On Wed, Oct 10, 2012 at 05:42:18PM -0700, Nitin Gupta wrote: > Change 130f315a (staging: zram: remove special handle of uncompressed page) > introduced a bug in the handling of incompressible pages which resulted in > memory allocation failure for such pages. > > When a page expands on compression, say from 4K to 4K+30, we were trying to > do zsmalloc(pool, 4K+30). However, the maximum size which zsmalloc can > allocate is PAGE_SIZE (for obvious reasons), so such allocation requests > always return failure (0). > > For a page that has compressed size larger than the original size (this may > happen with already compressed or random data), there is no point storing > the compressed version as that would take more space and would also require > time for decompression when needed again. So, the fix is to store any page, > whose compressed size exceeds a threshold (max_zpage_size), as-it-is i.e. > without compression. Memory required for storing this uncompressed page can > then be requested from zsmalloc which supports PAGE_SIZE sized allocations. > > Lastly, the fix checks that we do not attempt to "decompress" the page which > we stored in the uncompressed form -- we just memcpy() out such pages. So this fix needs to go to the stable 3.6 release also, right? thanks, greg k-h _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
