xfs: flush speculative space allocations when we run out of quota

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 <darrick.wong@oracle.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index e62fb5216341..ce463e3b61af 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;
+			goto error2;
+		}
 		if (error)
 			goto error1;
 
@@ -857,6 +873,7 @@ error0:	/* unlock inode, unreserve quota blocks, cancel trans */
 error1:	/* Just cancel transaction */
 	xfs_trans_cancel(tp);
 	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+error2:
 	return error;
 }