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Date:	Fri, 02 Dec 2011 13:20:05 +0100
From:	Sébastien Paumier 
	<sebastien.paumier@...v-mlv.fr>
To:	linux-kernel@...r.kernel.org
Subject: mmap

Hi,
I have a question about mmap's behavior when one tries to map a file asking for 
a length greater than the actual file size. When I run the attached code on a 
100 bytes file, I have the following output:

(... file content followed by zeros...)
n=4096
write: Bad address

So, it seems that the actual memory area provided by mmap is one page large and 
not the requested length of filesize+10000. I guess that 'write' writes less 
than requested because it was interrupted by the SIGBUS signal. And my question is:

shouldn't mmap either complain about the requested length or provide an 
accessible area of the requested length, instead of silently failing ?

Best regards,
Sébastien Paumier

View attachment "mmap.c" of type "text/x-csrc" (885 bytes)