Date: Wed, 13 Nov 2002 18:55:37 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Terry Lambert <tlambert2@mindspring.com> Cc: "Daniel O'Connor" <doconnor@gsoft.com.au>, Hans Zaunere <zaunere@yahoo.com>, freebsd-hackers@FreeBSD.ORG Subject: Re: Shared files within a jail Message-ID: <200211140255.gAE2tbBE024050@apollo.backplane.com> References: <20021113034726.75787.qmail@web12801.mail.yahoo.com> <1037159767.66058.34.camel@chowder.localdomain> <200211130530.gAD5UxNt067928@apollo.backplane.com> <3DD1FAB9.82607C41@mindspring.com> <200211131114.gADBE3lM069566@apollo.backplane.com> <3DD2DF3A.18489E80@mindspring.com> <200211132358.gADNwAVP012795@apollo.backplane.com> <3DD30492.68FE18E6@mindspring.com>
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:>
:> It should be calling VOP_BMAP through the VP stored in the VM
:> object, which will be the underlying file, not the nullfs.
:
:Probably, but it's not doing that. The NULLFS implement VOP_BMAP
:as vop_eopnotsupp; it doesn't fall through. Even if it did fall
:through, the vfs_default.c code is not really written with stacking
:in mind, it's written with a local-media FS in mind. VOP_BMAP is
:simply not implemented for NULLFS, and is nearly impossible to
:implement correctly for a stacking VFS layer in any case, given
:the object aliasing problem.
:
:This is a deeply ingrained bug in FreeBSD's implementation of VFS
:stacking.
I don't think it's doing that. As far as I can tell it is
calling VOP_GETPAGES, which will hit nullfs, and then nullfs should
simply call the underlying vnode's VOP_GETPAGES via the null_bypass()
function.
-Matt
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