Date: Wed, 19 Jun 2024 15:02:58 +0100 From: Doug Rabson <dfr@rabson.org> To: Baptiste Daroussin <bapt@freebsd.org> Cc: src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: e97ad33a89a7 - main - Add an implementation of the 9P filesystem Message-ID: <CACA0VUjcbf_pG=%2Bb0g_3ccU_w=vKzyPTwcf7D0ez=LYv6bknxg@mail.gmail.com> In-Reply-To: <mab7s6g3n7e64kjp6ygs5cqqrv6vl564qmkcpvw7p4jw3aofgo@tscl33lisgqk> References: <202406191213.45JCDPPP051964@gitrepo.freebsd.org> <mab7s6g3n7e64kjp6ygs5cqqrv6vl564qmkcpvw7p4jw3aofgo@tscl33lisgqk>
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--0000000000008ca9fd061b3ea80a Content-Type: text/plain; charset="UTF-8" On Wed, 19 Jun 2024 at 13:23, Baptiste Daroussin <bapt@freebsd.org> wrote: > On Wed 19 Jun 12:13, Doug Rabson wrote: > > The branch main has been updated by dfr: > > > > URL: > https://cgit.FreeBSD.org/src/commit/?id=e97ad33a89a78f55280b0485b3249ee9b907a718 > > > > commit e97ad33a89a78f55280b0485b3249ee9b907a718 > > Author: Doug Rabson <dfr@FreeBSD.org> > > AuthorDate: 2022-12-06 13:07:46 +0000 > > Commit: Doug Rabson <dfr@FreeBSD.org> > > CommitDate: 2024-06-19 12:12:04 +0000 > > > > Add an implementation of the 9P filesystem > > > > This is derived from swills@ fork of the Juniper virtfs with many > > changes by me including bug fixes, style improvements, clearer > layering > > and more consistent logging. The filesystem is renamed to p9fs to > better > > reflect its function and to prevent possible future confusion with > > virtio-fs. > > > > Several updates and fixes from Juniper have been integrated into this > > version by Val Packett and these contributions along with the > original > > Juniper authors are credited below. > > > > To use this with bhyve, add 'virtio_p9fs_load=YES' to loader.conf. > The > > bhyve virtio-9p device allows access from the guest to files on the > host > > by mapping a 'sharename' to a host path. It is possible to use p9fs > as a > > root filesystem by adding this to /boot/loader.conf: > > > > vfs.root.mountfrom="p9fs:sharename" > > > > for non-root filesystems add something like this to /etc/fstab: > > > > sharename /mnt p9fs rw 0 0 > > > > In both examples, substitute the share name used on the bhyve command > > line. > > > > The 9P filesystem protocol relies on stateful file opens which map > > protocol-level FIDs to host file descriptors. The FreeBSD vnode > > interface doesn't really support this and we use heuristics to guess > the > > right FID to use for file operations. This can be confused by > privilege > > lowering and does not guarantee that the FID created for a given file > > open is always used for file operations, even if the calling process > is > > using the file descriptor from the original open call. Improving this > > would involve changes to the vnode interface which is out-of-scope > for > > this import. > > > > First of all: thanks a lot! you say the changes in the vnode interface are > out > of scope for this import, which makes perfectly sense, but it is part of > your > TODO for later? > It is something I would like to work on but I'm not sure exactly when. I may try a quick-and-dirty approximation to get a better idea about how much in vnode will need to change. Basically, we need to track state from the VOP_OPEN in struct file so that we can match the right 9P fid with each i/o operation. This seems possible since we already have an f_data member in struct file. Doug. --0000000000008ca9fd061b3ea80a Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable <div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote">= <div dir=3D"ltr" class=3D"gmail_attr">On Wed, 19 Jun 2024 at 13:23, Baptist= e Daroussin <<a href=3D"mailto:bapt@freebsd.org">bapt@freebsd.org</a>>= ; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px= 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:= rgb(204,204,204);padding-left:1ex">On Wed 19 Jun 12:13, Doug Rabson wrote:<= br> > The branch main has been updated by dfr:<br> > <br> > URL: <a href=3D"https://cgit.FreeBSD.org/src/commit/?id=3De97ad33a89a7= 8f55280b0485b3249ee9b907a718" rel=3D"noreferrer" target=3D"_blank">https://= cgit.FreeBSD.org/src/commit/?id=3De97ad33a89a78f55280b0485b3249ee9b907a718<= /a><br> > <br> > commit e97ad33a89a78f55280b0485b3249ee9b907a718<br> > Author:=C2=A0 =C2=A0 =C2=A0Doug Rabson <dfr@FreeBSD.org><br> > AuthorDate: 2022-12-06 13:07:46 +0000<br> > Commit:=C2=A0 =C2=A0 =C2=A0Doug Rabson <dfr@FreeBSD.org><br> > CommitDate: 2024-06-19 12:12:04 +0000<br> > <br> >=C2=A0 =C2=A0 =C2=A0Add an implementation of the 9P filesystem<br> >=C2=A0 =C2=A0 =C2=A0<br> >=C2=A0 =C2=A0 =C2=A0This is derived from swills@ fork of the Juniper vi= rtfs with many<br> >=C2=A0 =C2=A0 =C2=A0changes by me including bug fixes, style improvemen= ts, clearer layering<br> >=C2=A0 =C2=A0 =C2=A0and more consistent logging. The filesystem is rena= med to p9fs to better<br> >=C2=A0 =C2=A0 =C2=A0reflect its function and to prevent possible future= confusion with<br> >=C2=A0 =C2=A0 =C2=A0virtio-fs.<br> >=C2=A0 =C2=A0 =C2=A0<br> >=C2=A0 =C2=A0 =C2=A0Several updates and fixes from Juniper have been in= tegrated into this<br> >=C2=A0 =C2=A0 =C2=A0version by Val Packett and these contributions alon= g with the original<br> >=C2=A0 =C2=A0 =C2=A0Juniper authors are credited below.<br> >=C2=A0 =C2=A0 =C2=A0<br> >=C2=A0 =C2=A0 =C2=A0To use this with bhyve, add 'virtio_p9fs_load= =3DYES' to loader.conf. The<br> >=C2=A0 =C2=A0 =C2=A0bhyve virtio-9p device allows access from the guest= to files on the host<br> >=C2=A0 =C2=A0 =C2=A0by mapping a 'sharename' to a host path. It= is possible to use p9fs as a<br> >=C2=A0 =C2=A0 =C2=A0root filesystem by adding this to /boot/loader.conf= :<br> >=C2=A0 =C2=A0 =C2=A0<br> >=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0vfs.root.mountfrom=3D&q= uot;p9fs:sharename"<br> >=C2=A0 =C2=A0 =C2=A0<br> >=C2=A0 =C2=A0 =C2=A0for non-root filesystems add something like this to= /etc/fstab:<br> >=C2=A0 =C2=A0 =C2=A0<br> >=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0sharename /mnt p9fs rw = 0 0<br> >=C2=A0 =C2=A0 =C2=A0<br> >=C2=A0 =C2=A0 =C2=A0In both examples, substitute the share name used on= the bhyve command<br> >=C2=A0 =C2=A0 =C2=A0line.<br> >=C2=A0 =C2=A0 =C2=A0<br> >=C2=A0 =C2=A0 =C2=A0The 9P filesystem protocol relies on stateful file = opens which map<br> >=C2=A0 =C2=A0 =C2=A0protocol-level FIDs to host file descriptors. The F= reeBSD vnode<br> >=C2=A0 =C2=A0 =C2=A0interface doesn't really support this and we us= e heuristics to guess the<br> >=C2=A0 =C2=A0 =C2=A0right FID to use for file operations.=C2=A0 This ca= n be confused by privilege<br> >=C2=A0 =C2=A0 =C2=A0lowering and does not guarantee that the FID create= d for a given file<br> >=C2=A0 =C2=A0 =C2=A0open is always used for file operations, even if th= e calling process is<br> >=C2=A0 =C2=A0 =C2=A0using the file descriptor from the original open ca= ll. Improving this<br> >=C2=A0 =C2=A0 =C2=A0would involve changes to the vnode interface which = is out-of-scope for<br> >=C2=A0 =C2=A0 =C2=A0this import.<br> >=C2=A0 =C2=A0 =C2=A0<br> <br> First of all: thanks a lot! you say the changes in the vnode interface are = out<br> of scope for this import, which makes perfectly sense, but it is part of yo= ur<br> TODO for later?<br></blockquote><div><br></div><div>It is something I would= like to work on but I'm not sure exactly when. I may try a quick-and-d= irty approximation to get a better idea about how much in vnode will need t= o change. Basically, we need to track state from the VOP_OPEN in struct fil= e so that we can match the right 9P fid with each i/o operation. This seems= possible since we already have an f_data member in struct file.</div><div>= <br></div><div>Doug.=C2=A0</div></div></div> --0000000000008ca9fd061b3ea80a--
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