[sorry for that html crap :(] On Friday 03 April 2009 01:36:12 David Howells wrote: > Nick Piggin <nickpiggin@xxxxxxxxxxxx> wrote: > > > 1) PG_mappedtodisk is basically PG_owner_priv_2. Please alias that and > > use it? Then at least we're down to 1 extra flag. > > 2) Why do you need another PG_private? PG_private for pagecache means > > that it should call into the filesystem when it needs to handle fs data > > attached to the page, right? So PG_private_2 doesn't really make sense > > in that respect. > > Won't that either break fs/buffer.c and fs/mpage.c or preclude the use of > FS-Cache with block-based filesystems that use the standard buffer wangling > routines? Haven't looked closely at how fscache works. Possibly you can't reuse mappedtodisk.... But PG_private. PG_private from the vm/vfs side means to call into the filesystem. So from that point, the filesystem should handle it. It just doesn't seem to make sense to have 2 flags for this. I mean, there is only the single aop that can be called, so having 2 VM visible flags doesn't help the VM do anything, and presumably your aop knows how to handle this, so it should be an fs private bit. Just give me a situation of why it won't work. > As I've previously stated, I want to be able to make ISO9660 use FS-Cache. > That rules out use of PG_mappedtodisk and PG_private for anything FS-Cache > related. > > We can actually reclaim PG_private, I think. There are patches to do that. > At the very least, we can probably reclaim the std buffering code's use of it. But that's peripheral issue. > If anything, avoiding the need for PG_fscache_write is probably easier - just > more memory intensive and slower. I could build a second radix tree for each > inode that kept track of which pages from that inode FS-Cache knows about, and > use the status bits in that node to keep track of what pages are being written > out to the cache. If it's not much slower, that would be nice. > We still need a way of triggering the page invalidation callbacks for in-use > pages, however. PG_private, as I've said, is not currently a viable option. Can you say exactly why not? -- 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
