_set(&log->l_last_sync_lsn, xlog_assign_lsn(1, 0));
+        xlog_assign_atomic_lsn(&log->l_tail_lsn, 1, 0);
+        xlog_assign_atomic_lsn(&log->l_last_sync_lsn, 1, 0);
         log->l_curr_cycle  = 1;     /* 0 is bad since this is initial value */
         xlog_assign_grant_head(&log->l_grant_reserve_head, 1, 0);
         xlog_assign_grant_head(&log->l_grant_write_head, 1, 0);
@@ -1189,7 +1183,6 @@ xlog_grant_push_ail(
 {
         xfs_lsn_t       threshold_lsn = 0;
         xfs_lsn_t       last_sync_lsn;
-        xfs_lsn_t       tail_lsn;
         int             free_blocks;
         int             free_bytes;
         int             threshold_block;
@@ -1198,7 +1191,6 @@ xlog_grant_push_ail(
 
         ASSERT(BTOBB(need_bytes) < log->l_logBBsize);
 
-        tail_lsn = log->l_tail_lsn;
         free_bytes = xlog_space_left(log, &log->l_grant_reserve_head);
         free_blocks = BTOBBT(free_bytes);
 
@@ -1213,8 +1205,9 @@ xlog_grant_push_ail(
         if (free_blocks >= free_threshold)
                 return;
 
-        threshold_block = BLOCK_LSN(tail_lsn) + free_threshold;
-        threshold_cycle = CYCLE_LSN(tail_lsn);
+        xlog_crack_atomic_lsn(&log->l_tail_lsn, &threshold_cycle,
+                                                &threshold_block);
+        threshold_block += free_threshold;
         if (threshold_block >= log->l_logBBsize) {
                 threshold_block -= log->l_logBBsize;
                 threshold_cycle += 1;
@@ -2828,11 +2821,11 @@ xlog_state_release_iclog(
 
         if (iclog->ic_state == XLOG_STATE_WANT_SYNC) {
                 /* update tail before writing to iclog */
-                xlog_assign_tail_lsn(log->l_mp);
+                xfs_lsn_t tail_lsn = xlog_assign_tail_lsn(log->l_mp);
                 sync++;
                 iclog->ic_state = XLOG_STATE_SYNCING;
-                iclog->ic_header.h_tail_lsn = cpu_to_be64(log->l_tail_lsn);
-                xlog_verify_tail_lsn(log, iclog, log->l_tail_lsn);
+                iclog->ic_header.h_tail_lsn = cpu_to_be64(tail_lsn);
+                xlog_verify_tail_lsn(log, iclog, tail_lsn);
                 /* cycle incremented when incrementing curr_block */
         }
         spin_unlock(&log->l_icloglock);
@@ -3435,7 +3428,7 @@ STATIC void
 xlog_verify_grant_tail(
         struct log      *log)
 {
-        xfs_lsn_t       tail_lsn = log->l_tail_lsn;
+        int             tail_cycle, tail_blocks;
         int             cycle, space;
 
         /*
@@ -3445,9 +3438,10 @@ xlog_verify_grant_tail(
          * check the byte count.
          */
         xlog_crack_grant_head(&log->l_grant_write_head, &cycle, &space);
-        if (CYCLE_LSN(tail_lsn) != cycle) {
-                ASSERT(cycle - 1 == CYCLE_LSN(tail_lsn));
-                ASSERT(space <= BBTOB(BLOCK_LSN(tail_lsn)));
+        xlog_crack_atomic_lsn(&log->l_tail_lsn, &tail_cycle, &tail_blocks);
+        if (tail_cycle != cycle) {
+                ASSERT(cycle - 1 == tail_cycle);
+                ASSERT(space <= BBTOB(tail_blocks));
         }
 }
 
diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index 958f356df10..d34af1c21ed 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h
@@ -53,7 +53,6 @@ struct xfs_mount;
         BTOBB(XLOG_MAX_ICLOGS << (xfs_sb_version_haslogv2(&log->l_mp->m_sb) ? \
          XLOG_MAX_RECORD_BSHIFT : XLOG_BIG_RECORD_BSHIFT))
 
-
 static inline xfs_lsn_t xlog_assign_lsn(uint cycle, uint block)
 {
         return ((xfs_lsn_t)cycle << 32) | block;
@@ -505,8 +504,6 @@ typedef struct log {
                                                  * log entries" */
         xlog_in_core_t          *l_iclog;       /* head log queue       */
         spinlock_t              l_icloglock;    /* grab to change iclog state */
-        xfs_lsn_t               l_tail_lsn;     /* lsn of 1st LR with unflushed
-                                                 * buffers */
         int                     l_curr_cycle;   /* Cycle number of log writes */
         int                     l_prev_cycle;   /* Cycle number before last
                                                  * block increment */
@@ -521,12 +518,15 @@ typedef struct log {
         int64_t                 l_grant_write_head;
 
         /*
-         * l_last_sync_lsn is an atomic so it can be set and read without
-         * needing to hold specific locks. To avoid operations contending with
-         * other hot objects, place it on a separate cacheline.
+         * l_last_sync_lsn and l_tail_lsn are atomics so they can be set and
+         * read without needing to hold specific locks. To avoid operations
+         * contending with other hot objects, place each of them on a separate
+         * cacheline.
          */
         /* lsn of last LR on disk */
         atomic64_t              l_last_sync_lsn ____cacheline_aligned_in_smp;
+        /* lsn of 1st LR with unflushed * buffers */
+        atomic64_t              l_tail_lsn ____cacheline_aligned_in_smp;
 
         /* The following field are used for debugging; need to hold icloglock */
 #ifdef DEBUG
@@ -566,6 +566,31 @@ int	xlog_write(struct log *log, struct xfs_log_vec *log_vector,
                                 xlog_in_core_t **commit_iclog, uint flags);
 
 /*
+ * When we crack an atomic LSN, we sample it first so that the value will not
+ * change while we are cracking it into the component values. This means we
+ * will always get consistent component values to work from. This should always
+ * be used to smaple and crack LSNs taht are stored and updated in atomic
+ * variables.
+ */
+static inline void
+xlog_crack_atomic_lsn(atomic64_t *lsn, uint *cycle, uint *block)
+{
+        xfs_lsn_t val = atomic64_read(lsn);
+
+        *cycle = CYCLE_LSN(val);
+        *block = BLOCK_LSN(val);
+}
+
+/*
+ * Calculate and assign a value to an atomic LSN variable from component pieces.
+ */
+static inline void
+xlog_assign_atomic_lsn(atomic64_t *lsn, uint cycle, uint block)
+{
+        atomic64_set(lsn, xlog_assign_lsn(cycle, block));
+}
+
+/*
  * When we crack the grrant head, we sample it first so that the value will not
  * change while we are cracking it into the component values. This means we
  * will always get consistent component values to work from.
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 18e1e18d714..204d8e5fa7f 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -936,7 +936,7 @@ xlog_find_tail(
         log->l_curr_cycle = be32_to_cpu(rhead->h_cycle);
         if (found == 2)
                 log->l_curr_cycle++;
-        log->l_tail_lsn = be64_to_cpu(rhead->h_tail_lsn);
+        atomic64_set(&log->l_tail_lsn, be64_to_cpu(rhead->h_tail_lsn));
         atomic64_set(&log->l_last_sync_lsn, be64_to_cpu(rhead->h_lsn));
         xlog_assign_grant_head(&log->l_grant_reserve_head, log->l_curr_cycle,
                                         BBTOB(log->l_curr_block));
@@ -971,7 +971,7 @@ xlog_find_tail(
         }
         after_umount_blk = (i + hblks + (int)
                 BTOBB(be32_to_cpu(rhead->h_len))) % log->l_logBBsize;
-        tail_lsn = log->l_tail_lsn;
+        tail_lsn = atomic64_read(&log->l_tail_lsn);
         if (*head_blk == after_umount_blk &&
             be32_to_cpu(rhead->h_num_logops) == 1) {
                 umount_data_blk = (i + hblks) % log->l_logBBsize;
@@ -986,12 +986,10 @@ xlog_find_tail(
                          * log records will point recovery to after the
                          * current unmount record.
                          */
-                        log->l_tail_lsn =
-                                xlog_assign_lsn(log->l_curr_cycle,
-                                                after_umount_blk);
-                        atomic64_set(&log->l_last_sync_lsn,
-                                xlog_assign_lsn(log->l_curr_cycle,
-                                                after_umount_blk));
+                        xlog_assign_atomic_lsn(&log->l_tail_lsn,
+                                        log->l_curr_cycle, after_umount_blk);
+                        xlog_assign_atomic_lsn(&log->l_last_sync_lsn,
+                                        log->l_curr_cycle, after_umount_blk);
                         *tail_blk = after_umount_blk;
 
                         /*