Now we have everything in place and we can allow idmapped mounts by setting the FS_ALLOW_IDMAP flag. Notice that real availability of idmapped mounts will depend on the fuse daemon. Fuse daemon have to set FUSE_ALLOW_IDMAP flag in the FUSE_INIT reply. To discuss: - we enable idmapped mounts support only if "default_permissions" mode is enabled, because otherwise we would need to deal with UID/GID mappings in the userspace side OR provide the userspace with idmapped req->in.h.uid/req->in.h.gid values which is not something that we probably want to. Idmapped mounts philosophy is not about faking caller uid/gid. Some extra links and examples: - libfuse support https://github.com/mihalicyn/libfuse/commits/idmap_support - fuse-overlayfs support: https://github.com/mihalicyn/fuse-overlayfs/commits/idmap_support - cephfs-fuse conversion example https://github.com/mihalicyn/ceph/commits/fuse_idmap - glusterfs conversion example https://github.com/mihalicyn/glusterfs/commits/fuse_idmap Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com> Reviewed-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Add some preparational changes in fuse_get_req/fuse_force_creds to handle idmappings. Miklos suggested [1], [2] to change the meaning of in.h.uid/in.h.gid fields when daemon declares support for idmapped mounts. In a new semantic, we fill uid/gid values in fuse header with a id-mapped caller uid/gid (for requests which create new inodes), for all the rest cases we just send -1 to userspace. No functional changes intended. Link: https://lore.kernel.org/all/CAJfpegsVY97_5mHSc06mSw79FehFWtoXT=hhTUK_E-Yhr7OAuQ@mail.gmail.com/ [1] Link: https://lore.kernel.org/all/CAJfpegtHQsEUuFq1k4ZbTD3E1h-GsrN3PWyv7X8cg6sfU_W2Yw@mail.gmail.com/ [2] Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Some FUSE daemons want to know if the received request is a resend request. The high bit of the fuse request ID is utilized for indicating this, enabling the receiver to perform appropriate handling. The init flag "FUSE_HAS_RESEND" is added to indicate this feature. Signed-off-by: Zhao Chen <winters.zc@antgroup.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
When a FUSE daemon panics and failover, we aim to minimize the impact on applications by reusing the existing FUSE connection. During this process, another daemon is employed to preserve the FUSE connection's file descriptor. The new started FUSE Daemon will takeover the fd and continue to provide service. However, it is possible for some inflight requests to be lost and never returned. As a result, applications awaiting replies would become stuck forever. To address this, we can resend these pending requests to the new started FUSE daemon. This patch introduces a new notification type "FUSE_NOTIFY_RESEND", which can trigger resending of the pending requests, ensuring they are properly processed again. Signed-off-by: Zhao Chen <winters.zc@antgroup.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
open_by_handle_at(2) can fail with -ESTALE with a valid handle returned by a previous name_to_handle_at(2) for evicted fuse inodes, which is especially common when entry_valid_timeout is 0, e.g. when the fuse daemon is in "cache=none" mode. The time sequence is like: name_to_handle_at(2) # succeed evict fuse inode open_by_handle_at(2) # fail The root cause is that, with 0 entry_valid_timeout, the dput() called in name_to_handle_at(2) will trigger iput -> evict(), which will send FUSE_FORGET to the daemon. The following open_by_handle_at(2) will send a new FUSE_LOOKUP request upon inode cache miss since the previous inode eviction. Then the fuse daemon may fail the FUSE_LOOKUP request with -ENOENT as the cached metadata of the requested inode has already been cleaned up during the previous FUSE_FORGET. The returned -ENOENT is treated as -ESTALE when open_by_handle_at(2) returns. This confuses the application somehow, as open_by_handle_at(2) fails when the previous name_to_handle_at(2) succeeds. The returned errno is also confusing as the requested file is not deleted and already there. It is reasonable to fail name_to_handle_at(2) early in this case, after which the application can fallback to open(2) to access files. Since this issue typically appears when entry_valid_timeout is 0 which is configured by the fuse daemon, the fuse daemon is the right person to explicitly disable the export when required. Also considering FUSE_EXPORT_SUPPORT actually indicates the support for lookups of "." and "..", and there are existing fuse daemons supporting export without FUSE_EXPORT_SUPPORT set, for compatibility, we add a new INIT flag for such purpose. Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
FUSE server calls the FUSE_DEV_IOC_BACKING_OPEN ioctl with a backing file descriptor. If the call succeeds, a backing file identifier is returned. A later change will be using this backing file id in a reply to OPEN request with the flag FOPEN_PASSTHROUGH to setup passthrough of file operations on the open FUSE file to the backing file. The FUSE server should call FUSE_DEV_IOC_BACKING_CLOSE ioctl to close the backing file by its id. This can be done at any time, but if an open reply with FOPEN_PASSTHROUGH flag is still in progress, the open may fail if the backing file is closed before the fuse file was opened. Setting up backing files requires a server with CAP_SYS_ADMIN privileges. For the backing file to be successfully setup, the backing file must implement both read_iter and write_iter file operations. The limitation on the level of filesystem stacking allowed for the backing file is enforced before setting up the backing file. Signed-off-by: Alessio Balsini <balsini@android.com> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
FUSE_PASSTHROUGH capability to passthrough FUSE operations to backing files will be made available with kernel config CONFIG_FUSE_PASSTHROUGH. When requesting FUSE_PASSTHROUGH, userspace needs to specify the max_stack_depth that is allowed for FUSE on top of backing files. Introduce the flag FOPEN_PASSTHROUGH and backing_id to fuse_open_out argument that can be used when replying to OPEN request, to setup passthrough of io operations on the fuse inode to a backing file. Introduce a refcounted fuse_backing object that will be used to associate an open backing file with a fuse inode. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Although DIRECT_IO_RELAX's initial usage is to allow shared mmap, its
description indicates a purpose of reducing memory footprint. This
may imply that it could be further used to relax other DIRECT_IO
operations in the future.
Replace it with a flag DIRECT_IO_ALLOW_MMAP which does only one thing,
allow shared mmap of DIRECT_IO files while still bypassing the cache
on regular reads and writes.
[Miklos] Also Keep DIRECT_IO_RELAX definition for backward compatibility.
Signed-off-by: Tyler Fanelli <tfanelli@redhat.com>
Fixes: e78662e818f9 ("fuse: add a new fuse init flag to relax restrictions in no cache mode")
Cc: <stable@vger.kernel.org> # v6.6
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Use the same structure as statx. 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>