Merge pull request #115 from versity/zab/utils_flush

Zab/utils flush

utils/man/scoutfs.8

@@ -623,11 +623,9 @@ space of the volume making the output much more useful for inspection.
 .TP
 .B "META-DEVICE"
 The path to the metadata device for the filesystem whose metadata will be
-printed.  Since this command reads via the host's buffer cache, it may not
-reflect the current blocks in the filesystem possibly written to the shared
-block devices from another host, unless
-.B blockdev \--flushbufs
-command is used first.
+printed.  An attempt will be made to flush the host's buffer cache for
+this device with the BLKFLSBUF ioctl, or with posix_fadvise() if
+the path refers to a regular file.
 .RE
 .PD
 

utils/src/dev.c

@@ -3,6 +3,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <unistd.h>
+#include <fcntl.h>
 #include <sys/ioctl.h>
 #include <linux/fs.h>
 #include <errno.h>
@@ -103,3 +104,44 @@ char *size_str(u64 nr, unsigned size)
 
 	return suffixes[i];
 }
+
+/*
+ * Try to flush the local read cache for a device.  This is only a best
+ * effort as these interfaces don't block waiting to fully purge the
+ * cache.  This is OK because it's used by cached readers that are known
+ * to be racy anyway.
+ */
+int flush_device(int fd)
+{
+	struct stat st;
+	int ret;
+
+	ret = fstat(fd, &st);
+	if (ret < 0) {
+		ret = -errno;
+		fprintf(stderr, "fstat failed: %s (%d)\n", strerror(errno), errno);
+		goto out;
+	}
+
+	if (S_ISREG(st.st_mode)) {
+		ret = posix_fadvise(fd, 0, st.st_size, POSIX_FADV_DONTNEED);
+		if (ret < 0) {
+			ret = -errno;
+			fprintf(stderr, "POSIX_FADV_DONTNEED failed: %s (%d)\n",
+				strerror(errno), errno);
+			goto out;
+		}
+
+	} else if (S_ISBLK(st.st_mode)) {
+		ret = ioctl(fd, BLKFLSBUF, 0);
+		if (ret < 0) {
+			ret = -errno;
+			fprintf(stderr, "BLKFLSBUF, failed: %s (%d)\n", strerror(errno), errno);
+			goto out;
+		}
+	}
+
+	ret = 0;
+out:
+	return ret;
+}

utils/src/dev.h

@@ -14,5 +14,6 @@ int device_size(char *path, int fd,
 		char *use_type, u64 *size_ret);
 float size_flt(u64 nr, unsigned size);
 char *size_str(u64 nr, unsigned size);
+int flush_device(int fd);
 
 #endif

utils/src/mkfs.c

@@ -118,6 +118,33 @@ struct mkfs_args {
 	struct scoutfs_quorum_slot slots[SCOUTFS_QUORUM_MAX_SLOTS];
 };
 
+static int open_mkfs_dev(struct mkfs_args *args, char *path, mode_t mode, char *which)
+{
+	int ret;
+	int fd = -1;
+
+	fd = open(path, mode);
+	if (fd < 0) {
+		ret = -errno;
+		fprintf(stderr, "failed to open %s dev '%s': %s (%d)\n",
+			which, path, strerror(errno), errno);
+		goto out;
+	}
+
+	ret = flush_device(fd);
+	if (ret < 0)
+		goto out;
+
+	if (!args->force)
+		ret = check_bdev(fd, path, which);
+
+out:
+	if (ret < 0 && fd >= 0)
+		close(fd);
+
+	return ret ?: fd;
+}
+
 /*
  * Make a new file system by writing:
  *  - super blocks
@@ -156,32 +183,17 @@ static int do_mkfs(struct mkfs_args *args)
 	gettimeofday(&tv, NULL);
 	pseudo_random_bytes(&fsid, sizeof(fsid));
 
-	meta_fd = open(args->meta_device, O_RDWR | O_EXCL);
+	meta_fd = open_mkfs_dev(args, args->meta_device, O_RDWR | O_EXCL, "meta");
 	if (meta_fd < 0) {
-		ret = -errno;
-		fprintf(stderr, "failed to open '%s': %s (%d)\n",
-			args->meta_device, strerror(errno), errno);
+		ret = meta_fd;
 		goto out;
 	}
-	if (!args->force) {
-		ret = check_bdev(meta_fd, args->meta_device, "meta");
-		if (ret)
-			return ret;
-	}
 
-	data_fd = open(args->data_device, O_RDWR | O_EXCL);
+	data_fd = open_mkfs_dev(args, args->data_device, O_RDWR | O_EXCL, "data");
 	if (data_fd < 0) {
-		ret = -errno;
-		fprintf(stderr, "failed to open '%s': %s (%d)\n",
-			args->data_device, strerror(errno), errno);
+		ret = data_fd;
 		goto out;
 	}
-	if (!args->force) {
-		ret = check_bdev(data_fd, args->data_device, "data");
-		if (ret)
-			return ret;
-	}
-
 
 	super = calloc(1, SCOUTFS_BLOCK_SM_SIZE);
 	bt = calloc(1, SCOUTFS_BLOCK_LG_SIZE);

utils/src/print.c

@@ -27,6 +27,7 @@
 #include "avl.h"
 #include "srch.h"
 #include "leaf_item_hash.h"
+#include "dev.h"
 
 static void print_block_header(struct scoutfs_block_header *hdr, int size)
 {
@@ -1107,7 +1108,12 @@ static int do_print(struct print_args *args)
 		return ret;
 	}
 
+	ret = flush_device(fd);
+	if (ret < 0)
+		goto out;
+
 	ret = print_volume(fd, args);
+out:
 	close(fd);
 	return ret;
 };