btrfs-progs: use less memory for pretty_size_mode buffers

Anand reports that the static buffers used for pertty size strings cause
a stack overflow on SPARC. Zach proposed to change the printf format to
wrap the number and the suffix into a macro. This would require to
change all callsites of pretty_size* and is not very convienient to
write.

This patch replaces the per-call-site static buffers with a limited
number for slots that would be used on each invokation of pretty_size
and wrap around. The number of array slots shall be 10 for now, in
current codebase there are no more than 2 calls to pretty_size in a
single argument list.

Reported-by: Anand Jain <Anand.Jain@oracle.com>
CC: Zach Brown <zab@zabbo.net>
Signed-off-by: David Sterba <dsterba@suse.cz>

1 files changed, 1 insertions, 6 deletions

diff --git a/utils.h b/utils.h
index 9b6a07b..7260035 100644
--- a/utils.h
+++ b/utils.h
@@ -129,12 +129,7 @@ int btrfs_device_already_in_root(struct btrfs_root *root, int fd,
 
 int pretty_size_snprintf(u64 size, char *str, size_t str_bytes, unsigned unit_mode);
 #define pretty_size(size) 	pretty_size_mode(size, UNITS_DEFAULT)
-#define pretty_size_mode(size, mode) 					      \
-	({								      \
-		static __thread char _str[32];				      \
-		(void)pretty_size_snprintf((size), _str, sizeof(_str), (mode)); \
-		_str;							      \
-	})
+const char *pretty_size_mode(u64 size, unsigned mode);
 
 int get_mountpt(char *dev, char *mntpt, size_t size);
 u64 parse_size(char *s);