xfs: Use try_cmpxchg() in xlog_cil_insert_pcp_aggregate()

Use !try_cmpxchg instead of cmpxchg (*ptr, old, new) != old in
xlog_cil_insert_pcp_aggregate().  x86 CMPXCHG instruction returns
success in ZF flag, so this change saves a compare after cmpxchg.

Also, try_cmpxchg implicitly assigns old *ptr value to "old" when
cmpxchg fails. There is no need to re-read the value in the loop.

Note that the value from *ptr should be read using READ_ONCE to
prevent the compiler from merging, refetching or reordering the read.

No functional change intended.

Signed-off-by: Uros Bizjak <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Cc: Chandan Babu R <[email protected]>
Cc: Darrick J. Wong <[email protected]>
Reviewed-by: Dave Chinner <[email protected]>
Signed-off-by: Carlos Maiolino <[email protected]>

0 files changed, 0 insertions, 0 deletions