Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > Looks like a reasonable patch, but the one thing you didn't say is whether > there is any code that relies on the incorrectly documented behavior? Sorry, yes. I've made an assumption in FS-Cache that I can rely on the result of radix_tree_tag_get() simply by wrapping it in an rcu_read_lock()'d section. This has proven not to be so, since the BUG_ON() at line 602 in lib/radix-tree.c triggered. I was protecting set/clear/delete from each other, but not protecting get from set/clear/delete. > How did you find this? Do we need to fix actual code too? The only user > seems to be your fscache/page.c thing, and I'm not seeing any locking > except for the rcu locking that is apparently not sufficient. As mentioned above, someone reported a bug in fscache that led me to this: https://www.redhat.com/archives/linux-cachefs/2010-April/msg00013.html I may need to fix fscache, but I wanted to see if anyone would suggest an alternate patch that would continue to let me make a test without having to grab the spinlock first. I'll update the patch to reflect this, whatever the final patch ends up being. David -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>