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Merge tag 'virtio-fs-5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse
Pull fuse virtio-fs support from Miklos Szeredi:
"Virtio-fs allows exporting directory trees on the host and mounting
them in guest(s).
This isn't actually a new filesystem, but a glue layer between the
fuse filesystem and a virtio based back-end.
It's similar in functionality to the existing virtio-9p solution, but
significantly faster in benchmarks and has better POSIX compliance.
Further permformance improvements can be achieved by sharing the page
cache between host and guest, allowing for faster I/O and reduced
memory use.
Kata Containers have been including the out-of-tree virtio-fs (with
the shared page cache patches as well) since version 1.7 as an
experimental feature. They have been active in development and plan to
switch from virtio-9p to virtio-fs as their default solution. There
has been interest from other sources as well.
The userspace infrastructure is slated to be merged into qemu once the
kernel part hits mainline.
This was developed by Vivek Goyal, Dave Gilbert and Stefan Hajnoczi"
* tag 'virtio-fs-5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
virtio-fs: add virtiofs filesystem
virtio-fs: add Documentation/filesystems/virtiofs.rst
fuse: reserve values for mapping protocol
Fix sparse warning:
fs/fuse/dev.c:468:6: warning: symbol 'fuse_args_to_req' was not declared. Should it be static?
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Fixes: 68583165f9 ("fuse: add pages to fuse_args")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This function has been made static, which now causes a compile-time
warning:
WARNING: "fuse_put_request" [vmlinux] is a static EXPORT_SYMBOL_GPL
Remove the unneeded export.
Fixes: 66abc3599c ("fuse: unexport request ops")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
account per-file, dentry, and inode data
blockdev/superblock and temporary per-request data was left alone, as
this usually isn't accounted
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Implements the optimization noted in commit f75fdf22b0 ("fuse: don't
use ->d_time"), as the additional memory can be significant. (In
particular, on SLAB configurations this 8-byte alloc becomes 32 bytes).
Per-dentry, this can consume significant memory.
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
unlock_page() was missing in case of an already in-flight write against the
same page.
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Fixes: ff17be0864 ("fuse: writepage: skip already in flight")
Cc: <stable@vger.kernel.org> # v3.13
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Add a basic file system module for virtio-fs. This does not yet contain
shared data support between host and guest or metadata coherency speedups.
However it is already significantly faster than virtio-9p.
Design Overview
===============
With the goal of designing something with better performance and local file
system semantics, a bunch of ideas were proposed.
- Use fuse protocol (instead of 9p) for communication between guest and
host. Guest kernel will be fuse client and a fuse server will run on
host to serve the requests.
- For data access inside guest, mmap portion of file in QEMU address space
and guest accesses this memory using dax. That way guest page cache is
bypassed and there is only one copy of data (on host). This will also
enable mmap(MAP_SHARED) between guests.
- For metadata coherency, there is a shared memory region which contains
version number associated with metadata and any guest changing metadata
updates version number and other guests refresh metadata on next access.
This is yet to be implemented.
How virtio-fs differs from existing approaches
==============================================
The unique idea behind virtio-fs is to take advantage of the co-location of
the virtual machine and hypervisor to avoid communication (vmexits).
DAX allows file contents to be accessed without communication with the
hypervisor. The shared memory region for metadata avoids communication in
the common case where metadata is unchanged.
By replacing expensive communication with cheaper shared memory accesses,
we expect to achieve better performance than approaches based on network
file system protocols. In addition, this also makes it easier to achieve
local file system semantics (coherency).
These techniques are not applicable to network file system protocols since
the communications channel is bypassed by taking advantage of shared memory
on a local machine. This is why we decided to build virtio-fs rather than
focus on 9P or NFS.
Caching Modes
=============
Like virtio-9p, different caching modes are supported which determine the
coherency level as well. The “cache=FOO” and “writeback” options control
the level of coherence between the guest and host filesystems.
- cache=none
metadata, data and pathname lookup are not cached in guest. They are
always fetched from host and any changes are immediately pushed to host.
- cache=always
metadata, data and pathname lookup are cached in guest and never expire.
- cache=auto
metadata and pathname lookup cache expires after a configured amount of
time (default is 1 second). Data is cached while the file is open
(close to open consistency).
- writeback/no_writeback
These options control the writeback strategy. If writeback is disabled,
then normal writes will immediately be synchronized with the host fs.
If writeback is enabled, then writes may be cached in the guest until
the file is closed or an fsync(2) performed. This option has no effect
on mmap-ed writes or writes going through the DAX mechanism.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
virtio-fs does not support aborting requests which are being
processed. That is requests which have been sent to fuse daemon on host.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Don't hold onto dentry in lru list if need to re-lookup it anyway at next
access. Only do this if explicitly enabled, otherwise it could result in
performance regression.
More advanced version of this patch would periodically flush out dentries
from the lru which have gone stale.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
As of now fuse_dev_alloc() both allocates a fuse device and installs it in
fuse_conn list. fuse_dev_alloc() can fail if fuse_device allocation fails.
virtio-fs needs to initialize multiple fuse devices (one per virtio queue).
It initializes one fuse device as part of call to fuse_fill_super_common()
and rest of the devices are allocated and installed after that.
But, we can't afford to fail after calling fuse_fill_super_common() as we
don't have a way to undo all the actions done by fuse_fill_super_common().
So to avoid failures after the call to fuse_fill_super_common(),
pre-allocate all fuse devices early and install them into fuse connection
later.
This patch provides two separate helpers for fuse device allocation and
fuse device installation in fuse_conn.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
The /dev/fuse device uses fiq->waitq and fasync to signal that requests are
available. These mechanisms do not apply to virtio-fs. This patch
introduces callbacks so alternative behavior can be used.
Note that queue_interrupt() changes along these lines:
spin_lock(&fiq->waitq.lock);
wake_up_locked(&fiq->waitq);
+ kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
spin_unlock(&fiq->waitq.lock);
- kill_fasync(&fiq->fasync, SIGIO, POLL_IN);
Since queue_request() and queue_forget() also call kill_fasync() inside
the spinlock this should be safe.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
fuse_fill_super() includes code to process the fd= option and link the
struct fuse_dev to the fd's struct file. In virtio-fs there is no file
descriptor because /dev/fuse is not used.
This patch extracts fuse_fill_super_common() so that both classic fuse and
virtio-fs can share the code to initialize a mount.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
File systems like virtio-fs need to do not have to play directly with
forget list data structures. There is a helper function use that instead.
Rename dequeue_forget() to fuse_dequeue_forget() and export it so that
stacked filesystems can use it.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
virtio-fs will need unique IDs for FORGET requests from outside
fs/fuse/dev.c. Make the symbol visible.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This will be used by virtio-fs to send init request to fuse server after
initialization of virt queues.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
virtio-fs will need to query the length of fuse_arg lists. Make the symbol
visible.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
virtio-fs will need to complete requests from outside fs/fuse/dev.c. Make
the symbol visible.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
The size of struct fuse_req was reduced from 392B to 144B on a non-debug
config, thus the sanitize_global_limit() helper was setting a larger
default limit. This doesn't really reflect reduction in the memory used by
requests, since the fields removed from fuse_req were added to fuse_args
derived structs; e.g. sizeof(struct fuse_writepages_args) is 248B, thus
resulting in slightly more memory being used for writepage requests
overalll (due to using 256B slabs).
Make the calculatation ignore the size of fuse_req and use the old 392B
value.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
The page array pointers are also duplicated across fuse_args_pages and
fuse_req. Get rid of the fuse_req ones.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
No need to duplicate the argument arrays in fuse_req, so just dereference
req->args instead of copying to the fuse_req internal ones.
This allows further cleanup of the fuse_req structure.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
All requests are now sent with one of the fuse_simple_... helpers. Get rid
of the old api from the fuse internal header.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Rename fuse_request_send_notify_reply() to fuse_simple_notify_reply() and
convert to passing fuse_args instead of fuse_req.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Since we cannot reserve the request structure up-front, make sure that the
request allocation doesn't fail using __GFP_NOFAIL.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Derive fuse_writepage_args from fuse_io_args.
Sending the request is tricky since it was done with fi->lock held, hence
we must either use atomic allocation or release the lock. Both are
possible so try atomic first and if it fails, release the lock and do the
regular allocation with GFP_NOFS and __GFP_NOFAIL. Both flags are
necessary for correct operation.
Move the page realloc function from dev.c to file.c and convert to using
fuse_writepage_args.
The last caller of fuse_write_fill() is gone, so get rid of it.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
The old fuse_read_fill() helper can be deleted, now that the last user is
gone.
The fuse_io_args struct is moved to fuse_i.h so it can be shared between
readdir/read code.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Need to extend fuse_io_args with 'attr_ver' and 'ff' members, that take the
functionality of the same named members in fuse_req.
fuse_short_read() can now take struct fuse_args_pages.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Change of semantics in fuse_async_req_send/fuse_send_(read|write): these
can now return error, in which case the 'end' callback isn't called, so the
fuse_io_args object needs to be freed.
Added verification that the return value is sane (less than or equal to the
requested read/write size).
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Create a helper named fuse_simple_background() that is similar to
fuse_simple_request(). Unlike the latter, it returns immediately and calls
the supplied 'end' callback when the reply is received.
The supplied 'args' pointer is stored in 'fuse_req' which allows the
callback to interpret the output arguments decoded from the reply.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Extract a fuse_write_flags() helper that converts ki_flags relevant write
to open flags.
The other parts of fuse_send_write() aren't used in the
fuse_perform_write() case.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Derive fuse_io_args from struct fuse_args_pages. This will be used for
both synchronous and asynchronous read/write requests.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This will allow the use of this function when converting to the simple api
(which doesn't use fuse_req).
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
fuse_simple_request() is converted to return length of last (instead of
single) out arg, since FUSE_IOCTL_OUT has two out args, the second of which
is variable length.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
fuse_req_pages_alloc() is moved to file.c, since its internal use by the
device code will eventually be removed.
Rename to fuse_pages_alloc() to signify that it's not only usable for
fuse_req page array.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Derive fuse_args_pages from fuse_args. This is used to handle requests
which use pages for input or output. The related flags are added to
fuse_args.
New FR_ALLOC_PAGES flags is added to indicate whether the page arrays in
fuse_req need to be freed by fuse_put_request() or not.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
We can use the "force" flag to make sure the DESTROY request is always sent
to userspace. So no need to keep it allocated during the lifetime of the
filesystem.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
In some cases it makes no sense to set pid/uid/gid fields in the request
header. Allow fuse_simple_background() to omit these. This is only
required in the "force" case, so for now just WARN if set otherwise.
Fold fuse_get_req_nofail_nopages() into its only caller. Comment is
obsolete anyway.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This will be used by fuse_force_forget().
We can expand fuse_request_send() into fuse_simple_request(). The
FR_WAITING bit has already been set, no need to check.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Add 'force' to fuse_args and use fuse_get_req_nofail_nopages() to allocate
the request in that case.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Instead of complex games with a reserved request, just use __GFP_NOFAIL.
Both calers (flush, readdir) guarantee that connection was already
initialized, so no need to wait for fc->initialized.
Also remove unneeded clearing of FR_BACKGROUND flag.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
...to make future expansion simpler. The hiearachical structure is a
historical thing that does not serve any practical purpose.
The generated code is excatly the same before and after the patch.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Linus Torvalds