[9fans] Two ramfs? - Plan9

This is a discussion on [9fans] Two ramfs? - Plan9 ; Hello, I'd like to write a small simple fileserver, and I've been advised everywhere to look at ramfs.c. I saw the src/cmd/ramfs.c, and I think I should be able to write mine simpler... For example, I'd like to take advantage ...

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Thread: [9fans] Two ramfs?

  1. [9fans] Two ramfs?

    Hello,

    I'd like to write a small simple fileserver, and I've been advised
    everywhere to look at ramfs.c.

    I saw the src/cmd/ramfs.c, and I think I should be able to write mine
    simpler... For example, I'd like to take advantage of the File/Tree
    interface (createfile(), ...), having all the files of the fs in
    memory.

    I found also src/lib9p/ramfs.c, which looks pretty much as what I
    want, but this doesn't tollerate remounting well at all (I guess).

    I tried it with some modifications (to get it compiled) in plan9port
    over linux (./ramfs -D -s test) and two "9p ls test" in a row makes
    the server die.

    Where can I see an example of a working fileserver which uses File,
    Tree, and the related functions?

    Thank you,
    LluĂ*s.

  2. Re: [9fans] Two ramfs?

    > I saw the src/cmd/ramfs.c, and I think I should be able to write mine
    > simpler... For example, I'd like to take advantage of the File/Tree
    > interface (createfile(), ...), having all the files of the fs in
    > memory.
    >
    > I found also src/lib9p/ramfs.c, which looks pretty much as what I
    > want, but this doesn't tollerate remounting well at all (I guess).
    >
    > I tried it with some modifications (to get it compiled) in plan9port
    > over linux (./ramfs -D -s test) and two "9p ls test" in a row makes
    > the server die.
    >
    > Where can I see an example of a working fileserver which uses File,
    > Tree, and the related functions?


    It's been a long time since I looked at that code, but it appears
    that the problem is that Tattach doesn't increment the reference
    count on its directory. Reattaching isn't very common in Plan 9
    (but is on p9p) so it's easy to believe this bug went unnoticed.

    Here is the fix, now in p9p:

    diff -r bcad073690c5 src/lib9p/srv.c
    --- a/src/lib9p/srv.c Fri Feb 01 07:54:19 2008 -0500
    +++ b/src/lib9p/srv.c Mon Feb 04 15:32:28 2008 -0500
    @@ -227,7 +227,7 @@ sattach(Srv *srv, Req *r)
    r->fid->uid = estrdup9p(r->ifcall.uname);
    if(srv->tree){
    r->fid->file = srv->tree->root;
    - /* BUG? incref(r->fid->file) ??? */
    + incref(&r->fid->file->ref);
    r->ofcall.qid = r->fid->file->dir.qid;
    r->fid->qid = r->ofcall.qid;
    }

    Russ


  3. Re: [9fans] Two ramfs?

    Thank you. I'll try to play with File and Tree now.

    btw, I had some problems on /tmp due to free space, getting messages
    from ./INSTALL as these:
    ....
    copy.o: No space left on device
    /tmp/cc2IGQH6.s: Assembler messages:
    /tmp/cc2IGQH6.s:3059: FATAL: Can't write copy.o: Invalid argument
    mk: 9c copy.c : exit status=exit(1)
    mk: for i in ... : exit status=exit(1)
    mk: for i in ... : exit status=exit(1)
    ....

    nevertheless, the INSTALL script returned errorlevel 0.

    I don't think this bothers many people, but I wasn't watching the
    command output, and I trusted the errorlevel.

    Regards.

    2008/2/4, Russ Cox :
    > > I saw the src/cmd/ramfs.c, and I think I should be able to write mine
    > > simpler... For example, I'd like to take advantage of the File/Tree
    > > interface (createfile(), ...), having all the files of the fs in
    > > memory.
    > >
    > > I found also src/lib9p/ramfs.c, which looks pretty much as what I
    > > want, but this doesn't tollerate remounting well at all (I guess).
    > >
    > > I tried it with some modifications (to get it compiled) in plan9port
    > > over linux (./ramfs -D -s test) and two "9p ls test" in a row makes
    > > the server die.
    > >
    > > Where can I see an example of a working fileserver which uses File,
    > > Tree, and the related functions?

    >
    > It's been a long time since I looked at that code, but it appears
    > that the problem is that Tattach doesn't increment the reference
    > count on its directory. Reattaching isn't very common in Plan 9
    > (but is on p9p) so it's easy to believe this bug went unnoticed.
    >
    > Here is the fix, now in p9p:
    >
    > diff -r bcad073690c5 src/lib9p/srv.c
    > --- a/src/lib9p/srv.c Fri Feb 01 07:54:19 2008 -0500
    > +++ b/src/lib9p/srv.c Mon Feb 04 15:32:28 2008 -0500
    > @@ -227,7 +227,7 @@ sattach(Srv *srv, Req *r)
    > r->fid->uid = estrdup9p(r->ifcall.uname);
    > if(srv->tree){
    > r->fid->file = srv->tree->root;
    > - /* BUG? incref(r->fid->file) ??? */
    > + incref(&r->fid->file->ref);
    > r->ofcall.qid = r->fid->file->dir.qid;
    > r->fid->qid = r->ofcall.qid;
    > }
    >
    > Russ
    >
    >


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