Improve parity fixing speed

HISTORY

@@ -1,8 +1,10 @@
 SnapRAID HISTORY
 ================
 
-11.4 2018/12
+11.4 2019/05
 ============
+ * Avoid unnecessary parity read when fixing the parity itself.
+   This improves the 'fix' speed when a parity file is completely missing.
  * Removed a build warning about major/minor defined now in sys/sysmacros.h.
 
 11.3 2018/11

cmdline/parity.c

@@ -184,6 +184,7 @@ int parity_create(struct snapraid_parity_handle* handle, const struct snapraid_p
 
 	handle->level = level;
 	handle->split_mac = 0;
+	handle->has_write_access = 0;
 
 	for (s = 0; s < parity->split_mac; ++s) {
 		struct snapraid_split_handle* split = &handle->split_map[s];
@@ -217,6 +218,9 @@ int parity_create(struct snapraid_parity_handle* handle, const struct snapraid_p
 			/* LCOV_EXCL_STOP */
 		}
 
+		/* the initial valid size is the size on disk */
+		split->valid_size = split->st.st_size;
+
 		/**
 		 * If the parity size is not yet set, set it now.
 		 * This happens when expanding the number of parities,
@@ -528,6 +532,10 @@ static int parity_handle_chsize(struct snapraid_split_handle* split, data_off_t
 		/* LCOV_EXCL_STOP */
 	}
 
+	/* if we shrink, update the valid size, but don't update when growing */
+	if (split->valid_size > split->st.st_size)
+		split->valid_size = split->st.st_size;
+
 	return 0;
 }
 
@@ -659,6 +667,7 @@ int parity_open(struct snapraid_parity_handle* handle, const struct snapraid_par
 
 	handle->level = level;
 	handle->split_mac = 0;
+	handle->has_write_access = 0;
 
 	/* mask of bits used by the block size */
 	block_mask = ((data_off_t)block_size) - 1;
@@ -697,6 +706,9 @@ int parity_open(struct snapraid_parity_handle* handle, const struct snapraid_par
 			/* LCOV_EXCL_STOP */
 		}
 
+		/* the initial valid size is the size on disk */
+		split->valid_size = split->st.st_size;
+
 		/**
 		 * If the parity size is not yet set, set it now.
 		 * This happens when expanding the number of parities,
@@ -770,6 +782,19 @@ int parity_close(struct snapraid_parity_handle* handle)
 		struct snapraid_split_handle* split = &handle->split_map[s];
 		int ret;
 
+		if (handle->has_write_access) {
+			/* truncate any data that we know it's not valid */
+			ret = ftruncate(split->f, split->valid_size);
+			if (ret != 0) {
+				/* LCOV_EXCL_START */
+				log_fatal("Error truncating the parity file '%s' to size %" PRIu64 ". %s.\n", split->path, split->valid_size, strerror(errno));
+				f_ret = -1;
+				/* LCOV_EXCL_STOP */
+
+				/* continue to close the others */
+			}
+		}
+
 		ret = close(split->f);
 		if (ret != 0) {
 			/* LCOV_EXCL_START */
@@ -826,6 +851,10 @@ int parity_write(struct snapraid_parity_handle* handle, block_off_t pos, unsigne
 		/* LCOV_EXCL_STOP */
 	}
 
+	/* update the valid range */
+	if (split->valid_size < offset + block_size)
+		split->valid_size = offset + block_size;
+
 	write_ret = pwrite(split->f, block_buffer, block_size, offset);
 	if (write_ret != (ssize_t)block_size) { /* conversion is safe because block_size is always small */
 		/* LCOV_EXCL_START */
@@ -867,6 +896,14 @@ int parity_read(struct snapraid_parity_handle* handle, block_off_t pos, unsigned
 		/* LCOV_EXCL_STOP */
 	}
 
+	/* if read is completely out of the valid range */
+	if (offset >= split->valid_size) {
+		/* LCOV_EXCL_START */
+		out("Missing data reading file '%s' at offset %" PRIu64 " for size %u.\n", split->path, offset, block_size);
+		return -1;
+		/* LCOV_EXCL_STOP */
+	}
+
 	count = 0;
 	do {
 		read_ret = pread(split->f, block_buffer + count, block_size - count, offset + count);

cmdline/parity.h

@@ -36,6 +36,13 @@ struct snapraid_split_handle {
 	 */
 	data_off_t size;
 
+	/**
+	 * Valid size of the parity split.
+	 * This is the size effectively written, and not the reult of a chsize operation.
+	 * It's used to make read operations failing if read over that size.
+	 */
+	data_off_t valid_size;
+
 	/**
 	 * Artificial size limit for testing.
 	 * 0 means unlimited.
@@ -47,6 +54,7 @@ struct snapraid_parity_handle {
 	struct snapraid_split_handle split_map[SPLIT_MAX];
 	unsigned split_mac; /**< Number of parity splits. */
 	unsigned level; /**< Level of the parity. */
+	int has_write_access; /**< If the parity is open for writing. */
 };
 
 /**

cmdline/support.h

@@ -109,7 +109,7 @@ void log_flush(void);
 /**
  * Pointer to log function.
  */
-typedef void fptr(const char* format, ...);
+typedef void fptr(const char* format, ...) __attribute__((format(attribute_printf, 1, 2)));
 
 /****************************************************************************/
 /* message */