* Re: [PATCH] btrfs-progs: use less memory for pretty_size_mode buffers
2015-02-27 18:37 [PATCH] btrfs-progs: use less memory for pretty_size_mode buffers David Sterba
@ 2015-03-06 19:21 ` Anand Jain
2015-03-09 10:38 ` David Sterba
0 siblings, 1 reply; 3+ messages in thread
From: Anand Jain @ 2015-03-06 19:21 UTC (permalink / raw)
To: David Sterba, linux-btrfs; +Cc: Zach Brown
On 02/27/2015 01:37 PM, David Sterba wrote:
> 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>
> ---
>
> Anand, please test on a real SPARC machine.
sorry for the delay David. The patch didn't fix.
I am on origin/integration-20150213 + the patch.
-------------------
(gdb) r fi show
Starting program: /root/anand/devel/btrfs fi show
[Thread debugging using libthread_db enabled]
Program received signal SIGSEGV, Segmentation fault.
0x00000800007caf18 in __vsnprintf_chk () from /lib64/libc.so.6
Missing separate debuginfos, use: debuginfo-install
glibc-2.12-1.132.0.8.el6.sparc64 libblkid-2.17.2-12.14.0.2.el6.sparc64
libuuid-2.17.2-12.14.0.2.el6.sparc64 lzo-2.03-3.1.el6.1.sparc64
zlib-1.2.3-29.el6.sparc64
(gdb) where
#0 0x00000800007caf18 in __vsnprintf_chk () from /lib64/libc.so.6
#1 0x00000800007cae88 in __snprintf_chk () from /lib64/libc.so.6
#2 0x000000000018609c in snprintf (size=<value optimized out>,
str=0x801000333e8 <Address 0x801000333e8 out of bounds>,
str_size=32, unit_mode=<value optimized out>) at
/usr/include/bits/stdio2.h:65
#3 pretty_size_snprintf (size=<value optimized out>, str=0x801000333e8
<Address 0x801000333e8 out of bounds>, str_size=32,
unit_mode=<value optimized out>) at utils.c:1463
#4 0x000000000010e6e8 in print_one_uuid (argc=<value optimized out>,
argv=<value optimized out>) at cmds-filesystem.c:424
#5 cmd_show (argc=<value optimized out>, argv=<value optimized out>) at
cmds-filesystem.c:948
#6 0x000000000010990c in handle_command_group (grp=0x2b9d30, argc=1,
argv=0x7fefffff408) at btrfs.c:143
#7 0x000000000010d150 in cmd_filesystem (argc=2, argv=0x7fefffff400) at
cmds-filesystem.c:1315
#8 0x0000000000109898 in main (argc=2, argv=0x7fefffff400) at btrfs.c:245
(gdb)
------------------
Thanks, Anand
> utils.c | 18 ++++++++++++++++++
> utils.h | 8 ++------
> 3 files changed, 21 insertions(+), 6 deletions(-)
>
> --- a/utils.c
> +++ b/utils.c
> @@ -1366,6 +1366,24 @@ 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[] =
> diff --git a/utils.h b/utils.h
> index 82ab5e82a3ff..539797c705b4 100644
> --- a/utils.h
> +++ b/utils.h
> @@ -103,12 +103,7 @@ 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);
> int btrfs_scan_block_devices(int run_ioctl);
> --
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