From: Andreas Dilger <adilger-m1MBpc4rdrD3fQ9qLvQP4Q@public.gmane.org>
Subject: Re: [RFC][PATCH 00/12] Enhanced file stat system call
Date: Wed, 25 Nov 2015 12:30:33 -0700
Message-ID: <E4DB425B-FE04-4A6A-806E-2BAFD0CB498E@dilger.ca>
References: <1502878.QisWlqATFu@merkaba> <20151120145422.18930.72662.stgit@warthog.procyon.org.uk> <4495.1448036915@warthog.procyon.org.uk> <20151125175153.GA30335@fieldses.org>
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Cc: David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Martin Steigerwald <martin-3kZCPVa5dk2azgQtNeiOUg@public.gmane.org>, arnd-r2nGTMty4D4@public.gmane.org,
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To: "J. Bruce Fields" <bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>
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On Nov 25, 2015, at 10:51 AM, J. Bruce Fields <bfields-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org> =
wrote:
>=20
> On Fri, Nov 20, 2015 at 04:28:35PM +0000, David Howells wrote:
>> Martin Steigerwald <martin-3kZCPVa5dk2azgQtNeiOUg@public.gmane.org> wrote:
>>=20
>>> Any plans to add limitations of filesystem to the call like maximum =
file
>>> size?  I know its mostly relevant for just for FAT32, but on any =
account
>>> rather than trying to write 4 GiB and then file, it would be good to =
at some
>>> time get a dialog at the beginning of the copy.
>>=20
>> Adding filesystem limits can be done.  I got a shopping list of =
things people
>> wanted a while back and I've worked off of that list.  I can add =
other things
>> - that's on of the reasons I left room for expansion.
>=20
> I ran across systemd/src/basic/path-util.c:fd_is_mount_point() the =
other
> day, and the contortions it goes through made me wonder if we should
> also add mnt_id and/or an is_mountpoint boolean--it's annoying to have
> to do name_to_handle_at() (not supported on all filesystems) just to =
get
> mnt_id.
>=20
> (Looking at it now I see it falls back on reading mount id from
> /proc/self/fdinfo/<fd>.  Maybe that's good enough.  May depend on
> whether there's a potential user that doesn't want to assume access to
> /proc?)

IMHO, it should be possible to get information about a file or directory
from the file itself (i.e. statx() or fsinfo() on the path/fd), rather =
than
having to grub around in a /proc file that the application magically has =
to
know about, and parse text files there for every file being handled.

Cheers, Andreas






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