btrfs-progs: constify the buffer pointer for write functions

The following functions accept a buffer for write, which can be marked
as const:

- btrfs_pwrite()
- write_data_to_disk()

Signed-off-by: Qu Wenruo <[email protected]>
Signed-off-by: David Sterba <[email protected]>

Author: adam900710

common/device-utils.h

@@ -54,16 +54,16 @@ ssize_t btrfs_direct_pread(int fd, void *buf, size_t count, off_t offset);
 ssize_t btrfs_direct_pwrite(int fd, const void *buf, size_t count, off_t offset);
 
 #ifdef BTRFS_ZONED
-static inline ssize_t btrfs_pwrite(int fd, void *buf, size_t count,
+static inline ssize_t btrfs_pwrite(int fd, const void *buf, size_t count,
 				   off_t offset, bool direct)
 {
 	if (!direct)
 		return pwrite(fd, buf, count, offset);
 
 	return btrfs_direct_pwrite(fd, buf, count, offset);
 }
-static inline ssize_t btrfs_pread(int fd, void *buf, size_t count, off_t offset,
-				  bool direct)
+static inline ssize_t btrfs_pread(int fd, void *buf, size_t count,
+				  off_t offset, bool direct)
 {
 	if (!direct)
 		return pread(fd, buf, count, offset);

kernel-shared/extent_io.c

@@ -477,7 +477,7 @@ int read_data_from_disk(struct btrfs_fs_info *info, void *buf, u64 logical,
  * Such data will be written to all mirrors and RAID56 P/Q will also be
  * properly handled.
  */
-int write_data_to_disk(struct btrfs_fs_info *info, void *buf, u64 offset,
+int write_data_to_disk(struct btrfs_fs_info *info, const void *buf, u64 offset,
 		       u64 bytes)
 {
 	struct btrfs_multi_bio *multi = NULL;

kernel-shared/extent_io.h

@@ -128,7 +128,7 @@ int set_extent_buffer_dirty(struct extent_buffer *eb);
 int btrfs_clear_buffer_dirty(struct extent_buffer *eb);
 int read_data_from_disk(struct btrfs_fs_info *info, void *buf, u64 logical,
 			u64 *len, int mirror);
-int write_data_to_disk(struct btrfs_fs_info *info, void *buf, u64 offset,
+int write_data_to_disk(struct btrfs_fs_info *info, const void *buf, u64 offset,
 		       u64 bytes);
 void extent_buffer_bitmap_clear(struct extent_buffer *eb, unsigned long start,
                                 unsigned long pos, unsigned long len);