On Fri, Jan 16, 2009 at 02:28:04PM +0900, MinChan Kim wrote: > Now, Anyone don't maintain cramfs. > I don't know who is maintain romfs. so I send this patch to linux-mm, > lkml, linux-dev. > > I am not sure my thought is right. > > When readpage is called, page with argument in readpage is just new > allocated because kernel can't find that page in page cache. > > At this time, any user process can't map the page to their address space. > so, I think D-cache aliasing probelm never occur. > > It make sense ? Sorry, no. You have to call fluch_dcache_page() in two situations -- when the kernel is going to read some data that userspace wrote, *and* when userspace is going to read some data that the kernel wrote. From a quick look at the patch, this seems to be the second case. The kernel wrote data to a pagecache page, and userspace should be able to read it. To understand why this is necessary, consider a processor which is virtually indexed and has a writeback cache. The kernel writes to a page, then a user process reads from the same page through a different address. The cache doesn't find the data the kernel wrote because it has a different virtual index, so userspace reads stale data. -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
