On Tue, Jan 17, 2017 at 10:07 PM, <willy@xxxxxxxxxxxxxxxxxxxxxx> wrote: > On Tue, Jan 17, 2017 at 10:01:30PM -0800, Dan Williams wrote: >> >> - Jan suggested [2] that we could use the radix tree as a cache to service DAX >> >> faults without needing to call into the filesystem. Are there any issues >> >> with this approach, and should we move forward with it as an optimization? >> > >> > Ahem. I believe I proposed this at last year's LSFMM. And I sent >> > patches to start that work. And Dan blocked it. So I'm not terribly >> > amused to see somebody else given credit for the idea. >> >> I "blocked" moving the phys to virt translation out of the driver >> since that mapping lifetime is device specific. > > The problem is that DAX currently assumes that there *is* a block driver, > and it might be a char device or no device at all (the two examples I > gave earlier). > >> However, I think caching the file offset to physical sector/address >> result is a great idea. > > OK, great. The lifetime problem I think you care about (hotplug) can be > handled by removing all the cached entries for every file on every file > on that block device ... I know there were prototype patches for that; > did they ever get merged? No, they didn't.. The last review comment was from Al. He wanted the mechanism converted from explicit calls at del_gendisk() time into a notifier chain since it's not just filesystems that may want to register for a block-device end-of-life event. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>