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xfs: convert l_tail_lsn to an atomic variable.

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log->l_tail_lsn is currently protected by the log grant lock. The
lock is only needed for serialising readers against writers, so we
don't really need the lock if we make the l_tail_lsn variable an
atomic. Converting the l_tail_lsn variable to an atomic64_t means we
can start to peel back the grant lock from various operations.

Also, provide functions to safely crack an atomic LSN variable into
it's component pieces and to recombined the components into an
atomic variable. Use them where appropriate.

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

Signed-off-by: Dave Chinner <dchinner@redhat.com>
This commit is contained in:
Dave Chinner
2010-12-21 12:28:39 +11:00
committed by Dave Chinner
parent 84f3c683c4
commit 1c3cb9ec07
4 changed files with 63 additions and 46 deletions
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2
fs/xfs/linux-2.6/xfs_trace.h
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@@ -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 "