1 files changed, 155 insertions, 136 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index a0c65adce1ab..68e35a3700ff 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -261,10 +261,65 @@ static const struct fs_parameter_spec btrfs_fs_parameters[] = {
 	{}
 };
 
-/* No support for restricting writes to btrfs devices yet... */
-static inline blk_mode_t btrfs_open_mode(struct fs_context *fc)
+static bool btrfs_match_compress_type(const char *string, const char *type, bool may_have_level)
 {
-	return sb_open_mode(fc->sb_flags) & ~BLK_OPEN_RESTRICT_WRITES;
+	const int len = strlen(type);
+
+	return (strncmp(string, type, len) == 0) &&
+		((may_have_level && string[len] == ':') || string[len] == '\0');
+}
+
+static int btrfs_parse_compress(struct btrfs_fs_context *ctx,
+				const struct fs_parameter *param, int opt)
+{
+	const char *string = param->string;
+
+	/*
+	 * Provide the same semantics as older kernels that don't use fs
+	 * context, specifying the "compress" option clears "force-compress"
+	 * without the need to pass "compress-force=[no|none]" before
+	 * specifying "compress".
+	 */
+	if (opt != Opt_compress_force && opt != Opt_compress_force_type)
+		btrfs_clear_opt(ctx->mount_opt, FORCE_COMPRESS);
+
+	if (opt == Opt_compress || opt == Opt_compress_force) {
+		ctx->compress_type = BTRFS_COMPRESS_ZLIB;
+		ctx->compress_level = BTRFS_ZLIB_DEFAULT_LEVEL;
+		btrfs_set_opt(ctx->mount_opt, COMPRESS);
+		btrfs_clear_opt(ctx->mount_opt, NODATACOW);
+		btrfs_clear_opt(ctx->mount_opt, NODATASUM);
+	} else if (btrfs_match_compress_type(string, "zlib", true)) {
+		ctx->compress_type = BTRFS_COMPRESS_ZLIB;
+		ctx->compress_level = btrfs_compress_str2level(BTRFS_COMPRESS_ZLIB,
+							       string + 4);
+		btrfs_set_opt(ctx->mount_opt, COMPRESS);
+		btrfs_clear_opt(ctx->mount_opt, NODATACOW);
+		btrfs_clear_opt(ctx->mount_opt, NODATASUM);
+	} else if (btrfs_match_compress_type(string, "lzo", false)) {
+		ctx->compress_type = BTRFS_COMPRESS_LZO;
+		ctx->compress_level = 0;
+		btrfs_set_opt(ctx->mount_opt, COMPRESS);
+		btrfs_clear_opt(ctx->mount_opt, NODATACOW);
+		btrfs_clear_opt(ctx->mount_opt, NODATASUM);
+	} else if (btrfs_match_compress_type(string, "zstd", true)) {
+		ctx->compress_type = BTRFS_COMPRESS_ZSTD;
+		ctx->compress_level = btrfs_compress_str2level(BTRFS_COMPRESS_ZSTD,
+							       string + 4);
+		btrfs_set_opt(ctx->mount_opt, COMPRESS);
+		btrfs_clear_opt(ctx->mount_opt, NODATACOW);
+		btrfs_clear_opt(ctx->mount_opt, NODATASUM);
+	} else if (btrfs_match_compress_type(string, "no", false) ||
+		   btrfs_match_compress_type(string, "none", false)) {
+		ctx->compress_level = 0;
+		ctx->compress_type = 0;
+		btrfs_clear_opt(ctx->mount_opt, COMPRESS);
+		btrfs_clear_opt(ctx->mount_opt, FORCE_COMPRESS);
+	} else {
+		btrfs_err(NULL, "unrecognized compression value %s", string);
+		return -EINVAL;
+	}
+	return 0;
 }
 
 static int btrfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
@@ -303,10 +358,9 @@ static int btrfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
 		break;
 	case Opt_device: {
 		struct btrfs_device *device;
-		blk_mode_t mode = btrfs_open_mode(fc);
 
 		mutex_lock(&uuid_mutex);
-		device = btrfs_scan_one_device(param->string, mode, false);
+		device = btrfs_scan_one_device(param->string, false);
 		mutex_unlock(&uuid_mutex);
 		if (IS_ERR(device))
 			return PTR_ERR(device);
@@ -336,53 +390,8 @@ static int btrfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
 		fallthrough;
 	case Opt_compress:
 	case Opt_compress_type:
-		/*
-		 * Provide the same semantics as older kernels that don't use fs
-		 * context, specifying the "compress" option clears
-		 * "force-compress" without the need to pass
-		 * "compress-force=[no|none]" before specifying "compress".
-		 */
-		if (opt != Opt_compress_force && opt != Opt_compress_force_type)
-			btrfs_clear_opt(ctx->mount_opt, FORCE_COMPRESS);
-
-		if (opt == Opt_compress || opt == Opt_compress_force) {
-			ctx->compress_type = BTRFS_COMPRESS_ZLIB;
-			ctx->compress_level = BTRFS_ZLIB_DEFAULT_LEVEL;
-			btrfs_set_opt(ctx->mount_opt, COMPRESS);
-			btrfs_clear_opt(ctx->mount_opt, NODATACOW);
-			btrfs_clear_opt(ctx->mount_opt, NODATASUM);
-		} else if (strncmp(param->string, "zlib", 4) == 0) {
-			ctx->compress_type = BTRFS_COMPRESS_ZLIB;
-			ctx->compress_level =
-				btrfs_compress_str2level(BTRFS_COMPRESS_ZLIB,
-							 param->string + 4);
-			btrfs_set_opt(ctx->mount_opt, COMPRESS);
-			btrfs_clear_opt(ctx->mount_opt, NODATACOW);
-			btrfs_clear_opt(ctx->mount_opt, NODATASUM);
-		} else if (strncmp(param->string, "lzo", 3) == 0) {
-			ctx->compress_type = BTRFS_COMPRESS_LZO;
-			ctx->compress_level = 0;
-			btrfs_set_opt(ctx->mount_opt, COMPRESS);
-			btrfs_clear_opt(ctx->mount_opt, NODATACOW);
-			btrfs_clear_opt(ctx->mount_opt, NODATASUM);
-		} else if (strncmp(param->string, "zstd", 4) == 0) {
-			ctx->compress_type = BTRFS_COMPRESS_ZSTD;
-			ctx->compress_level =
-				btrfs_compress_str2level(BTRFS_COMPRESS_ZSTD,
-							 param->string + 4);
-			btrfs_set_opt(ctx->mount_opt, COMPRESS);
-			btrfs_clear_opt(ctx->mount_opt, NODATACOW);
-			btrfs_clear_opt(ctx->mount_opt, NODATASUM);
-		} else if (strncmp(param->string, "no", 2) == 0) {
-			ctx->compress_level = 0;
-			ctx->compress_type = 0;
-			btrfs_clear_opt(ctx->mount_opt, COMPRESS);
-			btrfs_clear_opt(ctx->mount_opt, FORCE_COMPRESS);
-		} else {
-			btrfs_err(NULL, "unrecognized compression value %s",
-				  param->string);
+		if (btrfs_parse_compress(ctx, param, opt))
 			return -EINVAL;
-		}
 		break;
 	case Opt_ssd:
 		if (result.negated) {
@@ -945,12 +954,12 @@ static int btrfs_fill_super(struct super_block *sb,
 {
 	struct btrfs_inode *inode;
 	struct btrfs_fs_info *fs_info = btrfs_sb(sb);
-	int err;
+	int ret;
 
 	sb->s_maxbytes = MAX_LFS_FILESIZE;
 	sb->s_magic = BTRFS_SUPER_MAGIC;
 	sb->s_op = &btrfs_super_ops;
-	sb->s_d_op = &btrfs_dentry_operations;
+	set_default_d_op(sb, &btrfs_dentry_operations);
 	sb->s_export_op = &btrfs_export_ops;
 #ifdef CONFIG_FS_VERITY
 	sb->s_vop = &btrfs_verityops;
@@ -959,28 +968,28 @@ static int btrfs_fill_super(struct super_block *sb,
 	sb->s_time_gran = 1;
 	sb->s_iflags |= SB_I_CGROUPWB | SB_I_ALLOW_HSM;
 
-	err = super_setup_bdi(sb);
-	if (err) {
+	ret = super_setup_bdi(sb);
+	if (ret) {
 		btrfs_err(fs_info, "super_setup_bdi failed");
-		return err;
+		return ret;
 	}
 
-	err = open_ctree(sb, fs_devices);
-	if (err) {
-		btrfs_err(fs_info, "open_ctree failed: %d", err);
-		return err;
+	ret = open_ctree(sb, fs_devices);
+	if (ret) {
+		btrfs_err(fs_info, "open_ctree failed: %d", ret);
+		return ret;
 	}
 
 	inode = btrfs_iget(BTRFS_FIRST_FREE_OBJECTID, fs_info->fs_root);
 	if (IS_ERR(inode)) {
-		err = PTR_ERR(inode);
-		btrfs_handle_fs_error(fs_info, err, NULL);
+		ret = PTR_ERR(inode);
+		btrfs_handle_fs_error(fs_info, ret, NULL);
 		goto fail_close;
 	}
 
 	sb->s_root = d_make_root(&inode->vfs_inode);
 	if (!sb->s_root) {
-		err = -ENOMEM;
+		ret = -ENOMEM;
 		goto fail_close;
 	}
 
@@ -989,7 +998,7 @@ static int btrfs_fill_super(struct super_block *sb,
 
 fail_close:
 	close_ctree(fs_info);
-	return err;
+	return ret;
 }
 
 int btrfs_sync_fs(struct super_block *sb, int wait)
@@ -1826,10 +1835,9 @@ static int btrfs_get_tree_super(struct fs_context *fc)
 	struct btrfs_fs_info *fs_info = fc->s_fs_info;
 	struct btrfs_fs_context *ctx = fc->fs_private;
 	struct btrfs_fs_devices *fs_devices = NULL;
-	struct block_device *bdev;
 	struct btrfs_device *device;
 	struct super_block *sb;
-	blk_mode_t mode = btrfs_open_mode(fc);
+	blk_mode_t mode = sb_open_mode(fc->sb_flags);
 	int ret;
 
 	btrfs_ctx_to_info(fs_info, ctx);
@@ -1839,47 +1847,60 @@ static int btrfs_get_tree_super(struct fs_context *fc)
 	 * With 'true' passed to btrfs_scan_one_device() (mount time) we expect
 	 * either a valid device or an error.
 	 */
-	device = btrfs_scan_one_device(fc->source, mode, true);
+	device = btrfs_scan_one_device(fc->source, true);
 	ASSERT(device != NULL);
 	if (IS_ERR(device)) {
 		mutex_unlock(&uuid_mutex);
 		return PTR_ERR(device);
 	}
-
 	fs_devices = device->fs_devices;
+	/*
+	 * We cannot hold uuid_mutex calling sget_fc(), it will lead to a
+	 * locking order reversal with s_umount.
+	 *
+	 * So here we increase the holding number of fs_devices, this will ensure
+	 * the fs_devices itself won't be freed.
+	 */
+	btrfs_fs_devices_inc_holding(fs_devices);
 	fs_info->fs_devices = fs_devices;
-
-	ret = btrfs_open_devices(fs_devices, mode, &btrfs_fs_type);
 	mutex_unlock(&uuid_mutex);
-	if (ret)
-		return ret;
-
-	if (!(fc->sb_flags & SB_RDONLY) && fs_devices->rw_devices == 0) {
-		ret = -EACCES;
-		goto error;
-	}
 
-	bdev = fs_devices->latest_dev->bdev;
 
-	/*
-	 * From now on the error handling is not straightforward.
-	 *
-	 * If successful, this will transfer the fs_info into the super block,
-	 * and fc->s_fs_info will be NULL.  However if there's an existing
-	 * super, we'll still have fc->s_fs_info populated.  If we error
-	 * completely out it'll be cleaned up when we drop the fs_context,
-	 * otherwise it's tied to the lifetime of the super_block.
-	 */
 	sb = sget_fc(fc, btrfs_fc_test_super, set_anon_super_fc);
 	if (IS_ERR(sb)) {
-		ret = PTR_ERR(sb);
-		goto error;
+		mutex_lock(&uuid_mutex);
+		btrfs_fs_devices_dec_holding(fs_devices);
+		/*
+		 * Since the fs_devices is not opened, it can be freed at any
+		 * time after unlocking uuid_mutex.  We need to avoid double
+		 * free through put_fs_context()->btrfs_free_fs_info().
+		 * So here we reset fs_info->fs_devices to NULL, and let the
+		 * regular fs_devices reclaim path to handle it.
+		 *
+		 * This applies to all later branches where no fs_devices is
+		 * opened.
+		 */
+		fs_info->fs_devices = NULL;
+		mutex_unlock(&uuid_mutex);
+		return PTR_ERR(sb);
 	}
 
 	set_device_specific_options(fs_info);
 
 	if (sb->s_root) {
-		btrfs_close_devices(fs_devices);
+		/*
+		 * Not the first mount of the fs thus got an existing super block.
+		 * Will reuse the returned super block, fs_info and fs_devices.
+		 *
+		 * fc->s_fs_info is not touched and will be later freed by
+		 * put_fs_context() through btrfs_free_fs_context().
+		 */
+		ASSERT(fc->s_fs_info == fs_info);
+
+		mutex_lock(&uuid_mutex);
+		btrfs_fs_devices_dec_holding(fs_devices);
+		fs_info->fs_devices = NULL;
+		mutex_unlock(&uuid_mutex);
 		/*
 		 * At this stage we may have RO flag mismatch between
 		 * fc->sb_flags and sb->s_flags.  Caller should detect such
@@ -1887,9 +1908,32 @@ static int btrfs_get_tree_super(struct fs_context *fc)
 		 * needed.
 		 */
 	} else {
+		struct block_device *bdev;
+
+		/*
+		 * The first mount of the fs thus a new superblock, fc->s_fs_info
+		 * must be NULL, and the ownership of our fs_info and fs_devices is
+		 * transferred to the super block.
+		 */
+		ASSERT(fc->s_fs_info == NULL);
+
+		mutex_lock(&uuid_mutex);
+		btrfs_fs_devices_dec_holding(fs_devices);
+		ret = btrfs_open_devices(fs_devices, mode, sb);
+		if (ret < 0)
+			fs_info->fs_devices = NULL;
+		mutex_unlock(&uuid_mutex);
+		if (ret < 0) {
+			deactivate_locked_super(sb);
+			return ret;
+		}
+		if (!(fc->sb_flags & SB_RDONLY) && fs_devices->rw_devices == 0) {
+			deactivate_locked_super(sb);
+			return -EACCES;
+		}
+		bdev = fs_devices->latest_dev->bdev;
 		snprintf(sb->s_id, sizeof(sb->s_id), "%pg", bdev);
 		shrinker_debugfs_rename(sb->s_shrink, "sb-btrfs:%s", sb->s_id);
-		btrfs_sb(sb)->bdev_holder = &btrfs_fs_type;
 		ret = btrfs_fill_super(sb, fs_devices);
 		if (ret) {
 			deactivate_locked_super(sb);
@@ -1901,10 +1945,6 @@ static int btrfs_get_tree_super(struct fs_context *fc)
 
 	fc->root = dget(sb->s_root);
 	return 0;
-
-error:
-	btrfs_close_devices(fs_devices);
-	return ret;
 }
 
 /*
@@ -1980,17 +2020,13 @@ error:
  * btrfs or not, setting the whole super block RO.  To make per-subvolume mounting
  * work with different options work we need to keep backward compatibility.
  */
-static int btrfs_reconfigure_for_mount(struct fs_context *fc, struct vfsmount *mnt)
+static int btrfs_reconfigure_for_mount(struct fs_context *fc)
 {
 	int ret = 0;
 
-	if (fc->sb_flags & SB_RDONLY)
-		return ret;
-
-	down_write(&mnt->mnt_sb->s_umount);
-	if (!(fc->sb_flags & SB_RDONLY) && (mnt->mnt_sb->s_flags & SB_RDONLY))
+	if (!(fc->sb_flags & SB_RDONLY) && (fc->root->d_sb->s_flags & SB_RDONLY))
 		ret = btrfs_reconfigure(fc);
-	up_write(&mnt->mnt_sb->s_umount);
+
 	return ret;
 }
 
@@ -2035,25 +2071,18 @@ static int btrfs_get_tree_subvol(struct fs_context *fc)
 	 */
 	dup_fc->s_fs_info = fs_info;
 
-	/*
-	 * We'll do the security settings in our btrfs_get_tree_super() mount
-	 * loop, they were duplicated into dup_fc, we can drop the originals
-	 * here.
-	 */
-	security_free_mnt_opts(&fc->security);
-	fc->security = NULL;
+	ret = btrfs_get_tree_super(dup_fc);
+	if (ret)
+		goto error;
 
-	mnt = fc_mount(dup_fc);
-	if (IS_ERR(mnt)) {
-		put_fs_context(dup_fc);
-		return PTR_ERR(mnt);
-	}
-	ret = btrfs_reconfigure_for_mount(dup_fc, mnt);
+	ret = btrfs_reconfigure_for_mount(dup_fc);
+	up_write(&dup_fc->root->d_sb->s_umount);
+	if (ret)
+		goto error;
+	mnt = vfs_create_mount(dup_fc);
 	put_fs_context(dup_fc);
-	if (ret) {
-		mntput(mnt);
-		return ret;
-	}
+	if (IS_ERR(mnt))
+		return PTR_ERR(mnt);
 
 	/*
 	 * This free's ->subvol_name, because if it isn't set we have to
@@ -2067,25 +2096,15 @@ static int btrfs_get_tree_subvol(struct fs_context *fc)
 
 	fc->root = dentry;
 	return 0;
+error:
+	put_fs_context(dup_fc);
+	return ret;
 }
 
 static int btrfs_get_tree(struct fs_context *fc)
 {
-	/*
-	 * Since we use mount_subtree to mount the default/specified subvol, we
-	 * have to do mounts in two steps.
-	 *
-	 * First pass through we call btrfs_get_tree_subvol(), this is just a
-	 * wrapper around fc_mount() to call back into here again, and this time
-	 * we'll call btrfs_get_tree_super().  This will do the open_ctree() and
-	 * everything to open the devices and file system.  Then we return back
-	 * with a fully constructed vfsmount in btrfs_get_tree_subvol(), and
-	 * from there we can do our mount_subvol() call, which will lookup
-	 * whichever subvol we're mounting and setup this fc with the
-	 * appropriate dentry for the subvol.
-	 */
-	if (fc->s_fs_info)
-		return btrfs_get_tree_super(fc);
+	ASSERT(fc->s_fs_info == NULL);
+
 	return btrfs_get_tree_subvol(fc);
 }
 
@@ -2217,7 +2236,7 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
 		 * Scanning outside of mount can return NULL which would turn
 		 * into 0 error code.
 		 */
-		device = btrfs_scan_one_device(vol->name, BLK_OPEN_READ, false);
+		device = btrfs_scan_one_device(vol->name, false);
 		ret = PTR_ERR_OR_ZERO(device);
 		mutex_unlock(&uuid_mutex);
 		break;
@@ -2235,7 +2254,7 @@ static long btrfs_control_ioctl(struct file *file, unsigned int cmd,
 		 * Scanning outside of mount can return NULL which would turn
 		 * into 0 error code.
 		 */
-		device = btrfs_scan_one_device(vol->name, BLK_OPEN_READ, false);
+		device = btrfs_scan_one_device(vol->name, false);
 		if (IS_ERR_OR_NULL(device)) {
 			mutex_unlock(&uuid_mutex);
 			if (IS_ERR(device))