[PATCH] erofs: simplify RCU read critical sections

[PATCH] erofs: simplify RCU read critical sections

[Gao Xiang]

 - 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>
---
 fs/erofs/zdata.c | 32 ++++++++++++++------------------
 1 file changed, 14 insertions(+), 18 deletions(-)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index c6240dccbb0f..1c65b741b288 100644
--- 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();
-- 
2.43.5