fuse: allow private mappings of "direct_io" files

Allow MAP_PRIVATE mmaps of "direct_io" files.  This is necessary for
execute support.

MAP_SHARED mappings require some sort of coherency between the
underlying file and the mapping.  With "direct_io" it is difficult to
provide this, so for the moment just disallow shared (read-write and
read-only) mappings altogether.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

1 files changed, 11 insertions, 1 deletions

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 78a2c8333700..2b25133524a3 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1292,6 +1292,15 @@ static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma)
         return 0;
 }
 
+static int fuse_direct_mmap(struct file *file, struct vm_area_struct *vma)
+{
+        /* Can't provide the coherency needed for MAP_SHARED */
+        if (vma->vm_flags & VM_MAYSHARE)
+                return -ENODEV;
+
+        return generic_file_mmap(file, vma);
+}
+
 static int convert_fuse_file_lock(const struct fuse_file_lock *ffl,
                                   struct file_lock *fl)
 {
@@ -1926,6 +1935,7 @@ static const struct file_operations fuse_direct_io_file_operations = {
         .llseek         = fuse_file_llseek,
         .read           = fuse_direct_read,
         .write          = fuse_direct_write,
+        .mmap           = fuse_direct_mmap,
         .open           = fuse_open,
         .flush          = fuse_flush,
         .release        = fuse_release,
@@ -1935,7 +1945,7 @@ static const struct file_operations fuse_direct_io_file_operations = {
         .unlocked_ioctl = fuse_file_ioctl,
         .compat_ioctl   = fuse_file_compat_ioctl,
         .poll           = fuse_file_poll,
-        /* no mmap and splice_read */
+        /* no splice_read */
 };
 
 static const struct address_space_operations fuse_file_aops  = {