Date: Sat, 21 Aug 1999 19:08:23 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: John-Mark Gurney <gurney_j@efn.org> Cc: Wes Peters <wes@softweyr.com>, hackers@FreeBSD.ORG Subject: Re: mmap mapped segment length Message-ID: <199908220208.TAA75507@apollo.backplane.com> References: <199908210906.CAA17706@salsa.gv.tsc.tdk.com> <37BF4C99.67814B7@softweyr.com> <19990821184246.00134@hydrogen.fircrest.net>
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:Wes Peters scribbled this message on Aug 21:
:> Now I've got to go figure out what *I've* screwed up. I fstat the file before
:> mapping it and pass S.st_size as the map length. Is there any reason why
:> mmap would return non-NULL but map less than the requested size?
:
:no, there is NO reason why it wouldn't map the entire 50meg file...
:I have used ffsrecov w/ a 1.8gig file where I fstat it and map the entire
:file w/o a problem...
:
:also, mmap doesn't return NULL, it returns MAP_FAILED...
:
:the code for ffsrecov might give you some hints to make sure you aren't
:doing anything wrong...
:
:--
: John-Mark Gurney Voice: +1 541 684 8449
: Cu Networking P.O. Box 5693, 97405
I would compile the program -Wall -Wstrict-prototypes. If you get
warnings maybe the problem is that you've missed some important #include
files. Many system calls take off_t arguments, including mmap, and
without the correct prototype the compiler will not generate a good
argument stack.
mmap'ing a 50MB file definitely works. I run several databases which use
mmap() that are several hundred megabytes in size.
-Matt
Matthew Dillon
<dillon@backplane.com>
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