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>
In the iov_iter struct, separate the iterator type from the iterator
direction and use accessor functions to access them in most places.
Convert a bunch of places to use switch-statements to access them rather
then chains of bitwise-AND statements. This makes it easier to add further
iterator types. Also, this can be more efficient as to implement a switch
of small contiguous integers, the compiler can use ~50% fewer compare
instructions than it has to use bitwise-and instructions.
Further, cease passing the iterator type into the iterator setup function.
The iterator function can set that itself. Only the direction is required.
Signed-off-by: David Howells <dhowells@redhat.com>
In my testing, v9fs_fid_xattr_set will return successfully even if the
backend ext4 filesystem has no space to store xattr key-value. That will
cause inconsistent behavior between front end and back end. The reason is
that lsetxattr will be triggered by p9_client_clunk, and unfortunately we
did not catch the error. This patch will catch the error to notify upper
caller.
p9_client_clunk (in 9p)
p9_client_rpc(clnt, P9_TCLUNK, "d", fid->fid);
v9fs_clunk (in qemu)
put_fid
free_fid
v9fs_xattr_fid_clunk
v9fs_co_lsetxattr
s->ops->lsetxattr
ext4_xattr_user_set (in host ext4 filesystem)
Link: http://lkml.kernel.org/r/5B57EACC.2060900@huawei.com
Signed-off-by: Jun Piao <piaojun@huawei.com>
Cc: Eric Van Hensbergen <ericvh@gmail.com>
Cc: Ron Minnich <rminnich@sandia.gov>
Cc: Latchesar Ionkov <lucho@ionkov.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@vger.kernel.org
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
Add an additional "name" field to struct xattr_handler. When the name
is set, the handler matches attributes with exactly that name. When the
prefix is set instead, the handler matches attributes with the given
prefix and with a non-empty suffix.
This patch should avoid bugs like the one fixed in commit c361016a in
the future.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Now that the xattr handler is passed to the xattr handler operations, we
can use the same get and set operations for the user, trusted, and security
xattr namespaces. In those namespaces, we can access the full attribute
name by "reattaching" the name prefix the vfs has skipped for us. Add a
xattr_full_name helper to make this obvious in the code.
For the "system.posix_acl_access" and "system.posix_acl_default"
attributes, handler->prefix is the full attribute name; the suffix is the
empty string.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.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: Al Viro <viro@zeniv.linux.org.uk>
v9fs_fid_xattr_set is supposed to return 0 on success.
This corrects the behaviour introduced in commit
bdd5c28dcb
"9p: fix return value in case in v9fs_fid_xattr_set()"
(The function returns a negative error on error, as expected)
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
In case of error in the p9_client_write, the function v9fs_fid_xattr_set
should return its negative value, what was never being done.
In case of success it only retuned 0. Now it returns the 'offset'
variable (write_count total).
Signed-off-by: Geyslan G. Bem <geyslan@gmail.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Allow requests for security.* and trusted.* xattr name spaces
to pass through to server.
The new files are 99% cut and paste from fs/9p/xattr_user.c with the
namespaces changed. It has the intended effect in superficial testing.
I do not know much detail about how these namespaces are used, but passing
them through to the server, which can decide whether to handle them or not,
seems reasonable.
I want to support a use case where an ext4 file system is mounted via 9P,
then re-exported via samba to windows clients in a cluster. Windows wants
to store xattrs such as security.NTACL. This works when ext4 directly
backs samba, but not when 9P is inserted. This use case is documented here:
http://code.google.com/p/diod/issues/detail?id=95
Signed-off-by: Jim Garlick <garlick@llnl.gov>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Reduce object size by deduplicating formats.
Use vsprintf extension %pV.
Rename P9_DPRINTK uses to p9_debug, align arguments.
Add function for _p9_debug and macro to add __func__.
Add missing "\n"s to p9_debug uses.
Remove embedded function names as p9_debug adds it.
Remove P9_EPRINTK macro and convert use to pr_<level>.
Add and use pr_fmt and pr_<level>.
$ size fs/9p/built-in.o*
text data bss dec hex filename
62133 984 16000 79117 1350d fs/9p/built-in.o.new
67342 984 16928 85254 14d06 fs/9p/built-in.o.old
$ size net/9p/built-in.o*
text data bss dec hex filename
88792 4148 22024 114964 1c114 net/9p/built-in.o.new
94072 4148 23232 121452 1da6c net/9p/built-in.o.old
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
This patch implement fetching POSIX ACL from the server
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
The ACL value is fetched as a part of inode initialization
from the server and the permission checking function use the
cached value of the ACL
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
fixes:
CHECK fs/9p/xattr.c
fs/9p/xattr.c:73:6: warning: Using plain integer as NULL pointer
fs/9p/xattr.c:135:6: warning: Using plain integer as NULL pointer
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
