diff --git a/elem.h b/elem.h
index c402b64b..8a241ce1 100644
--- a/elem.h
+++ b/elem.h
@@ -30,7 +30,7 @@
 /**
  * Invalid position.
  */
-#define POS_INVALID -1
+#define POS_INVALID ((block_off_t)-1)
 
 /**
  * Basic block position type.
@@ -40,8 +40,9 @@ typedef uint32_t block_off_t;
 
 /**
  * Basic data position type.
+ * It's signed as file size and offset are usually signed.
  */
-typedef uint64_t data_off_t;
+typedef int64_t data_off_t;
 
 /**
  * Filter for paths.
@@ -76,7 +77,7 @@ struct snapraid_file {
 	data_off_t size; /**< Size of the file. */
 	struct snapraid_block* blockvec; /**< All the blocks of the file. */
 	block_off_t blockmax; /**< Number of blocks. */
-	uint64_t mtime; /**< Modification time. */
+	int64_t mtime; /**< Modification time. */
 	uint64_t inode; /**< Inode. */
 	int is_present; /**< If it's seen as present. */
 	int is_filtered; /**< If it's filtered out. */
diff --git a/handle.c b/handle.c
index 851b559f..50f53a74 100644
--- a/handle.c
+++ b/handle.c
@@ -251,7 +251,7 @@ int handle_read(struct snapraid_handle* handle, struct snapraid_block* block, un
 
 	read_ret = read(handle->f, block_buffer, read_size);
 #endif
-	if (read_ret != read_size) {
+	if (read_ret != (ssize_t)read_size) { /* conversion is safe because block_size is always small */
 		fprintf(stderr, "Error reading file '%s'. %s.\n", handle->path, strerror(errno));
 		return -1;
 	}
@@ -284,7 +284,7 @@ int handle_write(struct snapraid_handle* handle, struct snapraid_block* block, u
 
 	write_ret = write(handle->f, block_buffer, write_size);
 #endif
-	if (write_ret != write_size) {
+	if (write_ret != (ssize_t)write_size) { /* conversion is safe because block_size is always small */
 		fprintf(stderr, "Error writing file '%s'. %s.\n", handle->path, strerror(errno));
 		return -1;
 	}
@@ -295,28 +295,4 @@ int handle_write(struct snapraid_handle* handle, struct snapraid_block* block, u
 	return 0;
 }
 
-int handle_readahead(struct snapraid_handle* handle, struct snapraid_block* block, unsigned block_size)
-{
-#if HAVE_POSIX_FADVISE
-	data_off_t offset;
-	unsigned read_size;
-	int ret;
 
-	/* do nothing if the file is different */
-	if (handle->file != block->file)
-		return 0;
-
-	offset = block_file_pos(block) * (data_off_t)block_size;
-
-	read_size = block_file_size(block, block_size);
-
-	/* advise access of the next block */
-	ret = posix_fadvise(handle->f, offset, read_size, POSIX_FADV_WILLNEED);
-	if (ret != 0) {
-		fprintf(stderr, "Error advising file '%s'. %s.\n", handle->path, strerror(errno));
-		return -1;
-	}
-#endif
-
-	return 0;
-}
diff --git a/handle.h b/handle.h
index 2c48e77f..19833201 100644
--- a/handle.h
+++ b/handle.h
@@ -61,12 +61,5 @@ int handle_read(struct snapraid_handle* handle, struct snapraid_block* block, un
  */
 int handle_write(struct snapraid_handle* handle, struct snapraid_block* block, unsigned char* block_buffer, unsigned block_size);
 
-/**
- * Readahead optimization where available.
- * \note
- * It doesn't seem to give any speed improvement over posix_fadvise(POSIX_FADV_SEQUENTIAL).
- */
-int handle_readahead(struct snapraid_handle* handle, struct snapraid_block* block, unsigned block_size);
-
 #endif
 
diff --git a/parity.c b/parity.c
index e4f85fd5..5bec0b66 100644
--- a/parity.c
+++ b/parity.c
@@ -193,7 +193,7 @@ int parity_write(const char* path, int f, block_off_t pos, unsigned char* block_
 
 	write_ret = write(f, block_buffer, block_size);
 #endif
-	if (write_ret != block_size) {
+	if (write_ret != (ssize_t)block_size) { /* conversion is safe because block_size is always small */
 		if (errno == ENOSPC) {
 			fprintf(stderr, "Failed to grow parity file '%s' due lack of space.\n", path);
 		} else {
@@ -225,7 +225,7 @@ int parity_read(const char* path, int f, block_off_t pos, unsigned char* block_b
 
 	read_ret = read(f, block_buffer, block_size);
 #endif    
-	if (read_ret != block_size) {
+	if (read_ret != (ssize_t)block_size) { /* conversion is safe because block_size is always small */
 		fprintf(stderr, "Error reading file '%s'. %s.\n", path, strerror(errno));
 		return -1;
 	}
diff --git a/portable.h b/portable.h
index 9dbd93f8..91be3991 100644
--- a/portable.h
+++ b/portable.h
@@ -129,8 +129,8 @@
  */
 struct windows_stat {
 	uint64_t st_ino;
-	uint64_t st_size;
-	uint64_t st_mtime;
+	int64_t st_size;
+	int64_t st_mtime;
 	uint32_t st_mode;
 };