--- zzzz-none-000/linux-3.10.107/fs/btrfs/reada.c	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/fs/btrfs/reada.c	2021-02-04 17:41:59.000000000 +0000
@@ -66,7 +66,6 @@
 struct reada_extent {
 	u64			logical;
 	struct btrfs_key	top;
-	u32			blocksize;
 	int			err;
 	struct list_head	extctl;
 	int 			refcnt;
@@ -189,8 +188,8 @@
 			 */
 #ifdef DEBUG
 			if (rec->generation != generation) {
-				printk(KERN_DEBUG "generation mismatch for "
-						"(%llu,%d,%llu) %llu != %llu\n",
+				btrfs_debug(root->fs_info,
+					   "generation mismatch for (%llu,%d,%llu) %llu != %llu",
 				       key.objectid, key.type, key.offset,
 				       rec->generation, generation);
 			}
@@ -329,6 +328,7 @@
 	struct btrfs_device *prev_dev;
 	u32 blocksize;
 	u64 length;
+	int real_stripes;
 	int nzones = 0;
 	int i;
 	unsigned long index = logical >> PAGE_CACHE_SHIFT;
@@ -347,9 +347,8 @@
 	if (!re)
 		return NULL;
 
-	blocksize = btrfs_level_size(root, level);
+	blocksize = root->nodesize;
 	re->logical = logical;
-	re->blocksize = blocksize;
 	re->top = *top;
 	INIT_LIST_HEAD(&re->extctl);
 	spin_lock_init(&re->lock);
@@ -365,12 +364,14 @@
 		goto error;
 
 	if (bbio->num_stripes > BTRFS_MAX_MIRRORS) {
-		printk(KERN_ERR "btrfs readahead: more than %d copies not "
-				"supported", BTRFS_MAX_MIRRORS);
+		btrfs_err(root->fs_info,
+			   "readahead: more than %d copies not supported",
+			   BTRFS_MAX_MIRRORS);
 		goto error;
 	}
 
-	for (nzones = 0; nzones < bbio->num_stripes; ++nzones) {
+	real_stripes = bbio->num_stripes - bbio->num_tgtdevs;
+	for (nzones = 0; nzones < real_stripes; ++nzones) {
 		struct reada_zone *zone;
 
 		dev = bbio->stripes[nzones].dev;
@@ -427,8 +428,13 @@
 			continue;
 		}
 		if (!dev->bdev) {
-			/* cannot read ahead on missing device */
-			continue;
+			/*
+			 * cannot read ahead on missing device, but for RAID5/6,
+			 * REQ_GET_READ_MIRRORS return 1. So don't skip missing
+			 * device for such case.
+			 */
+			if (nzones > 1)
+				continue;
 		}
 		if (dev_replace_is_ongoing &&
 		    dev == fs_info->dev_replace.tgtdev) {
@@ -457,7 +463,7 @@
 	spin_unlock(&fs_info->reada_lock);
 	btrfs_dev_replace_unlock(&fs_info->dev_replace);
 
-	kfree(bbio);
+	btrfs_put_bbio(bbio);
 	return re;
 
 error:
@@ -482,7 +488,7 @@
 		kref_put(&zone->refcnt, reada_zone_release);
 		spin_unlock(&fs_info->reada_lock);
 	}
-	kfree(bbio);
+	btrfs_put_bbio(bbio);
 	kfree(re);
 	return re_exist;
 }
@@ -563,7 +569,7 @@
 	rec = kzalloc(sizeof(*rec), GFP_NOFS);
 	if (!rec) {
 		reada_extent_put(root->fs_info, re);
-		return -1;
+		return -ENOMEM;
 	}
 
 	rec->rc = rc;
@@ -654,7 +660,6 @@
 	int mirror_num = 0;
 	struct extent_buffer *eb = NULL;
 	u64 logical;
-	u32 blocksize;
 	int ret;
 	int i;
 	int need_kick = 0;
@@ -688,7 +693,7 @@
 		spin_unlock(&fs_info->reada_lock);
 		return 0;
 	}
-	dev->reada_next = re->logical + re->blocksize;
+	dev->reada_next = re->logical + fs_info->tree_root->nodesize;
 	re->refcnt++;
 
 	spin_unlock(&fs_info->reada_lock);
@@ -703,7 +708,6 @@
 		}
 	}
 	logical = re->logical;
-	blocksize = re->blocksize;
 
 	spin_lock(&re->lock);
 	if (re->scheduled_for == NULL) {
@@ -718,8 +722,8 @@
 		return 0;
 
 	atomic_inc(&dev->reada_in_flight);
-	ret = reada_tree_block_flagged(fs_info->extent_root, logical, blocksize,
-			 mirror_num, &eb);
+	ret = reada_tree_block_flagged(fs_info->extent_root, logical,
+			mirror_num, &eb);
 	if (ret)
 		__readahead_hook(fs_info->extent_root, NULL, logical, ret);
 	else if (eb)
@@ -792,10 +796,11 @@
 		/* FIXME we cannot handle this properly right now */
 		BUG();
 	}
-	rmw->work.func = reada_start_machine_worker;
+	btrfs_init_work(&rmw->work, btrfs_readahead_helper,
+			reada_start_machine_worker, NULL, NULL);
 	rmw->fs_info = fs_info;
 
-	btrfs_queue_worker(&fs_info->readahead_workers, &rmw->work);
+	btrfs_queue_work(fs_info->readahead_workers, &rmw->work);
 }
 
 #ifdef DEBUG
@@ -844,7 +849,7 @@
 				break;
 			printk(KERN_DEBUG
 				"  re: logical %llu size %u empty %d for %lld",
-				re->logical, re->blocksize,
+				re->logical, fs_info->tree_root->nodesize,
 				list_empty(&re->extctl), re->scheduled_for ?
 				re->scheduled_for->devid : -1);
 
@@ -879,7 +884,8 @@
 		}
 		printk(KERN_DEBUG
 			"re: logical %llu size %u list empty %d for %lld",
-			re->logical, re->blocksize, list_empty(&re->extctl),
+			re->logical, fs_info->tree_root->nodesize,
+			list_empty(&re->extctl),
 			re->scheduled_for ? re->scheduled_for->devid : -1);
 		for (i = 0; i < re->nzones; ++i) {
 			printk(KERN_CONT " zone %llu-%llu devs",
@@ -912,6 +918,7 @@
 	u64 start;
 	u64 generation;
 	int level;
+	int ret;
 	struct extent_buffer *node;
 	static struct btrfs_key max_key = {
 		.objectid = (u64)-1,
@@ -937,9 +944,10 @@
 	generation = btrfs_header_generation(node);
 	free_extent_buffer(node);
 
-	if (reada_add_block(rc, start, &max_key, level, generation)) {
+	ret = reada_add_block(rc, start, &max_key, level, generation);
+	if (ret) {
 		kfree(rc);
-		return ERR_PTR(-ENOMEM);
+		return ERR_PTR(ret);
 	}
 
 	reada_start_machine(root->fs_info);