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FAILED: patch "[PATCH] btrfs: skip devices without magic signature when mounting" failed to apply to 4.19-stable tree

PATCH [email protected] 1 participant 1 message Nov 3, 2020

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The patch below does not apply to the 4.19-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 <[email protected]>.

thanks,

greg k-h

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

From 96c2e067ed3e3e004580a643c76f58729206b829 Mon Sep 17 00:00:00 2001
From: Anand Jain <[email protected]>
Date: Wed, 30 Sep 2020 21:09:52 +0800
Subject: [PATCH] btrfs: skip devices without magic signature when mounting

Many things can happen after the device is scanned and before the device is mounted. One such thing is losing the BTRFS_MAGIC on the device. If it happens we still won't free that device from the memory and cause the userland confusion.

For example: As the BTRFS_IOC_DEV_INFO still carries the device path which does not have the BTRFS_MAGIC, 'btrfs fi show' still lists device which does not belong to the filesystem anymore:

  $ mkfs.btrfs -fq -draid1 -mraid1 /dev/sda /dev/sdb
  $ wipefs -a /dev/sdb
  # /dev/sdb does not contain magic signature
  $ mount -o degraded /dev/sda /btrfs
  $ btrfs fi show -m
  Label: none  uuid: 470ec6fb-646b-4464-b3cb-df1b26c527bd
	  Total devices 2 FS bytes used 128.00KiB
	  devid    1 size 3.00GiB used 571.19MiB path /dev/sda
	  devid    2 size 3.00GiB used 571.19MiB path /dev/sdb

We need to distinguish the missing signature and invalid superblock, so add a specific error code ENODATA for that. This also fixes failure of fstest btrfs/198.

CC [email protected] # 4.19+
Reviewed-by Josef Bacik <[email protected]>
Signed-off-by Anand Jain <[email protected]>
Reviewed-by David Sterba <[email protected]>
Signed-off-by David Sterba <[email protected]>
fs/btrfs/disk-io.c +6 -2
index 3d39f5d47ad3..764001609a15 100644
@@ -3424,8 +3424,12 @@ struct btrfs_super_block *btrfs_read_dev_one_super(struct block_device *bdev,
 		return ERR_CAST(page);
 
 	super = page_address(page);
-	if (btrfs_super_bytenr(super) != bytenr ||
-		    btrfs_super_magic(super) != BTRFS_MAGIC) {
+	if (btrfs_super_magic(super) != BTRFS_MAGIC) {
+		btrfs_release_disk_super(super);
+		return ERR_PTR(-ENODATA);
+	}
+
+	if (btrfs_super_bytenr(super) != bytenr) {
 		btrfs_release_disk_super(super);
 		return ERR_PTR(-EINVAL);
 	}
fs/btrfs/volumes.c +12 -6
index 46f4efd58652..58b9c419a2b6 100644
@@ -1198,17 +1198,23 @@ static int open_fs_devices(struct btrfs_fs_devices *fs_devices,
 {
 	struct btrfs_device *device;
 	struct btrfs_device *latest_dev = NULL;
+	struct btrfs_device *tmp_device;
 
 	flags |= FMODE_EXCL;
 
-	list_for_each_entry(device, &fs_devices->devices, dev_list) {
-		/* Just open everything we can; ignore failures here */
-		if (btrfs_open_one_device(fs_devices, device, flags, holder))
-			continue;
+	list_for_each_entry_safe(device, tmp_device, &fs_devices->devices,
+				 dev_list) {
+		int ret;
 
-		if (!latest_dev ||
-		    device->generation > latest_dev->generation)
+		ret = btrfs_open_one_device(fs_devices, device, flags, holder);
+		if (ret == 0 &&
+		    (!latest_dev || device->generation > latest_dev->generation)) {
 			latest_dev = device;
+		} else if (ret == -ENODATA) {
+			fs_devices->num_devices--;
+			list_del(&device->dev_list);
+			btrfs_free_device(device);
+		}
 	}
 	if (fs_devices->open_devices == 0)
 		return -EINVAL;