linux.git/fs/fuse/passthrough.c, branch for-next

backing-file: clean up the API

2024-11-11T09:45:03+00:00

 - Pass iocb to ctx->end_write() instead of file + pos

 - Get rid of ctx->user_file, which is redundant most of the time

 - Instead pass iocb to backing_file_splice_read and
   backing_file_splice_write

Signed-off-by: Miklos Szeredi 
Signed-off-by: Amir Goldstein

fuse: remove stray debug line

2024-10-25T15:05:49+00:00

It wasn't there when the patch was posted for review, but somehow made it
into the pull.

Link: https://lore.kernel.org/all/20240913104703.1673180-1-mszeredi@redhat.com/
Fixes: efad7153bf93 ("fuse: allow O_PATH fd for FUSE_DEV_IOC_BACKING_OPEN")
Signed-off-by: Miklos Szeredi

fuse: update inode size after extending passthrough write

2024-10-16T11:18:21+00:00

yangyun reported that libfuse test test_copy_file_range() copies zero
bytes from a newly written file when fuse passthrough is enabled.

The reason is that extending passthrough write is not updating the fuse
inode size and when vfs_copy_file_range() observes a zero size inode,
it returns without calling the filesystem copy_file_range() method.

Fix this by adjusting the fuse inode size after an extending passthrough
write.

This does not provide cache coherency of fuse inode attributes and
backing inode attributes, but it should prevent situations where fuse
inode size is too small, causing read/copy to be wrongly shortened.

Reported-by: yangyun 
Closes: https://github.com/libfuse/libfuse/issues/1048
Fixes: 57e1176e6086 ("fuse: implement read/write passthrough")
Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

fs: pass offset and result to backing_file end_write() callback

2024-10-16T11:17:45+00:00

This is needed for extending fuse inode size after fuse passthrough write.

Suggested-by: Miklos Szeredi 
Link: https://lore.kernel.org/linux-fsdevel/CAJfpegs=cvZ_NYy6Q_D42XhYS=Sjj5poM1b5TzXzOVvX=R36aA@mail.gmail.com/
Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

fuse: allow O_PATH fd for FUSE_DEV_IOC_BACKING_OPEN

2024-09-19T07:37:13+00:00

Only f_path is used from backing files registered with
FUSE_DEV_IOC_BACKING_OPEN, so it makes sense to allow O_PATH descriptors.

O_PATH files have an empty f_op, so don't check read_iter/write_iter.

Reviewed-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

fuse: verify zero padding in fuse_backing_map

2024-04-22T15:13:43+00:00

To allow us extending the interface in the future.

Fixes: 44350256ab94 ("fuse: implement ioctls to manage backing files")
Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

fuse: implement passthrough for mmap

2024-03-05T12:40:42+00:00

An mmap request for a file open in passthrough mode, maps the memory
directly to the backing file.

An mmap of a file in direct io mode, usually uses cached mmap and puts
the inode in caching io mode, which denies new passthrough opens of that
inode, because caching io mode is conflicting with passthrough io mode.

For the same reason, trying to mmap a direct io file, while there is
a passthrough file open on the same inode will fail with -ENODEV.

An mmap of a file in direct io mode, also needs to wait for parallel
dio writes in-progress to complete.

If a passthrough file is opened, while an mmap of another direct io
file is waiting for parallel dio writes to complete, the wait is aborted
and mmap fails with -ENODEV.

A FUSE server that uses passthrough and direct io opens on the same inode
that may also be mmaped, is advised to provide a backing fd also for the
files that are open in direct io mode (i.e. use the flags combination
FOPEN_DIRECT_IO | FOPEN_PASSTHROUGH), so that mmap will always use the
backing file, even if read/write do not passthrough.

Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

fuse: implement splice read/write passthrough

2024-03-05T12:40:42+00:00

This allows passing fstests generic/249 and generic/591.

Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

fuse: implement read/write passthrough

2024-03-05T12:40:42+00:00

Use the backing file read/write helpers to implement read/write
passthrough to a backing file.

After read/write, we invalidate a/c/mtime/size attributes.

Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

fuse: implement open in passthrough mode

2024-03-05T12:40:42+00:00

After getting a backing file id with FUSE_DEV_IOC_BACKING_OPEN ioctl,
a FUSE server can reply to an OPEN request with flag FOPEN_PASSTHROUGH
and the backing file id.

The FUSE server should reuse the same backing file id for all the open
replies of the same FUSE inode and open will fail (with -EIO) if a the
server attempts to open the same inode with conflicting io modes or to
setup passthrough to two different backing files for the same FUSE inode.
Using the same backing file id for several different inodes is allowed.

Opening a new file with FOPEN_DIRECT_IO for an inode that is already
open for passthrough is allowed, but only if the FOPEN_PASSTHROUGH flag
and correct backing file id are specified as well.

The read/write IO of such files will not use passthrough operations to
the backing file, but mmap, which does not support direct_io, will use
the backing file insead of using the page cache as it always did.

Even though all FUSE passthrough files of the same inode use the same
backing file as a backing inode reference, each FUSE file opens a unique
instance of a backing_file object to store the FUSE path that was used
to open the inode and the open flags of the specific open file.

The per-file, backing_file object is released along with the FUSE file.
The inode associated fuse_backing object is released when the last FUSE
passthrough file of that inode is released AND when the backing file id
is closed by the server using the FUSE_DEV_IOC_BACKING_CLOSE ioctl.

Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi