fs: introduce f_op->mmap_capabilities for nommu mmap support
Since "BDI: Provide backing device capability information [try #3]" the
backing_dev_info structure also provides flags for the kind of mmap
operation available in a nommu environment, which is entirely unrelated
to it's original purpose.
Introduce a new nommu-only file operation to provide this information to
the nommu mmap code instead. Splitting this from the backing_dev_info
structure allows to remove lots of backing_dev_info instance that aren't
otherwise needed, and entirely gets rid of the concept of providing a
backing_dev_info for a character device. It also removes the need for
the mtd_inodefs filesystem.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Tejun Heo <tj@kernel.org>
Acked-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 42efe13..1dada39 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1502,6 +1502,26 @@
#define HAVE_COMPAT_IOCTL 1
#define HAVE_UNLOCKED_IOCTL 1
+/*
+ * These flags let !MMU mmap() govern direct device mapping vs immediate
+ * copying more easily for MAP_PRIVATE, especially for ROM filesystems.
+ *
+ * NOMMU_MAP_COPY: Copy can be mapped (MAP_PRIVATE)
+ * NOMMU_MAP_DIRECT: Can be mapped directly (MAP_SHARED)
+ * NOMMU_MAP_READ: Can be mapped for reading
+ * NOMMU_MAP_WRITE: Can be mapped for writing
+ * NOMMU_MAP_EXEC: Can be mapped for execution
+ */
+#define NOMMU_MAP_COPY 0x00000001
+#define NOMMU_MAP_DIRECT 0x00000008
+#define NOMMU_MAP_READ VM_MAYREAD
+#define NOMMU_MAP_WRITE VM_MAYWRITE
+#define NOMMU_MAP_EXEC VM_MAYEXEC
+
+#define NOMMU_VMFLAGS \
+ (NOMMU_MAP_READ | NOMMU_MAP_WRITE | NOMMU_MAP_EXEC)
+
+
struct iov_iter;
struct file_operations {
@@ -1536,6 +1556,9 @@
long (*fallocate)(struct file *file, int mode, loff_t offset,
loff_t len);
void (*show_fdinfo)(struct seq_file *m, struct file *f);
+#ifndef CONFIG_MMU
+ unsigned (*mmap_capabilities)(struct file *);
+#endif
};
struct inode_operations {