Re: [PATCH 06/16] btrfs: extract mount options and features init code into its own init helper

[Qu Wenruo <wqu@suse.com>]

On 2022/9/22 08:06, Qu Wenruo wrote:
> This patch will extract the mount option parsing and features checking
> code into a new helper, open_ctree_features_init().
> 
> This extraction also did the following non-functional change:
> 
> - Add btrfs_fs_info::__options member
>    Currently the open_ctree_* helpers can only accept a single @fs_info
>    parameter, to parse the mount options we have to use a temporary
>    pointer for this purpose.
> 
>    Thankfully we don't need to do anything like freeing it.
> 
> - Move ssd optimization check into open_ctree_features_init()
> 
> - Move check_int related code into open_ctree_features_init()
>    The mount time integrity check doesn't rely on any tree blocks, thus
>    is safe to be called at feature init time.
> 
> - Separate @features variable into @incompat and @compat_ro
>    So there will be no confusion, and compiler should be clever enough
>    to optimize them out anyway.
> 
> - Properly return error for subpage initialization failure
>    Preivously we just goto fail_alloc label, relying on the default
>    -EINVAL error.
>    Now we can return a proper -ENOMEM error instead.
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> ---
>   fs/btrfs/ctree.h   |   6 ++
>   fs/btrfs/disk-io.c | 176 +++++++++++++++++++++++----------------------
>   2 files changed, 96 insertions(+), 86 deletions(-)
> 
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index 8b7b7a212da0..88dc3b2896d7 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -1106,6 +1106,12 @@ struct btrfs_fs_info {
>   	struct lockdep_map btrfs_trans_pending_ordered_map;
>   	struct lockdep_map btrfs_ordered_extent_map;
>   
> +	/*
> +	 * Temporary pointer to the mount option string.
> +	 * This is to workaround the fact that all open_ctree() init
> +	 * functions can only accept a single @fs_info pointer.
> +	 */
> +	char *__options;
>   #ifdef CONFIG_BTRFS_FS_REF_VERIFY
>   	spinlock_t ref_verify_lock;
>   	struct rb_root block_tree;
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index f4c04cb1c0d6..ec9038eeaa0f 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -3446,118 +3446,78 @@ static int open_ctree_super_init(struct btrfs_fs_info *fs_info)
>   	return ret;
>   }
>   
> -struct init_sequence {
> -	int (*init_func)(struct btrfs_fs_info *fs_info);
> -	void (*exit_func)(struct btrfs_fs_info *fs_info);
> -};
> -
> -static const struct init_sequence open_ctree_seq[] = {
> -	{
> -		.init_func = open_ctree_btree_inode_init,
> -		.exit_func = open_ctree_btree_inode_exit,
> -	}, {
> -		.init_func = open_ctree_super_init,
> -		.exit_func = NULL,
> -	}
> -};
> -
> -
> -int __cold open_ctree(struct super_block *sb, char *options)
> +static int open_ctree_features_init(struct btrfs_fs_info *fs_info)
>   {
> -	u64 generation;
> -	u64 features;
> -	bool open_ctree_res[ARRAY_SIZE(open_ctree_seq)] = {0};
> -	struct btrfs_fs_info *fs_info = btrfs_sb(sb);
> -	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
>   	int ret;
> -	int err = -EINVAL;
> -	int level;
> -	int i;
> -
> -	fs_info->sb = sb;
> -
> -	/* Caller should have already initialized fs_info->fs_devices. */
> -	ASSERT(fs_info->fs_devices);
> -
> -	for (i = 0; i < ARRAY_SIZE(open_ctree_seq); i++) {
> -		ret = open_ctree_seq[i].init_func(fs_info);
> -		if (ret < 0)
> -			goto fail;
> -		open_ctree_res[i] = true;
> -	}
> +	u64 incompat;
> +	u64 compat_ro;
>   
> -	ret = btrfs_parse_options(fs_info, options, fs_info->sb->s_flags);
> -	if (ret) {
> -		err = ret;
> -		goto fail_alloc;
> -	}
> +	ret = btrfs_parse_options(fs_info, fs_info->__options,
> +				  fs_info->sb->s_flags);
> +	if (ret)
> +		return ret;
>   
> -	features = btrfs_super_incompat_flags(fs_info->super_copy) &
> -		~BTRFS_FEATURE_INCOMPAT_SUPP;
> -	if (features) {
> +	incompat = btrfs_super_incompat_flags(fs_info->super_copy);
> +	if (incompat & ~BTRFS_FEATURE_INCOMPAT_SUPP) {
>   		btrfs_err(fs_info,
>   		    "cannot mount because of unsupported optional features (0x%llx)",
> -		    features);
> -		err = -EINVAL;
> -		goto fail_alloc;
> +		    incompat & ~BTRFS_FEATURE_INCOMPAT_SUPP);
> +		return -EINVAL;
>   	}
>   
> -	features = btrfs_super_incompat_flags(fs_info->super_copy);
> -	features |= BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF;
> +	incompat |= BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF;
>   	if (fs_info->compress_type == BTRFS_COMPRESS_LZO)
> -		features |= BTRFS_FEATURE_INCOMPAT_COMPRESS_LZO;
> +		incompat |= BTRFS_FEATURE_INCOMPAT_COMPRESS_LZO;
>   	else if (fs_info->compress_type == BTRFS_COMPRESS_ZSTD)
> -		features |= BTRFS_FEATURE_INCOMPAT_COMPRESS_ZSTD;
> +		incompat |= BTRFS_FEATURE_INCOMPAT_COMPRESS_ZSTD;
>   
>   	/*
>   	 * Flag our filesystem as having big metadata blocks if they are bigger
>   	 * than the page size.
>   	 */
>   	if (btrfs_super_nodesize(fs_info->super_copy) > PAGE_SIZE)
> -		features |= BTRFS_FEATURE_INCOMPAT_BIG_METADATA;
> +		incompat |= BTRFS_FEATURE_INCOMPAT_BIG_METADATA;
>   
>   	/*
>   	 * mixed block groups end up with duplicate but slightly offset
>   	 * extent buffers for the same range.  It leads to corruptions
>   	 */
> -	if ((features & BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS) &&
> +	if ((incompat & BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS) &&
>   	    (fs_info->sectorsize != fs_info->nodesize)) {
>   		btrfs_err(fs_info,
>   "unequal nodesize/sectorsize (%u != %u) are not allowed for mixed block groups",
>   			fs_info->nodesize, fs_info->sectorsize);
> -		goto fail_alloc;
> +		return -EINVAL;
>   	}
>   
>   	/*
>   	 * Needn't use the lock because there is no other task which will
>   	 * update the flag.
>   	 */
> -	btrfs_set_super_incompat_flags(fs_info->super_copy, features);
> +	btrfs_set_super_incompat_flags(fs_info->super_copy, incompat);
>   
> -	features = btrfs_super_compat_ro_flags(fs_info->super_copy) &
> -		~BTRFS_FEATURE_COMPAT_RO_SUPP;
> -	if (!sb_rdonly(fs_info->sb) && features) {
> +	compat_ro = btrfs_super_compat_ro_flags(fs_info->super_copy);
> +	if (!sb_rdonly(fs_info->sb) &&
> +	    (compat_ro & ~BTRFS_FEATURE_COMPAT_RO_SUPP)) {
>   		btrfs_err(fs_info,
>   	"cannot mount read-write because of unsupported optional features (0x%llx)",
> -		       features);
> -		err = -EINVAL;
> -		goto fail_alloc;
> +		       compat_ro & ~BTRFS_FEATURE_COMPAT_RO_SUPP);
> +		return -EINVAL;
>   	}
>   	/*
>   	 * We have unsupported RO compat features, although RO mounted, we
>   	 * should not cause any metadata write, including log replay.
>   	 * Or we could screw up whatever the new feature requires.
>   	 */
> -	if (unlikely(features && btrfs_super_log_root(fs_info->super_copy) &&
> +	if (unlikely((compat_ro & ~BTRFS_FEATURE_COMPAT_RO_SUPP)
> +		     && btrfs_super_log_root(fs_info->super_copy) &&
>   		     !btrfs_test_opt(fs_info, NOLOGREPLAY))) {
>   		btrfs_err(fs_info,
>   "cannot replay dirty log with unsupported compat_ro features (0x%llx), try rescue=nologreplay",
> -			  features);
> -		err = -EINVAL;
> -		goto fail_alloc;
> +			  compat_ro & ~BTRFS_FEATURE_COMPAT_RO_SUPP);
> +		return -EINVAL;
>   	}
>   
> -
>   	if (fs_info->sectorsize < PAGE_SIZE) {
>   		struct btrfs_subpage_info *subpage_info;
>   
> @@ -3577,11 +3537,73 @@ int __cold open_ctree(struct super_block *sb, char *options)
>   			   fs_info->sectorsize, PAGE_SIZE);
>   		subpage_info = kzalloc(sizeof(*subpage_info), GFP_KERNEL);
>   		if (!subpage_info)
> -			goto fail_alloc;
> +			return -ENOMEM;
>   		btrfs_init_subpage_info(subpage_info, fs_info->sectorsize);
>   		fs_info->subpage_info = subpage_info;
>   	}
>   
> +	if (!btrfs_test_opt(fs_info, NOSSD) &&
> +	    !fs_info->fs_devices->rotating)
> +		btrfs_set_and_info(fs_info, SSD, "enabling ssd optimizations");
> +
> +#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
> +	if (btrfs_test_opt(fs_info, CHECK_INTEGRITY)) {

Btrfs/220 would crash at this stage.

> +		ret = btrfsic_mount(fs_info, fs_info->fs_devices,
> +				    btrfs_test_opt(fs_info,
> +					CHECK_INTEGRITY_DATA) ? 1 : 0,
> +				    fs_info->check_integrity_print_mask);

Surprisingly btrfsic_mount() needs to btrfs logical address mapping at 
least, thus it can only be called after chunk tree being initialized.

Would move this into open_ctree_chunk_tree_init() instead.

Thanks,
Qu

> +		if (ret)
> +			btrfs_warn(fs_info,
> +				"failed to initialize integrity check module: %d",
> +				ret);
> +	}
> +#endif
> +
> +	return 0;
> +}
> +
> +struct init_sequence {
> +	int (*init_func)(struct btrfs_fs_info *fs_info);
> +	void (*exit_func)(struct btrfs_fs_info *fs_info);
> +};
> +
> +static const struct init_sequence open_ctree_seq[] = {
> +	{
> +		.init_func = open_ctree_btree_inode_init,
> +		.exit_func = open_ctree_btree_inode_exit,
> +	}, {
> +		.init_func = open_ctree_super_init,
> +		.exit_func = NULL,
> +	}, {
> +		.init_func = open_ctree_features_init,
> +		.exit_func = NULL,
> +	}
> +};
> +
> +int __cold open_ctree(struct super_block *sb, char *options)
> +{
> +	u64 generation;
> +	struct btrfs_fs_info *fs_info = btrfs_sb(sb);
> +	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
> +	bool open_ctree_res[ARRAY_SIZE(open_ctree_seq)] = {0};
> +	int ret;
> +	int err = -EINVAL;
> +	int level;
> +	int i;
> +
> +	fs_info->sb = sb;
> +	fs_info->__options = options;
> +
> +	/* Caller should have already initialized fs_info->fs_devices. */
> +	ASSERT(fs_info->fs_devices);
> +
> +	for (i = 0; i < ARRAY_SIZE(open_ctree_seq); i++) {
> +		ret = open_ctree_seq[i].init_func(fs_info);
> +		if (ret < 0)
> +			goto fail;
> +		open_ctree_res[i] = true;
> +	}
> +
>   	ret = btrfs_init_workqueues(fs_info);
>   	if (ret) {
>   		err = ret;
> @@ -3736,29 +3758,12 @@ int __cold open_ctree(struct super_block *sb, char *options)
>   	if (IS_ERR(fs_info->transaction_kthread))
>   		goto fail_cleaner;
>   
> -	if (!btrfs_test_opt(fs_info, NOSSD) &&
> -	    !fs_info->fs_devices->rotating) {
> -		btrfs_set_and_info(fs_info, SSD, "enabling ssd optimizations");
> -	}
> -
>   	/*
>   	 * Mount does not set all options immediately, we can do it now and do
>   	 * not have to wait for transaction commit
>   	 */
>   	btrfs_apply_pending_changes(fs_info);
>   
> -#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
> -	if (btrfs_test_opt(fs_info, CHECK_INTEGRITY)) {
> -		ret = btrfsic_mount(fs_info, fs_devices,
> -				    btrfs_test_opt(fs_info,
> -					CHECK_INTEGRITY_DATA) ? 1 : 0,
> -				    fs_info->check_integrity_print_mask);
> -		if (ret)
> -			btrfs_warn(fs_info,
> -				"failed to initialize integrity check module: %d",
> -				ret);
> -	}
> -#endif
>   	ret = btrfs_read_qgroup_config(fs_info);
>   	if (ret)
>   		goto fail_trans_kthread;
> @@ -3851,7 +3856,6 @@ int __cold open_ctree(struct super_block *sb, char *options)
>   fail_sb_buffer:
>   	btrfs_stop_all_workers(fs_info);
>   	btrfs_free_block_groups(fs_info);
> -fail_alloc:
>   	btrfs_mapping_tree_free(&fs_info->mapping_tree);
>   fail:
>   	for (i = ARRAY_SIZE(open_ctree_seq) - 1; i >= 0; i--) {