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Re: [Gnu-arch-users] Re: give us a hand with arch
From: |
Robin Farine |
Subject: |
Re: [Gnu-arch-users] Re: give us a hand with arch |
Date: |
29 Sep 2003 23:40:58 +0200 |
User-agent: |
Gnus/5.09 (Gnus v5.9.0) Emacs/21.2 |
>>>>> "Florian" == Florian Weimer <address@hidden> writes:
[...]
Florian> The last block of a file contains data after the actual
Florian> end of the file (back then, ReiserFS didn't optimize
Florian> these cases). This data is also present in the page
Florian> cache. You won't see it normally, because you cannot
Florian> read() beyond the end of the file, but mmap() can only
Florian> map complete pages, so you suddenly see the data (and it
Florian> was random data from kernel or user space, typically not
Florian> something which ever was on disk).
Ah yes, this is somewhat similar to the case of malloc'ed memory, it
would be an application bug to read/write past the end of the file,
but without disastrous effect on the kernel.
So I hope I understand your point better now, you cited an example
where Hans Reiser preferred optimization to correctness, source of
your prejudice.
I am not absolutely sure about this but I think that a POSIX kernel
should raise a SIGBUS when an application attempts an access between
the end of the file and the last page boundary. This would justify the
optimization.
--
rnf
- Re: [Gnu-arch-users] Re: give us a hand with arch, (continued)
- Re: [Gnu-arch-users] Re: give us a hand with arch, Samium Gromoff, 2003/09/29
- Re: [Gnu-arch-users] Re: give us a hand with arch, Miles Bader, 2003/09/29
- Re: [Gnu-arch-users] Re: give us a hand with arch, Tupshin Harper, 2003/09/29
- Re: [Gnu-arch-users] Re: give us a hand with arch, Robin Farine, 2003/09/29
- Re: [Gnu-arch-users] Re: give us a hand with arch, Florian Weimer, 2003/09/29
- Re: [Gnu-arch-users] Re: give us a hand with arch, Robin Farine, 2003/09/29
- Re: [Gnu-arch-users] Re: give us a hand with arch, Florian Weimer, 2003/09/29
- Re: [Gnu-arch-users] Re: give us a hand with arch,
Robin Farine <=
- Re: [Gnu-arch-users] Re: give us a hand with arch, Miles Bader, 2003/09/29
- Re: [Gnu-arch-users] Re: give us a hand with arch, Robin Farine, 2003/09/29
- Re: [Gnu-arch-users] Re: give us a hand with arch, Andrew Suffield, 2003/09/29
- [OT] psychofs (was: [Gnu-arch-users] Re: give us a hand with arch), Robin Farine, 2003/09/29
- Re: [Gnu-arch-users] Re: give us a hand with arch, David Brown, 2003/09/29
- Re: [Gnu-arch-users] Re: give us a hand with arch, Andrew Suffield, 2003/09/29
- Re: [Gnu-arch-users] Re: give us a hand with arch, Stephen J. Turnbull, 2003/09/29
- Re: [Gnu-arch-users] Re: give us a hand with arch, Charles Duffy, 2003/09/29
- Re: [Gnu-arch-users] Re: give us a hand with arch, Florian Weimer, 2003/09/30
- Re: [Gnu-arch-users] Re: give us a hand with arch, Bruce Stephens, 2003/09/29