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xfs: combine grant heads into a single 64 bit integer
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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>
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Dave Chinner authored and Dave Chinner committed Dec 21, 2010
1 parent 663e496 commit a69ed03
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Showing 4 changed files with 119 additions and 91 deletions.
10 changes: 6 additions & 4 deletions fs/xfs/linux-2.6/xfs_trace.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down
166 changes: 87 additions & 79 deletions fs/xfs/xfs_log.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);

Expand Down Expand Up @@ -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)
{
Expand Down Expand Up @@ -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;
Expand All @@ -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);

Expand All @@ -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;
Expand Down Expand Up @@ -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.
Expand All @@ -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 */
}


/*
Expand Down Expand Up @@ -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);

Expand Down Expand Up @@ -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);

Expand Down Expand Up @@ -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 */
Expand Down Expand Up @@ -2531,8 +2540,7 @@ xlog_grant_log_space(xlog_t *log,
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);
Expand All @@ -2558,10 +2566,8 @@ xlog_grant_log_space(xlog_t *log,
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);
Expand Down Expand Up @@ -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);

Expand Down Expand Up @@ -2662,8 +2667,7 @@ xlog_regrant_write_log_space(xlog_t *log,
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);
Expand All @@ -2688,8 +2692,7 @@ xlog_regrant_write_log_space(xlog_t *log,
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);
Expand Down Expand Up @@ -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);

Expand All @@ -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);

Expand Down Expand Up @@ -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);

Expand Down Expand Up @@ -3430,32 +3428,42 @@ 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
* tail. If the cycles are the same, we can't be overlapping.
* 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)));
}
}

Expand Down
26 changes: 22 additions & 4 deletions fs/xfs/xfs_log_priv.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down Expand Up @@ -560,6 +558,26 @@ int xlog_write(struct log *log, struct xfs_log_vec *log_vector,
struct xlog_ticket *tic, xfs_lsn_t *start_lsn,
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
*/
Expand Down
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