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, 3 insertions, 4 deletions

diff --git a/disk-io.c b/disk-io.c
index 0b83be71..76958aef 100644
--- a/disk-io.c
+++ b/disk-io.c
@@ -1212,7 +1212,7 @@ struct btrfs_fs_info *open_ctree_fs_info(const char *filename,
 
 	ret = stat(filename, &st);
 	if (ret < 0) {
-		error("cannot stat '%s': %s", filename, strerror(errno));
+		error("cannot stat '%s': %m", filename);
 		return NULL;
 	}
 	if (!(((st.st_mode & S_IFMT) == S_IFREG) || ((st.st_mode & S_IFMT) == S_IFBLK))) {
@@ -1225,7 +1225,7 @@ struct btrfs_fs_info *open_ctree_fs_info(const char *filename,
 
 	fp = open(filename, oflags);
 	if (fp < 0) {
-		error("cannot open '%s': %s", filename, strerror(errno));
+		error("cannot open '%s': %m", filename);
 		return NULL;
 	}
 	info = __open_ctree_fd(fp, filename, sb_bytenr, root_tree_bytenr,
@@ -1566,8 +1566,7 @@ write_err:
 	if (ret > 0)
 		fprintf(stderr, "WARNING: failed to write all sb data\n");
 	else
-		fprintf(stderr, "WARNING: failed to write sb: %s\n",
-			strerror(errno));
+		fprintf(stderr, "WARNING: failed to write sb: %m\n");
 	return ret;
 }