[RFC PATCH v2 08/21] fuse-bpf: Partially add mapping support

Daniel Rosenberg
2022-11-22T02:17:22Z

This adds a backing implementation for mapping, but no bpf counterpart
yet.

Signed-off-by: Daniel Rosenberg <drosen@google.com>
Signed-off-by: Paul Lawrence <paullawrence@google.com>
---
fs/fuse/backing.c | 37 +++++++++++++++++++++++++++++++++++++
fs/fuse/file.c | 6 ++++++
fs/fuse/fuse_i.h | 4 +++-
3 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/fs/fuse/backing.c b/fs/fuse/backing.c
index 670e82d68e36..8d862bc64acd 100644
--- a/fs/fuse/backing.c
+++ b/fs/fuse/backing.c
@@ -205,6 +205,43 @@ static void fuse_stat_to_attr(struct fuse_conn *fc, struct inode *inode,
attr->blksize = 1 << blkbits;
}

+ssize_t fuse_backing_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ int ret;
+ struct fuse_file *ff = file->private_data;
+ struct inode *fuse_inode = file_inode(file);
+ struct file *backing_file = ff->backing_file;
+ struct inode *backing_inode = file_inode(backing_file);
+
+ if (!backing_file->f_op->mmap)
+ return -ENODEV;
+
+ if (WARN_ON(file != vma->vm_file))
+ return -EIO;
+
+ vma->vm_file = get_file(backing_file);
+
+ ret = call_mmap(vma->vm_file, vma);
+
+ if (ret)
+ fput(backing_file);
+ else
+ fput(file);
+
+ if (file->f_flags & O_NOATIME)
+ return ret;
+
+ if ((!timespec64_equal(&fuse_inode->i_mtime, &backing_inode->i_mtime) ||
+ !timespec64_equal(&fuse_inode->i_ctime,
+ &backing_inode->i_ctime))) {
+ fuse_inode->i_mtime = backing_inode->i_mtime;
+ fuse_inode->i_ctime = backing_inode->i_ctime;
+ }
+ touch_atime(&file->f_path);
+
+ return ret;
+}
+
/*******************************************************************************
* Directory operations after here *
******************************************************************************/
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 503327be3942..24fd4f33105c 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2452,6 +2452,12 @@ static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma)
if (FUSE_IS_DAX(file_inode(file)))
return fuse_dax_mmap(file, vma);

+#ifdef CONFIG_FUSE_BPF
+ /* TODO - this is simply passthrough, not a proper BPF filter */
+ if (ff->backing_file)
+ return fuse_backing_mmap(file, vma);
+#endif
+
if (ff->open_flags & FOPEN_DIRECT_IO) {
/* Can't provide the coherency needed for MAP_SHARED */
if (vma->vm_flags & VM_MAYSHARE)
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index db3f703c700f..95d67afcff05 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1417,7 +1417,9 @@ static inline int fuse_bpf_access(int *out, struct inode *inode, int mask)

#endif // CONFIG_FUSE_BPF

-int fuse_handle_backing(struct fuse_bpf_entry *feb, struct path *backing_path);
+ssize_t fuse_backing_mmap(struct file *file, struct vm_area_struct *vma);
+
+int fuse_handle_backing(struct fuse_bpf_entry *fbe, struct path *backing_path);

int fuse_revalidate_backing(struct dentry *entry, unsigned int flags);

--
2.38.1.584.g0f3c55d4c2-goog