From: Qu Wenruo <wqu@suse.com>
Date: Tue, 26 Jan 2021 08:33:51 +0000 (+0800)
Subject: btrfs: attach private to dummy extent buffer pages
X-Git-Tag: iomap-folio-5.17-old~2062^2~56
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=09bc1f0fb845a6435e2c6c5d3c937f7a674e816a;p=users%2Fwilly%2Flinux.git

btrfs: attach private to dummy extent buffer pages

There are locations where we allocate dummy extent buffers for temporary
usage, like in tree_mod_log_rewind() or get_old_root().

These dummy extent buffers will be handled by the same eb accessors, and
if they don't have page::private subpage eb accessors could fail.

To address such problems, make __alloc_dummy_extent_buffer() attach
page private for dummy extent buffers too.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 1812813bdf63..b8ff05916b8f 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -5185,9 +5185,14 @@ struct extent_buffer *__alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
 
 	num_pages = num_extent_pages(eb);
 	for (i = 0; i < num_pages; i++) {
+		int ret;
+
 		eb->pages[i] = alloc_page(GFP_NOFS);
 		if (!eb->pages[i])
 			goto err;
+		ret = attach_extent_buffer_page(eb, eb->pages[i], NULL);
+		if (ret < 0)
+			goto err;
 	}
 	set_extent_buffer_uptodate(eb);
 	btrfs_set_header_nritems(eb, 0);
@@ -5195,8 +5200,10 @@ struct extent_buffer *__alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
 
 	return eb;
 err:
-	for (; i > 0; i--)
+	for (; i > 0; i--) {
+		detach_extent_buffer_page(eb, eb->pages[i - 1]);
 		__free_page(eb->pages[i - 1]);
+	}
 	__free_extent_buffer(eb);
 	return NULL;
 }