On Thu, Mar 31, 2022 at 06:56:32PM -0400, Jeff Layton wrote: > The inode_insert5 currently looks at I_CREATING to decide whether to > insert the inode into the sb list. This test is a bit ambiguous though > as I_CREATING state is not directly related to that list. > > This test is also problematic for some upcoming ceph changes to add > fscrypt support. We need to be able to allocate an inode using new_inode > and insert it into the hash later if we end up using it, and doing that > now means that we double add it and corrupt the list. > > What we really want to know in this test is whether the inode is already > in its superblock list, and then add it if it isn't. Have it test for > list_empty instead and ensure that we always initialize the list by > doing it in inode_init_once. It's only ever removed from the list with > list_del_init, so that should be sufficient. > > Suggested-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> > --- > fs/inode.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > > This is the alternate approach that Al suggested to me on IRC. I think > this is likely to be more robust in the long run, and we can avoid > exporting another symbol. Looks good to me. Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx> FWIW, I'm getting ready to resend patches originally written by Waiman Long years ago to convert the inode sb list to a different structure (per-cpu lists) for scalability reasons, but is still allows using list-empty() to check if the inode is on the list or not so I dont' see a problem with this change at all. > Al, if you're ok with this, would you mind taking this in via your tree? > I'd like to see this in sit in linux-next for a bit so we can see if any > benchmarks get dinged. I think that is unlikely - the sb inode list just doesn't show up in profiles until you are pushing several hundred thousand inodes a second through the inode cache and there really aren't a lot of worklaods out there that do that. At that point, sb list lock contention becomes the issue, not the requirement to add in-use inodes to the sb list... e.g. concurrent 'find <...> -ctime' operations on XFS hit sb list lock contention limits at about 600,000 inodes/s being, instantiated, stat()d and reclaimed from memory. With Waiman's dlist code I mention above, it'll do 1.5 million inodes/s for the same CPU usage. And a concurrent bulkstat workload goes from 600,000 inodes/s to over 6 million inodes/s for the same CPU usage. That bulkstat workload is hitting memory reclaim scalability limits as I'm turning over ~12GB/s of cached memory on a machine with only 16GB RAM... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
