Merge commit 'v2.6.26' into bkl-removal

1 files changed, 11 insertions, 4 deletions

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index afaee301b0ee..ad3d26ddfe31 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -2427,13 +2427,20 @@ restart:
         if (iclog->ic_size - iclog->ic_offset < 2*sizeof(xlog_op_header_t)) {
                 xlog_state_switch_iclogs(log, iclog, iclog->ic_size);
 
-                /* If I'm the only one writing to this iclog, sync it to disk */
-                if (atomic_read(&iclog->ic_refcnt) == 1) {
+                /*
+                 * If I'm the only one writing to this iclog, sync it to disk.
+                 * We need to do an atomic compare and decrement here to avoid
+                 * racing with concurrent atomic_dec_and_lock() calls in
+                 * xlog_state_release_iclog() when there is more than one
+                 * reference to the iclog.
+                 */
+                if (!atomic_add_unless(&iclog->ic_refcnt, -1, 1)) {
+                        /* we are the only one */
                         spin_unlock(&log->l_icloglock);
-                        if ((error = xlog_state_release_iclog(log, iclog)))
+                        error = xlog_state_release_iclog(log, iclog);
+                        if (error)
                                 return error;
                 } else {
-                        atomic_dec(&iclog->ic_refcnt);
                         spin_unlock(&log->l_icloglock);
                 }
                 goto restart;