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We added CONFIG_MANDATORY_FILE_LOCKING in 2015, and soon after turned it
off in Fedora and RHEL8. Several other distros have followed suit.
I've heard of one problem in all that time: Someone migrated from an
older distro that supported "-o mand" to one that didn't, and the host
had a fstab entry with "mand" in it which broke on reboot. They didn't
actually _use_ mandatory locking so they just removed the mount option
and moved on.
This patch rips out mandatory locking support wholesale from the kernel,
along with the Kconfig option and the Documentation file. It also
changes the mount code to ignore the "mand" mount option instead of
erroring out, and to throw a big, ugly warning.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Variable ret is set to -ENOENT and -ENOMEM but this value is never
read as it is overwritten or not used later on, hence it is a
redundant assignment and can be removed.
Cleans up the following clang-analyzer warning:
fs/afs/dir.c:2014:4: warning: Value stored to 'ret' is never read
[clang-analyzer-deadcode.DeadStores].
fs/afs/dir.c:659:2: warning: Value stored to 'ret' is never read
[clang-analyzer-deadcode.DeadStores].
[DH made the following modifications:
- In afs_rename(), -ENOMEM should be placed in op->error instead of ret,
rather than the assignment being removed entirely. afs_put_operation()
will pick it up from there and return it.
- If afs_sillyrename() fails, its error code should be placed in op->error
rather than in ret also.
]
Fixes: e49c7b2f6d ("afs: Build an abstraction around an "operation" concept")
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/1619691492-83866-1-git-send-email-jiapeng.chong@linux.alibaba.com
Link: https://lore.kernel.org/r/162609465444.3133237.7562832521724298900.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/162610729052.3408253.17364333638838151299.stgit@warthog.procyon.org.uk/ # v2
To quote Alexey[1]:
I was adding custom tracepoint to the kernel, grabbed full F34 kernel
.config, disabled modules and booted whole shebang as VM kernel.
Then did
perf record -a -e ...
It crashed:
general protection fault, probably for non-canonical address 0x435f5346592e4243: 0000 [#1] SMP PTI
CPU: 1 PID: 842 Comm: cat Not tainted 5.12.6+ #26
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014
RIP: 0010:t_show+0x22/0xd0
Then reproducer was narrowed to
# cat /sys/kernel/tracing/printk_formats
Original F34 kernel with modules didn't crash.
So I started to disable options and after disabling AFS everything
started working again.
The root cause is that AFS was placing char arrays content into a
section full of _pointers_ to strings with predictable consequences.
Non canonical address 435f5346592e4243 is "CB.YFS_" which came from
CM_NAME macro.
Steps to reproduce:
CONFIG_AFS=y
CONFIG_TRACING=y
# cat /sys/kernel/tracing/printk_formats
Fix this by the following means:
(1) Add enum->string translation tables in the event header with the AFS
and YFS cache/callback manager operations listed by RPC operation ID.
(2) Modify the afs_cb_call tracepoint to print the string from the
translation table rather than using the string at the afs_call name
pointer.
(3) Switch translation table depending on the service we're being accessed
as (AFS or YFS) in the tracepoint print clause. Will this cause
problems to userspace utilities?
Note that the symbolic representation of the YFS service ID isn't
available to this header, so I've put it in as a number. I'm not sure
if this is the best way to do this.
(4) Remove the name wrangling (CM_NAME) macro and put the names directly
into the afs_call_type structs in cmservice.c.
Fixes: 8e8d7f13b6 ("afs: Add some tracepoints")
Reported-by: Alexey Dobriyan (SK hynix) <adobriyan@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
cc: Andrew Morton <akpm@linux-foundation.org>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/YLAXfvZ+rObEOdc%2F@localhost.localdomain/ [1]
Link: https://lore.kernel.org/r/643721.1623754699@warthog.procyon.org.uk/
Link: https://lore.kernel.org/r/162430903582.2896199.6098150063997983353.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/162609463957.3133237.15916579353149746363.stgit@warthog.procyon.org.uk/ # v1 (repost)
Link: https://lore.kernel.org/r/162610726860.3408253.445207609466288531.stgit@warthog.procyon.org.uk/ # v2
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Merge tag 'netfs-fixes-20210621' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs
Pull netfs fixes from David Howells:
"This contains patches to fix netfs_write_begin() and afs_write_end()
in the following ways:
(1) In netfs_write_begin(), extract the decision about whether to skip
a page out to its own helper and have that clear around the region
to be written, but not clear that region. This requires the
filesystem to patch it up afterwards if the hole doesn't get
completely filled.
(2) Use offset_in_thp() in (1) rather than manually calculating the
offset into the page.
(3) Due to (1), afs_write_end() now needs to handle short data write
into the page by generic_perform_write(). I've adopted an
analogous approach to ceph of just returning 0 in this case and
letting the caller go round again.
It also adds a note that (in the future) the len parameter may extend
beyond the page allocated. This is because the page allocation is
deferred to write_begin() and that gets to decide what size of THP to
allocate."
Jeff Layton points out:
"The netfs fix in particular fixes a data corruption bug in cephfs"
* tag 'netfs-fixes-20210621' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
netfs: fix test for whether we can skip read when writing beyond EOF
afs: Fix afs_write_end() to handle short writes
Fix afs_write_end() to correctly handle a short copy into the intended
write region of the page. Two things are necessary:
(1) If the page is not up to date, then we should just return 0
(ie. indicating a zero-length copy). The loop in
generic_perform_write() will go around again, possibly breaking up the
iterator into discrete chunks[1].
This is analogous to commit b9de313cf0
for ceph.
(2) The page should not have been set uptodate if it wasn't completely set
up by netfs_write_begin() (this will be fixed in the next patch), so
we need to set uptodate here in such a case.
Also remove the assertion that was checking that the page was set uptodate
since it's now set uptodate if it wasn't already a few lines above. The
assertion was from when uptodate was set elsewhere.
Changes:
v3: Remove the handling of len exceeding the end of the page.
Fixes: 3003bbd069 ("afs: Use the netfs_write_begin() helper")
Reported-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/YMwVp268KTzTf8cN@zeniv-ca.linux.org.uk/ [1]
Link: https://lore.kernel.org/r/162367682522.460125.5652091227576721609.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/162391825688.1173366.3437507255136307904.stgit@warthog.procyon.org.uk/ # v2
If a task is killed during a page fault, it does not currently call
sb_end_pagefault(), which means that the filesystem cannot be frozen
at any time thereafter. This may be reported by lockdep like this:
====================================
WARNING: fsstress/10757 still has locks held!
5.13.0-rc4-build4+ #91 Not tainted
------------------------------------
1 lock held by fsstress/10757:
#0: ffff888104eac530
(
sb_pagefaults
as filesystem freezing is modelled as a lock.
Fix this by removing all the direct returns from within the function,
and using 'ret' to indicate whether we were interrupted or successful.
Fixes: 1cf7a1518a ("afs: Implement shared-writeable mmap")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/20210616154900.1958373-1-willy@infradead.org/
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In commit e87b03f583 ("afs: Prepare for use of THPs"), the return
value for afs_write_back_from_locked_page was changed from a number
of pages to a length in bytes. The loop in afs_writepages_region uses
the return value to compute the index that will be used to find dirty
pages in the next iteration, but treats it as a number of pages and
wrongly multiplies it by PAGE_SIZE. This gives a very large index value,
potentially skipping any dirty data that was not covered in the first
pass, which is limited to 256M.
This causes fsync(), and indirectly close(), to only do a partial
writeback of a large file's dirty data. The rest is eventually written
back by background threads after dirty_expire_centisecs.
Fixes: e87b03f583 ("afs: Prepare for use of THPs")
Signed-off-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeffrey Altman <jaltman@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/20210604175504.4055-1-marc.c.dionne@gmail.com/
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix rename of one directory over another such that the nlink on the deleted
directory is cleared to 0 rather than being decremented to 1.
This was causing the generic/035 xfstest to fail.
Fixes: e49c7b2f6d ("afs: Build an abstraction around an "operation" concept")
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/162194384460.3999479.7605572278074191079.stgit@warthog.procyon.org.uk/ # v1
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The generic/464 xfstest causes kAFS to emit occasional warnings of the
form:
kAFS: vnode modified {100055:8a} 30->31 YFS.StoreData64 (c=6015)
This indicates that the data version received back from the server did not
match the expected value (the DV should be incremented monotonically for
each individual modification op committed to a vnode).
What is happening is that a lookup call is doing a bulk status fetch
speculatively on a bunch of vnodes in a directory besides getting the
status of the vnode it's actually interested in. This is racing with a
StoreData operation (though it could also occur with, say, a MakeDir op).
On the client, a modification operation locks the vnode, but the bulk
status fetch only locks the parent directory, so no ordering is imposed
there (thereby avoiding an avenue to deadlock).
On the server, the StoreData op handler doesn't lock the vnode until it's
received all the request data, and downgrades the lock after committing the
data until it has finished sending change notifications to other clients -
which allows the status fetch to occur before it has finished.
This means that:
- a status fetch can access the target vnode either side of the exclusive
section of the modification
- the status fetch could start before the modification, yet finish after,
and vice-versa.
- the status fetch and the modification RPCs can complete in either order.
- the status fetch can return either the before or the after DV from the
modification.
- the status fetch might regress the locally cached DV.
Some of these are handled by the previous fix[1], but that's not sufficient
because it checks the DV it received against the DV it cached at the start
of the op, but the DV might've been updated in the meantime by a locally
generated modification op.
Fix this by the following means:
(1) Keep track of when we're performing a modification operation on a
vnode. This is done by marking vnode parameters with a 'modification'
note that causes the AFS_VNODE_MODIFYING flag to be set on the vnode
for the duration.
(2) Alter the speculation race detection to ignore speculative status
fetches if either the vnode is marked as being modified or the data
version number is not what we expected.
Note that whilst the "vnode modified" warning does get recovered from as it
causes the client to refetch the status at the next opportunity, it will
also invalidate the pagecache, so changes might get lost.
Fixes: a9e5c87ca7 ("afs: Fix speculative status fetch going out of order wrt to modifications")
Reported-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-and-reviewed-by: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://lore.kernel.org/r/160605082531.252452.14708077925602709042.stgit@warthog.procyon.org.uk/ [1]
Link: https://lore.kernel.org/linux-fsdevel/161961335926.39335.2552653972195467566.stgit@warthog.procyon.org.uk/ # v1
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Merge tag 'afs-netfs-lib-20210426' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs
Pull AFS updates from David Howells:
"Use the new netfs lib.
Begin the process of overhauling the use of the fscache API by AFS and
the introduction of support for features such as Transparent Huge
Pages (THPs).
- Add some support for THPs, including using core VM helper functions
to find details of pages.
- Use the ITER_XARRAY I/O iterator to mediate access to the pagecache
as this handles THPs and doesn't require allocation of large bvec
arrays.
- Delegate address_space read/pre-write I/O methods for AFS to the
netfs helper library. A method is provided to the library that
allows it to issue a read against the server.
This includes a change in use for PG_fscache (it now indicates a
DIO write in progress from the marked page), so a number of waits
need to be deployed for it.
- Split the core AFS writeback function to make it easier to modify
in future patches to handle writing to the cache. [This might
feasibly make more sense moved out into my fscache-iter branch].
I've tested these with "xfstests -g quick" against an AFS volume
(xfstests needs patching to make it work). With this, AFS without a
cache passes all expected xfstests; with a cache, there's an extra
failure, but that's also there before these patches. Fixing that
probably requires a greater overhaul (as can be found on my
fscache-iter branch, but that's for a later time).
Thanks should go to Marc Dionne and Jeff Altman of AuriStor for
exercising the patches in their test farm also"
Link: https://lore.kernel.org/lkml/3785063.1619482429@warthog.procyon.org.uk/
* tag 'afs-netfs-lib-20210426' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
afs: Use the netfs_write_begin() helper
afs: Use new netfs lib read helper API
afs: Use the fs operation ops to handle FetchData completion
afs: Prepare for use of THPs
afs: Extract writeback extension into its own function
afs: Wait on PG_fscache before modifying/releasing a page
afs: Use ITER_XARRAY for writing
afs: Set up the iov_iter before calling afs_extract_data()
afs: Log remote unmarshalling errors
afs: Don't truncate iter during data fetch
afs: Move key to afs_read struct
afs: Print the operation debug_id when logging an unexpected data version
afs: Pass page into dirty region helpers to provide THP size
afs: Disable use of the fscache I/O routines
Pull vfs inode type handling updates from Al Viro:
"We should never change the type bits of ->i_mode or the method tables
(->i_op and ->i_fop) of a live inode.
Unfortunately, not all filesystems took care to prevent that"
* 'work.inode-type-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
spufs: fix bogosity in S_ISGID handling
9p: missing chunk of "fs/9p: Don't update file type when updating file attributes"
openpromfs: don't do unlock_new_inode() until the new inode is set up
hostfs_mknod(): don't bother with init_special_inode()
cifs: have cifs_fattr_to_inode() refuse to change type on live inode
cifs: have ->mkdir() handle race with another client sanely
do_cifs_create(): don't set ->i_mode of something we had not created
gfs2: be careful with inode refresh
ocfs2_inode_lock_update(): make sure we don't change the type bits of i_mode
orangefs_inode_is_stale(): i_mode type bits do *not* form a bitmap...
vboxsf: don't allow to change the inode type
afs: Fix updating of i_mode due to 3rd party change
ceph: don't allow type or device number to change on non-I_NEW inodes
ceph: fix up error handling with snapdirs
new helper: inode_wrong_type()
afs_listxattr() lists all the available special afs xattrs (i.e. those in
the "afs.*" space), no matter what type of server we're dealing with. But
OpenAFS servers, for example, cannot deal with some of the extra-capable
attributes that AuriStor (YFS) servers provide. Unfortunately, the
presence of the afs.yfs.* attributes causes errors[1] for anything that
tries to read them if the server is of the wrong type.
Fix the problem by removing afs_listxattr() so that none of the special
xattrs are listed (AFS doesn't support xattrs). It does mean, however,
that getfattr won't list them, though they can still be accessed with
getxattr() and setxattr().
This can be tested with something like:
getfattr -d -m ".*" /afs/example.com/path/to/file
With this change, none of the afs.* attributes should be visible.
Changes:
ver #2:
- Hide all of the afs.* xattrs, not just the ACL ones.
Fixes: ae46578b96 ("afs: Get YFS ACLs and information through xattrs")
Reported-by: Gaja Sophie Peters <gaja.peters@math.uni-hamburg.de>
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Gaja Sophie Peters <gaja.peters@math.uni-hamburg.de>
Reviewed-by: Jeffrey Altman <jaltman@auristor.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: http://lists.infradead.org/pipermail/linux-afs/2021-March/003502.html [1]
Link: http://lists.infradead.org/pipermail/linux-afs/2021-March/003567.html # v1
Link: http://lists.infradead.org/pipermail/linux-afs/2021-March/003573.html # v2
If someone attempts to access YFS-related xattrs (e.g. afs.yfs.acl) on a
file on a non-YFS AFS server (such as OpenAFS), then the kernel will jump
to a NULL function pointer because the afs_fetch_acl_operation descriptor
doesn't point to a function for issuing an operation on a non-YFS
server[1].
Fix this by making afs_wait_for_operation() check that the issue_afs_rpc
method is set before jumping to it and setting -ENOTSUPP if not. This fix
also covers other potential operations that also only exist on YFS servers.
afs_xattr_get/set_yfs() then need to translate -ENOTSUPP to -ENODATA as the
former error is internal to the kernel.
The bug shows up as an oops like the following:
BUG: kernel NULL pointer dereference, address: 0000000000000000
[...]
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
[...]
Call Trace:
afs_wait_for_operation+0x83/0x1b0 [kafs]
afs_xattr_get_yfs+0xe6/0x270 [kafs]
__vfs_getxattr+0x59/0x80
vfs_getxattr+0x11c/0x140
getxattr+0x181/0x250
? __check_object_size+0x13f/0x150
? __fput+0x16d/0x250
__x64_sys_fgetxattr+0x64/0xb0
do_syscall_64+0x49/0xc0
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7fb120a9defe
This was triggered with "cp -a" which attempts to copy xattrs, including
afs ones, but is easier to reproduce with getfattr, e.g.:
getfattr -d -m ".*" /afs/openafs.org/
Fixes: e49c7b2f6d ("afs: Build an abstraction around an "operation" concept")
Reported-by: Gaja Sophie Peters <gaja.peters@math.uni-hamburg.de>
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Gaja Sophie Peters <gaja.peters@math.uni-hamburg.de>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
Reviewed-by: Jeffrey Altman <jaltman@auristor.com>
cc: linux-afs@lists.infradead.org
Link: http://lists.infradead.org/pipermail/linux-afs/2021-March/003498.html [1]
Link: http://lists.infradead.org/pipermail/linux-afs/2021-March/003566.html # v1
Link: http://lists.infradead.org/pipermail/linux-afs/2021-March/003572.html # v2
Fix afs_apply_status() to mask off the irrelevant bits from status->mode
when OR'ing them into i_mode. This can happen when a 3rd party chmod
occurs.
Also fix afs_inode_init_from_status() to mask off the mode bits when
initialising i_mode.
Fixes: 260a980317 ("[AFS]: Add "directory write" support.")
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Merge tag 'idmapped-mounts-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull idmapped mounts from Christian Brauner:
"This introduces idmapped mounts which has been in the making for some
time. Simply put, different mounts can expose the same file or
directory with different ownership. This initial implementation comes
with ports for fat, ext4 and with Christoph's port for xfs with more
filesystems being actively worked on by independent people and
maintainers.
Idmapping mounts handle a wide range of long standing use-cases. Here
are just a few:
- Idmapped mounts make it possible to easily share files between
multiple users or multiple machines especially in complex
scenarios. For example, idmapped mounts will be used in the
implementation of portable home directories in
systemd-homed.service(8) where they allow users to move their home
directory to an external storage device and use it on multiple
computers where they are assigned different uids and gids. This
effectively makes it possible to assign random uids and gids at
login time.
- It is possible to share files from the host with unprivileged
containers without having to change ownership permanently through
chown(2).
- It is possible to idmap a container's rootfs and without having to
mangle every file. For example, Chromebooks use it to share the
user's Download folder with their unprivileged containers in their
Linux subsystem.
- It is possible to share files between containers with
non-overlapping idmappings.
- Filesystem that lack a proper concept of ownership such as fat can
use idmapped mounts to implement discretionary access (DAC)
permission checking.
- They allow users to efficiently changing ownership on a per-mount
basis without having to (recursively) chown(2) all files. In
contrast to chown (2) changing ownership of large sets of files is
instantenous with idmapped mounts. This is especially useful when
ownership of a whole root filesystem of a virtual machine or
container is changed. With idmapped mounts a single syscall
mount_setattr syscall will be sufficient to change the ownership of
all files.
- Idmapped mounts always take the current ownership into account as
idmappings specify what a given uid or gid is supposed to be mapped
to. This contrasts with the chown(2) syscall which cannot by itself
take the current ownership of the files it changes into account. It
simply changes the ownership to the specified uid and gid. This is
especially problematic when recursively chown(2)ing a large set of
files which is commong with the aforementioned portable home
directory and container and vm scenario.
- Idmapped mounts allow to change ownership locally, restricting it
to specific mounts, and temporarily as the ownership changes only
apply as long as the mount exists.
Several userspace projects have either already put up patches and
pull-requests for this feature or will do so should you decide to pull
this:
- systemd: In a wide variety of scenarios but especially right away
in their implementation of portable home directories.
https://systemd.io/HOME_DIRECTORY/
- container runtimes: containerd, runC, LXD:To share data between
host and unprivileged containers, unprivileged and privileged
containers, etc. The pull request for idmapped mounts support in
containerd, the default Kubernetes runtime is already up for quite
a while now: https://github.com/containerd/containerd/pull/4734
- The virtio-fs developers and several users have expressed interest
in using this feature with virtual machines once virtio-fs is
ported.
- ChromeOS: Sharing host-directories with unprivileged containers.
I've tightly synced with all those projects and all of those listed
here have also expressed their need/desire for this feature on the
mailing list. For more info on how people use this there's a bunch of
talks about this too. Here's just two recent ones:
https://www.cncf.io/wp-content/uploads/2020/12/Rootless-Containers-in-Gitpod.pdfhttps://fosdem.org/2021/schedule/event/containers_idmap/
This comes with an extensive xfstests suite covering both ext4 and
xfs:
https://git.kernel.org/brauner/xfstests-dev/h/idmapped_mounts
It covers truncation, creation, opening, xattrs, vfscaps, setid
execution, setgid inheritance and more both with idmapped and
non-idmapped mounts. It already helped to discover an unrelated xfs
setgid inheritance bug which has since been fixed in mainline. It will
be sent for inclusion with the xfstests project should you decide to
merge this.
In order to support per-mount idmappings vfsmounts are marked with
user namespaces. The idmapping of the user namespace will be used to
map the ids of vfs objects when they are accessed through that mount.
By default all vfsmounts are marked with the initial user namespace.
The initial user namespace is used to indicate that a mount is not
idmapped. All operations behave as before and this is verified in the
testsuite.
Based on prior discussions we want to attach the whole user namespace
and not just a dedicated idmapping struct. This allows us to reuse all
the helpers that already exist for dealing with idmappings instead of
introducing a whole new range of helpers. In addition, if we decide in
the future that we are confident enough to enable unprivileged users
to setup idmapped mounts the permission checking can take into account
whether the caller is privileged in the user namespace the mount is
currently marked with.
The user namespace the mount will be marked with can be specified by
passing a file descriptor refering to the user namespace as an
argument to the new mount_setattr() syscall together with the new
MOUNT_ATTR_IDMAP flag. The system call follows the openat2() pattern
of extensibility.
The following conditions must be met in order to create an idmapped
mount:
- The caller must currently have the CAP_SYS_ADMIN capability in the
user namespace the underlying filesystem has been mounted in.
- The underlying filesystem must support idmapped mounts.
- The mount must not already be idmapped. This also implies that the
idmapping of a mount cannot be altered once it has been idmapped.
- The mount must be a detached/anonymous mount, i.e. it must have
been created by calling open_tree() with the OPEN_TREE_CLONE flag
and it must not already have been visible in the filesystem.
The last two points guarantee easier semantics for userspace and the
kernel and make the implementation significantly simpler.
By default vfsmounts are marked with the initial user namespace and no
behavioral or performance changes are observed.
The manpage with a detailed description can be found here:
1d7b902e28
In order to support idmapped mounts, filesystems need to be changed
and mark themselves with the FS_ALLOW_IDMAP flag in fs_flags. The
patches to convert individual filesystem are not very large or
complicated overall as can be seen from the included fat, ext4, and
xfs ports. Patches for other filesystems are actively worked on and
will be sent out separately. The xfstestsuite can be used to verify
that port has been done correctly.
The mount_setattr() syscall is motivated independent of the idmapped
mounts patches and it's been around since July 2019. One of the most
valuable features of the new mount api is the ability to perform
mounts based on file descriptors only.
Together with the lookup restrictions available in the openat2()
RESOLVE_* flag namespace which we added in v5.6 this is the first time
we are close to hardened and race-free (e.g. symlinks) mounting and
path resolution.
While userspace has started porting to the new mount api to mount
proper filesystems and create new bind-mounts it is currently not
possible to change mount options of an already existing bind mount in
the new mount api since the mount_setattr() syscall is missing.
With the addition of the mount_setattr() syscall we remove this last
restriction and userspace can now fully port to the new mount api,
covering every use-case the old mount api could. We also add the
crucial ability to recursively change mount options for a whole mount
tree, both removing and adding mount options at the same time. This
syscall has been requested multiple times by various people and
projects.
There is a simple tool available at
https://github.com/brauner/mount-idmapped
that allows to create idmapped mounts so people can play with this
patch series. I'll add support for the regular mount binary should you
decide to pull this in the following weeks:
Here's an example to a simple idmapped mount of another user's home
directory:
u1001@f2-vm:/$ sudo ./mount --idmap both:1000:1001:1 /home/ubuntu/ /mnt
u1001@f2-vm:/$ ls -al /home/ubuntu/
total 28
drwxr-xr-x 2 ubuntu ubuntu 4096 Oct 28 22:07 .
drwxr-xr-x 4 root root 4096 Oct 28 04:00 ..
-rw------- 1 ubuntu ubuntu 3154 Oct 28 22:12 .bash_history
-rw-r--r-- 1 ubuntu ubuntu 220 Feb 25 2020 .bash_logout
-rw-r--r-- 1 ubuntu ubuntu 3771 Feb 25 2020 .bashrc
-rw-r--r-- 1 ubuntu ubuntu 807 Feb 25 2020 .profile
-rw-r--r-- 1 ubuntu ubuntu 0 Oct 16 16:11 .sudo_as_admin_successful
-rw------- 1 ubuntu ubuntu 1144 Oct 28 00:43 .viminfo
u1001@f2-vm:/$ ls -al /mnt/
total 28
drwxr-xr-x 2 u1001 u1001 4096 Oct 28 22:07 .
drwxr-xr-x 29 root root 4096 Oct 28 22:01 ..
-rw------- 1 u1001 u1001 3154 Oct 28 22:12 .bash_history
-rw-r--r-- 1 u1001 u1001 220 Feb 25 2020 .bash_logout
-rw-r--r-- 1 u1001 u1001 3771 Feb 25 2020 .bashrc
-rw-r--r-- 1 u1001 u1001 807 Feb 25 2020 .profile
-rw-r--r-- 1 u1001 u1001 0 Oct 16 16:11 .sudo_as_admin_successful
-rw------- 1 u1001 u1001 1144 Oct 28 00:43 .viminfo
u1001@f2-vm:/$ touch /mnt/my-file
u1001@f2-vm:/$ setfacl -m u:1001:rwx /mnt/my-file
u1001@f2-vm:/$ sudo setcap -n 1001 cap_net_raw+ep /mnt/my-file
u1001@f2-vm:/$ ls -al /mnt/my-file
-rw-rwxr--+ 1 u1001 u1001 0 Oct 28 22:14 /mnt/my-file
u1001@f2-vm:/$ ls -al /home/ubuntu/my-file
-rw-rwxr--+ 1 ubuntu ubuntu 0 Oct 28 22:14 /home/ubuntu/my-file
u1001@f2-vm:/$ getfacl /mnt/my-file
getfacl: Removing leading '/' from absolute path names
# file: mnt/my-file
# owner: u1001
# group: u1001
user::rw-
user:u1001:rwx
group::rw-
mask::rwx
other::r--
u1001@f2-vm:/$ getfacl /home/ubuntu/my-file
getfacl: Removing leading '/' from absolute path names
# file: home/ubuntu/my-file
# owner: ubuntu
# group: ubuntu
user::rw-
user:ubuntu:rwx
group::rw-
mask::rwx
other::r--"
* tag 'idmapped-mounts-v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux: (41 commits)
xfs: remove the possibly unused mp variable in xfs_file_compat_ioctl
xfs: support idmapped mounts
ext4: support idmapped mounts
fat: handle idmapped mounts
tests: add mount_setattr() selftests
fs: introduce MOUNT_ATTR_IDMAP
fs: add mount_setattr()
fs: add attr_flags_to_mnt_flags helper
fs: split out functions to hold writers
namespace: only take read lock in do_reconfigure_mnt()
mount: make {lock,unlock}_mount_hash() static
namespace: take lock_mount_hash() directly when changing flags
nfs: do not export idmapped mounts
overlayfs: do not mount on top of idmapped mounts
ecryptfs: do not mount on top of idmapped mounts
ima: handle idmapped mounts
apparmor: handle idmapped mounts
fs: make helpers idmap mount aware
exec: handle idmapped mounts
would_dump: handle idmapped mounts
...
AF_RXRPC sockets use UDP ports in encap mode. This causes socket and dst
from an incoming packet to get stolen and attached to the UDP socket from
whence it is leaked when that socket is closed.
When a network namespace is removed, the wait for dst records to be cleaned
up happens before the cleanup of the rxrpc and UDP socket, meaning that the
wait never finishes.
Fix this by moving the rxrpc (and, by dependence, the afs) private
per-network namespace registrations to the device group rather than subsys
group. This allows cached rxrpc local endpoints to be cleared and their
UDP sockets closed before we try waiting for the dst records.
The symptom is that lines looking like the following:
unregister_netdevice: waiting for lo to become free
get emitted at regular intervals after running something like the
referenced syzbot test.
Thanks to Vadim for tracking this down and work out the fix.
Reported-by: syzbot+df400f2f24a1677cd7e0@syzkaller.appspotmail.com
Reported-by: Vadim Fedorenko <vfedorenko@novek.ru>
Fixes: 5271953cad ("rxrpc: Use the UDP encap_rcv hook")
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Vadim Fedorenko <vfedorenko@novek.ru>
Link: https://lore.kernel.org/r/161196443016.3868642.5577440140646403533.stgit@warthog.procyon.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Extend some inode methods with an additional user namespace argument. A
filesystem that is aware of idmapped mounts will receive the user
namespace the mount has been marked with. This can be used for
additional permission checking and also to enable filesystems to
translate between uids and gids if they need to. We have implemented all
relevant helpers in earlier patches.
As requested we simply extend the exisiting inode method instead of
introducing new ones. This is a little more code churn but it's mostly
mechanical and doesnt't leave us with additional inode methods.
Link: https://lore.kernel.org/r/20210121131959.646623-25-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
The generic_fillattr() helper fills in the basic attributes associated
with an inode. Enable it to handle idmapped mounts. If the inode is
accessed through an idmapped mount map it into the mount's user
namespace before we store the uid and gid. If the initial user namespace
is passed nothing changes so non-idmapped mounts will see identical
behavior as before.
Link: https://lore.kernel.org/r/20210121131959.646623-12-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
The posix acl permission checking helpers determine whether a caller is
privileged over an inode according to the acls associated with the
inode. Add helpers that make it possible to handle acls on idmapped
mounts.
The vfs and the filesystems targeted by this first iteration make use of
posix_acl_fix_xattr_from_user() and posix_acl_fix_xattr_to_user() to
translate basic posix access and default permissions such as the
ACL_USER and ACL_GROUP type according to the initial user namespace (or
the superblock's user namespace) to and from the caller's current user
namespace. Adapt these two helpers to handle idmapped mounts whereby we
either map from or into the mount's user namespace depending on in which
direction we're translating.
Similarly, cap_convert_nscap() is used by the vfs to translate user
namespace and non-user namespace aware filesystem capabilities from the
superblock's user namespace to the caller's user namespace. Enable it to
handle idmapped mounts by accounting for the mount's user namespace.
In addition the fileystems targeted in the first iteration of this patch
series make use of the posix_acl_chmod() and, posix_acl_update_mode()
helpers. Both helpers perform permission checks on the target inode. Let
them handle idmapped mounts. These two helpers are called when posix
acls are set by the respective filesystems to handle this case we extend
the ->set() method to take an additional user namespace argument to pass
the mount's user namespace down.
Link: https://lore.kernel.org/r/20210121131959.646623-9-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
The number of dirent records used by an AFS directory entry should be
calculated using the assumption that there is a 16-byte name field in the
first block, rather than a 20-byte name field (which is actually the case).
This miscalculation is historic and effectively standard, so we have to use
it.
The calculation we need to use is:
1 + (((strlen(name) + 1) + 15) >> 5)
where we are adding one to the strlen() result to account for the NUL
termination.
Fix this by the following means:
(1) Create an inline function to do the calculation for a given name
length.
(2) Use the function to calculate the number of records used for a dirent
in afs_dir_iterate_block().
Use this to move the over-end check out of the loop since it only
needs to be done once.
Further use this to only go through the loop for the 2nd+ records
composing an entry. The only test there now is for if the record is
allocated - and we already checked the first block at the top of the
outer loop.
(3) Add a max name length check in afs_dir_iterate_block().
(4) Make afs_edit_dir_add() and afs_edit_dir_remove() use the function
from (1) to calculate the number of blocks rather than doing it
incorrectly themselves.
Fixes: 63a4681ff3 ("afs: Locally edit directory data for mkdir/create/unlink/...")
Fixes: ^1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Marc Dionne <marc.dionne@auristor.com>
AFS has a structured layout in its directory contents (AFS dirs are
downloaded as files and parsed locally by the client for lookup/readdir).
The slots in the directory are defined by union afs_xdr_dirent. This,
however, only directly allows a name of a length that will fit into that
union. To support a longer name, the next 1-8 contiguous entries are
annexed to the first one and the name flows across these.
afs_dir_iterate_block() uses strnlen(), limited to the space to the end of
the page, to find out how long the name is. This worked fine until
6a39e62abb. With that commit, the compiler determines the size of the
array and asserts that the string fits inside that array. This is a
problem for AFS because we *expect* it to overflow one or more arrays.
A similar problem also occurs in afs_dir_scan_block() when a directory file
is being locally edited to avoid the need to redownload it. There strlen()
was being used safely because each page has the last byte set to 0 when the
file is downloaded and validated (in afs_dir_check_page()).
Fix this by changing the afs_xdr_dirent union name field to an
indeterminate-length array and dropping the overflow field.
(Note that whilst looking at this, I realised that the calculation of the
number of slots a dirent used is non-standard and not quite right, but I'll
address that in a separate patch.)
The issue can be triggered by something like:
touch /afs/example.com/thisisaveryveryverylongname
and it generates a report that looks like:
detected buffer overflow in strnlen
------------[ cut here ]------------
kernel BUG at lib/string.c:1149!
...
RIP: 0010:fortify_panic+0xf/0x11
...
Call Trace:
afs_dir_iterate_block+0x12b/0x35b
afs_dir_iterate+0x14e/0x1ce
afs_do_lookup+0x131/0x417
afs_lookup+0x24f/0x344
lookup_open.isra.0+0x1bb/0x27d
open_last_lookups+0x166/0x237
path_openat+0xe0/0x159
do_filp_open+0x48/0xa4
? kmem_cache_alloc+0xf5/0x16e
? __clear_close_on_exec+0x13/0x22
? _raw_spin_unlock+0xa/0xb
do_sys_openat2+0x72/0xde
do_sys_open+0x3b/0x58
do_syscall_64+0x2d/0x3a
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Fixes: 6a39e62abb ("lib: string.h: detect intra-object overflow in fortified string functions")
Reported-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Marc Dionne <marc.dionne@auristor.com>
cc: Daniel Axtens <dja@axtens.net>
There's a memory leak in afs_parse_source() whereby multiple source=
parameters overwrite fc->source in the fs_context struct without freeing
the previously recorded source.
Fix this by only permitting a single source parameter and rejecting with
an error all subsequent ones.
This was caught by syzbot with the kernel memory leak detector, showing
something like the following trace:
unreferenced object 0xffff888114375440 (size 32):
comm "repro", pid 5168, jiffies 4294923723 (age 569.948s)
backtrace:
slab_post_alloc_hook+0x42/0x79
__kmalloc_track_caller+0x125/0x16a
kmemdup_nul+0x24/0x3c
vfs_parse_fs_string+0x5a/0xa1
generic_parse_monolithic+0x9d/0xc5
do_new_mount+0x10d/0x15a
do_mount+0x5f/0x8e
__do_sys_mount+0xff/0x127
do_syscall_64+0x2d/0x3a
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Fixes: 13fcc68370 ("afs: Add fs_context support")
Reported-by: syzbot+86dc6632faaca40133ab@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When doing a lookup in a directory, the afs filesystem uses a bulk
status fetch to speculatively retrieve the statuses of up to 48 other
vnodes found in the same directory and it will then either update extant
inodes or create new ones - effectively doing 'lookup ahead'.
To avoid the possibility of deadlocking itself, however, the filesystem
doesn't lock all of those inodes; rather just the directory inode is
locked (by the VFS).
When the operation completes, afs_inode_init_from_status() or
afs_apply_status() is called, depending on whether the inode already
exists, to commit the new status.
A case exists, however, where the speculative status fetch operation may
straddle a modification operation on one of those vnodes. What can then
happen is that the speculative bulk status RPC retrieves the old status,
and whilst that is happening, the modification happens - which returns
an updated status, then the modification status is committed, then we
attempt to commit the speculative status.
This results in something like the following being seen in dmesg:
kAFS: vnode modified {100058:861} 8->9 YFS.InlineBulkStatus
showing that for vnode 861 on volume 100058, we saw YFS.InlineBulkStatus
say that the vnode had data version 8 when we'd already recorded version
9 due to a local modification. This was causing the cache to be
invalidated for that vnode when it shouldn't have been. If it happens
on a data file, this might lead to local changes being lost.
Fix this by ignoring speculative status updates if the data version
doesn't match the expected value.
Note that it is possible to get a DV regression if a volume gets
restored from a backup - but we should get a callback break in such a
case that should trigger a recheck anyway. It might be worth checking
the volume creation time in the volsync info and, if a change is
observed in that (as would happen on a restore), invalidate all caches
associated with the volume.
Fixes: 5cf9dd55a0 ("afs: Prospectively look up extra files when doing a single lookup")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When afs_write_end() is called with copied == 0, it tries to set the
dirty region, but there's no way to actually encode a 0-length region in
the encoding in page->private.
"0,0", for example, indicates a 1-byte region at offset 0. The maths
miscalculates this and sets it incorrectly.
Fix it to just do nothing but unlock and put the page in this case. We
don't actually need to mark the page dirty as nothing presumably
changed.
Fixes: 65dd2d6072 ("afs: Alter dirty range encoding in page->private")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The cleanup for the yfs_store_opaque_acl2_operation calls the wrong
function to destroy the ACL content buffer. It's an afs_acl struct, not
a yfs_acl struct - and the free function for latter may pass invalid
pointers to kfree().
Fix this by using the afs_acl_put() function. The yfs_acl_put()
function is then no longer used and can be removed.
general protection fault, probably for non-canonical address 0x7ebde00000000: 0000 [#1] SMP PTI
...
RIP: 0010:compound_head+0x0/0x11
...
Call Trace:
virt_to_cache+0x8/0x51
kfree+0x5d/0x79
yfs_free_opaque_acl+0x16/0x29
afs_put_operation+0x60/0x114
__vfs_setxattr+0x67/0x72
__vfs_setxattr_noperm+0x66/0xe9
vfs_setxattr+0x67/0xce
setxattr+0x14e/0x184
__do_sys_fsetxattr+0x66/0x8f
do_syscall_64+0x2d/0x3a
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Fixes: e49c7b2f6d ("afs: Build an abstraction around an "operation" concept")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When using the afs.yfs.acl xattr to change an AuriStor ACL, a warning
can be generated when the request is marshalled because the buffer
pointer isn't increased after adding the last element, thereby
triggering the check at the end if the ACL wasn't empty. This just
causes something like the following warning, but doesn't stop the call
from happening successfully:
kAFS: YFS.StoreOpaqueACL2: Request buffer underflow (36<108)
Fix this simply by increasing the count prior to the check.
Fixes: f5e4546347 ("afs: Implement YFS ACL setting")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The dirty region bounds stored in page->private on an afs page are 15 bits
on a 32-bit box and can, at most, represent a range of up to 32K within a
32K page with a resolution of 1 byte. This is a problem for powerpc32 with
64K pages enabled.
Further, transparent huge pages may get up to 2M, which will be a problem
for the afs filesystem on all 32-bit arches in the future.
Fix this by decreasing the resolution. For the moment, a 64K page will
have a resolution determined from PAGE_SIZE. In the future, the page will
need to be passed in to the helper functions so that the page size can be
assessed and the resolution determined dynamically.
Note that this might not be the ideal way to handle this, since it may
allow some leakage of undirtied zero bytes to the server's copy in the case
of a 3rd-party conflict. Fixing that would require a separately allocated
record and is a more complicated fix.
Fixes: 4343d00872 ("afs: Get rid of the afs_writeback record")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Fix afs_invalidatepage() to adjust the dirty region recorded in
page->private when truncating a page. If the dirty region is entirely
removed, then the private data is cleared and the page dirty state is
cleared.
Without this, if the page is truncated and then expanded again by truncate,
zeros from the expanded, but no-longer dirty region may get written back to
the server if the page gets laundered due to a conflicting 3rd-party write.
It mustn't, however, shorten the dirty region of the page if that page is
still mmapped and has been marked dirty by afs_page_mkwrite(), so a flag is
stored in page->private to record this.
Fixes: 4343d00872 ("afs: Get rid of the afs_writeback record")
Signed-off-by: David Howells <dhowells@redhat.com>
Currently, page->private on an afs page is used to store the range of
dirtied data within the page, where the range includes the lower bound, but
excludes the upper bound (e.g. 0-1 is a range covering a single byte).
This, however, requires a superfluous bit for the last-byte bound so that
on a 4KiB page, it can say 0-4096 to indicate the whole page, the idea
being that having both numbers the same would indicate an empty range.
This is unnecessary as the PG_private bit is clear if it's an empty range
(as is PG_dirty).
Alter the way the dirty range is encoded in page->private such that the
upper bound is reduced by 1 (e.g. 0-0 is then specified the same single
byte range mentioned above).
Applying this to both bounds frees up two bits, one of which can be used in
a future commit.
This allows the afs filesystem to be compiled on ppc32 with 64K pages;
without this, the following warnings are seen:
../fs/afs/internal.h: In function 'afs_page_dirty_to':
../fs/afs/internal.h:881:15: warning: right shift count >= width of type [-Wshift-count-overflow]
881 | return (priv >> __AFS_PAGE_PRIV_SHIFT) & __AFS_PAGE_PRIV_MASK;
| ^~
../fs/afs/internal.h: In function 'afs_page_dirty':
../fs/afs/internal.h:886:28: warning: left shift count >= width of type [-Wshift-count-overflow]
886 | return ((unsigned long)to << __AFS_PAGE_PRIV_SHIFT) | from;
| ^~
Fixes: 4343d00872 ("afs: Get rid of the afs_writeback record")
Signed-off-by: David Howells <dhowells@redhat.com>
The afs filesystem uses page->private to store the dirty range within a
page such that in the event of a conflicting 3rd-party write to the server,
we write back just the bits that got changed locally.
However, there are a couple of problems with this:
(1) I need a bit to note if the page might be mapped so that partial
invalidation doesn't shrink the range.
(2) There aren't necessarily sufficient bits to store the entire range of
data altered (say it's a 32-bit system with 64KiB pages or transparent
huge pages are in use).
So wrap the accesses in inline functions so that future commits can change
how this works.
Also move them out of the tracing header into the in-directory header.
There's not really any need for them to be in the tracing header.
Signed-off-by: David Howells <dhowells@redhat.com>
In afs, page->private is set to indicate the dirty region of a page. This
is done in afs_write_begin(), but that can't take account of whether the
copy into the page actually worked.
Fix this by moving the change of page->private into afs_write_end().
Fixes: 4343d00872 ("afs: Get rid of the afs_writeback record")
Signed-off-by: David Howells <dhowells@redhat.com>
