1 files changed, 245 insertions, 189 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 161694b66038..6e71a2a78363 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -61,12 +61,21 @@
 #include "tests/btrfs-tests.h"
 
 #include "qgroup.h"
-#include "backref.h"
 #define CREATE_TRACE_POINTS
 #include <trace/events/btrfs.h>
 
 static const struct super_operations btrfs_super_ops;
+
+/*
+ * Types for mounting the default subvolume and a subvolume explicitly
+ * requested by subvol=/path. That way the callchain is straightforward and we
+ * don't have to play tricks with the mount options and recursive calls to
+ * btrfs_mount.
+ *
+ * The new btrfs_root_fs_type also servers as a tag for the bdev_holder.
+ */
 static struct file_system_type btrfs_fs_type;
+static struct file_system_type btrfs_root_fs_type;
 
 static int btrfs_remount(struct super_block *sb, int *flags, char *data);
 
@@ -98,30 +107,6 @@ const char *btrfs_decode_error(int errno)
 	return errstr;
 }
 
-/* btrfs handle error by forcing the filesystem readonly */
-static void btrfs_handle_error(struct btrfs_fs_info *fs_info)
-{
-	struct super_block *sb = fs_info->sb;
-
-	if (sb_rdonly(sb))
-		return;
-
-	if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state)) {
-		sb->s_flags |= MS_RDONLY;
-		btrfs_info(fs_info, "forced readonly");
-		/*
-		 * Note that a running device replace operation is not
-		 * canceled here although there is no way to update
-		 * the progress. It would add the risk of a deadlock,
-		 * therefore the canceling is omitted. The only penalty
-		 * is that some I/O remains active until the procedure
-		 * completes. The next time when the filesystem is
-		 * mounted writeable again, the device replace
-		 * operation continues.
-		 */
-	}
-}
-
 /*
  * __btrfs_handle_fs_error decodes expected errors from the caller and
  * invokes the approciate error response.
@@ -137,7 +122,7 @@ void __btrfs_handle_fs_error(struct btrfs_fs_info *fs_info, const char *function
 
 	/*
 	 * Special case: if the error is EROFS, and we're already
-	 * under MS_RDONLY, then it is safe here.
+	 * under SB_RDONLY, then it is safe here.
 	 */
 	if (errno == -EROFS && sb_rdonly(sb))
   		return;
@@ -168,8 +153,23 @@ void __btrfs_handle_fs_error(struct btrfs_fs_info *fs_info, const char *function
 	set_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state);
 
 	/* Don't go through full error handling during mount */
-	if (sb->s_flags & MS_BORN)
-		btrfs_handle_error(fs_info);
+	if (!(sb->s_flags & SB_BORN))
+		return;
+
+	if (sb_rdonly(sb))
+		return;
+
+	/* btrfs handle error by forcing the filesystem readonly */
+	sb->s_flags |= SB_RDONLY;
+	btrfs_info(fs_info, "forced readonly");
+	/*
+	 * Note that a running device replace operation is not canceled here
+	 * although there is no way to update the progress. It would add the
+	 * risk of a deadlock, therefore the canceling is omitted. The only
+	 * penalty is that some I/O remains active until the procedure
+	 * completes. The next time when the filesystem is mounted writeable
+	 * again, the device replace operation continues.
+	 */
 }
 
 #ifdef CONFIG_PRINTK
@@ -202,7 +202,6 @@ static struct ratelimit_state printk_limits[] = {
 
 void btrfs_printk(const struct btrfs_fs_info *fs_info, const char *fmt, ...)
 {
-	struct super_block *sb = fs_info->sb;
 	char lvl[PRINTK_MAX_SINGLE_HEADER_LEN + 1] = "\0";
 	struct va_format vaf;
 	va_list args;
@@ -228,7 +227,8 @@ void btrfs_printk(const struct btrfs_fs_info *fs_info, const char *fmt, ...)
 	vaf.va = &args;
 
 	if (__ratelimit(ratelimit))
-		printk("%sBTRFS %s (device %s): %pV\n", lvl, type, sb->s_id, &vaf);
+		printk("%sBTRFS %s (device %s): %pV\n", lvl, type,
+			fs_info ? fs_info->sb->s_id : "<unknown>", &vaf);
 
 	va_end(args);
 }
@@ -292,7 +292,7 @@ void __btrfs_panic(struct btrfs_fs_info *fs_info, const char *function,
 	vaf.va = &args;
 
 	errstr = btrfs_decode_error(errno);
-	if (fs_info && (fs_info->mount_opt & BTRFS_MOUNT_PANIC_ON_FATAL_ERROR))
+	if (fs_info && (btrfs_test_opt(fs_info, PANIC_ON_FATAL_ERROR)))
 		panic(KERN_CRIT "BTRFS panic (device %s) in %s:%d: %pV (errno=%d %s)\n",
 			s_id, function, line, &vaf, errno, errstr);
 
@@ -326,6 +326,9 @@ enum {
 #ifdef CONFIG_BTRFS_DEBUG
 	Opt_fragment_data, Opt_fragment_metadata, Opt_fragment_all,
 #endif
+#ifdef CONFIG_BTRFS_FS_REF_VERIFY
+	Opt_ref_verify,
+#endif
 	Opt_err,
 };
 
@@ -387,6 +390,9 @@ static const match_table_t tokens = {
 	{Opt_fragment_metadata, "fragment=metadata"},
 	{Opt_fragment_all, "fragment=all"},
 #endif
+#ifdef CONFIG_BTRFS_FS_REF_VERIFY
+	{Opt_ref_verify, "ref_verify"},
+#endif
 	{Opt_err, NULL},
 };
 
@@ -399,7 +405,7 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 			unsigned long new_flags)
 {
 	substring_t args[MAX_OPT_ARGS];
-	char *p, *num, *orig = NULL;
+	char *p, *num;
 	u64 cache_gen;
 	int intarg;
 	int ret = 0;
@@ -422,16 +428,6 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 	if (!options)
 		goto check;
 
-	/*
-	 * strsep changes the string, duplicate it because parse_options
-	 * gets called twice
-	 */
-	options = kstrdup(options, GFP_KERNEL);
-	if (!options)
-		return -ENOMEM;
-
-	orig = options;
-
 	while ((p = strsep(&options, ",")) != NULL) {
 		int token;
 		if (!*p)
@@ -448,7 +444,8 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 		case Opt_subvolrootid:
 		case Opt_device:
 			/*
-			 * These are parsed by btrfs_parse_early_options
+			 * These are parsed by btrfs_parse_subvol_options
+			 * and btrfs_parse_early_options
 			 * and can be happily ignored here.
 			 */
 			break;
@@ -501,7 +498,18 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 			    token == Opt_compress_force ||
 			    strncmp(args[0].from, "zlib", 4) == 0) {
 				compress_type = "zlib";
+
 				info->compress_type = BTRFS_COMPRESS_ZLIB;
+				info->compress_level = BTRFS_ZLIB_DEFAULT_LEVEL;
+				/*
+				 * args[0] contains uninitialized data since
+				 * for these tokens we don't expect any
+				 * parameter.
+				 */
+				if (token != Opt_compress &&
+				    token != Opt_compress_force)
+					info->compress_level =
+					  btrfs_compress_str2level(args[0].from);
 				btrfs_set_opt(info->mount_opt, COMPRESS);
 				btrfs_clear_opt(info->mount_opt, NODATACOW);
 				btrfs_clear_opt(info->mount_opt, NODATASUM);
@@ -549,9 +557,9 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 			      compress_force != saved_compress_force)) ||
 			    (!btrfs_test_opt(info, COMPRESS) &&
 			     no_compress == 1)) {
-				btrfs_info(info, "%s %s compression",
+				btrfs_info(info, "%s %s compression, level %d",
 					   (compress_force) ? "force" : "use",
-					   compress_type);
+					   compress_type, info->compress_level);
 			}
 			compress_force = false;
 			break;
@@ -617,7 +625,7 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 			break;
 		case Opt_acl:
 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
-			info->sb->s_flags |= MS_POSIXACL;
+			info->sb->s_flags |= SB_POSIXACL;
 			break;
 #else
 			btrfs_err(info, "support for ACL not compiled in!");
@@ -625,7 +633,7 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 			goto out;
 #endif
 		case Opt_noacl:
-			info->sb->s_flags &= ~MS_POSIXACL;
+			info->sb->s_flags &= ~SB_POSIXACL;
 			break;
 		case Opt_notreelog:
 			btrfs_set_and_info(info, NOTREELOG,
@@ -825,6 +833,12 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 			btrfs_set_opt(info->mount_opt, FRAGMENT_DATA);
 			break;
 #endif
+#ifdef CONFIG_BTRFS_FS_REF_VERIFY
+		case Opt_ref_verify:
+			btrfs_info(info, "doing ref verification");
+			btrfs_set_opt(info->mount_opt, REF_VERIFY);
+			break;
+#endif
 		case Opt_err:
 			btrfs_info(info, "unrecognized mount option '%s'", p);
 			ret = -EINVAL;
@@ -837,7 +851,7 @@ check:
 	/*
 	 * Extra check for current option against current flag
 	 */
-	if (btrfs_test_opt(info, NOLOGREPLAY) && !(new_flags & MS_RDONLY)) {
+	if (btrfs_test_opt(info, NOLOGREPLAY) && !(new_flags & SB_RDONLY)) {
 		btrfs_err(info,
 			  "nologreplay must be used with ro mount option");
 		ret = -EINVAL;
@@ -854,7 +868,6 @@ out:
 		btrfs_info(info, "disk space caching is enabled");
 	if (!ret && btrfs_test_opt(info, FREE_SPACE_TREE))
 		btrfs_info(info, "using free space tree");
-	kfree(orig);
 	return ret;
 }
 
@@ -865,11 +878,60 @@ out:
  * only when we need to allocate a new super block.
  */
 static int btrfs_parse_early_options(const char *options, fmode_t flags,
-		void *holder, char **subvol_name, u64 *subvol_objectid,
-		struct btrfs_fs_devices **fs_devices)
+		void *holder, struct btrfs_fs_devices **fs_devices)
 {
 	substring_t args[MAX_OPT_ARGS];
 	char *device_name, *opts, *orig, *p;
+	int error = 0;
+
+	if (!options)
+		return 0;
+
+	/*
+	 * strsep changes the string, duplicate it because btrfs_parse_options
+	 * gets called later
+	 */
+	opts = kstrdup(options, GFP_KERNEL);
+	if (!opts)
+		return -ENOMEM;
+	orig = opts;
+
+	while ((p = strsep(&opts, ",")) != NULL) {
+		int token;
+
+		if (!*p)
+			continue;
+
+		token = match_token(p, tokens, args);
+		if (token == Opt_device) {
+			device_name = match_strdup(&args[0]);
+			if (!device_name) {
+				error = -ENOMEM;
+				goto out;
+			}
+			error = btrfs_scan_one_device(device_name,
+					flags, holder, fs_devices);
+			kfree(device_name);
+			if (error)
+				goto out;
+		}
+	}
+
+out:
+	kfree(orig);
+	return error;
+}
+
+/*
+ * Parse mount options that are related to subvolume id
+ *
+ * The value is later passed to mount_subvol()
+ */
+static int btrfs_parse_subvol_options(const char *options, fmode_t flags,
+		char **subvol_name, u64 *subvol_objectid)
+{
+	substring_t args[MAX_OPT_ARGS];
+	char *opts, *orig, *p;
 	char *num = NULL;
 	int error = 0;
 
@@ -877,8 +939,8 @@ static int btrfs_parse_early_options(const char *options, fmode_t flags,
 		return 0;
 
 	/*
-	 * strsep changes the string, duplicate it because parse_options
-	 * gets called twice
+	 * strsep changes the string, duplicate it because
+	 * btrfs_parse_early_options gets called later
 	 */
 	opts = kstrdup(options, GFP_KERNEL);
 	if (!opts)
@@ -917,18 +979,6 @@ static int btrfs_parse_early_options(const char *options, fmode_t flags,
 		case Opt_subvolrootid:
 			pr_warn("BTRFS: 'subvolrootid' mount option is deprecated and has no effect\n");
 			break;
-		case Opt_device:
-			device_name = match_strdup(&args[0]);
-			if (!device_name) {
-				error = -ENOMEM;
-				goto out;
-			}
-			error = btrfs_scan_one_device(device_name,
-					flags, holder, fs_devices);
-			kfree(device_name);
-			if (error)
-				goto out;
-			break;
 		default:
 			break;
 		}
@@ -1133,7 +1183,7 @@ static int btrfs_fill_super(struct super_block *sb,
 	sb->s_xattr = btrfs_xattr_handlers;
 	sb->s_time_gran = 1;
 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
-	sb->s_flags |= MS_POSIXACL;
+	sb->s_flags |= SB_POSIXACL;
 #endif
 	sb->s_flags |= SB_I_VERSION;
 	sb->s_iflags |= SB_I_CGROUPWB;
@@ -1166,7 +1216,7 @@ static int btrfs_fill_super(struct super_block *sb,
 	}
 
 	cleancache_init_fs(sb);
-	sb->s_flags |= MS_ACTIVE;
+	sb->s_flags |= SB_ACTIVE;
 	return 0;
 
 fail_close:
@@ -1205,8 +1255,8 @@ int btrfs_sync_fs(struct super_block *sb, int wait)
 			 * happens. The pending operations are delayed to the
 			 * next commit after thawing.
 			 */
-			if (__sb_start_write(sb, SB_FREEZE_WRITE, false))
-				__sb_end_write(sb, SB_FREEZE_WRITE);
+			if (sb_start_write_trylock(sb))
+				sb_end_write(sb);
 			else
 				return 0;
 			trans = btrfs_start_transaction(root, 0);
@@ -1220,7 +1270,7 @@ int btrfs_sync_fs(struct super_block *sb, int wait)
 static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 {
 	struct btrfs_fs_info *info = btrfs_sb(dentry->d_sb);
-	char *compress_type;
+	const char *compress_type;
 
 	if (btrfs_test_opt(info, DEGRADED))
 		seq_puts(seq, ",degraded");
@@ -1236,16 +1286,13 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 					     num_online_cpus() + 2, 8))
 		seq_printf(seq, ",thread_pool=%d", info->thread_pool_size);
 	if (btrfs_test_opt(info, COMPRESS)) {
-		if (info->compress_type == BTRFS_COMPRESS_ZLIB)
-			compress_type = "zlib";
-		else if (info->compress_type == BTRFS_COMPRESS_LZO)
-			compress_type = "lzo";
-		else
-			compress_type = "zstd";
+		compress_type = btrfs_compress_type2str(info->compress_type);
 		if (btrfs_test_opt(info, FORCE_COMPRESS))
 			seq_printf(seq, ",compress-force=%s", compress_type);
 		else
 			seq_printf(seq, ",compress=%s", compress_type);
+		if (info->compress_level)
+			seq_printf(seq, ":%d", info->compress_level);
 	}
 	if (btrfs_test_opt(info, NOSSD))
 		seq_puts(seq, ",nossd");
@@ -1261,7 +1308,7 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 		seq_puts(seq, ",flushoncommit");
 	if (btrfs_test_opt(info, DISCARD))
 		seq_puts(seq, ",discard");
-	if (!(info->sb->s_flags & MS_POSIXACL))
+	if (!(info->sb->s_flags & SB_POSIXACL))
 		seq_puts(seq, ",noacl");
 	if (btrfs_test_opt(info, SPACE_CACHE))
 		seq_puts(seq, ",space_cache");
@@ -1305,6 +1352,8 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 	if (btrfs_test_opt(info, FRAGMENT_METADATA))
 		seq_puts(seq, ",fragment=metadata");
 #endif
+	if (btrfs_test_opt(info, REF_VERIFY))
+		seq_puts(seq, ",ref_verify");
 	seq_printf(seq, ",subvolid=%llu",
 		  BTRFS_I(d_inode(dentry))->root->root_key.objectid);
 	seq_puts(seq, ",subvol=");
@@ -1338,86 +1387,12 @@ static inline int is_subvolume_inode(struct inode *inode)
 	return 0;
 }
 
-/*
- * This will add subvolid=0 to the argument string while removing any subvol=
- * and subvolid= arguments to make sure we get the top-level root for path
- * walking to the subvol we want.
- */
-static char *setup_root_args(char *args)
-{
-	char *buf, *dst, *sep;
-
-	if (!args)
-		return kstrdup("subvolid=0", GFP_KERNEL);
-
-	/* The worst case is that we add ",subvolid=0" to the end. */
-	buf = dst = kmalloc(strlen(args) + strlen(",subvolid=0") + 1,
-			GFP_KERNEL);
-	if (!buf)
-		return NULL;
-
-	while (1) {
-		sep = strchrnul(args, ',');
-		if (!strstarts(args, "subvol=") &&
-		    !strstarts(args, "subvolid=")) {
-			memcpy(dst, args, sep - args);
-			dst += sep - args;
-			*dst++ = ',';
-		}
-		if (*sep)
-			args = sep + 1;
-		else
-			break;
-	}
-	strcpy(dst, "subvolid=0");
-
-	return buf;
-}
-
 static struct dentry *mount_subvol(const char *subvol_name, u64 subvol_objectid,
-				   int flags, const char *device_name,
-				   char *data)
+				   const char *device_name, struct vfsmount *mnt)
 {
 	struct dentry *root;
-	struct vfsmount *mnt = NULL;
-	char *newargs;
 	int ret;
 
-	newargs = setup_root_args(data);
-	if (!newargs) {
-		root = ERR_PTR(-ENOMEM);
-		goto out;
-	}
-
-	mnt = vfs_kern_mount(&btrfs_fs_type, flags, device_name, newargs);
-	if (PTR_ERR_OR_ZERO(mnt) == -EBUSY) {
-		if (flags & MS_RDONLY) {
-			mnt = vfs_kern_mount(&btrfs_fs_type, flags & ~MS_RDONLY,
-					     device_name, newargs);
-		} else {
-			mnt = vfs_kern_mount(&btrfs_fs_type, flags | MS_RDONLY,
-					     device_name, newargs);
-			if (IS_ERR(mnt)) {
-				root = ERR_CAST(mnt);
-				mnt = NULL;
-				goto out;
-			}
-
-			down_write(&mnt->mnt_sb->s_umount);
-			ret = btrfs_remount(mnt->mnt_sb, &flags, NULL);
-			up_write(&mnt->mnt_sb->s_umount);
-			if (ret < 0) {
-				root = ERR_PTR(ret);
-				goto out;
-			}
-		}
-	}
-	if (IS_ERR(mnt)) {
-		root = ERR_CAST(mnt);
-		mnt = NULL;
-		goto out;
-	}
-
 	if (!subvol_name) {
 		if (!subvol_objectid) {
 			ret = get_default_subvol_objectid(btrfs_sb(mnt->mnt_sb),
@@ -1473,7 +1448,6 @@ static struct dentry *mount_subvol(const char *subvol_name, u64 subvol_objectid,
 
 out:
 	mntput(mnt);
-	kfree(newargs);
 	kfree(subvol_name);
 	return root;
 }
@@ -1531,11 +1505,11 @@ static int setup_security_options(struct btrfs_fs_info *fs_info,
 /*
  * Find a superblock for the given device / mount point.
  *
- * Note:  This is based on get_sb_bdev from fs/super.c with a few additions
- *	  for multiple device setup.  Make sure to keep it in sync.
+ * Note: This is based on mount_bdev from fs/super.c with a few additions
+ *       for multiple device setup.  Make sure to keep it in sync.
  */
-static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags,
-		const char *device_name, void *data)
+static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
+		int flags, const char *device_name, void *data)
 {
 	struct block_device *bdev = NULL;
 	struct super_block *s;
@@ -1543,27 +1517,17 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags,
 	struct btrfs_fs_info *fs_info = NULL;
 	struct security_mnt_opts new_sec_opts;
 	fmode_t mode = FMODE_READ;
-	char *subvol_name = NULL;
-	u64 subvol_objectid = 0;
 	int error = 0;
 
-	if (!(flags & MS_RDONLY))
+	if (!(flags & SB_RDONLY))
 		mode |= FMODE_WRITE;
 
 	error = btrfs_parse_early_options(data, mode, fs_type,
-					  &subvol_name, &subvol_objectid,
 					  &fs_devices);
 	if (error) {
-		kfree(subvol_name);
 		return ERR_PTR(error);
 	}
 
-	if (subvol_name || subvol_objectid != BTRFS_FS_TREE_OBJECTID) {
-		/* mount_subvol() will free subvol_name. */
-		return mount_subvol(subvol_name, subvol_objectid, flags,
-				    device_name, data);
-	}
-
 	security_init_mnt_opts(&new_sec_opts);
 	if (data) {
 		error = parse_security_options(data, &new_sec_opts);
@@ -1601,13 +1565,13 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags,
 	if (error)
 		goto error_fs_info;
 
-	if (!(flags & MS_RDONLY) && fs_devices->rw_devices == 0) {
+	if (!(flags & SB_RDONLY) && fs_devices->rw_devices == 0) {
 		error = -EACCES;
 		goto error_close_devices;
 	}
 
 	bdev = fs_devices->latest_bdev;
-	s = sget(fs_type, btrfs_test_super, btrfs_set_super, flags | MS_NOSEC,
+	s = sget(fs_type, btrfs_test_super, btrfs_set_super, flags | SB_NOSEC,
 		 fs_info);
 	if (IS_ERR(s)) {
 		error = PTR_ERR(s);
@@ -1617,7 +1581,7 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags,
 	if (s->s_root) {
 		btrfs_close_devices(fs_devices);
 		free_fs_info(fs_info);
-		if ((flags ^ s->s_flags) & MS_RDONLY)
+		if ((flags ^ s->s_flags) & SB_RDONLY)
 			error = -EBUSY;
 	} else {
 		snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
@@ -1647,6 +1611,84 @@ error_sec_opts:
 	return ERR_PTR(error);
 }
 
+/*
+ * Mount function which is called by VFS layer.
+ *
+ * In order to allow mounting a subvolume directly, btrfs uses mount_subtree()
+ * which needs vfsmount* of device's root (/).  This means device's root has to
+ * be mounted internally in any case.
+ *
+ * Operation flow:
+ *   1. Parse subvol id related options for later use in mount_subvol().
+ *
+ *   2. Mount device's root (/) by calling vfs_kern_mount().
+ *
+ *      NOTE: vfs_kern_mount() is used by VFS to call btrfs_mount() in the
+ *      first place. In order to avoid calling btrfs_mount() again, we use
+ *      different file_system_type which is not registered to VFS by
+ *      register_filesystem() (btrfs_root_fs_type). As a result,
+ *      btrfs_mount_root() is called. The return value will be used by
+ *      mount_subtree() in mount_subvol().
+ *
+ *   3. Call mount_subvol() to get the dentry of subvolume. Since there is
+ *      "btrfs subvolume set-default", mount_subvol() is called always.
+ */
+static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags,
+		const char *device_name, void *data)
+{
+	struct vfsmount *mnt_root;
+	struct dentry *root;
+	fmode_t mode = FMODE_READ;
+	char *subvol_name = NULL;
+	u64 subvol_objectid = 0;
+	int error = 0;
+
+	if (!(flags & SB_RDONLY))
+		mode |= FMODE_WRITE;
+
+	error = btrfs_parse_subvol_options(data, mode,
+					  &subvol_name, &subvol_objectid);
+	if (error) {
+		kfree(subvol_name);
+		return ERR_PTR(error);
+	}
+
+	/* mount device's root (/) */
+	mnt_root = vfs_kern_mount(&btrfs_root_fs_type, flags, device_name, data);
+	if (PTR_ERR_OR_ZERO(mnt_root) == -EBUSY) {
+		if (flags & SB_RDONLY) {
+			mnt_root = vfs_kern_mount(&btrfs_root_fs_type,
+				flags & ~SB_RDONLY, device_name, data);
+		} else {
+			mnt_root = vfs_kern_mount(&btrfs_root_fs_type,
+				flags | SB_RDONLY, device_name, data);
+			if (IS_ERR(mnt_root)) {
+				root = ERR_CAST(mnt_root);
+				goto out;
+			}
+
+			down_write(&mnt_root->mnt_sb->s_umount);
+			error = btrfs_remount(mnt_root->mnt_sb, &flags, NULL);
+			up_write(&mnt_root->mnt_sb->s_umount);
+			if (error < 0) {
+				root = ERR_PTR(error);
+				mntput(mnt_root);
+				goto out;
+			}
+		}
+	}
+	if (IS_ERR(mnt_root)) {
+		root = ERR_CAST(mnt_root);
+		goto out;
+	}
+
+	/* mount_subvol() will free subvol_name and mnt_root */
+	root = mount_subvol(subvol_name, subvol_objectid, device_name, mnt_root);
+
+out:
+	return root;
+}
+
 static void btrfs_resize_thread_pool(struct btrfs_fs_info *fs_info,
 				     int new_pool_size, int old_pool_size)
 {
@@ -1684,11 +1726,11 @@ static inline void btrfs_remount_begin(struct btrfs_fs_info *fs_info,
 {
 	if (btrfs_raw_test_opt(old_opts, AUTO_DEFRAG) &&
 	    (!btrfs_raw_test_opt(fs_info->mount_opt, AUTO_DEFRAG) ||
-	     (flags & MS_RDONLY))) {
+	     (flags & SB_RDONLY))) {
 		/* wait for any defraggers to finish */
 		wait_event(fs_info->transaction_wait,
 			   (atomic_read(&fs_info->defrag_running) == 0));
-		if (flags & MS_RDONLY)
+		if (flags & SB_RDONLY)
 			sync_filesystem(fs_info->sb);
 	}
 }
@@ -1748,10 +1790,10 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
 	btrfs_resize_thread_pool(fs_info,
 		fs_info->thread_pool_size, old_thread_pool_size);
 
-	if ((bool)(*flags & MS_RDONLY) == sb_rdonly(sb))
+	if ((bool)(*flags & SB_RDONLY) == sb_rdonly(sb))
 		goto out;
 
-	if (*flags & MS_RDONLY) {
+	if (*flags & SB_RDONLY) {
 		/*
 		 * this also happens on 'umount -rf' or on shutdown, when
 		 * the filesystem is busy.
@@ -1763,10 +1805,10 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
 		/* avoid complains from lockdep et al. */
 		up(&fs_info->uuid_tree_rescan_sem);
 
-		sb->s_flags |= MS_RDONLY;
+		sb->s_flags |= SB_RDONLY;
 
 		/*
-		 * Setting MS_RDONLY will put the cleaner thread to
+		 * Setting SB_RDONLY will put the cleaner thread to
 		 * sleep at the next loop if it's already active.
 		 * If it's already asleep, we'll leave unused block
 		 * groups on disk until we're mounted read-write again
@@ -1793,7 +1835,7 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
 			goto restore;
 		}
 
-		if (!btrfs_check_rw_degradable(fs_info)) {
+		if (!btrfs_check_rw_degradable(fs_info, NULL)) {
 			btrfs_warn(fs_info,
 				"too many missing devices, writeable remount is not allowed");
 			ret = -EACCES;
@@ -1838,7 +1880,7 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
 				goto restore;
 			}
 		}
-		sb->s_flags &= ~MS_RDONLY;
+		sb->s_flags &= ~SB_RDONLY;
 
 		set_bit(BTRFS_FS_OPEN, &fs_info->flags);
 	}
@@ -1848,9 +1890,9 @@ out:
 	return 0;
 
 restore:
-	/* We've hit an error - don't reset MS_RDONLY */
+	/* We've hit an error - don't reset SB_RDONLY */
 	if (sb_rdonly(sb))
-		old_flags |= MS_RDONLY;
+		old_flags |= SB_RDONLY;
 	sb->s_flags = old_flags;
 	fs_info->mount_opt = old_opts;
 	fs_info->compress_type = old_compress_type;
@@ -1945,8 +1987,10 @@ static int btrfs_calc_avail_data_space(struct btrfs_fs_info *fs_info,
 
 	rcu_read_lock();
 	list_for_each_entry_rcu(device, &fs_devices->devices, dev_list) {
-		if (!device->in_fs_metadata || !device->bdev ||
-		    device->is_tgtdev_for_dev_replace)
+		if (!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA,
+						&device->dev_state) ||
+		    !device->bdev ||
+		    test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state))
 			continue;
 
 		if (i >= nr_devices)
@@ -2112,7 +2156,7 @@ static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	 * succeed even if the Avail is zero. But this is better than the other
 	 * way around.
 	 */
-	thresh = 4 * 1024 * 1024;
+	thresh = SZ_4M;
 
 	if (!mixed && total_free_meta - thresh < block_rsv->size)
 		buf->f_bavail = 0;
@@ -2147,6 +2191,15 @@ static struct file_system_type btrfs_fs_type = {
 	.kill_sb	= btrfs_kill_super,
 	.fs_flags	= FS_REQUIRES_DEV | FS_BINARY_MOUNTDATA,
 };
+
+static struct file_system_type btrfs_root_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "btrfs",
+	.mount		= btrfs_mount_root,
+	.kill_sb	= btrfs_kill_super,
+	.fs_flags	= FS_REQUIRES_DEV | FS_BINARY_MOUNTDATA,
+};
+
 MODULE_ALIAS_FS("btrfs");
 
 static int btrfs_control_open(struct inode *inode, struct file *file)
@@ -2180,11 +2233,11 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
 	switch (cmd) {
 	case BTRFS_IOC_SCAN_DEV:
 		ret = btrfs_scan_one_device(vol->name, FMODE_READ,
-					    &btrfs_fs_type, &fs_devices);
+					    &btrfs_root_fs_type, &fs_devices);
 		break;
 	case BTRFS_IOC_DEVICES_READY:
 		ret = btrfs_scan_one_device(vol->name, FMODE_READ,
-					    &btrfs_fs_type, &fs_devices);
+					    &btrfs_root_fs_type, &fs_devices);
 		if (ret)
 			break;
 		ret = !(fs_devices->num_devices == fs_devices->total_devices);
@@ -2242,7 +2295,7 @@ static int btrfs_show_devname(struct seq_file *m, struct dentry *root)
 	while (cur_devices) {
 		head = &cur_devices->devices;
 		list_for_each_entry(dev, head, dev_list) {
-			if (dev->missing)
+			if (test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state))
 				continue;
 			if (!dev->name)
 				continue;
@@ -2297,7 +2350,7 @@ static struct miscdevice btrfs_misc = {
 MODULE_ALIAS_MISCDEV(BTRFS_MINOR);
 MODULE_ALIAS("devname:btrfs-control");
 
-static int btrfs_interface_init(void)
+static int __init btrfs_interface_init(void)
 {
 	return misc_register(&btrfs_misc);
 }
@@ -2307,7 +2360,7 @@ static void btrfs_interface_exit(void)
 	misc_deregister(&btrfs_misc);
 }
 
-static void btrfs_print_mod_info(void)
+static void __init btrfs_print_mod_info(void)
 {
 	pr_info("Btrfs loaded, crc32c=%s"
 #ifdef CONFIG_BTRFS_DEBUG
@@ -2319,6 +2372,9 @@ static void btrfs_print_mod_info(void)
 #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
 			", integrity-checker=on"
 #endif
+#ifdef CONFIG_BTRFS_FS_REF_VERIFY
+			", ref-verify=on"
+#endif
 			"\n",
 			btrfs_crc32c_impl());
 }