Date: Wed, 13 Nov 2002 15:58:10 -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: <200211132358.gADNwAVP012795@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>
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:> I'm fairly sure the VM issues were fixed when VOP_GETVOBJECT was
:> added. A file accessed via a null mount will have the same VM object
:> as the file in the original filesystem. I'm not 100% sure about
:> that, I wasn't the one who did it, but I seem to recall it being
:> discussed.
:
:VOP_GETVOBJECT is a different name, but the VOP was my suggestion,
:to allow an upper layer to obtain a backing object, and to
:collapse intermediate layers.
:
:The issue is that the NULLFS getpages falls through the the
:vfs_default.c vop_stdgetpages(), which calls the function
:vnode_pager_generic_getpages(), which in turn, calls VOP_BMAP(),
:which in null_vnops.c is vop_eopnotsupp(), so it falls back to
:vnode_pager_input_smlfs(), which VOP_BMAP()'s *again*, but off
:the device.
:
:At which point, you've lost coherency.
:
:-- Terry
It should be calling VOP_BMAP through the VP stored in the VM
object, which will be the underlying file, not the nullfs.
-Matt
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