On 09/06/2016 11:51 PM, Xiao Guangrong wrote: > In order to fix this bug, we make 'file->version' indicate the next VMA > we want to handle This new approach makes it more likely that we'll skip a new VMA that gets inserted in between the read()s. But, I guess that's OK. We don't exactly claim to be giving super up-to-date data at the time of read(). With the old code, was there also a case that we could print out the same virtual address range more than once? It seems like that could happen if we had a VMA split between two reads. I think this introduces one oddity: if you have a VMA merge between two reads(), you might get the same virtual address range twice in your output. This didn't happen before because we would have just skipped over the area that got merged. Take two example VMAs: vma-A: (0x1000 -> 0x2000) vma-B: (0x2000 -> 0x3000) read() #1: prints vma-A, sets m->version=0x2000 Now, merge A/B to make C: vma-C: (0x1000 -> 0x3000) read() #2: find_vma(m->version=0x2000), returns vma-C, prints vma-C The user will see two VMAs in their output: A: 0x1000->0x2000 C: 0x1000->0x3000 Will it confuse them to see the same virtual address range twice? Or is there something preventing that happening that I'm missing? -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
