forked from pool/u-boot
Guillaume GARDET
94fa8803fd
OBS-URL: https://build.opensuse.org/request/show/909895 OBS-URL: https://build.opensuse.org/package/show/hardware:boot/u-boot?expand=0&rev=149
92 lines
3.1 KiB
Diff
92 lines
3.1 KiB
Diff
From 6d31a7a47e0a3f66304fb033a9e8c9a78e1bc661 Mon Sep 17 00:00:00 2001
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From: "Matwey V. Kornilov" <matwey.kornilov@gmail.com>
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Date: Sun, 1 Aug 2021 23:52:16 +0300
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Subject: [PATCH] btrfs: Use default subvolume as filesystem root
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BTRFS volume consists of a number of subvolumes which can be mounted separately
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from each other. The top-level subvolume always exists even if no subvolumes
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were created manually. A subvolume can be denoted as the default subvolume i.e.
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the subvolume which is mounted by default.
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The default "default subvolume" is the top-level one, but this is far from the
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common practices used in the wild. For instance, openSUSE provides an OS
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snapshot/rollback feature based on BTRFS. To achieve this, the actual OS root
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filesystem is located into a separate subvolume which is "default" but not
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"top-level". That means that the /boot/dtb/ directory is also located inside
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this default subvolume instead of top-level one.
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However, the existing btrfs u-boot driver always uses the top-level subvolume
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as the filesystem root. This behaviour 1) is inconsistent with
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mount /dev/sda1 /target
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command, which mount the default subvolume 2) leads to the issues when
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/boot/dtb cannot be found properly (see the reference).
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This patch uses the default subvolume as the filesystem root to overcome
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mentioned issues.
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Reference: https://bugzilla.suse.com/show_bug.cgi?id=1185656
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Signed-off-by: Matwey V. Kornilov <matwey.kornilov@gmail.com>
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Reviewed-by: Qu Wenruo <wqu@suse.com>
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---
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fs/btrfs/disk-io.c | 38 +++++++++++++++++++++++++++++++++++---
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1 file changed, 35 insertions(+), 3 deletions(-)
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diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
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index 349411c3cc..12f9579fcf 100644
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--- a/fs/btrfs/disk-io.c
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+++ b/fs/btrfs/disk-io.c
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@@ -804,6 +804,30 @@ static int setup_root_or_create_block(struct btrfs_fs_info *fs_info,
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return 0;
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}
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+static int get_default_subvolume(struct btrfs_fs_info *fs_info,
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+ struct btrfs_key *key_ret)
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+{
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+ struct btrfs_root *root = fs_info->tree_root;
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+ struct btrfs_dir_item *dir_item;
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+ struct btrfs_path path;
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+ int ret = 0;
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+
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+ btrfs_init_path(&path);
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+
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+ dir_item = btrfs_lookup_dir_item(NULL, root, &path,
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+ BTRFS_ROOT_TREE_DIR_OBJECTID,
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+ "default", 7, 0);
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+ if (IS_ERR(dir_item)) {
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+ ret = PTR_ERR(dir_item);
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+ goto out;
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+ }
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+
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+ btrfs_dir_item_key_to_cpu(path.nodes[0], dir_item, key_ret);
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+out:
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+ btrfs_release_path(&path);
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+ return ret;
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+}
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+
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int btrfs_setup_all_roots(struct btrfs_fs_info *fs_info)
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{
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struct btrfs_super_block *sb = fs_info->super_copy;
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@@ -833,9 +857,17 @@ int btrfs_setup_all_roots(struct btrfs_fs_info *fs_info)
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fs_info->last_trans_committed = generation;
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- key.objectid = BTRFS_FS_TREE_OBJECTID;
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- key.type = BTRFS_ROOT_ITEM_KEY;
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- key.offset = (u64)-1;
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+ ret = get_default_subvolume(fs_info, &key);
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+ if (ret) {
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+ /*
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+ * The default dir item isn't there. Linux kernel behaviour is
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+ * to silently use the top-level subvolume in this case.
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+ */
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+ key.objectid = BTRFS_FS_TREE_OBJECTID;
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+ key.type = BTRFS_ROOT_ITEM_KEY;
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+ key.offset = (u64)-1;
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+ }
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+
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fs_info->fs_root = btrfs_read_fs_root(fs_info, &key);
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if (IS_ERR(fs_info->fs_root))
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