[RFC PATCH v4 08/36] fuse-bpf: Partially add mapping support

Daniel Rosenberg
2024-03-29T01:54:17Z

This adds a backing implementation for mapping, but is not currently
hooked into the infrastructure that will call the bpf programs.

Signed-off-by: Daniel Rosenberg <drosen@google.com>
Signed-off-by: Paul Lawrence <paullawrence@google.com>
---
fs/fuse/backing.c | 41 +++++++++++++++++++++++++++++++++++++++++
fs/fuse/file.c | 6 ++++++
fs/fuse/fuse_i.h | 4 +++-
3 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/fs/fuse/backing.c b/fs/fuse/backing.c
index a94d99ff9862..331b3f23ef78 100644
--- a/fs/fuse/backing.c
+++ b/fs/fuse/backing.c
@@ -210,6 +210,47 @@ 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);
+ struct timespec64 mtime, bmtime, ctime, bctime;
+
+ 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;
+
+ mtime = inode_get_mtime(fuse_inode);
+ bmtime = inode_get_mtime(backing_inode);
+ ctime = inode_get_ctime(fuse_inode);
+ bctime = inode_get_ctime(backing_inode);
+ if ((!timespec64_equal(&mtime, &bmtime) ||
+ !timespec64_equal(&ctime, &bctime))) {
+ inode_set_mtime_to_ts(fuse_inode, bmtime);
+ inode_set_ctime_to_ts(fuse_inode, bctime);
+ }
+ touch_atime(&file->f_path);
+
+ return ret;
+}
+
/*******************************************************************************
* Directory operations after here *
******************************************************************************/
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 41a2e88e8646..b15a0c30fec8 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2486,6 +2486,12 @@ 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 FUSE_DIRECT_IO_ALLOW_MMAP isn't set.
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 08ee98b7bb95..5f76ba3c1e4b 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -1455,7 +1455,9 @@ 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);

--
2.44.0.478.gd926399ef9-goog