[PATCH 0/5] xfs: run eofblocks scan on ENOSPC

[Brian Foster <bfoster@redhat.com>]

Hi all,

The purpose of this series is to help address the inefficient use of
preallocation for larger files on smaller filesystems. When the
filesystem is small, so is the 5% low free space threshold that enables
preallocation throttling. When the low free space threshold is reduced
to a couple GB or so, we can ram into ENOSPC prematurely due to larger,
active preallocations.

We resolve this condition with an eofblocks scan in the pre-existing
ENOSPC retry write sequence. The scan resets outstanding preallocations
such that throttling is guaranteed an opportunity to manage future
preallocations gracefully into ENOSPC and thus ensures closer to 100%
utilization before ENOSPC is reported to userspace.

Patches 1-3 make some small enhancements to the eofblocks scanner that
facilitate running a scan in the context of a write. Patch 4 adds the
actual scan-on-ENOSPC policy. Patch 5 updates the preallocation
throttling algorithm to take quota free space into account.

Thoughts, reviews, flames appreciated.

Brian

Brian Foster (5):
  xfs: do eofb filtering before dirty check
  xfs: add flush flag to xfs_eofblocks
  xfs: add scan owner field to xfs_eofblocks
  xfs: run an eofblocks scan on ENOSPC/EDQUOT
  xfs: squash prealloc while over quota free space as well

 fs/xfs/xfs_dquot.h  | 15 +++++++++
 fs/xfs/xfs_file.c   | 32 +++++++++++++++++--
 fs/xfs/xfs_fs.h     |  4 ++-
 fs/xfs/xfs_icache.c | 90 +++++++++++++++++++++++++++++++++++++++++++++++------
 fs/xfs/xfs_icache.h |  3 ++
 fs/xfs/xfs_iomap.c  | 20 ++++++++----
 6 files changed, 145 insertions(+), 19 deletions(-)

-- 
1.8.3.1

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