On Wed, Apr 26, 2017 at 10:04:26AM +1000, Dave Chinner wrote: > On Tue, Apr 25, 2017 at 10:25:03AM +0200, Luis R. Rodriguez wrote: > > I checked with Jan Kara and he believes the current code is correct but that > > its the comment that that may be misleading. As per Jan the race is between > > getting an inode reclaimed and grabbing it. Ie, XFS frees the inodes by RCU. > > However it doesn't actually *reuse* the inode until RCU period passes > > (unlike inodes allocated from slab with SLAB_RCU can be). So it can happen > > ..... I initially tried using SLAB_DESTROY_BY_RCU which meant the > RCU grace period did not prevent reallocation of inodes that had > been freed. Hence this check was (once) necessary to prevent the > reclaim index going whacky on a reallocated inode. Alright this helps, but why does *having* the RCU grace period prevent such type of race ? I can see it helping but removing completely such a race as a possibility ? Also, just so I understand I am following, this then implicates our reclaim rate is directly linked to the RCU grace period ? Luis -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
