Date: Thu, 03 Jan 2008 08:57:39 +0200 From: Danny Braniss <danny@cs.huji.ac.il> To: Eric Anderson <anderson@freebsd.org> Cc: freebsd-hackers@freebsd.org Subject: Re: nfs v2/v3 and diskless boot problem Message-ID: <E1JAK1L-000HRX-FV@cs1.cs.huji.ac.il> In-Reply-To: Your message of Wed, 02 Jan 2008 10:22:28 -0600 .
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> Danny Braniss wrote: > >> Danny Braniss wrote: > >>> there is an undocumented option: > >>> boot-nfsroot-options > >>> that the diskeless boot can use. I tried > >>> boot-nfsroot-options = "nfsv3" > >>> since the pxeboot does the initial mount via nfsv2, and this has at least > >>> one problem: removing a file from the readonly / will hang the system. > >>> > >>> so, the remount to v3 works in the case that the root is served by a Freebsd > >>> nfs server, but fails if it's NetAPP. The reason is that the v2 filehandle > >>> is 32 bytes, and when switching to V3 it becomes 28bytes - sizeof(fhandle_t). > >>> This is not liked by the NetApp, which correctly gives error 1001: BADHANDLE > >>> :-) > >>> > >>> While I'm trying to come up with a solution, I am wondering if someone > >>> can shed some light: > >>> - is sizeof(fhandle_t) == 28 bytes is mystical, or changing it to > >>> 32 bytes will start WW3? > >> > >> NFSv3 file handles (by spec) can be up to 64bytes. > > > > true, but in freebsd, look at sys/nfs/nfsproto.h > > #define NFSX_V2FH 32 > > #define NFSX_V3FH (sizeof (fhandle_t)) > > #define NFSX_V4FH 128 > > > > so for v3 it's 28 bytes. (fhandle_t is defined in sys/mount.h) > > > > > >> I'm not 100% sure what is happening, but it sounds like the file handle > >> for the mount point or maybe one of the directories is not getting reset > >> on remount. > >> > >> When do you get the BADHANDLE error? Can you capture a > >> tshark/wireshark/tcpdump of the remount and error? > > > > I did, and if you look in sys/nfsclient/nfs_vfsops.c, nfs_convert_diskless is responsible > > for chopping off the 4 extra bytes. BTW, I tried to change the bcopy count to NFSX_V2FH/32, and > > it panics the kernel :-( > > > > danny > > > oh - looks like this says it all: > http://fxr.googlebit.com/source/sys/nfsclient/nfsdiskless.h?v=8-CURRENT#L51 > that's where the boot-nfsroot-options comes from:-) if you notice, the filehandle for v3 is 64 bytes, but only 28 are used. but as I mentioned initially, this ONLY works when the server is FreeBSD, and breaks for other servers, ie NetAPP. AND the initial question stands: what's in a filehandle, or can it be > 28bytes. danny
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