Not all inode attributes are supported by all filesystems, but for the
basic stats (which are returned by stat(2) and friends) all of them will
have some value, even if that doesn't reflect a real attribute of the file.
Btime is different, in that filesystems are free to report or not report a
value in statx. If the value is available, then STATX_BTIME bit is set in
stx_mask.
When caching the value of btime, remember the availability of the attribute
as well as the value (if available). This is done by using the
FUSE_I_BTIME bit in fuse_inode->state to indicate availability, while using
fuse_inode->inval_mask & STATX_BTIME to indicate the state of the cache
itself (i.e. set if cache is invalid, and cleared if cache is valid).
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Allow querying btime. When btime is requested in mask, then FUSE_STATX
request is sent. Otherwise keep using FUSE_GETATTR.
The userspace interface for statx matches that of the statx(2) API.
However there are limitations on how this interface is used:
- returned basic stats and btime are used, stx_attributes, etc. are
ignored
- always query basic stats and btime, regardless of what was requested
- requested sync type is ignored, the default is passed to the server
- if server returns with some attributes missing from the result_mask,
then no attributes will be cached
- btime is not cached yet (next patch will fix that)
For new inodes initialize fi->inval_mask to "all invalid", instead of "all
valid" as previously. Also only clear basic stats from inval_mask when
caching attributes. This will result in the caching logic not thinking
that btime is cached.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Next patch will introduce yet another type attribute reply. Add a macro
that can handle attribute timeouts for all of the structs.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
FOPEN_DIRECT_IO is usually set by fuse daemon to indicate need of strong
coherency, e.g. network filesystems. Thus shared mmap is disabled since it
leverages page cache and may write to it, which may cause inconsistence.
But FOPEN_DIRECT_IO can be used not for coherency but to reduce memory
footprint as well, e.g. reduce guest memory usage with virtiofs.
Therefore, add a new fuse init flag FUSE_DIRECT_IO_RELAX to relax
restrictions in that mode, currently, it allows shared mmap. One thing to
note is to make sure it doesn't break coherency in your use case.
Signed-off-by: Hao Xu <howeyxu@tencent.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Merge tag 'fuse-update-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse
Pull fuse updates from Miklos Szeredi:
- Fix regression in fileattr permission checking
- Fix possible hang during PID namespace destruction
- Add generic support for request extensions
- Add supplementary group list extension
- Add limited support for supplying supplementary groups in create
requests
- Documentation fixes
* tag 'fuse-update-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
fuse: add inode/permission checks to fileattr_get/fileattr_set
fuse: fix all W=1 kernel-doc warnings
fuse: in fuse_flush only wait if someone wants the return code
fuse: optional supplementary group in create requests
fuse: add request extension
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Merge tag 'fs.idmapped.v6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping
Pull vfs idmapping updates from Christian Brauner:
- Last cycle we introduced the dedicated struct mnt_idmap type for
mount idmapping and the required infrastucture in 256c8aed2b ("fs:
introduce dedicated idmap type for mounts"). As promised in last
cycle's pull request message this converts everything to rely on
struct mnt_idmap.
Currently we still pass around the plain namespace that was attached
to a mount. This is in general pretty convenient but it makes it easy
to conflate namespaces that are relevant on the filesystem with
namespaces that are relevant on the mount level. Especially for
non-vfs developers without detailed knowledge in this area this was a
potential source for bugs.
This finishes the conversion. Instead of passing the plain namespace
around this updates all places that currently take a pointer to a
mnt_userns with a pointer to struct mnt_idmap.
Now that the conversion is done all helpers down to the really
low-level helpers only accept a struct mnt_idmap argument instead of
two namespace arguments.
Conflating mount and other idmappings will now cause the compiler to
complain loudly thus eliminating the possibility of any bugs. This
makes it impossible for filesystem developers to mix up mount and
filesystem idmappings as they are two distinct types and require
distinct helpers that cannot be used interchangeably.
Everything associated with struct mnt_idmap is moved into a single
separate file. With that change no code can poke around in struct
mnt_idmap. It can only be interacted with through dedicated helpers.
That means all filesystems are and all of the vfs is completely
oblivious to the actual implementation of idmappings.
We are now also able to extend struct mnt_idmap as we see fit. For
example, we can decouple it completely from namespaces for users that
don't require or don't want to use them at all. We can also extend
the concept of idmappings so we can cover filesystem specific
requirements.
In combination with the vfs{g,u}id_t work we finished in v6.2 this
makes this feature substantially more robust and thus difficult to
implement wrong by a given filesystem and also protects the vfs.
- Enable idmapped mounts for tmpfs and fulfill a longstanding request.
A long-standing request from users had been to make it possible to
create idmapped mounts for tmpfs. For example, to share the host's
tmpfs mount between multiple sandboxes. This is a prerequisite for
some advanced Kubernetes cases. Systemd also has a range of use-cases
to increase service isolation. And there are more users of this.
However, with all of the other work going on this was way down on the
priority list but luckily someone other than ourselves picked this
up.
As usual the patch is tiny as all the infrastructure work had been
done multiple kernel releases ago. In addition to all the tests that
we already have I requested that Rodrigo add a dedicated tmpfs
testsuite for idmapped mounts to xfstests. It is to be included into
xfstests during the v6.3 development cycle. This should add a slew of
additional tests.
* tag 'fs.idmapped.v6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping: (26 commits)
shmem: support idmapped mounts for tmpfs
fs: move mnt_idmap
fs: port vfs{g,u}id helpers to mnt_idmap
fs: port fs{g,u}id helpers to mnt_idmap
fs: port i_{g,u}id_into_vfs{g,u}id() to mnt_idmap
fs: port i_{g,u}id_{needs_}update() to mnt_idmap
quota: port to mnt_idmap
fs: port privilege checking helpers to mnt_idmap
fs: port inode_owner_or_capable() to mnt_idmap
fs: port inode_init_owner() to mnt_idmap
fs: port acl to mnt_idmap
fs: port xattr to mnt_idmap
fs: port ->permission() to pass mnt_idmap
fs: port ->fileattr_set() to pass mnt_idmap
fs: port ->set_acl() to pass mnt_idmap
fs: port ->get_acl() to pass mnt_idmap
fs: port ->tmpfile() to pass mnt_idmap
fs: port ->rename() to pass mnt_idmap
fs: port ->mknod() to pass mnt_idmap
fs: port ->mkdir() to pass mnt_idmap
...
Permission to create an object (create, mkdir, symlink, mknod) needs to
take supplementary groups into account.
Add a supplementary group request extension. This can contain an arbitrary
number of group IDs and can be added to any request. This extension is not
added to any request by default.
Add FUSE_CREATE_SUPP_GROUP init flag to enable supplementary group info in
creation requests. This adds just a single supplementary group that
matches the parent group in the case described above. In other cases the
extension is not added.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Will need to add supplementary groups to create messages, so add the
general concept of a request extension. A request extension is appended to
the end of the main request. It has a header indicating the size and type
of the extension.
The create security context (fuse_secctx_*) is similar to the generic
request extension, so include that as well in a backward compatible manner.
Add the total extension length to the request header. The offset of the
extension block within the request can be calculated by:
inh->len - inh->total_extlen * 8
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This cycle we ported all filesystems to the new posix acl api. While
looking at further simplifications in this area to remove the last
remnants of the generic dummy posix acl handlers we realized that we
regressed fuse daemons that don't set FUSE_POSIX_ACL but still make use
of posix acls.
With the change to a dedicated posix acl api interacting with posix acls
doesn't go through the old xattr codepaths anymore and instead only
relies the get acl and set acl inode operations.
Before this change fuse daemons that don't set FUSE_POSIX_ACL were able
to get and set posix acl albeit with two caveats. First, that posix acls
aren't cached. And second, that they aren't used for permission checking
in the vfs.
We regressed that use-case as we currently refuse to retrieve any posix
acls if they aren't enabled via FUSE_POSIX_ACL. So older fuse daemons
would see a change in behavior.
We can restore the old behavior in multiple ways. We could change the
new posix acl api and look for a dedicated xattr handler and if we find
one prefer that over the dedicated posix acl api. That would break the
consistency of the new posix acl api so we would very much prefer not to
do that.
We could introduce a new ACL_*_CACHE sentinel that would instruct the
vfs permission checking codepath to not call into the filesystem and
ignore acls.
But a more straightforward fix for v6.2 is to do the same thing that
Overlayfs does and give fuse a separate get acl method for permission
checking. Overlayfs uses this to express different needs for vfs
permission lookup and acl based retrieval via the regular system call
path as well. Let fuse do the same for now. This way fuse can continue
to refuse to retrieve posix acls for daemons that don't set
FUSE_POSXI_ACL for permission checking while allowing a fuse server to
retrieve it via the usual system calls.
In the future, we could extend the get acl inode operation to not just
pass a simple boolean to indicate rcu lookup but instead make it a flag
argument. Then in addition to passing the information that this is an
rcu lookup to the filesystem we could also introduce a flag that tells
the filesystem that this is a request from the vfs to use these acls for
permission checking. Then fuse could refuse the get acl request for
permission checking when the daemon doesn't have FUSE_POSIX_ACL set in
the same get acl method. This would also help Overlayfs and allow us to
remove the second method for it as well.
But since that change is more invasive as we need to update the get acl
inode operation for multiple filesystems we should not do this as a fix
for v6.2. Instead we will do this for the v6.3 merge window.
Fwiw, since posix acls are now always correctly translated in the new
posix acl api we could also allow them to be used for daemons without
FUSE_POSIX_ACL that are not mounted on the host. But this is behavioral
change and again if dones should be done for v6.3. For now, let's just
restore the original behavior.
A nice side-effect of this change is that for fuse daemons with and
without FUSE_POSIX_ACL the same code is used for posix acls in a
backwards compatible way. This also means we can remove the legacy xattr
handlers completely. We've also added comments to explain the expected
behavior for daemons without FUSE_POSIX_ACL into the code.
Fixes: 318e66856d ("xattr: use posix acl api")
Signed-off-by: Seth Forshee (Digital Ocean) <sforshee@kernel.org>
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Convert to struct mnt_idmap.
Last cycle we merged the necessary infrastructure in
256c8aed2b ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.
Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.
Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.
Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Convert to struct mnt_idmap.
Last cycle we merged the necessary infrastructure in
256c8aed2b ("fs: introduce dedicated idmap type for mounts").
This is just the conversion to struct mnt_idmap.
Currently we still pass around the plain namespace that was attached to a
mount. This is in general pretty convenient but it makes it easy to
conflate namespaces that are relevant on the filesystem with namespaces
that are relevent on the mount level. Especially for non-vfs developers
without detailed knowledge in this area this can be a potential source for
bugs.
Once the conversion to struct mnt_idmap is done all helpers down to the
really low-level helpers will take a struct mnt_idmap argument instead of
two namespace arguments. This way it becomes impossible to conflate the two
eliminating the possibility of any bugs. All of the vfs and all filesystems
only operate on struct mnt_idmap.
Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
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Merge tag 'fuse-update-6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse
Pull fuse update from Miklos Szeredi:
- Allow some write requests to proceed in parallel
- Fix a performance problem with allow_sys_admin_access
- Add a special kind of invalidation that doesn't immediately purge
submounts
- On revalidation treat the target of rename(RENAME_NOREPLACE) the same
as open(O_EXCL)
- Use type safe helpers for some mnt_userns transformations
* tag 'fuse-update-6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
fuse: Rearrange fuse_allow_current_process checks
fuse: allow non-extending parallel direct writes on the same file
fuse: remove the unneeded result variable
fuse: port to vfs{g,u}id_t and associated helpers
fuse: Remove user_ns check for FUSE_DEV_IOC_CLONE
fuse: always revalidate rename target dentry
fuse: add "expire only" mode to FUSE_NOTIFY_INVAL_ENTRY
fs/fuse: Replace kmap() with kmap_local_page()
This is a followup to a previous commit of mine [0], which added the
allow_sys_admin_access && capable(CAP_SYS_ADMIN) check. This patch
rearranges the order of checks in fuse_allow_current_process without
changing functionality.
Commit 9ccf47b26b ("fuse: Add module param for CAP_SYS_ADMIN access
bypassing allow_other") added allow_sys_admin_access &&
capable(CAP_SYS_ADMIN) check to the beginning of the function, with the
reasoning that allow_sys_admin_access should be an 'escape hatch' for users
with CAP_SYS_ADMIN, allowing them to skip any subsequent checks.
However, placing this new check first results in many capable() calls when
allow_sys_admin_access is set, where another check would've also returned
1. This can be problematic when a BPF program is tracing capable() calls.
At Meta we ran into such a scenario recently. On a host where
allow_sys_admin_access is set but most of the FUSE access is from processes
which would pass other checks - i.e. they don't need CAP_SYS_ADMIN 'escape
hatch' - this results in an unnecessary capable() call for each fs op. We
also have a daemon tracing capable() with BPF and doing some data
collection, so tracing these extraneous capable() calls has the potential
to regress performance for an application doing many FUSE ops.
So rearrange the order of these checks such that CAP_SYS_ADMIN 'escape
hatch' is checked last. Add a small helper, fuse_permissible_uidgid, to
make the logic easier to understand. Previously, if allow_other is set on
the fuse_conn, uid/git checking doesn't happen as current_in_userns result
is returned. These semantics are maintained here: fuse_permissible_uidgid
check only happens if allow_other is not set.
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Add a flag to entry expiration that lets the filesystem expire a dentry
without kicking it out from the cache immediately.
This makes a difference for overmounted dentries, where plain invalidation
would detach all submounts before dropping the dentry from the cache. If
only expiry is set on the dentry, then any overmounts are left alone and
until ->d_revalidate() is called.
Note: ->d_revalidate() is not called for the case of following a submount,
so invalidation will only be triggered for the non-overmounted case. The
dentry could also be mounted in a different mount instance, in which case
any submounts will still be detached.
Suggested-by: Jakob Blomer <jblomer@cern.ch>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
The current way of setting and getting posix acls through the generic
xattr interface is error prone and type unsafe. The vfs needs to
interpret and fixup posix acls before storing or reporting it to
userspace. Various hacks exist to make this work. The code is hard to
understand and difficult to maintain in it's current form. Instead of
making this work by hacking posix acls through xattr handlers we are
building a dedicated posix acl api around the get and set inode
operations. This removes a lot of hackiness and makes the codepaths
easier to maintain. A lot of background can be found in [1].
Since some filesystem rely on the dentry being available to them when
setting posix acls (e.g., 9p and cifs) they cannot rely on set acl inode
operation. But since ->set_acl() is required in order to use the generic
posix acl xattr handlers filesystems that do not implement this inode
operation cannot use the handler and need to implement their own
dedicated posix acl handlers.
Update the ->set_acl() inode method to take a dentry argument. This
allows all filesystems to rely on ->set_acl().
As far as I can tell all codepaths can be switched to rely on the dentry
instead of just the inode. Note that the original motivation for passing
the dentry separate from the inode instead of just the dentry in the
xattr handlers was because of security modules that call
security_d_instantiate(). This hook is called during
d_instantiate_new(), d_add(), __d_instantiate_anon(), and
d_splice_alias() to initialize the inode's security context and possibly
to set security.* xattrs. Since this only affects security.* xattrs this
is completely irrelevant for posix acls.
Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1]
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
This is basically equivalent to the FUSE_CREATE operation which creates and
opens a regular file.
Add a new FUSE_TMPFILE operation, otherwise just reuse the protocol and the
code for FUSE_CREATE.
Acked-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
All filesystems have now been converted to use ->readahead, so
remove the ->readpages operation and fix all the comments that
used to refer to it.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
In FOPEN_DIRECT_IO mode, fuse_file_write_iter() calls
fuse_direct_write_iter(), which normally calls fuse_direct_io(), which then
imports the write buffer with fuse_get_user_pages(), which uses
iov_iter_get_pages() to grab references to userspace pages instead of
actually copying memory.
On the filesystem device side, these pages can then either be read to
userspace (via fuse_dev_read()), or splice()d over into a pipe using
fuse_dev_splice_read() as pipe buffers with &nosteal_pipe_buf_ops.
This is wrong because after fuse_dev_do_read() unlocks the FUSE request,
the userspace filesystem can mark the request as completed, causing write()
to return. At that point, the userspace filesystem should no longer have
access to the pipe buffer.
Fix by copying pages coming from the user address space to new pipe
buffers.
Reported-by: Jann Horn <jannh@google.com>
Fixes: c3021629a0 ("fuse: support splice() reading from fuse device")
Cc: <stable@vger.kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
When the per inode DAX hint changes while the file is still *opened*, it
is quite complicated and maybe fragile to dynamically change the DAX
state.
Hence mark the inode and corresponding dentries as DONE_CACHE once the
per inode DAX hint changes, so that the inode instance will be evicted
and freed as soon as possible once the file is closed and the last
reference to the inode is put. And then when the file gets reopened next
time, the new instantiated inode will reflect the new DAX state.
In summary, when the per inode DAX hint changes for an *opened* file, the
DAX state of the file won't be updated until this file is closed and
reopened later.
Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Among the FUSE_INIT phase, client shall advertise per inode DAX if it's
mounted with "dax=inode". Then server is aware that client is in per
inode DAX mode, and will construct per-inode DAX attribute accordingly.
Server shall also advertise support for per inode DAX. If server doesn't
support it while client is mounted with "dax=inode", client will
silently fallback to "dax=never" since "dax=inode" is advisory only.
Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
DAX may be limited in some specific situation. When the number of usable
DAX windows is under watermark, the recalim routine will be triggered to
reclaim some DAX windows. It may have a negative impact on the
performance, since some processes may need to wait for DAX windows to be
recalimed and reused then. To mitigate the performance degradation, the
overall DAX window need to be expanded larger.
However, simply expanding the DAX window may not be a good deal in some
scenario. To maintain one DAX window chunk (i.e., 2MB in size), 32KB
(512 * 64 bytes) memory footprint will be consumed for page descriptors
inside guest, which is greater than the memory footprint if it uses
guest page cache when DAX disabled. Thus it'd better disable DAX for
those files smaller than 32KB, to reduce the demand for DAX window and
thus avoid the unworthy memory overhead.
Per inode DAX feature is introduced to address this issue, by offering a
finer grained control for dax to users, trying to achieve a balance
between performance and memory overhead.
The FUSE_ATTR_DAX flag in FUSE_LOOKUP reply is used to indicate whether
DAX should be enabled or not for corresponding file. Currently the state
whether DAX is enabled or not for the file is initialized only when
inode is instantiated.
Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
We add 'always', 'never', and 'inode' (default). '-o dax' continues to
operate the same which is equivalent to 'always'.
The following behavior is consistent with that on ext4/xfs:
- The default behavior (when neither '-o dax' nor
'-o dax=always|never|inode' option is specified) is equal to 'inode'
mode, while 'dax=inode' won't be printed among the mount option list.
- The 'inode' mode is only advisory. It will silently fallback to 'never'
mode if fuse server doesn't support that.
Also noted that by the time of this commit, 'inode' mode is actually equal
to 'always' mode, before the per inode DAX flag is introduced in the
following patch.
Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
When a new inode is created, send its security context to server along with
creation request (FUSE_CREAT, FUSE_MKNOD, FUSE_MKDIR and FUSE_SYMLINK).
This gives server an opportunity to create new file and set security
context (possibly atomically). In all the configurations it might not be
possible to set context atomically.
Like nfs and ceph, use security_dentry_init_security() to dermine security
context of inode and send it with create, mkdir, mknod, and symlink
requests.
Following is the information sent to server.
fuse_sectx_header, fuse_secctx, xattr_name, security_context
- struct fuse_secctx_header
This contains total number of security contexts being sent and total
size of all the security contexts (including size of
fuse_secctx_header).
- struct fuse_secctx
This contains size of security context which follows this structure.
There is one fuse_secctx instance per security context.
- xattr name string
This string represents name of xattr which should be used while setting
security context.
- security context
This is the actual security context whose size is specified in
fuse_secctx struct.
Also add the FUSE_SECURITY_CTX flag for the `flags` field of the
fuse_init_out struct. When this flag is set the kernel will append the
security context for a newly created inode to the request (create, mkdir,
mknod, and symlink). The server is responsible for ensuring that the inode
appears atomically (preferrably) with the requested security context.
For example, If the server is using SELinux and backed by a "real" linux
file system that supports extended attributes it can write the security
context value to /proc/thread-self/attr/fscreate before making the syscall
to create the inode.
This patch is based on patch from Chirantan Ekbote <chirantan@chromium.org>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
fuse_update_attributes() refreshes metadata for internal use.
Each use needs a particular set of attributes to be refreshed, but
currently that cannot be expressed and all but atime are refreshed.
Add a mask argument, which lets fuse_update_get_attr() to decide based on
the cache_mask and the inval_mask whether a GETATTR call is needed or not.
Reported-by: Yongji Xie <xieyongji@bytedance.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
If writeback_cache is enabled, then the size, mtime and ctime attributes of
regular files are always valid in the kernel's cache. They are retrieved
from userspace only when the inode is freshly looked up.
Add a more generic "cache_mask", that indicates which attributes are
currently valid in cache.
This patch doesn't change behavior.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Extend the fuse_write_update_attr() helper to invalidate cached attributes
after a write.
This has already been done in all cases except in fuse_notify_store(), so
this is mostly a cleanup.
fuse_direct_write_iter() calls fuse_direct_IO() which already calls
fuse_write_update_attr(), so don't repeat that again in the former.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This function already updates the attr_version in fuse_inode, regardless of
whether the size was changed or not.
Rename the helper to fuse_write_update_attr() to reflect the more generic
nature.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Only invalidate attributes that the operation might have changed.
Introduce two constants for common combinations of changed attributes:
FUSE_STATX_MODIFY: file contents are modified but not size
FUSE_STATX_MODSIZE: size and/or file contents modified
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
In writeback cache mode mtime/ctime updates are cached, and flushed to the
server using the ->write_inode() callback.
Closing the file will result in a dirty inode being immediately written,
but in other cases the inode can remain dirty after all references are
dropped. This result in the inode being written back from reclaim, which
can deadlock on a regular allocation while the request is being served.
The usual mechanisms (GFP_NOFS/PF_MEMALLOC*) don't work for FUSE, because
serving a request involves unrelated userspace process(es).
Instead do the same as for dirty pages: make sure the inode is written
before the last reference is gone.
- fallocate(2)/copy_file_range(2): these call file_update_time() or
file_modified(), so flush the inode before returning from the call
- unlink(2), link(2) and rename(2): these call fuse_update_ctime(), so
flush the ctime directly from this helper
Reported-by: chenguanyou <chenguanyou@xiaomi.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
The ->put_super callback is called from generic_shutdown_super() in case of
a fully initialized sb. This is called from kill_***_super(), which is
called from ->kill_sb instances.
Fuse uses ->put_super to destroy the fs specific fuse_mount and drop the
reference to the fuse_conn, while it does the same on each error case
during sb setup.
This patch moves the destruction from fuse_put_super() to
fuse_mount_destroy(), called at the end of all ->kill_sb instances. A
follup patch will clean up the error paths.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Merge tag 'fuse-update-5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse
Pull fuse updates from Miklos Szeredi:
- Allow mounting an active fuse device. Previously the fuse device
would always be mounted during initialization, and sharing a fuse
superblock was only possible through mount or namespace cloning
- Fix data flushing in syncfs (virtiofs only)
- Fix data flushing in copy_file_range()
- Fix a possible deadlock in atomic O_TRUNC
- Misc fixes and cleanups
* tag 'fuse-update-5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
fuse: remove unused arg in fuse_write_file_get()
fuse: wait for writepages in syncfs
fuse: flush extending writes
fuse: truncate pagecache on atomic_o_trunc
fuse: allow sharing existing sb
fuse: move fget() to fuse_get_tree()
fuse: move option checking into fuse_fill_super()
fuse: name fs_context consistently
fuse: fix use after free in fuse_read_interrupt()
In case of fuse the MM subsystem doesn't guarantee that page writeback
completes by the time ->sync_fs() is called. This is because fuse
completes page writeback immediately to prevent DoS of memory reclaim by
the userspace file server.
This means that fuse itself must ensure that writes are synced before
sending the SYNCFS request to the server.
Introduce sync buckets, that hold a counter for the number of outstanding
write requests. On syncfs replace the current bucket with a new one and
wait until the old bucket's counter goes down to zero.
It is possible to have multiple syncfs calls in parallel, in which case
there could be more than one waited-on buckets. Descendant buckets must
not complete until the parent completes. Add a count to the child (new)
bucket until the (parent) old bucket completes.
Use RCU protection to dereference the current bucket and to wake up an
emptied bucket. Use fc->lock to protect against parallel assignments to
the current bucket.
This leaves just the counter to be a possible scalability issue. The
fc->num_waiting counter has a similar issue, so both should be addressed at
the same time.
Reported-by: Amir Goldstein <amir73il@gmail.com>
Fixes: 2d82ab251e ("virtiofs: propagate sync() to file server")
Cc: <stable@vger.kernel.org> # v5.14
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Merge tag 'ovl-update-5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs
Pull overlayfs update from Miklos Szeredi:
- Copy up immutable/append/sync/noatime attributes (Amir Goldstein)
- Improve performance by enabling RCU lookup.
- Misc fixes and improvements
The reason this touches so many files is that the ->get_acl() method now
gets a "bool rcu" argument. The ->get_acl() API was updated based on
comments from Al and Linus:
Link: https://lore.kernel.org/linux-fsdevel/CAJfpeguQxpd6Wgc0Jd3ks77zcsAv_bn0q17L3VNnnmPKu11t8A@mail.gmail.com/
* tag 'ovl-update-5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
ovl: enable RCU'd ->get_acl()
vfs: add rcu argument to ->get_acl() callback
ovl: fix BUG_ON() in may_delete() when called from ovl_cleanup()
ovl: use kvalloc in xattr copy-up
ovl: update ctime when changing fileattr
ovl: skip checking lower file's i_writecount on truncate
ovl: relax lookup error on mismatch origin ftype
ovl: do not set overlay.opaque for new directories
ovl: add ovl_allow_offline_changes() helper
ovl: disable decoding null uuid with redirect_dir
ovl: consistent behavior for immutable/append-only inodes
ovl: copy up sync/noatime fileattr flags
ovl: pass ovl_fs to ovl_check_setxattr()
fs: add generic helper for filling statx attribute flags
Add a rcu argument to the ->get_acl() callback to allow
get_cached_acl_rcu() to call the ->get_acl() method in the next patch.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Use invalidate_lock instead of fuse's private i_mmap_sem. The intended
purpose is exactly the same. By this conversion we fix a long standing
race between hole punching and read(2) / readahead(2) paths that can
lead to stale page cache contents.
CC: Miklos Szeredi <miklos@szeredi.hu>
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Server responds to LOOKUP and other ops (READDIRPLUS/CREATE/MKNOD/...)
with ourarg containing nodeid and generation.
If a fuse inode is found in inode cache with the same nodeid but different
generation, the existing fuse inode should be unhashed and marked "bad" and
a new inode with the new generation should be hashed instead.
This can happen, for example, with passhrough fuse filesystem that returns
the real filesystem ino/generation on lookup and where real inode numbers
can get recycled due to real files being unlinked not via the fuse
passthrough filesystem.
With current code, this situation will not be detected and an old fuse
dentry that used to point to an older generation real inode, can be used to
access a completely new inode, which should be accessed only via the new
dentry.
Note that because the FORGET message carries the nodeid w/o generation, the
server should wait to get FORGET counts for the nlookup counts of the old
and reused inodes combined, before it can free the resources associated to
that nodeid.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This function used to be called from fuse_dentry_automount(). This code
was moved to fuse_get_tree_submount() in the same file since then. It
is unlikely there will ever be another user. No need to be extern in
this case.
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
The creation of a submount is open-coded in fuse_dentry_automount().
This brings a lot of complexity and we recently had to fix bugs
because we weren't setting SB_BORN or because we were unlocking
sb->s_umount before sb was fully configured. Most of these could
have been avoided by using the mount API instead of open-coding.
Basically, this means coming up with a proper ->get_tree()
implementation for submounts and call vfs_get_tree(), or better
fc_mount().
The creation of the superblock for submounts is quite different from
the root mount. Especially, it doesn't require to allocate a FUSE
filesystem context, nor to parse parameters.
Introduce a dedicated context ops for submounts to make this clear.
This is just a placeholder for now, fuse_get_tree_submount() will
be populated in a subsequent patch.
Only visible change is that we stop allocating/freeing a useless FUSE
filesystem context with submounts.
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Even if POSIX doesn't mandate it, linux users legitimately expect sync() to
flush all data and metadata to physical storage when it is located on the
same system. This isn't happening with virtiofs though: sync() inside the
guest returns right away even though data still needs to be flushed from
the host page cache.
This is easily demonstrated by doing the following in the guest:
$ dd if=/dev/zero of=/mnt/foo bs=1M count=5K ; strace -T -e sync sync
5120+0 records in
5120+0 records out
5368709120 bytes (5.4 GB, 5.0 GiB) copied, 5.22224 s, 1.0 GB/s
sync() = 0 <0.024068>
and start the following in the host when the 'dd' command completes
in the guest:
$ strace -T -e fsync /usr/bin/sync virtiofs/foo
fsync(3) = 0 <10.371640>
There are no good reasons not to honor the expected behavior of sync()
actually: it gives an unrealistic impression that virtiofs is super fast
and that data has safely landed on HW, which isn't the case obviously.
Implement a ->sync_fs() superblock operation that sends a new FUSE_SYNCFS
request type for this purpose. Provision a 64-bit placeholder for possible
future extensions. Since the file server cannot handle the wait == 0 case,
we skip it to avoid a gratuitous roundtrip. Note that this is
per-superblock: a FUSE_SYNCFS is send for the root mount and for each
submount.
Like with FUSE_FSYNC and FUSE_FSYNCDIR, lack of support for FUSE_SYNCFS in
the file server is treated as permanent success. This ensures
compatibility with older file servers: the client will get the current
behavior of sync() not being propagated to the file server.
Note that such an operation allows the file server to DoS sync(). Since a
typical FUSE file server is an untrusted piece of software running in
userspace, this is disabled by default. Only enable it with virtiofs for
now since virtiofsd is supposedly trusted by the guest kernel.
Reported-by: Robert Krawitz <rlk@redhat.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
If an incoming FUSE request can't fit on the virtqueue, the request is
placed onto a workqueue so a worker can try to resubmit it later where
there will (hopefully) be space for it next time.
This is fine for requests that aren't larger than a virtqueue's maximum
capacity. However, if a request's size exceeds the maximum capacity of the
virtqueue (even if the virtqueue is empty), it will be doomed to a life of
being placed on the workqueue, removed, discovered it won't fit, and placed
on the workqueue yet again.
Furthermore, from section 2.6.5.3.1 (Driver Requirements: Indirect
Descriptors) of the virtio spec:
"A driver MUST NOT create a descriptor chain longer than the Queue
Size of the device."
To fix this, limit the number of pages FUSE will use for an overall
request. This way, each request can realistically fit on the virtqueue
when it is decomposed into a scattergather list and avoid violating section
2.6.5.3.1 of the virtio spec.
Signed-off-by: Connor Kuehl <ckuehl@redhat.com>
Reviewed-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fuse client needs to send additional information to file server when it
calls SETXATTR(system.posix_acl_access), so add extra flags field to the
structure.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
There are two modes for write(2) and friends in fuse:
a) write through (update page cache, send sync WRITE request to userspace)
b) buffered write (update page cache, async writeout later)
The write through method kept all the page cache pages locked that were
used for the request. Keeping more than one page locked is deadlock prone
and Qian Cai demonstrated this with trinity fuzzing.
The reason for keeping the pages locked is that concurrent mapped reads
shouldn't try to pull possibly stale data into the page cache.
For full page writes, the easy way to fix this is to make the cached page
be the authoritative source by marking the page PG_uptodate immediately.
After this the page can be safely unlocked, since mapped/cached reads will
take the written data from the cache.
Concurrent mapped writes will now cause data in the original WRITE request
to be updated; this however doesn't cause any data inconsistency and this
scenario should be exceedingly rare anyway.
If the WRITE request returns with an error in the above case, currently the
page is not marked uptodate; this means that a concurrent read will always
read consistent data. After this patch the page is uptodate between
writing to the cache and receiving the error: there's window where a cached
read will read the wrong data. While theoretically this could be a
regression, it is unlikely to be one in practice, since this is normal for
buffered writes.
In case of a partial page write to an already uptodate page the locking is
also unnecessary, with the above caveats.
Partial write of a not uptodate page still needs to be handled. One way
would be to read the complete page before doing the write. This is not
possible, since it might break filesystems that don't expect any READ
requests when the file was opened O_WRONLY.
The other solution is to serialize the synchronous write with reads from
the partial pages. The easiest way to do this is to keep the partial pages
locked. The problem is that a write() may involve two such pages (one head
and one tail). This patch fixes it by only locking the partial tail page.
If there's a partial head page as well, then split that off as a separate
WRITE request.
Reported-by: Qian Cai <cai@lca.pw>
Link: https://lore.kernel.org/linux-fsdevel/4794a3fa3742a5e84fb0f934944204b55730829b.camel@lca.pw/
Fixes: ea9b9907b8 ("fuse: implement perform_write")
Cc: <stable@vger.kernel.org> # v2.6.26
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Since fuse just passes ioctl args through to/from server, converting to the
fileattr API is more involved, than most other filesystems.
Both .fileattr_set() and .fileattr_get() need to obtain an open file to
operate on. The simplest way is with the following sequence:
FUSE_OPEN
FUSE_IOCTL
FUSE_RELEASE
If this turns out to be a performance problem, it could be optimized for
the case when there's already a file (any file) open for the inode.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
