The following is also in lvm2app.h

/**
 * This type defines a couple of special percent values. The PERCENT_0 and
 * PERCENT_100 constants designate *exact* percentages: values are never
 * rounded to either of these two.
 */
typedef enum {
        PERCENT_0 = 0,
        PERCENT_1 = 1000000,
        PERCENT_100 = 100 * PERCENT_1,
        PERCENT_INVALID = -1,
        PERCENT_MERGE_FAILED = -2
} percent_range_t;

typedef int32_t percent_t;


This means that -1 or -2 may be returned by properties that are percentages.

How about we extend this by doing something like:

typedef struct lvm_property_value {
        uint32_t is_settable:1;
        uint32_t is_string:1;
        uint32_t is_integer:1;
        uint32_t is_valid:1;
        uint32_t is_signed:1;
        uint32_t padding:27;
        union {
                const char *string;
                uint64_t integer;
                int64_t signed_integer;
        } value;
} lvm_property_value_t;

This should preserve backwards compatibility and provide a signed value.  We could also add data type for double precision floating-point, although I'm not sure we have a need for it at this time.

Some of the values returned don't need 8 bytes for representation, but I don't think we improve things by adding numerous types for the different integer sizes.

Patches committed upstream for this:

https://www.redhat.com/archives/lvm-devel/2015-May/msg00059.html
https://www.redhat.com/archives/lvm-devel/2015-May/msg00060.html

Created attachment 1083589 [details]
Test code for lvm_lv_get_property lvm2app fn

Test code using lvm2app and its lvm_lv_get_property to get integer property values is attached.

Compile with: gcc -llvm2app test_new.c -o test_new

Then test with: ./test_new vg_name lv_name lv_integer_field

For example: 

$ ./test vg lvol0 lv_major
"lv_major" property value for vg/lvol0 is signed integer.
Found "lv_major" property for vg/lvol0: -1

$ ./test vg lvol0 lv_size 
"lv_size" property value for vg/lvol0 is unsigned integer.
Found "lv_size" property for vg/lvol0: 4194304

Created attachment 1083602 [details]
Test code for lvm_lv_get_property lvm2app fn (old interface)

And the code for the older interface (the test_new.c code is not compilable with older lvm2app library!).

$ gcc -llvm2app test_old.c -o test_old

$ ./test_old vg lvol0 lv_major
Found "lv_major" property for vg/lvol0: 18446744073709551615

$ ./test_old vg lvol0 lv_size 
Found "lv_size" property for vg/lvol0: 4194304

(So you can see that in the older version, the value is considered unsinged and hence it's incorrectly printed as unsigned number instead of signed one.)

Verified.

# ./test_new vg_virt175 lv_root lv_major
"lv_major" property value for vg_virt175/lv_root is signed integer.
Found "lv_major" property for vg_virt175/lv_root: -1

# ./test_new vg_virt175 lv_root lv_size
"lv_size" property value for vg_virt175/lv_root is unsigned integer.
Found "lv_size" property for vg_virt175/lv_root: 7436500992

# ./test_old vg_virt175 lv_root lv_major
Found "lv_major" property for vg_virt175/lv_root: 18446744073709551615

# ./test_old vg_virt175 lv_root lv_size
Found "lv_size" property for vg_virt175/lv_root: 7436500992


Tested on:

2.6.32-616.el6.x86_64

lvm2-2.02.141-2.el6    BUILT: Wed Feb 10 14:49:03 CET 2016
lvm2-libs-2.02.141-2.el6    BUILT: Wed Feb 10 14:49:03 CET 2016
lvm2-cluster-2.02.141-2.el6    BUILT: Wed Feb 10 14:49:03 CET 2016
udev-147-2.71.el6    BUILT: Wed Feb 10 14:07:17 CET 2016
device-mapper-1.02.115-2.el6    BUILT: Wed Feb 10 14:49:03 CET 2016
device-mapper-libs-1.02.115-2.el6    BUILT: Wed Feb 10 14:49:03 CET 2016
device-mapper-event-1.02.115-2.el6    BUILT: Wed Feb 10 14:49:03 CET 2016
device-mapper-event-libs-1.02.115-2.el6    BUILT: Wed Feb 10 14:49:03 CET 2016
device-mapper-persistent-data-0.6.2-0.1.rc1.el6    BUILT: Wed Feb 10 16:52:15 CET 2016

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2016-0964.html