Re: [syzbot] [btrfs?] kernel BUG in __extent_writepage_io (2)

Edward Adam Davis
2024-08-29T11:52:34Z

#syz test

diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index 10ac5f657e38..4e2c30acca67 100644
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -384,6 +384,8 @@ static void try_merge_map(struct btrfs_inode *inode, struct extent_map *em)
free_extent_map(merge);
dec_evictable_extent_maps(inode);
}
+ printk("em: %p, blockstart: %llu, mblockstart: %llu, %s\n", em,
+ extent_map_block_start(em), em->flags & EXTENT_FLAG_MERGED, __func__);
}

/*
@@ -493,7 +495,11 @@ static int add_extent_mapping(struct btrfs_inode *inode,
if (ret)
return ret;

+ printk("em: %p, blockstart: %llu, em refs: %d, %s\n",
+ em, extent_map_block_start(em), refcount_read(&em->refs), __func__);
setup_extent_mapping(inode, em, modified);
+ printk("setuped, em: %p, blockstart: %llu, em refs: %d, %s\n",
+ em, extent_map_block_start(em), refcount_read(&em->refs), __func__);

if (!btrfs_is_testing(fs_info) && is_fstree(btrfs_root_id(root)))
percpu_counter_inc(&fs_info->evictable_extent_maps);
@@ -743,6 +749,11 @@ int btrfs_add_extent_mapping(struct btrfs_inode *inode,
}
free_extent_map(existing);
}
+ } else if (!ret) {
+ if (em->flags & EXTENT_FLAG_MERGED)
+ ASSERT(extent_map_block_start(em) != EXTENT_MAP_HOLE);
+ else
+ return -EINVAL;
}

ASSERT(ret == 0 || ret == -EEXIST);
diff --git a/fs/btrfs/extent_map.h b/fs/btrfs/extent_map.h
index 5154a8f1d26c..a84ef0c7d601 100644
--- a/fs/btrfs/extent_map.h
+++ b/fs/btrfs/extent_map.h
@@ -154,6 +154,7 @@ static inline u64 extent_map_block_start(const struct extent_map *em)
if (em->disk_bytenr < EXTENT_MAP_LAST_BYTE) {
if (extent_map_is_compressed(em))
return em->disk_bytenr;
+ printk("em: %p, disk byte nr: %llu, offset: %llu, %s\n", em, em->disk_bytenr, em->offset, __func__);
return em->disk_bytenr + em->offset;
}
return em->disk_bytenr;
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index b1b6564ab68f..45f3b31aacc3 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -6958,7 +6958,9 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
}

write_lock(&em_tree->lock);
+ printk("em: %p, blockstart: %llu, start: %llu, len: %llu, %s\n", em, extent_map_block_start(em), start, len, __func__);
ret = btrfs_add_extent_mapping(inode, &em, start, len);
+ printk("ret: %d, em: %p, blockstart: %llu, start: %llu, len: %llu, %s\n", ret, em, extent_map_block_start(em), start, len, __func__);
write_unlock(&em_tree->lock);
out:
btrfs_free_path(path);