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xfs: garbage collect old cowextsz reservations

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Trim CoW reservations made on behalf of a cowextsz hint if they get too
old or we run low on quota, so long as we don't have dirty data awaiting
writeback or directio operations in progress.

Garbage collection of the cowextsize extents are kept separate from
prealloc extent reaping because setting the CoW prealloc lifetime to a
(much) higher value than the regular prealloc extent lifetime has been
useful for combatting CoW fragmentation on VM hosts where the VMs
experience bursty write behaviors and we can keep the utilization ratios
low enough that we don't start to run out of space.  IOWs, it benefits
us to keep the CoW fork reservations around for as long as we can unless
we run out of blocks or hit inode reclaim.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Darrick J. Wong 2016-10-03 09:11:46 -07:00
parent 90e2056d76
commit 83104d449e
15 changed files with 287 additions and 32 deletions
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38
fs/xfs/xfs_reflink.c
View file

@ -304,6 +304,9 @@ retry:
goto out_unlock;
}
if (end_fsb != orig_end_fsb)
xfs_inode_set_cowblocks_tag(ip);
trace_xfs_reflink_cow_alloc(ip, &got);
done:
*offset_fsb = end_fsb;
@ -1562,6 +1565,7 @@ next:
/* Clear the inode flag. */
trace_xfs_reflink_unset_inode_flag(ip);
ip->i_d.di_flags2 &= ~XFS_DIFLAG2_REFLINK;
xfs_inode_clear_cowblocks_tag(ip);
xfs_trans_ijoin(*tpp, ip, 0);
xfs_trans_log_inode(*tpp, ip, XFS_ILOG_CORE);
@ -1662,3 +1666,37 @@ out:
trace_xfs_reflink_unshare_error(ip, error, _RET_IP_);
return error;
}
/*
* Does this inode have any real CoW reservations?
*/
bool
xfs_reflink_has_real_cow_blocks(
struct xfs_inode *ip)
{
struct xfs_bmbt_irec irec;
struct xfs_ifork *ifp;
struct xfs_bmbt_rec_host *gotp;
xfs_extnum_t idx;
if (!xfs_is_reflink_inode(ip))
return false;
/* Go find the old extent in the CoW fork. */
ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
gotp = xfs_iext_bno_to_ext(ifp, 0, &idx);
while (gotp) {
xfs_bmbt_get_all(gotp, &irec);
if (!isnullstartblock(irec.br_startblock))
return true;
/* Roll on... */
idx++;
if (idx >= ifp->if_bytes / sizeof(xfs_bmbt_rec_t))
break;
gotp = xfs_iext_get_ext(ifp, idx);
}
return false;
}