bcachefs: Don't fail mount if device has been removed

Also - make sure to show the devices we actually have open in /proc
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/fs.c

@@ -1428,6 +1428,24 @@ static int bch2_remount(struct super_block *sb, int *flags, char *data)
 	return ret;
 }
 
+static int bch2_show_devname(struct seq_file *seq, struct dentry *root)
+{
+	struct bch_fs *c = root->d_sb->s_fs_info;
+	struct bch_dev *ca;
+	unsigned i;
+	bool first = true;
+
+	for_each_online_member(ca, c, i) {
+		if (!first)
+			seq_putc(seq, ':');
+		first = false;
+		seq_puts(seq, "/dev/");
+		seq_puts(seq, ca->name);
+	}
+
+	return 0;
+}
+
 static int bch2_show_options(struct seq_file *seq, struct dentry *root)
 {
 	struct bch_fs *c = root->d_sb->s_fs_info;
@@ -1451,7 +1469,6 @@ static int bch2_show_options(struct seq_file *seq, struct dentry *root)
 	}
 
 	return 0;
-
 }
 
 static const struct super_operations bch_super_operations = {
@@ -1461,6 +1478,7 @@ static const struct super_operations bch_super_operations = {
 	.evict_inode	= bch2_evict_inode,
 	.sync_fs	= bch2_sync_fs,
 	.statfs		= bch2_statfs,
+	.show_devname	= bch2_show_devname,
 	.show_options	= bch2_show_options,
 	.remount_fs	= bch2_remount,
 #if 0

fs/bcachefs/super.c

@@ -1790,7 +1790,6 @@ int bch2_dev_resize(struct bch_fs *c, struct bch_dev *ca, u64 nbuckets)
 /* return with ref on ca->ref: */
 struct bch_dev *bch2_dev_lookup(struct bch_fs *c, const char *path)
 {
-
 	struct bch_dev *ca;
 	dev_t dev;
 	unsigned i;
@@ -1816,6 +1815,7 @@ struct bch_fs *bch2_fs_open(char * const *devices, unsigned nr_devices,
 {
 	struct bch_sb_handle *sb = NULL;
 	struct bch_fs *c = NULL;
+	struct bch_sb_field_members *mi;
 	unsigned i, best_sb = 0;
 	const char *err;
 	int ret = -ENOMEM;
@@ -1851,10 +1851,22 @@ struct bch_fs *bch2_fs_open(char * const *devices, unsigned nr_devices,
 		    le64_to_cpu(sb[best_sb].sb->seq))
 			best_sb = i;
 
-	for (i = 0; i < nr_devices; i++) {
+	mi = bch2_sb_get_members(sb[best_sb].sb);
+
+	i = 0;
+	while (i < nr_devices) {
+		if (i != best_sb &&
+		    !bch2_dev_exists(sb[best_sb].sb, mi, sb[i].sb->dev_idx)) {
+			pr_info("%pg has been removed, skipping", sb[i].bdev);
+			bch2_free_super(&sb[i]);
+			array_remove_item(sb, nr_devices, i);
+			continue;
+		}
+
 		err = bch2_dev_in_fs(sb[best_sb].sb, sb[i].sb);
 		if (err)
 			goto err_print;
+		i++;
 	}
 
 	ret = -ENOMEM;