| Message ID | 157343511427.1948946.2692071497822316839.stgit@magnolia (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | xfs: various fixes | expand |
On Sun, Nov 10, 2019 at 05:18:34PM -0800, Darrick J. Wong wrote: > From: Darrick J. Wong <darrick.wong@oracle.com> > > Make sure we attach dquots to both inodes before swapping their extents. > This was found via manual code inspection by looking for places where we > could call xfs_trans_mod_dquot without dquots attached to inodes, and > confirmed by instrumenting the kernel and running xfs/328. Looks good: Reviewed-by: Christoph Hellwig <hch@lst.de> Btw, for while I've been wondering if we could just get rid of the concepts of attached dquots. With the radix-tree/xarray looks up are be fairly cheap, and could be done lockless using RCU. So we could try to just kill the concept of attaching the dquot to the inode and just look it up once per operation, where operation preferally is something high-level like the actual file/inode operation and not a low-level thing inside xfs.
On Mon, Nov 11, 2019 at 12:05:03AM -0800, Christoph Hellwig wrote: > On Sun, Nov 10, 2019 at 05:18:34PM -0800, Darrick J. Wong wrote: > > From: Darrick J. Wong <darrick.wong@oracle.com> > > > > Make sure we attach dquots to both inodes before swapping their extents. > > This was found via manual code inspection by looking for places where we > > could call xfs_trans_mod_dquot without dquots attached to inodes, and > > confirmed by instrumenting the kernel and running xfs/328. > > Looks good: > > Reviewed-by: Christoph Hellwig <hch@lst.de> > > Btw, for while I've been wondering if we could just get rid of the > concepts of attached dquots. With the radix-tree/xarray looks up > are be fairly cheap, and could be done lockless using RCU. So we could > try to just kill the concept of attaching the dquot to the inode and > just look it up once per operation, where operation preferally is > something high-level like the actual file/inode operation and not a > low-level thing inside xfs. If the dquots are not attached to the inode, how would you pass the 3 dquots per inode down the stack to where they are actually used inside the filesystem? I mean, we have to get the dquots attached to the transaction so we can update them in xfs_trans_commit -> xfs_trans_apply_dquot_deltas(), so somehow we'd have to get them from the high level file/inode operations down to the XFS transaction context. And things like writeback need dquots attached for delayed allocation, so various aops would need to do dquot lookups, too... I can see the advantage of doing rcu dquot cache lookups in the xfs context where we are attaching the dquots to the transaction rather than attaching them to the inode, but I can't see how the "do it at a high level" aspect of this would work.... Cheers, Dave.
On Wed, Nov 13, 2019 at 09:14:48AM +1100, Dave Chinner wrote: > If the dquots are not attached to the inode, how would you pass the > 3 dquots per inode down the stack to where they are actually used > inside the filesystem? I mean, we have to get the dquots attached to > the transaction so we can update them in xfs_trans_commit -> > xfs_trans_apply_dquot_deltas(), so somehow we'd have to get them > from the high level file/inode operations down to the XFS > transaction context. And things like writeback need dquots attached > for delayed allocation, so various aops would need to do dquot > lookups, too... My prime idea was to attach them to the transaction and keep them over transaction roles. Then see what is left and probably use an on-stack struct containing three dquots. At that point I know if that idea was feasible, because if we have too many deep callstacks where we need to pass that struct it obviously isn't. > I can see the advantage of doing rcu dquot cache lookups in the xfs > context where we are attaching the dquots to the transaction rather > than attaching them to the inode, but I can't see how the "do it at > a high level" aspect of this would work.... Most of our ops really just have one transaction / set of rolled over permanent transactions, because if they didn't they wouldn't be atomic..
diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c index 9d731b71e84f..2efd78a9719e 100644 --- a/fs/xfs/xfs_bmap_util.c +++ b/fs/xfs/xfs_bmap_util.c @@ -1569,6 +1569,14 @@ xfs_swap_extents( goto out_unlock; } + error = xfs_qm_dqattach(ip); + if (error) + goto out_unlock; + + error = xfs_qm_dqattach(tip); + if (error) + goto out_unlock; + error = xfs_swap_extent_flush(ip); if (error) goto out_unlock;