erofs: simplify RCU read critical sections

 - use scoped_guard() for RCU read critical section in
   z_erofs_decompress_kickoff();

 - simplify the RCU critical section loop in
   z_erofs_pcluster_begin().

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index c6240dccbb0f096497f7a4b3deff909d3ce19291..1c65b741b28837c3fb8c38e333bb34c7cd518ffb 100644 (file)
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -806,6 +806,7 @@ static int z_erofs_pcluster_begin(struct z_erofs_frontend *fe)
        struct super_block *sb = fe->inode->i_sb;
        struct z_erofs_pcluster *pcl = NULL;
        void *ptr = NULL;
+       bool needretry;
        int ret;
 
        DBG_BUGON(fe->pcl);
@@ -825,19 +826,16 @@ static int z_erofs_pcluster_begin(struct z_erofs_frontend *fe)
                }
                ptr = map->buf.page;
        } else {
-               while (1) {
+               do {
                        rcu_read_lock();
                        pcl = xa_load(&EROFS_SB(sb)->managed_pslots, map->m_pa);
-                       if (!pcl || z_erofs_get_pcluster(pcl)) {
-                               DBG_BUGON(pcl && map->m_pa != pcl->pos);
-                               rcu_read_unlock();
-                               break;
-                       }
+                       needretry = pcl && !z_erofs_get_pcluster(pcl);
                        rcu_read_unlock();
-               }
+               } while (needretry);
        }
 
        if (pcl) {
+               DBG_BUGON(map->m_pa != pcl->pos);
                fe->pcl = pcl;
                ret = -EEXIST;
        } else {
@@ -1459,21 +1457,19 @@ static void z_erofs_decompress_kickoff(struct z_erofs_decompressqueue *io,
                if (sbi->sync_decompress == EROFS_SYNC_DECOMPRESS_AUTO)
                        sbi->sync_decompress = EROFS_SYNC_DECOMPRESS_FORCE_ON;
 #ifdef CONFIG_EROFS_FS_PCPU_KTHREAD
-               struct kthread_worker *worker;
+               scoped_guard(rcu) {
+                       struct kthread_worker *worker;
 
-               rcu_read_lock();
-               worker = rcu_dereference(
+                       worker = rcu_dereference(
                                z_erofs_pcpu_workers[raw_smp_processor_id()]);
-               if (!worker) {
-                       INIT_WORK(&io->u.work, z_erofs_decompressqueue_work);
-                       queue_work(z_erofs_workqueue, &io->u.work);
-               } else {
-                       kthread_queue_work(worker, &io->u.kthread_work);
+                       if (worker) {
+                               kthread_queue_work(worker, &io->u.kthread_work);
+                               return;
+                       }
                }
-               rcu_read_unlock();
-#else
-               queue_work(z_erofs_workqueue, &io->u.work);
+               INIT_WORK(&io->u.work, z_erofs_decompressqueue_work);
 #endif
+               queue_work(z_erofs_workqueue, &io->u.work);
                return;
        }
        gfp_flag = memalloc_noio_save();