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From: Eric Biggers <ebiggers@kernel.org>
To: Daniel Rosenberg <drosen@google.com>
Cc: kernel-team@android.com, Theodore Ts'o <tytso@mit.edu>,
	Jonathan Corbet <corbet@lwn.net>,
	Richard Weinberger <richard@nod.at>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net,
	linux-fscrypt@vger.kernel.org, linux-mtd@lists.infradead.org,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel@vger.kernel.org, Jaegeuk Kim <jaegeuk@kernel.org>,
	linux-ext4@vger.kernel.org,
	Gabriel Krisman Bertazi <krisman@collabora.com>
Subject: Re: [f2fs-dev] [PATCH v7 1/8] unicode: Add utf8_casefold_iter
Date: Tue, 11 Feb 2020 19:38:00 -0800
Message-ID: <20200212033800.GC870@sol.localdomain> (raw)
In-Reply-To: <20200208013552.241832-2-drosen@google.com>

On Fri, Feb 07, 2020 at 05:35:45PM -0800, Daniel Rosenberg wrote:
> This function will allow other uses of unicode to act upon a casefolded
> string without needing to allocate their own copy of one.
> 
> The actor function can return an nonzero value to exit early.
> 
> Signed-off-by: Daniel Rosenberg <drosen@google.com>
> ---
>  fs/unicode/utf8-core.c  | 25 ++++++++++++++++++++++++-
>  include/linux/unicode.h | 10 ++++++++++
>  2 files changed, 34 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/unicode/utf8-core.c b/fs/unicode/utf8-core.c
> index 2a878b739115d..db050bf59a32b 100644
> --- a/fs/unicode/utf8-core.c
> +++ b/fs/unicode/utf8-core.c
> @@ -122,9 +122,32 @@ int utf8_casefold(const struct unicode_map *um, const struct qstr *str,
>  	}
>  	return -EINVAL;
>  }
> -
>  EXPORT_SYMBOL(utf8_casefold);
>  
> +int utf8_casefold_iter(const struct unicode_map *um, const struct qstr *str,
> +		    struct utf8_itr_context *ctx)
> +{
> +	const struct utf8data *data = utf8nfdicf(um->version);
> +	struct utf8cursor cur;
> +	int c;
> +	int res = 0;
> +	int pos = 0;
> +
> +	if (utf8ncursor(&cur, data, str->name, str->len) < 0)
> +		return -EINVAL;
> +
> +	while ((c = utf8byte(&cur))) {
> +		if (c < 0)
> +			return c;
> +		res = ctx->actor(ctx, c, pos);
> +		pos++;
> +		if (res)
> +			return res;
> +	}
> +	return res;
> +}
> +EXPORT_SYMBOL(utf8_casefold_iter);

Indirect function calls are expensive these days for various reasons, including
Spectre mitigations and CFI.  Are you sure it's okay from a performance
perspective to make an indirect call for every byte of the pathname?

> +typedef int (*utf8_itr_actor_t)(struct utf8_itr_context *, int byte, int pos);

The byte argument probably should be 'u8', to avoid confusion about whether it's
a byte or a Unicode codepoint.

- Eric


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Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-08  1:35 [f2fs-dev] [PATCH v7 0/8] Support fof Casefolding and Encryption Daniel Rosenberg via Linux-f2fs-devel
2020-02-08  1:35 ` [f2fs-dev] [PATCH v7 1/8] unicode: Add utf8_casefold_iter Daniel Rosenberg via Linux-f2fs-devel
2020-02-12  3:38   ` Eric Biggers [this message]
2020-02-14 21:47     ` Daniel Rosenberg via Linux-f2fs-devel
2020-02-17 19:02       ` Gabriel Krisman Bertazi
2020-02-08  1:35 ` [f2fs-dev] [PATCH v7 2/8] fs: Add standard casefolding support Daniel Rosenberg via Linux-f2fs-devel
2020-02-08  2:12   ` Al Viro
2020-02-10 23:11     ` Daniel Rosenberg via Linux-f2fs-devel
2020-02-10 23:42       ` Al Viro
2020-02-12  6:34         ` Eric Biggers
2020-02-12  6:57           ` Eric Biggers
2020-02-20  2:27             ` Daniel Rosenberg via Linux-f2fs-devel
2020-02-12  3:55   ` Eric Biggers
2020-02-08  1:35 ` [f2fs-dev] [PATCH v7 3/8] f2fs: Use generic " Daniel Rosenberg via Linux-f2fs-devel
2020-02-12  4:05   ` Eric Biggers
2020-02-08  1:35 ` [f2fs-dev] [PATCH v7 4/8] ext4: " Daniel Rosenberg via Linux-f2fs-devel
2020-02-08  1:35 ` [f2fs-dev] [PATCH v7 5/8] fscrypt: Have filesystems handle their d_ops Daniel Rosenberg via Linux-f2fs-devel
2020-02-12  4:33   ` Eric Biggers
2020-02-08  1:35 ` [f2fs-dev] [PATCH v7 6/8] f2fs: Handle casefolding with Encryption Daniel Rosenberg via Linux-f2fs-devel
2020-02-12  5:10   ` Eric Biggers
2020-02-12  5:55     ` Al Viro
2020-02-12  6:06       ` Eric Biggers
2020-02-12  5:47   ` Eric Biggers
2020-02-08  1:35 ` [f2fs-dev] [PATCH v7 7/8] ext4: Hande casefolding with encryption Daniel Rosenberg via Linux-f2fs-devel
2020-02-12  5:59   ` Eric Biggers
2020-02-08  1:35 ` [f2fs-dev] [PATCH v7 8/8] ext4: Optimize match for casefolded encrypted dirs Daniel Rosenberg via Linux-f2fs-devel
2020-02-12  6:12 ` [f2fs-dev] [PATCH v7 0/8] Support fof Casefolding and Encryption Eric Biggers
2020-02-13  0:01   ` Daniel Rosenberg via Linux-f2fs-devel

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