On Mon, Jan 11, 2021 at 06:18:37PM -0800, Darrick J. Wong wrote:
> On Tue, Jan 12, 2021 at 12:40:45PM +1100, Dave Chinner wrote:
> > On Mon, Jan 11, 2021 at 05:31:26PM -0800, Darrick J. Wong wrote:
> > > On Tue, Jan 12, 2021 at 12:22:49PM +1100, Dave Chinner wrote:
> > > > On Mon, Jan 11, 2021 at 03:23:05PM -0800, Darrick J. Wong wrote:
> > > > > From: Darrick J. Wong <djwong@xxxxxxxxxx>
> > > > >
> > > > > If a fs modification (creation, file write, reflink, etc.) is unable to
> > > > > reserve enough quota to handle the modification, try clearing whatever
> > > > > space the filesystem might have been hanging onto in the hopes of
> > > > > speeding up the filesystem. The flushing behavior will become
> > > > > particularly important when we add deferred inode inactivation because
> > > > > that will increase the amount of space that isn't actively tied to user
> > > > > data.
> > > > >
> > > > > Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
> > > > > ---
> > > > > fs/xfs/xfs_bmap_util.c | 16 ++++++++++++++++
> > > > > fs/xfs/xfs_file.c | 2 +-
> > > > > fs/xfs/xfs_icache.c | 9 +++++++--
> > > > > fs/xfs/xfs_icache.h | 2 +-
> > > > > fs/xfs/xfs_inode.c | 17 +++++++++++++++++
> > > > > fs/xfs/xfs_ioctl.c | 2 ++
> > > > > fs/xfs/xfs_iomap.c | 20 +++++++++++++++++++-
> > > > > fs/xfs/xfs_reflink.c | 40 +++++++++++++++++++++++++++++++++++++---
> > > > > fs/xfs/xfs_trace.c | 1 +
> > > > > fs/xfs/xfs_trace.h | 40 ++++++++++++++++++++++++++++++++++++++++
> > > > > 10 files changed, 141 insertions(+), 8 deletions(-)
> > > > >
> > > > >
> > > > > diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> > > > > index 7371a7f7c652..437fdc8a8fbd 100644
> > > > > --- a/fs/xfs/xfs_bmap_util.c
> > > > > +++ b/fs/xfs/xfs_bmap_util.c
> > > > > @@ -761,6 +761,7 @@ xfs_alloc_file_space(
> > > > > */
> > > > > while (allocatesize_fsb && !error) {
> > > > > xfs_fileoff_t s, e;
> > > > > + bool cleared_space = false;
> > > > >
> > > > > /*
> > > > > * Determine space reservations for data/realtime.
> > > > > @@ -803,6 +804,7 @@ xfs_alloc_file_space(
> > > > > /*
> > > > > * Allocate and setup the transaction.
> > > > > */
> > > > > +retry:
> > > > > error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks,
> > > > > resrtextents, 0, &tp);
> > > > >
> > > > > @@ -819,6 +821,20 @@ xfs_alloc_file_space(
> > > > > xfs_ilock(ip, XFS_ILOCK_EXCL);
> > > > > error = xfs_trans_reserve_quota_nblks(tp, ip, qblocks,
> > > > > 0, quota_flag);
> > > > > + /*
> > > > > + * We weren't able to reserve enough quota to handle fallocate.
> > > > > + * Flush any disk space that was being held in the hopes of
> > > > > + * speeding up the filesystem. We hold the IOLOCK so we cannot
> > > > > + * do a synchronous scan.
> > > > > + */
> > > > > + if ((error == -ENOSPC || error == -EDQUOT) && !cleared_space) {
> > > > > + xfs_trans_cancel(tp);
> > > > > + xfs_iunlock(ip, XFS_ILOCK_EXCL);
> > > > > + cleared_space = xfs_inode_free_quota_blocks(ip, false);
> > > > > + if (cleared_space)
> > > > > + goto retry;
> > > > > + return error;
> > > >
> > > > Can't say I'm a fan of repeating this everywhere. Can we move this
> > > > into xfs_trans_reserve_quota_nblks() with a "retry" flag such that
> > > > we do:
> > > >
> > > > error = xfs_trans_reserve_quota_nblks(tp, ip, qblocks, 0,
> > > > quota_flag, &retry);
> > > > if (error) {
> > > > /* tp already cancelled, inode unlocked */
> > > > return error;
> > > > }
> > > > if (retry) {
> > > > /* tp already cancelled, inode unlocked */
> > > > goto retry;
> > > > }
> > >
> > > Assuming you'd be interested in the same kind of change being applied to
> > > the next patch (kick the inode reclaim from xfs_trans_reserve on ENOSPC)
> > > then yes, that seems like a nice cleanup.
> >
> > *nod*
> >
> > It definitely seems to me to be cleaner to put all this GC stuff
> > into the transaction setup code that does the actual space
> > reservation, and then simply have the code that is setting up the
> > transactions handle failures appropriately.
>
> I tried converting this and it wasn't as easy as I thought.
>
> The downside is that now we have a function that sometimes consumes the
> transaction and the ILOCK, and there's still the question of what to do
> if xfs_inode_free_quota_blocks doesn't find any space to free.
>
> By leaving all the ugliness in the call sites, we maintain the property
> that the function that allocates the transaction and ilocks the inode
> also gets to iunlock and free the tp, and we can also skip the retry if
> the eofblocks flush doesn't clear anything.
>
> It might be easier to rework this as a xfs_trans_alloc_quota function
> wherein you feed it a tres, the inode, the number of blocks you want,
> and whether or not this is an rt extent; and either it reserves and
> locks everything for you, or returns failure. The downside is that
> doesn't work for reflink since it doesn't always require quota
> reservation to remap an extent.
>
> But it's pretty late in the day and my brain is scrambled eggs so I'll
> defer until tomorrow.
...until three days later. You were right, it wasn't so difficult to
make xfs_trans_reserve_quota_nblks cancel the transaction on all errors,
and run the scan if it hit edquot/enospc.
--D
> --D
>
> > Cheers,
> >
> > Dave.
> > --
> > Dave Chinner
> > david@xxxxxxxxxxxxx
