----- Original Message -----
 Hi,Dave
 
 I modified RETURN_ON_ERROR to FAULT_ON_ERROR in all readmem,patch has > attached.
 The reason for adding "decompress success"  is that i want indicate that zram
 address is different from the normal address,and calling zram_decompress not
 only readmem failures,but also decompression failures etc.i add "This page
 has swaped to zram"/"zram decompress success" as the signature log,and
these
 log only printed when pc->debug >= 2.
 
 When gcore read UVA address,there may be many page fault happened,we can only
 deal with zram swap,"not mapped" and other types of swap will not be
 processed.For debug request,we may need the signature log for zram.
 so i think it's better to keep this log. 
OK fine, but please move the message out of readmem(), and put it at the end of 
try_zram_decompress() where it really belongs.  You'll have to replace the 
"PAGEOFFSET(addr)" argument with "ulonglong addr", and then do the
PAGEOFFSET()
in try_zram_decompress().
Also, this doesn't compile cleanly on 32-bit architectures:
$ make warn
TARGET: X86
 CRASH: 7.2.9rc10
   GDB: 7.6
...
cc -c -g -DX86 -m32 -D_FILE_OFFSET_BITS=64 -DLZO -DSNAPPY -DGDB_7_6  diskdump.c -Wall -O2
-Wstrict-prototypes -Wmissing-prototypes -fstack-protector -Wformat-security 
diskdump.c: In function 'lookup_swap_cache':
diskdump.c:2657:2: warning: right shift count >= width of type [enabled by default]
  swp_type = __swp_type(pte_val);
  ^
diskdump.c:2659:3: warning: right shift count >= width of type [enabled by default]
   swp_offset = (ulonglong)__swp_offset(pte_val);
   ^
diskdump.c: In function 'try_zram_decompress':
diskdump.c:2709:3: warning: right shift count >= width of type [enabled by default]
   swap_info += (__swp_type(pte_val) * sizeof(void *));
   ^
diskdump.c:2713:3: warning: right shift count >= width of type [enabled by default]
   swap_info += (SIZE(swap_info_struct) * __swp_type(pte_val));
   ^
diskdump.c:2745:4: warning: right shift count >= width of type [enabled by default]
    swp_offset = (ulonglong)__swp_offset(pte_val);
...
Thanks,
  Dave