[PATCH] hfs: don't dirty unchanged inode

If inode size hasn't changed, don't do anything further in truncate, which
also prevents a dirty inode, what might upset some readonly devices quite
badly.
Signed-off-by: NRoman Zippel <zippel@linux-m68k.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

fs/hfs/extent.c

@@ -482,7 +482,8 @@ void hfs_file_truncate(struct inode *inode)
 		page_cache_release(page);
 		mark_inode_dirty(inode);
 		return;
-	}
+	} else if (inode->i_size == HFS_I(inode)->phys_size)
+		return;
 	size = inode->i_size + HFS_SB(sb)->alloc_blksz - 1;
 	blk_cnt = size / HFS_SB(sb)->alloc_blksz;
 	alloc_cnt = HFS_I(inode)->alloc_blocks;

fs/hfsplus/extents.c

@@ -461,7 +461,9 @@ void hfsplus_file_truncate(struct inode *inode)
 		page_cache_release(page);
 		mark_inode_dirty(inode);
 		return;
-	}
+	} else if (inode->i_size == HFSPLUS_I(inode).phys_size)
+		return;
+
 	blk_cnt = (inode->i_size + HFSPLUS_SB(sb).alloc_blksz - 1) >> HFSPLUS_SB(sb).alloc_blksz_shift;
 	alloc_cnt = HFSPLUS_I(inode).alloc_blocks;
 	if (blk_cnt == alloc_cnt)