On Fri, Apr 15, 2011 at 11:54 PM, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > On Fri, Apr 15, 2011 at 2:09 PM, Andi Kleen <ak@xxxxxxxxxxxxxxx> wrote: >> On 4/15/2011 11:39 AM, Tim Chen wrote: >>> >>> During RCU walk in path_lookupat and path_openat, the rcu lookup >>> frequently failed because when root directory was looked up, seq number >>> was not properly set in nameidata. ÂWe dropped out of RCU walk in >>> nameidata_drop_rcu due to mismatch in directory entry's seq number. ÂWe >>> reverted to slow path walk that need to take references. >> >> Thanks Tim. Adding Andrew, Linus too. IMHO this fix is quite important to >> actually make the fabled RCU dcache work -- without it it's just slower >> because >> it will fallback nearly allways. > > Well, only for absolute paths, but yes. > > I think all my benchmarking was for thing like "git diff", which are > all about the relative paths and wouldn't have triggered this case. > > So this patch does look correct, and yes, should also be stable material for 38. > > And it's pretty fundamental. But I'd like to get a few more acks > exactly because it's so fundamental. Al and Nick sadly are both gone. > Anybody else feel like they know something about the path lookup code? > > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Linus > I see this patch was pushed. What's with fs-synchronize_rcu-when-unregister_filesystem-success-not-failure.patch from [1]? - Sedat - [1] https://patchwork.kernel.org/patch/707322/ -- 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
