3 files changed, 36 insertions, 3 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 41133b064d72..4be231e0d2bd 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3044,7 +3044,13 @@ static void set_avail_alloc_bits(struct btrfs_fs_info *fs_info, u64 flags)
 
 u64 btrfs_reduce_alloc_profile(struct btrfs_root *root, u64 flags)
 {
-        u64 num_devices = root->fs_info->fs_devices->rw_devices;
+        /*
+         * we add in the count of missing devices because we want
+         * to make sure that any RAID levels on a degraded FS
+         * continue to be honored.
+         */
+        u64 num_devices = root->fs_info->fs_devices->rw_devices +
+                root->fs_info->fs_devices->missing_devices;
 
         if (num_devices == 1)
                 flags &= ~(BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID0);
@@ -7891,7 +7897,14 @@ static u64 update_block_group_flags(struct btrfs_root *root, u64 flags)
         u64 stripped = BTRFS_BLOCK_GROUP_RAID0 |
                 BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID10;
 
-        num_devices = root->fs_info->fs_devices->rw_devices;
+        /*
+         * we add in the count of missing devices because we want
+         * to make sure that any RAID levels on a degraded FS
+         * continue to be honored.
+         */
+        num_devices = root->fs_info->fs_devices->rw_devices +
+                root->fs_info->fs_devices->missing_devices;
+
         if (num_devices == 1) {
                 stripped |= BTRFS_BLOCK_GROUP_DUP;
                 stripped = flags & ~stripped;
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 91851b555e2e..177b73179590 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -413,12 +413,16 @@ static noinline int device_list_add(const char *path,
 
                 device->fs_devices = fs_devices;
                 fs_devices->num_devices++;
-        } else if (strcmp(device->name, path)) {
+        } else if (!device->name || strcmp(device->name, path)) {
                 name = kstrdup(path, GFP_NOFS);
                 if (!name)
                         return -ENOMEM;
                 kfree(device->name);
                 device->name = name;
+                if (device->missing) {
+                        fs_devices->missing_devices--;
+                        device->missing = 0;
+                }
         }
 
         if (found_transid > fs_devices->latest_trans) {
@@ -1238,6 +1242,9 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path)
 
         device->fs_devices->num_devices--;
 
+        if (device->missing)
+                root->fs_info->fs_devices->missing_devices--;
+
         next_device = list_entry(root->fs_info->fs_devices->devices.next,
                                  struct btrfs_device, dev_list);
         if (device->bdev == root->fs_info->sb->s_bdev)
@@ -3084,7 +3091,9 @@ static struct btrfs_device *add_missing_dev(struct btrfs_root *root,
         device->devid = devid;
         device->work.func = pending_bios_fn;
         device->fs_devices = fs_devices;
+        device->missing = 1;
         fs_devices->num_devices++;
+        fs_devices->missing_devices++;
         spin_lock_init(&device->io_lock);
         INIT_LIST_HEAD(&device->dev_alloc_list);
         memcpy(device->uuid, dev_uuid, BTRFS_UUID_SIZE);
@@ -3282,6 +3291,15 @@ static int read_one_dev(struct btrfs_root *root,
                         device = add_missing_dev(root, devid, dev_uuid);
                         if (!device)
                                 return -ENOMEM;
+                } else if (!device->missing) {
+                        /*
+                         * this happens when a device that was properly setup
+                         * in the device info lists suddenly goes bad.
+                         * device->bdev is NULL, and so we have to set
+                         * device->missing to one here
+                         */
+                        root->fs_info->fs_devices->missing_devices++;
+                        device->missing = 1;
                 }
         }
 
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 31b0fabdd2ea..a668c0116982 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -45,6 +45,7 @@ struct btrfs_device {
         int barriers;
         int writeable;
         int in_fs_metadata;
+        int missing;
 
         spinlock_t io_lock;
 
@@ -94,6 +95,7 @@ struct btrfs_fs_devices {
         u64 num_devices;
         u64 open_devices;
         u64 rw_devices;
+        u64 missing_devices;
         u64 total_rw_bytes;
         struct block_device *latest_bdev;