[PATCH 26/34] xfs: combine grant heads into a single 64 bit integer

Dave Chinner
2010-12-21T07:28:34Z

Prepare for switching the grant heads to atomic variables by
combining the two 32 bit values that make up the grant head into a
single 64 bit variable. Provide wrapper functions to combine and
split the grant heads appropriately for calculations and use them as
necessary.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
fs/xfs/linux-2.6/xfs_trace.h | 10 ++-
fs/xfs/xfs_log.c | 166 ++++++++++++++++++++++--------------------
fs/xfs/xfs_log_priv.h | 26 ++++++-
fs/xfs/xfs_log_recover.c | 8 +-
4 files changed, 119 insertions(+), 91 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_trace.h b/fs/xfs/linux-2.6/xfs_trace.h
index 69b9e1f..3ff6b35 100644
--- a/fs/xfs/linux-2.6/xfs_trace.h
+++ b/fs/xfs/linux-2.6/xfs_trace.h
@@ -786,10 +786,12 @@ DECLARE_EVENT_CLASS(xfs_loggrant_class,
__entry->flags = tic->t_flags;
__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;
- __entry->grant_write_bytes = log->l_grant_write_bytes;
+ xlog_crack_grant_head(&log->l_grant_reserve_head,
+ &__entry->grant_reserve_cycle,
+ &__entry->grant_reserve_bytes);
+ xlog_crack_grant_head(&log->l_grant_write_head,
+ &__entry->grant_write_cycle,
+ &__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;
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 9a4b9ed..6bba8b4 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -47,7 +47,7 @@ STATIC xlog_t * xlog_alloc_log(xfs_mount_t *mp,
xfs_buftarg_t *log_target,
xfs_daddr_t blk_offset,
int num_bblks);
-STATIC int xlog_space_left(xlog_t *log, int cycle, int bytes);
+STATIC int xlog_space_left(struct log *log, int64_t *head);
STATIC int xlog_sync(xlog_t *log, xlog_in_core_t *iclog);
STATIC void xlog_dealloc_log(xlog_t *log);

@@ -100,32 +100,44 @@ STATIC int xlog_iclogs_empty(xlog_t *log);
static void
xlog_grant_sub_space(
struct log *log,
- int *cycle,
- int *space,
+ int64_t *head,
int bytes)
{
- *space -= bytes;
- if (*space < 0) {
- *space += log->l_logsize;
- (*cycle)--;
+ int cycle, space;
+
+ xlog_crack_grant_head(head, &cycle, &space);
+
+ space -= bytes;
+ if (space < 0) {
+ space += log->l_logsize;
+ cycle--;
}
+
+ xlog_assign_grant_head(head, cycle, space);
}

static void
xlog_grant_add_space(
struct log *log,
- int *cycle,
- int *space,
+ int64_t *head,
int bytes)
{
- int tmp = log->l_logsize - *space;
+ int tmp;
+ int cycle, space;
+
+ xlog_crack_grant_head(head, &cycle, &space);
+
+ tmp = log->l_logsize - space;
if (tmp > bytes)
- *space += bytes;
+ space += bytes;
else {
- *space = bytes - tmp;
- (*cycle)++;
+ space = bytes - tmp;
+ cycle++;
}
+
+ xlog_assign_grant_head(head, cycle, space);
}
+
static void
xlog_tic_reset_res(xlog_ticket_t *tic)
{
@@ -654,7 +666,7 @@ xfs_log_move_tail(xfs_mount_t *mp,
{
xlog_ticket_t *tic;
xlog_t *log = mp->m_log;
- int need_bytes, free_bytes, cycle, bytes;
+ int need_bytes, free_bytes;

if (XLOG_FORCED_SHUTDOWN(log))
return;
@@ -680,9 +692,7 @@ xfs_log_move_tail(xfs_mount_t *mp,
if (log->l_flags & XLOG_ACTIVE_RECOVERY)
panic("Recovery problem");
#endif
- cycle = log->l_grant_write_cycle;
- bytes = log->l_grant_write_bytes;
- free_bytes = xlog_space_left(log, cycle, bytes);
+ free_bytes = xlog_space_left(log, &log->l_grant_write_head);
list_for_each_entry(tic, &log->l_writeq, t_queue) {
ASSERT(tic->t_flags & XLOG_TIC_PERM_RESERV);

@@ -699,9 +709,7 @@ xfs_log_move_tail(xfs_mount_t *mp,
if (log->l_flags & XLOG_ACTIVE_RECOVERY)
panic("Recovery problem");
#endif
- cycle = log->l_grant_reserve_cycle;
- bytes = log->l_grant_reserve_bytes;
- free_bytes = xlog_space_left(log, cycle, bytes);
+ free_bytes = xlog_space_left(log, &log->l_grant_reserve_head);
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;
@@ -814,21 +822,26 @@ xlog_assign_tail_lsn(xfs_mount_t *mp)
* result is that we return the size of the log as the amount of space left.
*/
STATIC int
-xlog_space_left(xlog_t *log, int cycle, int bytes)
+xlog_space_left(
+ struct log *log,
+ int64_t *head)
{
- int free_bytes;
- int tail_bytes;
- int tail_cycle;
+ int free_bytes;
+ int tail_bytes;
+ int tail_cycle;
+ int head_cycle;
+ 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);
- if ((tail_cycle == cycle) && (bytes >= tail_bytes)) {
- free_bytes = log->l_logsize - (bytes - tail_bytes);
- } else if ((tail_cycle + 1) < cycle) {
+ 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)
return 0;
- } else if (tail_cycle < cycle) {
- ASSERT(tail_cycle == (cycle - 1));
- free_bytes = tail_bytes - bytes;
+ else if (tail_cycle < head_cycle) {
+ ASSERT(tail_cycle == (head_cycle - 1));
+ free_bytes = tail_bytes - head_bytes;
} else {
/*
* The reservation head is behind the tail.
@@ -839,12 +852,12 @@ xlog_space_left(xlog_t *log, int cycle, int bytes)
"xlog_space_left: head behind tail\n"
" tail_cycle = %d, tail_bytes = %d\n"
" GH cycle = %d, GH bytes = %d",
- tail_cycle, tail_bytes, cycle, bytes);
+ tail_cycle, tail_bytes, head_cycle, head_bytes);
ASSERT(0);
free_bytes = log->l_logsize;
}
return free_bytes;
-} /* xlog_space_left */
+}

/*
@@ -1001,8 +1014,8 @@ xlog_alloc_log(xfs_mount_t *mp,
/* log->l_tail_lsn = 0x100000000LL; cycle = 1; current block = 0 */
log->l_last_sync_lsn = log->l_tail_lsn;
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;
+ xlog_assign_grant_head(&log->l_grant_reserve_head, 1, 0);
+ xlog_assign_grant_head(&log->l_grant_write_head, 1, 0);
INIT_LIST_HEAD(&log->l_reserveq);
INIT_LIST_HEAD(&log->l_writeq);

@@ -1190,9 +1203,7 @@ xlog_grant_push_ail(xfs_mount_t *mp,
ASSERT(BTOBB(need_bytes) < log->l_logBBsize);

spin_lock(&log->l_grant_lock);
- free_bytes = xlog_space_left(log,
- log->l_grant_reserve_cycle,
- log->l_grant_reserve_bytes);
+ free_bytes = xlog_space_left(log, &log->l_grant_reserve_head);
tail_lsn = log->l_tail_lsn;
free_blocks = BTOBBT(free_bytes);

@@ -1325,10 +1336,8 @@ xlog_sync(xlog_t *log,

/* move grant heads by roundoff in sync */
spin_lock(&log->l_grant_lock);
- xlog_grant_add_space(log, &log->l_grant_reserve_cycle,
- &log->l_grant_reserve_bytes, roundoff);
- xlog_grant_add_space(log, &log->l_grant_write_cycle,
- &log->l_grant_write_bytes, roundoff);
+ xlog_grant_add_space(log, &log->l_grant_reserve_head, roundoff);
+ xlog_grant_add_space(log, &log->l_grant_write_head, roundoff);
spin_unlock(&log->l_grant_lock);

/* put cycle number in every block */
@@ -2531,8 +2540,7 @@ redo:
if (XLOG_FORCED_SHUTDOWN(log))
goto error_return;

- free_bytes = xlog_space_left(log, log->l_grant_reserve_cycle,
- log->l_grant_reserve_bytes);
+ free_bytes = xlog_space_left(log, &log->l_grant_reserve_head);
if (free_bytes < need_bytes) {
if (list_empty(&tic->t_queue))
list_add_tail(&tic->t_queue, &log->l_reserveq);
@@ -2558,10 +2566,8 @@ redo:
list_del_init(&tic->t_queue);

/* we've got enough space */
- xlog_grant_add_space(log, &log->l_grant_reserve_cycle,
- &log->l_grant_reserve_bytes, need_bytes);
- xlog_grant_add_space(log, &log->l_grant_write_cycle,
- &log->l_grant_write_bytes, need_bytes);
+ xlog_grant_add_space(log, &log->l_grant_reserve_head, need_bytes);
+ xlog_grant_add_space(log, &log->l_grant_write_head, need_bytes);
trace_xfs_log_grant_exit(log, tic);
xlog_verify_grant_head(log, 1);
xlog_verify_grant_tail(log);
@@ -2622,8 +2628,7 @@ xlog_regrant_write_log_space(xlog_t *log,
need_bytes = tic->t_unit_res;
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);
+ free_bytes = xlog_space_left(log, &log->l_grant_write_head);
list_for_each_entry(ntic, &log->l_writeq, t_queue) {
ASSERT(ntic->t_flags & XLOG_TIC_PERM_RESERV);

@@ -2662,8 +2667,7 @@ redo:
if (XLOG_FORCED_SHUTDOWN(log))
goto error_return;

- free_bytes = xlog_space_left(log, log->l_grant_write_cycle,
- log->l_grant_write_bytes);
+ free_bytes = xlog_space_left(log, &log->l_grant_write_head);
if (free_bytes < need_bytes) {
if (list_empty(&tic->t_queue))
list_add_tail(&tic->t_queue, &log->l_writeq);
@@ -2688,8 +2692,7 @@ redo:
list_del_init(&tic->t_queue);

/* we've got enough space */
- xlog_grant_add_space(log, &log->l_grant_write_cycle,
- &log->l_grant_write_bytes, need_bytes);
+ xlog_grant_add_space(log, &log->l_grant_write_head, need_bytes);
trace_xfs_log_regrant_write_exit(log, tic);
xlog_verify_grant_head(log, 1);
xlog_verify_grant_tail(log);
@@ -2730,12 +2733,10 @@ xlog_regrant_reserve_log_space(xlog_t *log,
ticket->t_cnt--;

spin_lock(&log->l_grant_lock);
- xlog_grant_sub_space(log, &log->l_grant_reserve_cycle,
- &log->l_grant_reserve_bytes,
- ticket->t_curr_res);
- xlog_grant_sub_space(log, &log->l_grant_write_cycle,
- &log->l_grant_write_bytes,
- ticket->t_curr_res);
+ xlog_grant_sub_space(log, &log->l_grant_reserve_head,
+ ticket->t_curr_res);
+ xlog_grant_sub_space(log, &log->l_grant_write_head,
+ ticket->t_curr_res);
ticket->t_curr_res = ticket->t_unit_res;
xlog_tic_reset_res(ticket);

@@ -2749,9 +2750,8 @@ xlog_regrant_reserve_log_space(xlog_t *log,
return;
}

- xlog_grant_add_space(log, &log->l_grant_reserve_cycle,
- &log->l_grant_reserve_bytes,
- ticket->t_unit_res);
+ xlog_grant_add_space(log, &log->l_grant_reserve_head,
+ ticket->t_unit_res);

trace_xfs_log_regrant_reserve_exit(log, ticket);

@@ -2799,10 +2799,8 @@ xlog_ungrant_log_space(xlog_t *log,
bytes += ticket->t_unit_res*ticket->t_cnt;
}

- xlog_grant_sub_space(log, &log->l_grant_reserve_cycle,
- &log->l_grant_reserve_bytes, bytes);
- xlog_grant_sub_space(log, &log->l_grant_write_cycle,
- &log->l_grant_write_bytes, bytes);
+ xlog_grant_sub_space(log, &log->l_grant_reserve_head, bytes);
+ xlog_grant_sub_space(log, &log->l_grant_write_head, bytes);

trace_xfs_log_ungrant_exit(log, ticket);

@@ -3430,22 +3428,31 @@ xlog_verify_dest_ptr(
STATIC void
xlog_verify_grant_head(xlog_t *log, int equals)
{
- if (log->l_grant_reserve_cycle == log->l_grant_write_cycle) {
- if (equals)
- ASSERT(log->l_grant_reserve_bytes >= log->l_grant_write_bytes);
- else
- ASSERT(log->l_grant_reserve_bytes > log->l_grant_write_bytes);
- } else {
- ASSERT(log->l_grant_reserve_cycle-1 == log->l_grant_write_cycle);
- ASSERT(log->l_grant_write_bytes >= log->l_grant_reserve_bytes);
- }
-} /* xlog_verify_grant_head */
+ int reserve_cycle, reserve_space;
+ int write_cycle, write_space;
+
+ xlog_crack_grant_head(&log->l_grant_reserve_head,
+ &reserve_cycle, &reserve_space);
+ xlog_crack_grant_head(&log->l_grant_write_head,
+ &write_cycle, &write_space);
+
+ if (reserve_cycle == write_cycle) {
+ if (equals)
+ ASSERT(reserve_space >= write_space);
+ else
+ ASSERT(reserve_space > write_space);
+ } else {
+ ASSERT(reserve_cycle - 1 == write_cycle);
+ ASSERT(write_space >= reserve_space);
+ }
+}

STATIC void
xlog_verify_grant_tail(
struct log *log)
{
xfs_lsn_t tail_lsn = log->l_tail_lsn;
+ int cycle, space;

/*
* Check to make sure the grant write head didn't just over lap the
@@ -3453,9 +3460,10 @@ xlog_verify_grant_tail(
* Otherwise, make sure that the cycles differ by exactly one and
* check the byte count.
*/
- if (CYCLE_LSN(tail_lsn) != log->l_grant_write_cycle) {
- ASSERT(log->l_grant_write_cycle - 1 == CYCLE_LSN(tail_lsn));
- ASSERT(log->l_grant_write_bytes <= BBTOB(BLOCK_LSN(tail_lsn)));
+ 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)));
}
}

diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
index a5b3c02..2f74c80 100644
--- a/fs/xfs/xfs_log_priv.h
+++ b/fs/xfs/xfs_log_priv.h
@@ -518,10 +518,8 @@ typedef struct log {
spinlock_t l_grant_lock ____cacheline_aligned_in_smp;
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;
- int l_grant_write_bytes;
+ int64_t l_grant_reserve_head;
+ int64_t l_grant_write_head;

/* The following field are used for debugging; need to hold icloglock */
#ifdef DEBUG
@@ -561,6 +559,26 @@ int xlog_write(struct log *log, struct xfs_log_vec *log_vector,
xlog_in_core_t **commit_iclog, uint flags);

/*
+ * 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.
+ */
+static inline void
+xlog_crack_grant_head(int64_t *head, int *cycle, int *space)
+{
+ int64_t val = *head;
+
+ *cycle = val >> 32;
+ *space = val & 0xffffffff;
+}
+
+static inline void
+xlog_assign_grant_head(int64_t *head, int cycle, int space)
+{
+ *head = ((int64_t)cycle << 32) | space;
+}
+
+/*
* Committed Item List interfaces
*/
int xlog_cil_init(struct log *log);
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 4abe7a9..1550404 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -938,10 +938,10 @@ xlog_find_tail(
log->l_curr_cycle++;
log->l_tail_lsn = be64_to_cpu(rhead->h_tail_lsn);
log->l_last_sync_lsn = be64_to_cpu(rhead->h_lsn);
- log->l_grant_reserve_cycle = log->l_curr_cycle;
- log->l_grant_reserve_bytes = BBTOB(log->l_curr_block);
- log->l_grant_write_cycle = log->l_curr_cycle;
- log->l_grant_write_bytes = BBTOB(log->l_curr_block);
+ xlog_assign_grant_head(&log->l_grant_reserve_head, log->l_curr_cycle,
+ BBTOB(log->l_curr_block));
+ xlog_assign_grant_head(&log->l_grant_write_head, log->l_curr_cycle,
+ BBTOB(log->l_curr_block));

/*
* Look for unmount record. If we find it, then we know there