FAILED: patch "[PATCH] btrfs: use proper endianness accessors for super_copy" failed to apply to 4.9-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From 3c181c12c431fe33b669410d663beb9cceefcd1b Mon Sep 17 00:00:00 2001
From: Anand Jain <anand.jain@oracle.com>
Date: Thu, 22 Feb 2018 21:58:42 +0800
Subject: [PATCH] btrfs: use proper endianness accessors for super_copy

The fs_info::super_copy is a byte copy of the on-disk structure and all
members must use the accessor macros/functions to obtain the right
value.  This was missing in update_super_roots and in sysfs readers.

Moving between opposite endianness hosts will report bogus numbers in
sysfs, and mount may fail as the root will not be restored correctly. If
the filesystem is always used on a same endian host, this will not be a
problem.

Fix this by using the btrfs_set_super...() functions to set
fs_info::super_copy values, and for the sysfs, use the cached
fs_info::nodesize/sectorsize values.

CC: stable@vger.kernel.org
Fixes: df93589a17378 ("btrfs: export more from FS_INFO to sysfs")
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index a8bafed931f4..d11c70bff5a9 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -423,7 +423,7 @@ static ssize_t btrfs_nodesize_show(struct kobject *kobj,
 {
 	struct btrfs_fs_info *fs_info = to_fs_info(kobj);
 
-	return snprintf(buf, PAGE_SIZE, "%u\n", fs_info->super_copy->nodesize);
+	return snprintf(buf, PAGE_SIZE, "%u\n", fs_info->nodesize);
 }
 
 BTRFS_ATTR(, nodesize, btrfs_nodesize_show);
@@ -433,8 +433,7 @@ static ssize_t btrfs_sectorsize_show(struct kobject *kobj,
 {
 	struct btrfs_fs_info *fs_info = to_fs_info(kobj);
 
-	return snprintf(buf, PAGE_SIZE, "%u\n",
-			fs_info->super_copy->sectorsize);
+	return snprintf(buf, PAGE_SIZE, "%u\n", fs_info->sectorsize);
 }
 
 BTRFS_ATTR(, sectorsize, btrfs_sectorsize_show);
@@ -444,8 +443,7 @@ static ssize_t btrfs_clone_alignment_show(struct kobject *kobj,
 {
 	struct btrfs_fs_info *fs_info = to_fs_info(kobj);
 
-	return snprintf(buf, PAGE_SIZE, "%u\n",
-			fs_info->super_copy->sectorsize);
+	return snprintf(buf, PAGE_SIZE, "%u\n", fs_info->sectorsize);
 }
 
 BTRFS_ATTR(, clone_alignment, btrfs_clone_alignment_show);
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 04f07144b45c..9220f004001c 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1722,19 +1722,23 @@ static void update_super_roots(struct btrfs_fs_info *fs_info)
 
 	super = fs_info->super_copy;
 
+	/* update latest btrfs_super_block::chunk_root refs */
 	root_item = &fs_info->chunk_root->root_item;
-	super->chunk_root = root_item->bytenr;
-	super->chunk_root_generation = root_item->generation;
-	super->chunk_root_level = root_item->level;
+	btrfs_set_super_chunk_root(super, root_item->bytenr);
+	btrfs_set_super_chunk_root_generation(super, root_item->generation);
+	btrfs_set_super_chunk_root_level(super, root_item->level);
 
+	/* update latest btrfs_super_block::root refs */
 	root_item = &fs_info->tree_root->root_item;
-	super->root = root_item->bytenr;
-	super->generation = root_item->generation;
-	super->root_level = root_item->level;
+	btrfs_set_super_root(super, root_item->bytenr);
+	btrfs_set_super_generation(super, root_item->generation);
+	btrfs_set_super_root_level(super, root_item->level);
+
 	if (btrfs_test_opt(fs_info, SPACE_CACHE))
-		super->cache_generation = root_item->generation;
+		btrfs_set_super_cache_generation(super, root_item->generation);
 	if (test_bit(BTRFS_FS_UPDATE_UUID_TREE_GEN, &fs_info->flags))
-		super->uuid_tree_generation = root_item->generation;
+		btrfs_set_super_uuid_tree_generation(super,
+						     root_item->generation);
 }
 
 int btrfs_transaction_in_commit(struct btrfs_fs_info *info)