[PATCH 046/102] xfs: share code for grant head availability checks

Dave Chinner
2012-08-23T05:03:39Z

From: Christoph Hellwig <hch@infradead.org>

Upstream commit: 42ceedb3caffe67c4ec0dfbb78ce410832d429b9

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>
---
fs/xfs/xfs_log.c | 133 ++++++++++++++++++++++++------------------------------
1 file changed, 60 insertions(+), 73 deletions(-)

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index ad16114..795c4c2 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)
{
@@ -2559,59 +2613,18 @@ 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;

@@ -2624,16 +2637,13 @@ 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;
@@ -2642,33 +2652,10 @@ 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;