btrfs-progs: treewide: Replace strerror(errno) with %m.

As btrfs is specific to Linux, %m can be used instead of strerror(errno)
in format strings. This has some size reduction benefits for embedded
systems.

glibc, musl, and uclibc-ng all support %m as a modifier to printf.
A quick glance at the BIONIC libc source indicates that it has
support for %m as well. BSDs and Windows do not but I do believe
them to be beyond the scope of btrfs-progs.

Compiled sizes on Ubuntu 16.04:

Before:
3916512 btrfs
233688  libbtrfs.so.0.1
4899    bcp
2367672 btrfs-convert
2208488 btrfs-corrupt-block
13302   btrfs-debugfs
2152160 btrfs-debug-tree
2136024 btrfs-find-root
2287592 btrfs-image
2144600 btrfs-map-logical
2130760 btrfs-select-super
2152608 btrfstune
2131760 btrfs-zero-log
2277752 mkfs.btrfs
9166    show-blocks

After:
3908744 btrfs
233256  libbtrfs.so.0.1
4899    bcp
2366560 btrfs-convert
2207432 btrfs-corrupt-block
13302   btrfs-debugfs
2151104 btrfs-debug-tree
2134968 btrfs-find-root
2281864 btrfs-image
2143536 btrfs-map-logical
2129704 btrfs-select-super
2151552 btrfstune
2130696 btrfs-zero-log
2276272 mkfs.btrfs
9166    show-blocks

Total savings: 23928 (24 kilo)bytes

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 12 insertions, 20 deletions

diff --git a/cmds-subvolume.c b/cmds-subvolume.c
index dc626a64..8a473f7a 100644
--- a/cmds-subvolume.c
+++ b/cmds-subvolume.c
@@ -210,7 +210,7 @@ static int cmd_subvol_create(int argc, char **argv)
 	}
 
 	if (res < 0) {
-		error("cannot create subvolume: %s", strerror(errno));
+		error("cannot create subvolume: %m");
 		goto out;
 	}
 
@@ -325,8 +325,7 @@ again:
 	cpath = realpath(path, NULL);
 	if (!cpath) {
 		ret = errno;
-		error("cannot find real path for '%s': %s",
-			path, strerror(errno));
+		error("cannot find real path for '%s': %m", path);
 		goto out;
 	}
 	dupdname = strdup(cpath);
@@ -348,8 +347,7 @@ again:
 	strncpy_null(args.name, vname);
 	res = ioctl(fd, BTRFS_IOC_SNAP_DESTROY, &args);
 	if(res < 0 ){
-		error("cannot delete '%s/%s': %s", dname, vname,
-			strerror(errno));
+		error("cannot delete '%s/%s': %m", dname, vname);
 		ret = 1;
 		goto out;
 	}
@@ -357,8 +355,7 @@ again:
 	if (commit_mode == COMMIT_EACH) {
 		res = wait_for_commit(fd);
 		if (res < 0) {
-			error("unable to wait for commit after '%s': %s",
-				path, strerror(errno));
+			error("unable to wait for commit after '%s': %m", path);
 			ret = 1;
 		}
 	} else if (commit_mode == COMMIT_AFTER) {
@@ -415,8 +412,8 @@ keep_fd:
 				if (res < 0) {
 					uuid_unparse(seen->fsid, uuidbuf);
 					error(
-			"unable to do final sync after deletion: %s, fsid: %s",
-						strerror(errno), uuidbuf);
+			"unable to do final sync after deletion: %m, fsid: %s",
+						uuidbuf);
 					ret = 1;
 				} else if (verbose > 0) {
 					uuid_unparse(seen->fsid, uuidbuf);
@@ -776,7 +773,7 @@ static int cmd_subvol_snapshot(int argc, char **argv)
 	res = ioctl(fddst, BTRFS_IOC_SNAP_CREATE_V2, &args);
 
 	if (res < 0) {
-		error("cannot snapshot '%s': %s", subvol, strerror(errno));
+		error("cannot snapshot '%s': %m", subvol);
 		goto out;
 	}
 
@@ -819,8 +816,7 @@ static int cmd_subvol_get_default(int argc, char **argv)
 
 	ret = btrfs_list_get_default_subvolume(fd, &default_id);
 	if (ret) {
-		error("failed to look up default subvolume: %s",
-			strerror(errno));
+		error("failed to look up default subvolume: %m");
 		goto out;
 	}
 
@@ -868,7 +864,7 @@ static const char * const cmd_subvol_set_default_usage[] = {
 
 static int cmd_subvol_set_default(int argc, char **argv)
 {
-	int	ret=0, fd, e;
+	int	ret=0, fd;
 	u64	objectid;
 	char	*path;
 	char	*subvolid;
@@ -915,11 +911,9 @@ static int cmd_subvol_set_default(int argc, char **argv)
 	}
 
 	ret = ioctl(fd, BTRFS_IOC_DEFAULT_SUBVOL, &objectid);
-	e = errno;
 	close_file_or_dir(fd, dirstream);
 	if (ret < 0) {
-		error("unable to set a new default subvolume: %s",
-			strerror(e));
+		error("unable to set a new default subvolume: %m");
 		return 1;
 	}
 	return 0;
@@ -963,8 +957,7 @@ static int cmd_subvol_find_new(int argc, char **argv)
 
 	ret = ioctl(fd, BTRFS_IOC_SYNC);
 	if (ret < 0) {
-		error("sync ioctl failed on '%s': %s",
-			subvol, strerror(errno));
+		error("sync ioctl failed on '%s': %m", subvol);
 		close_file_or_dir(fd, dirstream);
 		return 1;
 	}
@@ -1039,8 +1032,7 @@ static int cmd_subvol_show(int argc, char **argv)
 	memset(&get_ri, 0, sizeof(get_ri));
 	fullpath = realpath(argv[optind], NULL);
 	if (!fullpath) {
-		error("cannot find real path for '%s': %s",
-			argv[optind], strerror(errno));
+		error("cannot find real path for '%s': %m", argv[optind]);
 		goto out;
 	}