[Cluster-devel] [GFS2 PATCH 4/4] gfs2: allow fallocate to max out quotas/fs efficiently

[Abhi Das <adas@redhat.com>]

With the addition of gfs2_quota_lck_chk_ret_allow() and
gfs2_inpl_rsrv_ret_max_avl(), we can quickly get an estimate of
how many more blocks are available for allocation restricted by
quota and fs size respectively.
By trying to allocate what's available instead of guessing, we
can max out quotas or the filesystem efficiently.

Bear in mind that this applies only when the requested fallocate
operation would otherwise error out with -EDQUOT or -ENOSPC without
utilizing all the blocks that might still be available.

Signed-off-by: Abhi Das <adas@redhat.com>
---
 fs/gfs2/file.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index c9482ae..9d8e03a 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -805,6 +805,7 @@ static long __gfs2_fallocate(struct file *file, int mode, loff_t offset, loff_t
 	loff_t bsize_mask = ~((loff_t)sdp->sd_sb.sb_bsize - 1);
 	loff_t next = (offset + len - 1) >> sdp->sd_sb.sb_bsize_shift;
 	loff_t max_chunk_size = UINT_MAX & bsize_mask;
+	u32 allow;
 
 	next = (next + 1) << sdp->sd_sb.sb_bsize_shift;
 
@@ -828,20 +829,25 @@ static long __gfs2_fallocate(struct file *file, int mode, loff_t offset, loff_t
 			offset += bytes;
 			continue;
 		}
-		error = gfs2_quota_lock_check(ip, bytes >> sdp->sd_sb.sb_bsize_shift);
-		if (error)
+	quota_retry:
+		error = gfs2_quota_lck_chk_ret_allow(ip, 
+						     bytes >> sdp->sd_sb.sb_bsize_shift,
+						     &allow);
+		if (error) {
+			if (error == -EDQUOT && allow) {
+				bytes = allow << sdp->sd_sb.sb_bsize_shift;
+				goto quota_retry;
+			}
 			return error;
-retry:
+		}
+	retry:
 		gfs2_write_calc_reserv(ip, bytes, &data_blocks, &ind_blocks);
 
 		ap.target = data_blocks + ind_blocks;
-		error = gfs2_inplace_reserve(ip, &ap);
+		error = gfs2_inpl_rsrv_ret_max_avl(ip, &ap, &allow);
 		if (error) {
-			if (error == -ENOSPC && bytes > sdp->sd_sb.sb_bsize) {
-				bytes >>= 1;
-				bytes &= bsize_mask;
-				if (bytes == 0)
-					bytes = sdp->sd_sb.sb_bsize;
+			if (error == -ENOSPC && allow) {
+				bytes = allow << sdp->sd_sb.sb_bsize_shift;
 				goto retry;
 			}
 			goto out_qunlock;
-- 
1.8.1.4