From: Uros Bizjak <ubizjak@xxxxxxxxx>
commit 20195d011c840b01fa91a85ebcd099ca95fbf8fc upstream.
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 <ubizjak@xxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Chandan Babu R <chandan.babu@xxxxxxxxxx>
Cc: Darrick J. Wong <djwong@xxxxxxxxxx>
Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
Signed-off-by: Carlos Maiolino <cem@xxxxxxxxxx>
Signed-off-by: Catherine Hoang <catherine.hoang@xxxxxxxxxx>
Acked-by: Darrick J. Wong <djwong@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/xfs/xfs_log_cil.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)
--- a/fs/xfs/xfs_log_cil.c
+++ b/fs/xfs/xfs_log_cil.c
@@ -156,7 +156,6 @@ xlog_cil_insert_pcp_aggregate(
struct xfs_cil *cil,
struct xfs_cil_ctx *ctx)
{
- struct xlog_cil_pcp *cilpcp;
int cpu;
int count = 0;
@@ -171,13 +170,11 @@ xlog_cil_insert_pcp_aggregate(
* structures that could have a nonzero space_used.
*/
for_each_cpu(cpu, &ctx->cil_pcpmask) {
- int old, prev;
+ struct xlog_cil_pcp *cilpcp = per_cpu_ptr(cil->xc_pcp, cpu);
+ int old = READ_ONCE(cilpcp->space_used);
- cilpcp = per_cpu_ptr(cil->xc_pcp, cpu);
- do {
- old = cilpcp->space_used;
- prev = cmpxchg(&cilpcp->space_used, old, 0);
- } while (old != prev);
+ while (!try_cmpxchg(&cilpcp->space_used, &old, 0))
+ ;
count += old;
}
atomic_add(count, &ctx->space_used);
Patches currently in stable-queue which might be from catherine.hoang@xxxxxxxxxx are
queue-6.6/xfs-return-bool-from-xfs_attr3_leaf_add.patch
queue-6.6/xfs-fix-a-sloppy-memory-handling-bug-in-xfs_iroot_realloc.patch
queue-6.6/xfs-streamline-xfs_filestream_pick_ag.patch
queue-6.6/xfs-merge-xfs_attr_leaf_try_add-into-xfs_attr_leaf_addname.patch
queue-6.6/xfs-don-t-free-cowblocks-from-under-dirty-pagecache-on-unshare.patch
queue-6.6/xfs-pass-the-exact-range-to-initialize-to-xfs_initialize_perag.patch
queue-6.6/xfs-assert-a-valid-limit-in-xfs_rtfind_forw.patch
queue-6.6/xfs-don-t-use-__gfp_retry_mayfail-in-xfs_initialize_perag.patch
queue-6.6/xfs-use-try_cmpxchg-in-xlog_cil_insert_pcp_aggregate.patch
queue-6.6/xfs-don-t-ifdef-around-the-exact-minlen-allocations.patch
queue-6.6/xfs-reduce-unnecessary-searches-when-searching-for-the-best-extents.patch
queue-6.6/xfs-validate-inumber-in-xfs_iget.patch
queue-6.6/xfs-support-lowmode-allocations-in-xfs_bmap_exact_minlen_extent_alloc.patch
queue-6.6/xfs-skip-background-cowblock-trims-on-inodes-open-for-write.patch
queue-6.6/xfs-remove-empty-declartion-in-header-file.patch
queue-6.6/xfs-fold-xfs_bmap_alloc_userdata-into-xfs_bmapi_allocate.patch
queue-6.6/xfs-update-the-file-system-geometry-after-recoverying-superblock-buffers.patch
queue-6.6/xfs-call-xfs_bmap_exact_minlen_extent_alloc-from-xfs_bmap_btalloc.patch
queue-6.6/xfs-distinguish-extra-split-from-real-enospc-from-xfs_attr_node_try_addname.patch
queue-6.6/xfs-error-out-when-a-superblock-buffer-update-reduces-the-agcount.patch
queue-6.6/xfs-update-the-pag-for-the-last-ag-at-recovery-time.patch
queue-6.6/xfs-check-for-delayed-allocations-before-setting-extsize.patch
queue-6.6/xfs-fix-a-typo.patch
queue-6.6/xfs-distinguish-extra-split-from-real-enospc-from-xfs_attr3_leaf_split.patch
