Add some additional debug flags to assist with debugging
cache changes. Also add some additional open modes so we
can track cache state in fids more directly.
Signed-off-by: Eric Van Hensbergen <ericvh@kernel.org>
Add P9_ERRMAX macro to 9P protocol header which reflects the maximum
error string length of Rerror replies for 9p2000 and 9p2000.u protocol
versions. Unfortunately a maximum error string length is not defined by
the 9p2000 spec, picking 128 as value for now, as this seems to be a
common max. size for POSIX error strings in practice.
9p2000.L protocol version uses Rlerror replies instead which does not
contain an error string.
Link: https://lkml.kernel.org/r/3f23191d21032e7c14852b1e1a4ae26417a36739.1657920926.git.linux_oss@crudebyte.com
Signed-off-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
This adds a tracepoint event for 9p fid lifecycle tracing: when a fid
is created, its reference count increased/decreased, and freed.
The new 9p_fid_ref tracepoint should help anyone wishing to debug any
fid problem such as missing clunk (destroy) or use-after-free.
Link: https://lkml.kernel.org/r/20220612085330.1451496-6-asmadeus@codewreck.org
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Now that all transports are split into modules it may happen that no
transports are registered when v9fs_get_default_trans() is called.
When that is the case try to load more transports from modules.
Link: https://lkml.kernel.org/r/20211103193823.111007-5-linux@weissschuh.net
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
[Dominique: constify v9fs_get_trans_by_name argument as per patch1v2]
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Fix race issue in fid contention.
Eric's and Greg's patch offer a mechanism to fix open-unlink-f*syscall
bug in 9p. But there is race issue in fid parallel accesses.
As Greg's patch stores all of fids from opened files into according inode,
so all the lookup fid ops can retrieve fid from inode preferentially. But
there is no mechanism to handle the fid contention issue. For example,
there are two threads get the same fid in the same time and one of them
clunk the fid before the other thread ready to discard the fid. In this
scenario, it will lead to some fatal problems, even kernel core dump.
I introduce a mechanism to fix this race issue. A counter field introduced
into p9_fid struct to store the reference counter to the fid. When a fid
is allocated from the inode or dentry, the counter will increase, and
will decrease at the end of its occupation. It is guaranteed that the
fid won't be clunked before the reference counter go down to 0, then
we can avoid the clunked fid to be used.
tests:
race issue test from the old test case:
for file in {01..50}; do touch f.${file}; done
seq 1 1000 | xargs -n 1 -P 50 -I{} cat f.* > /dev/null
open-unlink-f*syscall test:
I have tested for f*syscall include: ftruncate fstat fchown fchmod faccessat.
Link: http://lkml.kernel.org/r/20200923141146.90046-5-jianyong.wu@arm.com
Fixes: 478ba09edc ("fs/9p: search open fids first")
Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
A user doesn't necessarily want to wait for all the requested data to
be available, since the waiting time for each request is unbounded.
The new method permits sending one read request at a time and getting
the response ASAP, allowing to use 9pnet with synthetic file systems
representing arbitrary data streams.
Link: http://lkml.kernel.org/r/20200205204053.12751-1-l29ah@cock.li
Signed-off-by: Sergey Alirzaev <l29ah@cock.li>
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
Based on 1 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation this program is
distributed in the hope that it will be useful but without any
warranty without even the implied warranty of merchantability or
fitness for a particular purpose see the gnu general public license
for more details you should have received a copy of the gnu general
public license along with this program if not write to free software
foundation 51 franklin street fifth floor boston ma 02111 1301 usa
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-only
has been chosen to replace the boilerplate/reference in 27 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Reviewed-by: Alexios Zavras <alexios.zavras@intel.com>
Reviewed-by: Steve Winslow <swinslow@gmail.com>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190528170026.981318839@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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>
Having a specific cache for the fcall allocations helps speed up
end-to-end latency.
The caches will automatically be merged if there are multiple caches
of items with the same size so we do not need to try to share a cache
between different clients of the same size.
Since the msize is negotiated with the server, only allocate the cache
after that negotiation has happened - previous allocations or
allocations of different sizes (e.g. zero-copy fcall) are made with
kmalloc directly.
Some figures on two beefy VMs with Connect-IB (sriov) / trans=rdma,
with ior running 32 processes in parallel doing small 32 bytes IOs:
- no alloc (4.18-rc7 request cache): 65.4k req/s
- non-power of two alloc, no patch: 61.6k req/s
- power of two alloc, no patch: 62.2k req/s
- non-power of two alloc, with patch: 64.7k req/s
- power of two alloc, with patch: 65.1k req/s
Link: http://lkml.kernel.org/r/1532943263-24378-2-git-send-email-asmadeus@codewreck.org
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
Acked-by: Jun Piao <piaojun@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Greg Kurz <groug@kaod.org>
