gf-complete alignment constraints

[Loic Dachary <loic@dachary.org>]

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Hi Kevin,

I've hit the following stack trace (and I can reproduce it which is nice ;-)

#0  __GI_exit (status=1) at exit.c:104
#1  0x00007ffff18f3312 in gf_set_region_data (rd=0x7fffd9b8b0a0, gf=0x485dd40, src=0x4a7b31f, dest=0x4d25800, bytes=2048, val=143, xor=1, align=16) at erasure-code/jerasure/gf-complete/src/gf.c:817
#2  0x00007ffff1932364 in gf_w8_split_multiply_region_sse (gf=0x485dd40, src=0x4a7b31f, dest=0x4d25800, val=143, bytes=2048, xor=1) at erasure-code/jerasure/gf-complete/src/gf_w8.c:1071
#3  0x00007ffff18db9cc in galois_w08_region_multiply (region=0x4a7b31f "", multby=143, nbytes=2048, r2=0x4d25800 "root:x:0:\ndaemon:x:1:\nbin:x:2:\nsys:x:3:\nadm:x:4:loic,swift,syslog\ntty:x:5:\ndisk:x:6:\nlp:x:7:\nmail:x:8:\nnews:x:9:\nuucp:x:10:\nman:x:12:\nproxy:x:13:\nkmem:x:15:\ndialout:x:20:\nfax:x:21:\nvoice:x:22:\ncdrom:x"..., add=1) at erasure-code/jerasure/jerasure/src/galois.c:295
#4  0x00007ffff18ddb42 in jerasure_matrix_dotprod (k=2, w=8, matrix_row=0x47fa558, src_ids=0x0, dest_id=3, data_ptrs=0x7fffd9b8b260, coding_ptrs=0x7fffd9b8b270, size=2048) at erasure-code/jerasure/jerasure/src/jerasure.c:626

https://github.com/ceph/gf-complete/blob/v1/src/gf.c#L811 indeed checks that src=0x4a7b31f, dest=0x4d25800 are aligned and finds they are not. If I'm not mistaken src comes from https://github.com/ceph/jerasure/blob/v2/src/galois.c#L294 which will allocate it via https://github.com/ceph/jerasure/blob/v2/src/galois.c#L292 i.e https://github.com/ceph/jerasure/blob/v2/src/galois.c#L191 and then https://github.com/ceph/jerasure/blob/v2/src/galois.c#L175 which does a malloc that does not enforce alignment.

Should we relax the requirements or make sure https://github.com/ceph/jerasure/blob/v2/src/galois.c#L175 uses a logic similar to https://github.com/ceph/ceph/blob/giant/src/common/buffer.cc#L235 ?

Cheers
-- 
Loïc Dachary, Artisan Logiciel Libre


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