Messages in this thread | | | Date | Thu, 7 Jun 2007 12:19:19 +0530 | From | "Nitin Gupta" <> | Subject | Re: [RFC] LZO de/compression support - take 7 |
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On 6/6/07, Nitin Gupta <nitingupta910@gmail.com> wrote: > On 6/6/07, Christoph Hellwig <hch@infradead.org> wrote: > > On Wed, Jun 06, 2007 at 06:04:17PM +0530, Nitin Gupta wrote: > > > Hi, > > > > > > This is kernel port of LZO1X-1 compressor and LZO1X decompressor (safe > > > version only). > > > > > > * Changes since 'take 6' (Full Changelog after this): > > > 1) Fixed unaligned memory access problems as pointed out by author -- > > > LZO_UNALIGNED_OK_{2,4} collapsed to UNALIGNED_OK which is #defined for > > > archs that allow unaligned access (see lib/lzo1x/Makefile). For other > > > archs, we fall down to byte-by-byte access avoiding any unaligned > > > access. In original code, LZO_UNALIGNED_OK_{2,4} resp. describe if we > > > can do unaligned access for ushort and uint32. > > > > Please use get_unaligned() for any unaligned access in kernel space. > > > > > > Done. >
Just as a side note: I think retaining code to do byte-by-byte access also is worth it, such as: + #ifdef UNALIGNED_OK + if (get_unaligned((const unsigned short *)m_pos) == + get_unaligned((const unsigned short *)ip)) { +#else + if (m_pos[0] != ip[0] || m_pos[1] != ip[1]) { +#endif
Since on archs where unaligned access is slower than byte-by-byte access (e.g. where unaligned access dirty work is done in s/w), we do not want to use get_unaligned() - instead simply byte-by-byte access is better.
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