| Message ID | 20210604161156.408496-5-groug@kaod.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | fuse: Some fixes for submounts | expand |
On 04.06.21 18:11, Greg Kurz wrote: > 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> > --- > fs/fuse/fuse_i.h | 5 +++++ > fs/fuse/inode.c | 16 ++++++++++++++++ > fs/fuse/virtio_fs.c | 3 +++ > 3 files changed, 24 insertions(+) Reviewed-by: Max Reitz <mreitz@redhat.com>
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index 7e463e220053..862ad317bc89 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -1097,6 +1097,11 @@ int fuse_fill_super_submount(struct super_block *sb, */ bool fuse_mount_remove(struct fuse_mount *fm); +/* + * Setup context ops for submounts + */ +int fuse_init_fs_context_submount(struct fs_context *fsc); + /* * Shut down the connection (possibly sending DESTROY request). */ diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 393e36b74dc4..fa96a3762ea2 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -1313,6 +1313,22 @@ int fuse_fill_super_submount(struct super_block *sb, return 0; } +static int fuse_get_tree_submount(struct fs_context *fsc) +{ + return 0; +} + +static const struct fs_context_operations fuse_context_submount_ops = { + .get_tree = fuse_get_tree_submount, +}; + +int fuse_init_fs_context_submount(struct fs_context *fsc) +{ + fsc->ops = &fuse_context_submount_ops; + return 0; +} +EXPORT_SYMBOL_GPL(fuse_init_fs_context_submount); + int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx) { struct fuse_dev *fud = NULL; diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c index bcb8a02e2d8b..e68467cc765c 100644 --- a/fs/fuse/virtio_fs.c +++ b/fs/fuse/virtio_fs.c @@ -1496,6 +1496,9 @@ static int virtio_fs_init_fs_context(struct fs_context *fsc) { struct fuse_fs_context *ctx; + if (fsc->purpose == FS_CONTEXT_FOR_SUBMOUNT) + return fuse_init_fs_context_submount(fsc); + ctx = kzalloc(sizeof(struct fuse_fs_context), GFP_KERNEL); if (!ctx) return -ENOMEM;
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> --- fs/fuse/fuse_i.h | 5 +++++ fs/fuse/inode.c | 16 ++++++++++++++++ fs/fuse/virtio_fs.c | 3 +++ 3 files changed, 24 insertions(+)