@@ -3849,7 +3849,7 @@ static void btrfs_end_super_write(struct bio *bio)
}
struct btrfs_super_block *btrfs_read_dev_one_super(struct block_device *bdev,
- int copy_num)
+ int copy_num, bool drop_cache)
{
struct btrfs_super_block *super;
struct page *page;
@@ -3867,6 +3867,11 @@ struct btrfs_super_block *btrfs_read_dev_one_super(struct block_device *bdev,
if (bytenr + BTRFS_SUPER_INFO_SIZE >= bdev_nr_bytes(bdev))
return ERR_PTR(-EINVAL);
+ if (drop_cache)
+ truncate_inode_pages_range(bdev->bd_inode->i_mapping,
+ round_down(bytenr, PAGE_SIZE),
+ round_up(bytenr + BTRFS_SUPER_INFO_SIZE,
+ PAGE_SIZE) - 1);
page = read_cache_page_gfp(mapping, bytenr >> PAGE_SHIFT, GFP_NOFS);
if (IS_ERR(page))
return ERR_CAST(page);
@@ -3898,7 +3903,7 @@ struct btrfs_super_block *btrfs_read_dev_super(struct block_device *bdev)
* later supers, using BTRFS_SUPER_MIRROR_MAX instead
*/
for (i = 0; i < 1; i++) {
- super = btrfs_read_dev_one_super(bdev, i);
+ super = btrfs_read_dev_one_super(bdev, i, false);
if (IS_ERR(super))
continue;
@@ -49,7 +49,7 @@ void __cold close_ctree(struct btrfs_fs_info *fs_info);
int write_all_supers(struct btrfs_fs_info *fs_info, int max_mirrors);
struct btrfs_super_block *btrfs_read_dev_super(struct block_device *bdev);
struct btrfs_super_block *btrfs_read_dev_one_super(struct block_device *bdev,
- int copy_num);
+ int copy_num, bool drop_cache);
int btrfs_commit_super(struct btrfs_fs_info *fs_info);
struct btrfs_root *btrfs_read_tree_root(struct btrfs_root *tree_root,
struct btrfs_key *key);
@@ -3690,6 +3690,8 @@ static long btrfs_ioctl_fs_info(struct btrfs_fs_info *fs_info,
fi_args->max_id = device->devid;
}
rcu_read_unlock();
+ pr_info("%s: num_devices=%llu max=%llu\n", __func__,
+ fs_devices->num_devices, fi_args->max_id);
memcpy(&fi_args->fsid, fs_devices->fsid, sizeof(fi_args->fsid));
fi_args->nodesize = fs_info->nodesize;
@@ -2548,11 +2548,69 @@ static int btrfs_freeze(struct super_block *sb)
return btrfs_commit_transaction(trans);
}
+static int check_dev_super(struct btrfs_device *dev)
+{
+ struct btrfs_fs_info *fs_info = dev->fs_info;
+ struct btrfs_super_block *sb;
+ int ret = 0;
+
+ /* This should be called with fs still frozen. */
+ ASSERT(test_bit(BTRFS_FS_FROZEN, &fs_info->flags));
+
+ /* Missing dev, no need to check. */
+ if (!dev->bdev)
+ return 0;
+
+ /* Only need to check the primary super block. */
+ sb = btrfs_read_dev_one_super(dev->bdev, 0, true);
+ if (IS_ERR(sb))
+ return PTR_ERR(sb);
+
+ if (memcmp(sb->fsid, dev->fs_devices->fsid, BTRFS_FSID_SIZE)) {
+ btrfs_err(fs_info, "fsid doesn't match, has %pU expect %pU",
+ sb->fsid, dev->fs_devices->fsid);
+ ret = -EUCLEAN;
+ goto out;
+ }
+
+ if (btrfs_super_generation(sb) != fs_info->last_trans_committed) {
+ btrfs_err(fs_info, "transid mismatch, has %llu expect %llu",
+ btrfs_super_generation(sb),
+ fs_info->last_trans_committed);
+ ret = -EUCLEAN;
+ goto out;
+ }
+out:
+ btrfs_release_disk_super(sb);
+ return ret;
+}
+
static int btrfs_unfreeze(struct super_block *sb)
{
struct btrfs_fs_info *fs_info = btrfs_sb(sb);
+ struct btrfs_device *device;
+ int ret = 0;
+ /*
+ * Make sure the fs is not changed by accident (like hibernation then
+ * modified by other OS).
+ * If we found anything wrong, we mark the fs error immediately.
+ */
+ list_for_each_entry(device, &fs_info->fs_devices->devices, dev_list) {
+ ret = check_dev_super(device);
+ if (ret < 0) {
+ btrfs_handle_fs_error(fs_info, ret,
+ "filesystem got modified unexpectedly");
+ break;
+ }
+ }
clear_bit(BTRFS_FS_FROZEN, &fs_info->flags);
+
+ /*
+ * We still return 0, to allow VFS layer to unfreeze the fs even above
+ * checks failed. This allows VFS to unfreeze us, and since the
+ * fs is either fine or RO, we're safe to continue.
+ */
return 0;
}
@@ -2017,7 +2017,7 @@ void btrfs_scratch_superblocks(struct btrfs_fs_info *fs_info,
struct page *page;
int ret;
- disk_super = btrfs_read_dev_one_super(bdev, copy_num);
+ disk_super = btrfs_read_dev_one_super(bdev, copy_num, false);
if (IS_ERR(disk_super))
continue;
[BACKGROUND] There is an incident report that, one user hibernated the system, with one btrfs on removable device still mounted. Then by some incident, the btrfs got mounted and modified by another system/OS, then back to the hibernated system. After resuming from the hibernation, new write happened into the victim btrfs. Now the fs is completely broken, since the underlying btrfs is no longer the same one before the hibernation, and the user lost their data due to various transid mismatch. [REPRODUCER] We can emulate the situation using the following small script: truncate -s 1G $dev mkfs.btrfs -f $dev mount $dev $mnt fsstress -w -d $mnt -n 500 sync xfs_freeze -f $mnt cp $dev $dev.backup # There is no way to mount the same cloned fs on the same system, # as the conflicting fsid will be rejected by btrfs. # Thus here we have to wipe the fs using a different btrfs. mkfs.btrfs -f $dev.backup dd if=$dev.backup of=$dev bs=1M xfs_freeze -u $mnt fsstress -w -d $mnt -n 20 umount $mnt btrfs check $dev The final fsck will fail due to some tree blocks has incorrect fsid. This is enough to emulate the problem hit by the unfortunate user. [ENHANCEMENT] Although such case should not be that common, it can still happen from time to time. From the view of btrfs, we can detect any unexpected super block change, and if there is any unexpected change, we just mark the fs RO, and thaw the fs. By this we can limit the damage to minimal, and I hope no one would lose their data by this anymore. Link: https://lore.kernel.org/linux-btrfs/83bf3b4b-7f4c-387a-b286-9251e3991e34@bluemole.com/ Signed-off-by: Qu Wenruo <wqu@suse.com> --- fs/btrfs/disk-io.c | 9 +++++-- fs/btrfs/disk-io.h | 2 +- fs/btrfs/ioctl.c | 2 ++ fs/btrfs/super.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++ fs/btrfs/volumes.c | 2 +- 5 files changed, 69 insertions(+), 4 deletions(-)