From: Miklos Szeredi <miklos@szeredi.hu>
To: Florian Weimer <fweimer@redhat.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>,
Christian Brauner <brauner@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-api@vger.kernel.org, linux-man@vger.kernel.org,
linux-security-module@vger.kernel.org,
Karel Zak <kzak@redhat.com>, Ian Kent <raven@themaw.net>,
David Howells <dhowells@redhat.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Christian Brauner <christian@brauner.io>,
Amir Goldstein <amir73il@gmail.com>
Subject: Re: [RFC PATCH 2/3] add statmnt(2) syscall
Date: Tue, 26 Sep 2023 16:33:50 +0200 [thread overview]
Message-ID: <CAJfpegvKECAFNhWYKfGbSWVX8pycQxsHnCr6KSqrQrR+u77yAg@mail.gmail.com> (raw)
In-Reply-To: <87wmwdnhj1.fsf@oldenburg.str.redhat.com>
On Tue, 26 Sept 2023 at 16:19, Florian Weimer <fweimer@redhat.com> wrote:
> getdents gets away with this buffer size because applications can copy
> out all the data from struct dirent if they need long-term storage.
> They have to do that because the usual readdir interface overwrites the
> buffer, potentially at the next readdir call. This means the buffer
> size does not introduce an amount of memory fragmention that is
> dependent on the directory size.
>
> With an opaque, pointer-carrying struct, copying out the data is not
> possible in a generic fashion. Only the parts that the application
> knows about can be copied out. So I think it's desirable to have a
> fairly exact allocation.
Okay, so let's add a 'size' field to the struct, which is set to the
size used (as opposed to the size of the buffer). That should solve
copying without wasting a single byte of memory.
Otherwise the format is fully copyable, since the strings are denoted
with an offset, which doesn't change after the buffer is copied.
Thanks,
Miklos
next prev parent reply other threads:[~2023-09-26 14:34 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-13 15:22 [RFC PATCH 0/3] quering mount attributes Miklos Szeredi
2023-09-13 15:22 ` [RFC PATCH 1/3] add unique mount ID Miklos Szeredi
2023-09-14 9:03 ` Christian Brauner
2023-09-14 9:30 ` Miklos Szeredi
2023-09-14 9:36 ` Christian Brauner
2023-09-14 9:43 ` Miklos Szeredi
2023-09-14 10:06 ` Christian Brauner
2023-09-15 1:31 ` Ian Kent
2023-09-13 15:22 ` [RFC PATCH 2/3] add statmnt(2) syscall Miklos Szeredi
2023-09-14 6:11 ` Amir Goldstein
2023-09-15 1:05 ` Ian Kent
2023-09-14 9:27 ` Christian Brauner
2023-09-14 10:13 ` Miklos Szeredi
2023-09-14 15:26 ` Christian Brauner
2023-09-15 8:56 ` Miklos Szeredi
2023-09-18 13:51 ` Christian Brauner
2023-09-18 14:14 ` Miklos Szeredi
2023-09-18 14:24 ` Christian Brauner
2023-09-18 14:32 ` Miklos Szeredi
2023-09-18 14:40 ` Christian Brauner
2023-09-18 14:51 ` Miklos Szeredi
2023-09-18 15:22 ` Christian Brauner
2023-09-18 15:39 ` Miklos Szeredi
2023-09-19 0:37 ` Matthew House
2023-09-19 8:02 ` Miklos Szeredi
2023-09-19 9:07 ` Christian Brauner
2023-09-19 10:51 ` Miklos Szeredi
2023-09-19 12:41 ` Christian Brauner
2023-09-19 12:59 ` Miklos Szeredi
2023-09-19 13:18 ` Christian Brauner
2023-09-19 21:28 ` Matthew House
2023-09-20 9:42 ` Miklos Szeredi
2023-09-20 13:26 ` Matthew House
2023-09-21 7:34 ` Miklos Szeredi
2023-09-26 13:48 ` Florian Weimer
2023-09-26 14:06 ` Miklos Szeredi
2023-09-26 14:19 ` Florian Weimer
2023-09-26 14:33 ` Miklos Szeredi [this message]
2023-09-26 14:39 ` Florian Weimer
2023-09-26 14:36 ` Christian Brauner
2023-09-26 14:13 ` Christian Brauner
2023-09-18 20:58 ` Andreas Dilger
2023-09-19 12:50 ` Christian Brauner
2023-09-20 0:33 ` Dave Chinner
2023-09-18 14:29 ` Jeff Layton
2023-09-18 14:35 ` Christian Brauner
2023-09-20 9:43 ` David Laight
2023-09-14 20:39 ` Paul Moore
2023-09-15 9:10 ` Miklos Szeredi
2023-09-17 18:18 ` Sargun Dhillon
2023-09-17 23:36 ` Ian Kent
2023-09-18 13:05 ` Christian Brauner
2023-09-25 12:57 ` Arnd Bergmann
2023-09-25 13:04 ` Christian Brauner
2023-09-25 13:13 ` Miklos Szeredi
2023-09-25 13:19 ` Christian Brauner
2023-09-25 13:20 ` Miklos Szeredi
2023-09-25 15:46 ` Arnd Bergmann
2023-09-26 10:05 ` Christian Brauner
2023-09-27 8:46 ` Miklos Szeredi
2023-09-13 15:22 ` [RFC PATCH 3/3] add listmnt(2) syscall Miklos Szeredi
2023-09-14 6:00 ` Amir Goldstein
2023-09-14 8:50 ` Miklos Szeredi
2023-09-14 10:01 ` Christian Brauner
2023-09-15 1:00 ` Ian Kent
2023-09-17 0:54 ` Matthew House
2023-09-17 14:32 ` Miklos Szeredi
2023-09-18 13:15 ` Christian Brauner
2023-09-19 16:47 ` Paul Moore
2023-09-28 10:07 ` Miklos Szeredi
2023-10-04 19:22 ` Paul Moore
2023-09-14 6:47 ` [RFC PATCH 0/3] quering mount attributes Amir Goldstein
2023-09-15 1:20 ` Ian Kent
2023-09-15 3:06 ` Amir Goldstein
2023-09-16 2:04 ` Ian Kent
2023-09-16 2:19 ` Ian Kent
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