patch update
Found a better way translate pfn to page,PTOB.
Besides,fix a issue with low probability of decompression failure
________________________________________
From: 赵乾利
Sent: Saturday, April 4, 2020 14:46
To: Dave Anderson
Cc: d hatayama; Discussion list for crash utility usage, maintenance and development
Subject: Re: 答复: [External Mail]Re: [Crash-utility] zram decompress support for gcore/crash-utility
Hi,Dave
As you suggestion,i have made changes.
Calling pfn_to_map to get page address was a wrong use,it just work in SPARSEMEM
I'm looking for a interface like pfn_to_page,so i found two ways
1.pfn_to_map seems to work,and i didn't notice SPARSEMEM restriction
2.Combining pfn_to_phys and phy_to_page,but pfn_to_phys defined as a static function
i wrote this feature in gcore-command before,pfn_to_map not defined as static,so i can call directly....
Now,I use the following code to implement,this should work
+ phys_to_page((obj >> OBJ_INDEX_BITS) << PAGESHIFT(), &page);
Thanks
________________________________________
From: Dave Anderson <anderson@xxxxxxxxxx>
Sent: Saturday, April 4, 2020 4:14
To: 赵乾利
Cc: d hatayama; Discussion list for crash utility usage, maintenance and development
Subject: Re: 答复: [External Mail]Re: [Crash-utility] zram decompress support for gcore/crash-utility
----- Original Message -----
> Hi,Dave
>
> As per your suggestion, I updated the patch,and compiled successfully on
> arm64, x86,ppc64 architecture
>
The patch does compile cleanly, although I haven't tried compiling it on an s390x, but
I'll do that soon.
A couple issues with the patch:
+ if (!strncmp(name, "lzo", strlen("lzo"))) {
+ lzo_init();
+ decompressor = (void *)lzo1x_decompress_safe;
+ } else {//todo,support more compressor
+ error(WARNING, "Only support lzo compressor\n");
+ return 0;
+ }
lzo_init() will have already been called by is_diskdump() here during session
initialization if the dumpfile is a compressed kdump:
#ifdef LZO
if (lzo_init() == LZO_E_OK)
dd->flags |= LZO_SUPPORTED;
#endif
So try_zram_decompress() should check if (dd->flags & LZO_SUPPORTED) has been set before
calling lzo_init() again.
And while I don't object to exporting swap_info_init(), I do have a problem with pfn_to_map():
+void swap_info_init(void);
+ulong pfn_to_map(ulong);
...
+ obj >>= OBJ_TAG_BITS;
+ page = pfn_to_map(obj >> OBJ_INDEX_BITS);
+ obj_idx = (obj & OBJ_INDEX_MASK);
The pfn_to_map() function is only relevant if the kernel is configured with SPARSEMEM.
I don't see why the exported phys_to_page() function could not be used here?
Thanks,
Dave
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