9p/net: xen: fix false positive printf format overflow warning

Use the constant to make the compiler happy about this warning:
net/9p/trans_xen.c: In function ‘xen_9pfs_front_changed’:
net/9p/trans_xen.c:444:39: warning: ‘%d’ directive writing between 1 and 11 bytes into a region of size 8 [-Wformat-overflow=]
444 | sprintf(str, "ring-ref%d", i);
| ^~
In function ‘xen_9pfs_front_init’,
inlined from ‘xen_9pfs_front_changed’ at net/9p/trans_xen.c:516:8,
inlined from ‘xen_9pfs_front_changed’ at net/9p/trans_xen.c:504:13:
net/9p/trans_xen.c:444:30: note: directive argument in the range [-2147483644, 2147483646]
444 | sprintf(str, "ring-ref%d", i);
| ^~~~~~~~~~~~
net/9p/trans_xen.c:444:17: note: ‘sprintf’ output between 10 and 20 bytes into a destination of size 16
444 | sprintf(str, "ring-ref%d", i);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
net/9p/trans_xen.c: In function ‘xen_9pfs_front_changed’:
net/9p/trans_xen.c:450:45: warning: ‘%d’ directive writing between 1 and 11 bytes into a region of size 2 [-Wformat-overflow=]
450 | sprintf(str, "event-channel-%d", i);
| ^~
In function ‘xen_9pfs_front_init’,
inlined from ‘xen_9pfs_front_changed’ at net/9p/trans_xen.c:516:8,
inlined from ‘xen_9pfs_front_changed’ at net/9p/trans_xen.c:504:13:
net/9p/trans_xen.c:450:30: note: directive argument in the range [-2147483644, 2147483646]
450 | sprintf(str, "event-channel-%d", i);
| ^~~~~~~~~~~~~~~~~~
net/9p/trans_xen.c:450:17: note: ‘sprintf’ output between 16 and 26 bytes into a destination of size 16
450 | sprintf(str, "event-channel-%d", i);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

There is no change in logic: there only are a constant number of rings,
and there also already is a BUILD_BUG_ON that checks if that constant
goes over 9 as anything bigger would no longer fit the event-channel-%d
destination size.

In theory having that size as part of the struct means it could be
modified by another thread and makes the compiler lose track of possible
values for 'i' here, using the constant directly here makes it work.

Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Message-ID: <20231025103445.1248103-3-asmadeus@codewreck.org>
Reviewed-by: Christian Schoenebeck <linux_oss@crudebyte.com>

9p/xen : Fix use after free bug in xen_9pfs_front_remove due to race condition

In xen_9pfs_front_probe, it calls xen_9pfs_front_alloc_dataring
to init priv->rings and bound &ring->work with p9_xen_response.

When it calls xen_9pfs_front_event_handler to handle IRQ requests,
it will finally call schedule_work to start the work.

When we call xen_9pfs_front_remove to remove the driver, there
may be a sequence as follows:

Fix it by finishing the work before cleanup in xen_9pfs_front_free.

Note that, this bug is found by static analysis, which might be
false positive.

CPU0 CPU1

|p9_xen_response
xen_9pfs_front_remove|
xen_9pfs_front_free|
kfree(priv) |
//free priv |
|p9_tag_lookup
|//use priv->client

Fixes: 71ebd71921e4 ("xen/9pfs: connect to the backend")
Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Signed-off-by: Eric Van Hensbergen <ericvh@kernel.org>

9p/xen: fix connection sequence

Today the connection sequence of the Xen 9pfs frontend doesn't match
the documented sequence. It can work reliably only for a PV 9pfs device
having been added at boot time already, as the frontend is not waiting
for the backend to have set its state to "XenbusStateInitWait" before
reading the backend properties from Xenstore.

Fix that by following the documented sequence [1] (the documentation
has a bug, so the reference is for the patch fixing that).

[1]: https://lore.kernel.org/xen-devel/20230130090937.31623-1-jgross@suse.com/T/#u

Link: https://lkml.kernel.org/r/20230130113036.7087-3-jgross@suse.com
Fixes: 868eb122739a ("xen/9pfs: introduce Xen 9pfs transport driver")
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Signed-off-by: Eric Van Hensbergen <ericvh@kernel.org>

9p/xen: fix version parsing

When connecting the Xen 9pfs frontend to the backend, the "versions"
Xenstore entry written by the backend is parsed in a wrong way.

The "versions" entry is defined to contain the versions supported by
the backend separated by commas (e.g. "1,2"). Today only version "1"
is defined. Unfortunately the frontend doesn't look for "1" being
listed in the entry, but it is expecting the entry to have the value
"1".

This will result in failure as soon as the backend will support e.g.
versions "1" and "2".

Fix that by scanning the entry correctly.

Link: https://lkml.kernel.org/r/20230130113036.7087-2-jgross@suse.com
Fixes: 71ebd71921e4 ("xen/9pfs: connect to the backend")
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Signed-off-by: Eric Van Hensbergen <ericvh@kernel.org>

xen: make remove callback of xen driver void returned

Since commit fc7a6209d571 ("bus: Make remove callback return void")
forces bus_type::remove be void-returned, it doesn't make much sense for
any bus based driver implementing remove callbalk to return non-void to
its caller.

This change is for xen bus based drivers.

Acked-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Dawei Li <set_pte_at@outlook.com>
Link: https://lore.kernel.org/r/TYCP286MB23238119AB4DF190997075C9CAE39@TYCP286MB2323.JPNP286.PROD.OUTLOOK.COM
Signed-off-by: Juergen Gross <jgross@suse.com>

9p/client: fix data race on req->status

KCSAN reported a race between writing req->status in p9_client_cb and
accessing it in p9_client_rpc's wait_event.

Accesses to req itself is protected by the data barrier (writing req
fields, write barrier, writing status // reading status, read barrier,
reading other req fields), but status accesses themselves apparently
also must be annotated properly with WRITE_ONCE/READ_ONCE when we
access it without locks.

Follows:
- error paths writing status in various threads all can notify
p9_client_rpc, so these all also need WRITE_ONCE
- there's a similar read loop in trans_virtio for zc case that also
needs READ_ONCE
- other reads in trans_fd should be protected by the trans_fd lock and
lists state machine, as corresponding writers all are within trans_fd
and should be under the same lock. If KCSAN complains on them we likely
will have something else to fix as well, so it's better to leave them
unmarked and look again if required.

Link: https://lkml.kernel.org/r/20221205124756.426350-1-asmadeus@codewreck.org
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Suggested-by: Marco Elver <elver@google.com>
Acked-by: Marco Elver <elver@google.com>
Reviewed-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

9p/xen: do not memcpy header into req->rc

while 'h' is packed and can be assumed to match the request payload,
req->rc is a struct p9_fcall which is not packed and that memcpy
could be wrong.

Fix this by copying each fields individually instead.

Reported-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Reviewed-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Suggested-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Link: https://lkml.kernel.org/r/alpine.DEB.2.22.394.2211211454540.1049131@ubuntu-linux-20-04-desktop
Link: https://lkml.kernel.org/r/20221122001025.119121-1-asmadeus@codewreck.org
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

9p/xen: check logical size for buffer size

trans_xen did not check the data fits into the buffer before copying
from the xen ring, but we probably should.
Add a check that just skips the request and return an error to
userspace if it did not fit

Tested-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Link: https://lkml.kernel.org/r/20221118135542.63400-1-asmadeus@codewreck.org
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

net/9p: add __init/__exit annotations to module init/exit funcs

xen transport was missing annotations

Link: https://lkml.kernel.org/r/20220909103546.73015-1-xiujianfeng@huawei.com
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

net/9p: add 'pooled_rbuffers' flag to struct p9_trans_module

This is a preparatory change for the subsequent patch: the RDMA
transport pulls the buffers for its 9p response messages from a
shared pool. [1] So this case has to be considered when choosing
an appropriate response message size in the subsequent patch.

Link: https://lore.kernel.org/all/Ys3jjg52EIyITPua@codewreck.org/ [1]
Link: https://lkml.kernel.org/r/79d24310226bc4eb037892b5c097ec4ad4819a03.1657920926.git.linux_oss@crudebyte.com
Signed-off-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

9p: Add client parameter to p9_req_put()

This is to aid in adding mempools, in the next patch.

Link: https://lkml.kernel.org/r/20220704014243.153050-2-kent.overstreet@gmail.com
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

xen: switch gnttab_end_foreign_access() to take a struct page pointer

Instead of a virtual kernel address use a pointer of the associated
struct page as second parameter of gnttab_end_foreign_access().

Most users have that pointer available already and are creating the
virtual address from it, risking problems in case the memory is
located in highmem.

gnttab_end_foreign_access() itself won't need to get the struct page
from the address again.

Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

xen/grant-table: remove readonly parameter from functions

The gnttab_end_foreign_access() family of functions is taking a
"readonly" parameter, which isn't used. Remove it from the function
parameters.

Signed-off-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220311103429.12845-3-jgross@suse.com
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

xen/9p: use alloc/free_pages_exact()

Instead of __get_free_pages() and free_pages() use alloc_pages_exact()
and free_pages_exact(). This is in preparation of a change of
gnttab_end_foreign_access() which will prohibit use of high-order
pages.

By using the local variable "order" instead of ring->intf->ring_order
in the error path of xen_9pfs_front_alloc_dataring() another bug is
fixed, as the error path can be entered before ring->intf->ring_order
is being set.

By using alloc_pages_exact() the size in bytes is specified for the
allocation, which fixes another bug for the case of
order < (PAGE_SHIFT - XEN_PAGE_SHIFT).

This is part of CVE-2022-23041 / XSA-396.

Reported-by: Simon Gaiser <simon@invisiblethingslab.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
V4:
- new patch

9p/xen: autoload when xenbus service is available

Link: https://lkml.kernel.org/r/20211103193823.111007-4-linux@weissschuh.net
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

9p: fix file headers

- add missing SPDX-License-Identifier
- remove (sometimes incorrect) file name from file header

Link: http://lkml.kernel.org/r/20211102134608.1588018-2-dominique.martinet@atmark-techno.com
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

net/9p: autoload transport modules

Automatically load transport modules based on the trans= parameter
passed to mount.
This removes the requirement for the user to know which module to use.

Link: http://lkml.kernel.org/r/20211017134611.4330-1-linux@weissschuh.net
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

9p/xen: Fix end of loop tests for list_for_each_entry

This patch addresses the following problems:
- priv can never be NULL, so this part of the check is useless
- if the loop ran through the whole list, priv->client is invalid and
it is more appropriate and sufficient to check for the end of
list_for_each_entry loop condition.

Link: http://lkml.kernel.org/r/20210727000709.225032-1-harshvardhan.jha@oracle.com
Signed-off-by: Harshvardhan Jha <harshvardhan.jha@oracle.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Tested-by: Stefano Stabellini <sstabellini@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

9p/xen: Fix format argument warning

Fix follow warnings:
[net/9p/trans_xen.c:454]: (warning) %u in format string (no. 1) requires
'unsigned int' but the argument type is 'int'.
[net/9p/trans_xen.c:460]: (warning) %u in format string (no. 1) requires
'unsigned int' but the argument type is 'int'.

Link: http://lkml.kernel.org/r/20201009080552.89918-1-yebin10@huawei.com
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Ye Bin <yebin10@huawei.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>

treewide: Use fallthrough pseudo-keyword

Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

9p/xen: increase XEN_9PFS_RING_ORDER

Increase XEN_9PFS_RING_ORDER to 9 for performance reason. Order 9 is the
max allowed by the protocol.

We can't assume that all backends will support order 9. The xenstore
property max-ring-page-order specifies the max order supported by the
backend. We'll use max-ring-page-order for the size of the ring.

This means that the size of the ring is not static
(XEN_FLEX_RING_SIZE(9)) anymore. Change XEN_9PFS_RING_SIZE to take an
argument and base the calculation on the order chosen at setup time.

Finally, modify p9_xen_trans.maxsize to be divided by 4 compared to the
original value. We need to divide it by 2 because we have two rings
coming off the same order allocation: the in and out rings. This was a
mistake in the original code. Also divide it further by 2 because we
don't want a single request/reply to fill up the entire ring. There can
be multiple requests/replies outstanding at any given time and if we use
the full ring with one, we risk forcing the backend to wait for the
client to read back more replies before continuing, which is not
performant.

Link: http://lkml.kernel.org/r/20200521193242.15953-1-sstabellini@kernel.org
Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>

9p/xen: Add cleanup path in p9_trans_xen_init

If xenbus_register_frontend() fails in p9_trans_xen_init,
we should call v9fs_unregister_trans() to do cleanup.

Link: http://lkml.kernel.org/r/20190430143933.19368-1-yuehaibing@huawei.com
Cc: stable@vger.kernel.org
Fixes: 868eb122739a ("xen/9pfs: introduce Xen 9pfs transport driver")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>

9p: mark expected switch fall-through

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

This patch fixes the following warning:

net/9p/trans_xen.c:514:6: warning: this statement may fall through [-Wimplicit-fallthrough=]

Warning level 3 was used: -Wimplicit-fallthrough=3

This patch is part of the ongoing efforts to enabling
-Wimplicit-fallthrough

Link: http://lkml.kernel.org/r/20190123071632.GA8039@embeddedor
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>

9p: Add refcount to p9_req_t

To avoid use-after-free(s), use a refcount to keep track of the
usable references to any instantiated struct p9_req_t.

This commit adds p9_req_put(), p9_req_get() and p9_req_try_get() as
wrappers to kref_put(), kref_get() and kref_get_unless_zero().
These are used by the client and the transports to keep track of
valid requests' references.

p9_free_req() is added back and used as callback by kref_put().

Add SLAB_TYPESAFE_BY_RCU as it ensures that the memory freed by
kmem_cache_free() will not be reused for another type until the rcu
synchronisation period is over, so an address gotten under rcu read
lock is safe to inc_ref() without corrupting random memory while
the lock is held.

Link: http://lkml.kernel.org/r/1535626341-20693-1-git-send-email-asmadeus@codewreck.org
Co-developed-by: Dominique Martinet <dominique.martinet@cea.fr>
Signed-off-by: Tomas Bortoli <tomasbortoli@gmail.com>
Reported-by: syzbot+467050c1ce275af2a5b8@syzkaller.appspotmail.com
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>

9p: embed fcall in req to round down buffer allocs

'msize' is often a power of two, or at least page-aligned, so avoiding
an overhead of two dozen bytes for each allocation will help the
allocator do its work and reduce memory fragmentation.

Link: http://lkml.kernel.org/r/1533825236-22896-1-git-send-email-asmadeus@codewreck.org
Suggested-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
Reviewed-by: Greg Kurz <groug@kaod.org>
Acked-by: Jun Piao <piaojun@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>

9p/xen: fix check for xenbus_read error in front_probe

If the xen bus exists but does not expose the proper interface, it is
possible to get a non-zero length but still some error, leading to
strcmp failing trying to load invalid memory addresses e.g.
fffffffffffffffe.

There is then no need to check length when there is no error, as the
xenbus driver guarantees that the string is nul-terminated.

Link: http://lkml.kernel.org/r/1534236007-10170-1-git-send-email-asmadeus@codewreck.org
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Latchesar Ionkov <lucho@ionkov.net>

9p: fix multiple NULL-pointer-dereferences

Added checks to prevent GPFs from raising.

Link: http://lkml.kernel.org/r/20180727110558.5479-1-tomasbortoli@gmail.com
Signed-off-by: Tomas Bortoli <tomasbortoli@gmail.com>
Reported-by: syzbot+1a262da37d3bead15c39@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>

net/9p/trans_xen.c: don't inclide rwlock.h directly

rwlock.h should not be included directly. Instead linux/splinlock.h
should be included. One thing it does is to break the RT build.

Link: http://lkml.kernel.org/r/20180504100319.11880-1-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Ron Minnich <rminnich@sandia.gov>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

net/9p: fix spelling mistake: "suspsend" -> "suspend"

Trivial fix to spelling mistake in dev_warn message text

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

9p: add missing module license for xen transport

The 9P of Xen module is missing required license and module information.
See https://bugzilla.kernel.org/show_bug.cgi?id=198109

Reported-by: Alan Bartlett <ajb@elrepo.org>
Fixes: 868eb122739a ("xen/9pfs: introduce Xen 9pfs transport driver")
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/9p: Switch to wait_event_killable()

Because userspace gets Very Unhappy when calls like stat() and execve()
return -EINTR on 9p filesystem mounts. For instance, when bash is
looking in PATH for things to execute and some SIGCHLD interrupts
stat(), bash can throw a spurious 'command not found' since it doesn't
retry the stat().

In practice, hitting the problem is rare and needs a really
slow/bogged down 9p server.

Cc: stable@vger.kernel.org
Signed-off-by: Tuomas Tynkkynen <tuomas@tuxera.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

xen/9pfs: p9_trans_xen_init and p9_trans_xen_exit can be static

Fixes the following sparse warnings:

net/9p/trans_xen.c:528:5: warning:
symbol 'p9_trans_xen_init' was not declared. Should it be static?
net/9p/trans_xen.c:540:6: warning:
symbol 'p9_trans_xen_exit' was not declared. Should it be static?

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

xen/9pfs: fix return value check in xen_9pfs_front_probe()

In case of error, the function xenbus_read() returns ERR_PTR() and never
returns NULL. The NULL test in the return value check should be replaced
with IS_ERR().

Fixes: 71ebd71921e4 ("xen/9pfs: connect to the backend")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

xen/9pfs: initialize len to 0 to detect xenbus_read errors

In order to use "len" to check for xenbus_read errors properly, we need
to initialize len to 0 before passing it to xenbus_read.

CC: dan.carpenter@oracle.com
CC: jgross@suse.com
CC: boris.ostrovsky@oracle.com
CC: Eric Van Hensbergen <ericvh@gmail.com>
CC: Ron Minnich <rminnich@sandia.gov>
CC: Latchesar Ionkov <lucho@ionkov.net>
CC: v9fs-developer@lists.sourceforge.net
Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

xen/9pfs: receive responses

Upon receiving a notification from the backend, schedule the
p9_xen_response work_struct. p9_xen_response checks if any responses are
available, if so, it reads them one by one, calling p9_client_cb to send
them up to the 9p layer (p9_client_cb completes the request). Handle the
ring following the Xen 9pfs specification.

CC: groug@kaod.org
CC: jgross@suse.com
CC: Eric Van Hensbergen <ericvh@gmail.com>
CC: Ron Minnich <rminnich@sandia.gov>
CC: Latchesar Ionkov <lucho@ionkov.net>
CC: v9fs-developer@lists.sourceforge.net

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

xen/9pfs: send requests to the backend

Implement struct p9_trans_module create and close functions by looking
at the available Xen 9pfs frontend-backend connections. We don't expect
many frontend-backend connections, thus walking a list is OK.

Send requests to the backend by copying each request to one of the
available rings (each frontend-backend connection comes with multiple
rings). Handle the ring and notifications following the 9pfs
specification. If there are not enough free bytes on the ring for the
request, wait on the wait_queue: the backend will send a notification
after consuming more requests.

CC: groug@kaod.org
CC: jgross@suse.com
CC: Eric Van Hensbergen <ericvh@gmail.com>
CC: Ron Minnich <rminnich@sandia.gov>
CC: Latchesar Ionkov <lucho@ionkov.net>
CC: v9fs-developer@lists.sourceforge.net

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

xen/9pfs: connect to the backend

Implement functions to handle the xenbus handshake. Upon connection,
allocate the rings according to the protocol specification.

Initialize a work_struct and a wait_queue. The work_struct will be used
to schedule work upon receiving an event channel notification from the
backend. The wait_queue will be used to wait when the ring is full and
we need to send a new request.

CC: groug@kaod.org
CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
CC: Eric Van Hensbergen <ericvh@gmail.com>
CC: Ron Minnich <rminnich@sandia.gov>
CC: Latchesar Ionkov <lucho@ionkov.net>
CC: v9fs-developer@lists.sourceforge.net

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

xen/9pfs: introduce Xen 9pfs transport driver

Introduce the Xen 9pfs transport driver: add struct xenbus_driver to
register as a xenbus driver and add struct p9_trans_module to register
as v9fs driver.

All functions are empty stubs for now.

CC: groug@kaod.org
CC: jgross@suse.com
CC: Eric Van Hensbergen <ericvh@gmail.com>
CC: Ron Minnich <rminnich@sandia.gov>
CC: Latchesar Ionkov <lucho@ionkov.net>
CC: v9fs-developer@lists.sourceforge.net

Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>