On Mon, Dec 21, 2015 at 06:15:12PM +0100, Jan Kara wrote: > On Fri 18-12-15 22:22:15, Ross Zwisler wrote: > > Add support for tracking dirty DAX entries in the struct address_space > > radix tree. This tree is already used for dirty page writeback, and it > > already supports the use of exceptional (non struct page*) entries. > > > > In order to properly track dirty DAX pages we will insert new exceptional > > entries into the radix tree that represent dirty DAX PTE or PMD pages. > > These exceptional entries will also contain the writeback addresses for the > > PTE or PMD faults that we can use at fsync/msync time. > > > > There are currently two types of exceptional entries (shmem and shadow) > > that can be placed into the radix tree, and this adds a third. We rely on > > the fact that only one type of exceptional entry can be found in a given > > radix tree based on its usage. This happens for free with DAX vs shmem but > > we explicitly prevent shadow entries from being added to radix trees for > > DAX mappings. > > > > The only shadow entries that would be generated for DAX radix trees would > > be to track zero page mappings that were created for holes. These pages > > would receive minimal benefit from having shadow entries, and the choice > > to have only one type of exceptional entry in a given radix tree makes the > > logic simpler both in clear_exceptional_entry() and in the rest of DAX. > > > > Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx> > > The patch looks good to me. Just one comment: When we have this exclusion > between different types of exceptional entries, there is no real need to > have separate counters of 'shadow' and 'dax' entries, is there? We can have > one 'nrexceptional' counter and don't have to grow struct inode > unnecessarily which would be really welcome since DAX isn't a mainstream > feature. Could you please change the code? Thanks! Sure, this sounds good. Thanks! -- 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>