fs: get mnt_writers count for an open backing file's real path
A writeable mapped backing file can perform writes to the real inode.
Therefore, the real path mount must be kept writable so long as the
writable map exists.
This may not be strictly needed for ovelrayfs private upper mount,
but it is correct to take the mnt_writers count in the vfs helper.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://lore.kernel.org/r/20231009153712.1566422-2-amir73il@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
diff --git a/fs/internal.h b/fs/internal.h
index f08d8fe..4e93a68 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -96,13 +96,20 @@ struct file *alloc_empty_file_noaccount(int flags, const struct cred *cred);
struct file *alloc_empty_backing_file(int flags, const struct cred *cred);
void release_empty_file(struct file *f);
+static inline void file_put_write_access(struct file *file)
+{
+ put_write_access(file->f_inode);
+ mnt_put_write_access(file->f_path.mnt);
+ if (unlikely(file->f_mode & FMODE_BACKING))
+ mnt_put_write_access(backing_file_real_path(file)->mnt);
+}
+
static inline void put_file_access(struct file *file)
{
if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) {
i_readcount_dec(file->f_inode);
} else if (file->f_mode & FMODE_WRITER) {
- put_write_access(file->f_inode);
- mnt_put_write_access(file->f_path.mnt);
+ file_put_write_access(file);
}
}
