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xfs: convert l_last_sync_lsn to an atomic variable

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log->l_last_sync_lsn is updated in only one critical spot - log
buffer Io completion - and is protected by the grant lock here. This
requires the grant lock to be taken for every log buffer IO
completion. Converting the l_last_sync_lsn variable to an atomic64_t
means that we do not need to take the grant lock in log buffer IO
completion to update it.

This also removes the need for explicitly holding a spinlock to read
the l_last_sync_lsn on 32 bit platforms.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Dave Chinner
2010-12-03 22:11:29 +11:00
committed by Dave Chinner
parent 2ced19cbae
commit 84f3c683c4
3 changed files with 36 additions and 34 deletions
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6
fs/xfs/xfs_log_recover.c
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@@ -937,7 +937,7 @@ xlog_find_tail(
if (found == 2)
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);
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));
xlog_assign_grant_head(&log->l_grant_write_head, log->l_curr_cycle,
@@ -989,9 +989,9 @@ xlog_find_tail(
log->l_tail_lsn =
xlog_assign_lsn(log->l_curr_cycle,
after_umount_blk);
log->l_last_sync_lsn =
atomic64_set(&log->l_last_sync_lsn,
xlog_assign_lsn(log->l_curr_cycle,
after_umount_blk);
after_umount_blk));
*tail_blk = after_umount_blk;
/*