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From: Gabriel Krisman Bertazi <krisman@collabora.com>
To: Daniel Rosenberg <drosen@google.com>
Cc: 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,
	Eric Biggers <ebiggers@kernel.org>,
	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, kernel-team@android.com
Subject: Re: [f2fs-dev] [PATCH v7 1/8] unicode: Add utf8_casefold_iter
Date: Mon, 17 Feb 2020 14:02:10 -0500
Message-ID: <8536b95971.fsf@collabora.com> (raw)
In-Reply-To: <CA+PiJmT_8EzyFO283_E62+UC6vtCGOJXKHAFqnH3QM9LA+PHAw@mail.gmail.com> (Daniel Rosenberg's message of "Fri, 14 Feb 2020 13:47:37 -0800")

Daniel Rosenberg <drosen@google.com> writes:

> On Tue, Feb 11, 2020 at 7:38 PM Eric Biggers <ebiggers@kernel.org> wrote:
>>
>> 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.
>>

just for the record, we use int utf8byte because it can fail
error codes, but that is not the case here.  It should be u8.

>
> Gabriel, what do you think here? I could change it to either exposing
> the things necessary to do the hashing in libfs, or instead of the
> general purpose iterator, just have a hash function inside of unicode
> that will compute the hash given a seed value.

Sorry for the delay, I'm away on a long vacation and intentionally
staying away from my laptop :)

Eric has a very good point, if not prohibitively, it is unnecessarily
expensive for a hot path.  Why not expose utf8ncursor and utf8byte to
libfs and implement the hash in libfs?

-- 
Gabriel Krisman Bertazi


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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
2020-02-14 21:47     ` Daniel Rosenberg via Linux-f2fs-devel
2020-02-17 19:02       ` Gabriel Krisman Bertazi [this message]
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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