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btrfs-progs: use less memory for pretty_size_mode buffers

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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>
This commit is contained in:
David Sterba 2015-02-27 19:37:24 +01:00
parent 4ceffd0927
commit 6d7999d5b7
2 changed files with 19 additions and 6 deletions
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18
utils.c
View File

@ -1479,6 +1479,24 @@ out:
return ret;
}
/*
* Note: this function uses a static per-thread buffer. Do not call this
* function more than 10 times within one argument list!
*/
const char *pretty_size_mode(u64 size, unsigned mode)
{
static __thread int ps_index = 0;
static __thread char ps_array[10][32];
char *ret;
ret = ps_array[ps_index];
ps_index++;
ps_index %= 10;
(void)pretty_size_snprintf(size, ret, 32, mode);
return ret;
}
static const char* unit_suffix_binary[] =
{ "B", "KiB", "MiB", "GiB", "TiB", "PiB", "EiB"};
static const char* unit_suffix_decimal[] =

7
utils.h
View File

@ -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);