gfs2: allow quota_check and inplace_reserve to return available blocks

struct gfs2_alloc_parms is passed to gfs2_quota_check() and
gfs2_inplace_reserve() with ap->target containing the number of
blocks being requested for allocation in the current operation.

We add a new field to struct gfs2_alloc_parms called 'allowed'.
gfs2_quota_check() and gfs2_inplace_reserve() return the max
blocks allowed by quota and the max blocks allowed by the chosen
rgrp respectively in 'allowed'.

A new field 'min_target', when non-zero, tells gfs2_quota_check()
and gfs2_inplace_reserve() to not return -EDQUOT/-ENOSPC when
there are atleast 'min_target' blocks allowable/available. The
assumption is that the caller is ok with just 'min_target' blocks
and will likely proceed with allocating them.

Signed-off-by: Abhi Das <adas@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Acked-by: Steven Whitehouse <swhiteho@redhat.com>

fs/gfs2/incore.h

@@ -302,7 +302,9 @@ struct gfs2_blkreserv {
  */
 struct gfs2_alloc_parms {
 	u64 target;
+	u32 min_target;
 	u32 aflags;
+	u64 allowed;
 };
 
 enum {

fs/gfs2/quota.c

@@ -1094,15 +1094,33 @@ static int print_message(struct gfs2_quota_data *qd, char *type)
 	return 0;
 }
 
+/**
+ * gfs2_quota_check - check if allocating new blocks will exceed quota
+ * @ip:  The inode for which this check is being performed
+ * @uid: The uid to check against
+ * @gid: The gid to check against
+ * @ap:  The allocation parameters. ap->target contains the requested
+ *       blocks. ap->min_target, if set, contains the minimum blks
+ *       requested.
+ *
+ * Returns: 0 on success.
+ *                  min_req = ap->min_target ? ap->min_target : ap->target;
+ *                  quota must allow atleast min_req blks for success and
+ *                  ap->allowed is set to the number of blocks allowed
+ *
+ *          -EDQUOT otherwise, quota violation. ap->allowed is set to number
+ *                  of blocks available.
+ */
 int gfs2_quota_check(struct gfs2_inode *ip, kuid_t uid, kgid_t gid,
 		     struct gfs2_alloc_parms *ap)
 {
 	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
 	struct gfs2_quota_data *qd;
-	s64 value;
+	s64 value, warn, limit;
 	unsigned int x;
 	int error = 0;
 
+	ap->allowed = UINT_MAX; /* Assume we are permitted a whole lot */
 	if (!test_bit(GIF_QD_LOCKED, &ip->i_flags))
 		return 0;
 
@@ -1116,29 +1134,37 @@ int gfs2_quota_check(struct gfs2_inode *ip, kuid_t uid, kgid_t gid,
 		      qid_eq(qd->qd_id, make_kqid_gid(gid))))
 			continue;
 
+		warn = (s64)be64_to_cpu(qd->qd_qb.qb_warn);
+		limit = (s64)be64_to_cpu(qd->qd_qb.qb_limit);
 		value = (s64)be64_to_cpu(qd->qd_qb.qb_value);
 		spin_lock(&qd_lock);
-		value += qd->qd_change + ap->target;
+		value += qd->qd_change;
 		spin_unlock(&qd_lock);
 
-		if (be64_to_cpu(qd->qd_qb.qb_limit) && (s64)be64_to_cpu(qd->qd_qb.qb_limit) < value) {
-			print_message(qd, "exceeded");
-			quota_send_warning(qd->qd_id,
-					   sdp->sd_vfs->s_dev, QUOTA_NL_BHARDWARN);
-			error = -EDQUOT;
-			break;
-		} else if (be64_to_cpu(qd->qd_qb.qb_warn) &&
-			   (s64)be64_to_cpu(qd->qd_qb.qb_warn) < value &&
+		if (limit > 0 && (limit - value) < ap->allowed)
+			ap->allowed = limit - value;
+		/* If we can't meet the target */
+		if (limit && limit < (value + (s64)ap->target)) {
+			/* If no min_target specified or we don't meet
+			 * min_target, return -EDQUOT */
+			if (!ap->min_target || ap->min_target > ap->allowed) {
+				print_message(qd, "exceeded");
+				quota_send_warning(qd->qd_id,
+						   sdp->sd_vfs->s_dev,
+						   QUOTA_NL_BHARDWARN);
+				error = -EDQUOT;
+				break;
+			}
+		} else if (warn && warn < value &&
 			   time_after_eq(jiffies, qd->qd_last_warn +
-					 gfs2_tune_get(sdp,
-						gt_quota_warn_period) * HZ)) {
+					 gfs2_tune_get(sdp, gt_quota_warn_period)
+					 * HZ)) {
 			quota_send_warning(qd->qd_id,
 					   sdp->sd_vfs->s_dev, QUOTA_NL_BSOFTWARN);
 			error = print_message(qd, "warning");
 			qd->qd_last_warn = jiffies;
 		}
 	}
-
 	return error;
 }
 

fs/gfs2/rgrp.c

@@ -1946,10 +1946,18 @@ static inline int fast_to_acquire(struct gfs2_rgrpd *rgd)
  * @ip: the inode to reserve space for
  * @ap: the allocation parameters
  *
- * Returns: errno
+ * We try our best to find an rgrp that has at least ap->target blocks
+ * available. After a couple of passes (loops == 2), the prospects of finding
+ * such an rgrp diminish. At this stage, we return the first rgrp that has
+ * atleast ap->min_target blocks available. Either way, we set ap->allowed to
+ * the number of blocks available in the chosen rgrp.
+ *
+ * Returns: 0 on success,
+ *          -ENOMEM if a suitable rgrp can't be found
+ *          errno otherwise
  */
 
-int gfs2_inplace_reserve(struct gfs2_inode *ip, const struct gfs2_alloc_parms *ap)
+int gfs2_inplace_reserve(struct gfs2_inode *ip, struct gfs2_alloc_parms *ap)
 {
 	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
 	struct gfs2_rgrpd *begin = NULL;
@@ -2012,7 +2020,7 @@ int gfs2_inplace_reserve(struct gfs2_inode *ip, const struct gfs2_alloc_parms *a
 		/* Skip unuseable resource groups */
 		if ((rs->rs_rbm.rgd->rd_flags & (GFS2_RGF_NOALLOC |
 						 GFS2_RDF_ERROR)) ||
-		    (ap->target > rs->rs_rbm.rgd->rd_extfail_pt))
+		    (loops == 0 && ap->target > rs->rs_rbm.rgd->rd_extfail_pt))
 			goto skip_rgrp;
 
 		if (sdp->sd_args.ar_rgrplvb)
@@ -2027,11 +2035,13 @@ int gfs2_inplace_reserve(struct gfs2_inode *ip, const struct gfs2_alloc_parms *a
 			goto check_rgrp;
 
 		/* If rgrp has enough free space, use it */
-		if (rs->rs_rbm.rgd->rd_free_clone >= ap->target) {
+		if (rs->rs_rbm.rgd->rd_free_clone >= ap->target ||
+		    (loops == 2 && ap->min_target &&
+		     rs->rs_rbm.rgd->rd_free_clone >= ap->min_target)) {
 			ip->i_rgd = rs->rs_rbm.rgd;
+			ap->allowed = ip->i_rgd->rd_free_clone;
 			return 0;
 		}
-
 check_rgrp:
 		/* Check for unlinked inodes which can be reclaimed */
 		if (rs->rs_rbm.rgd->rd_flags & GFS2_RDF_CHECK)

fs/gfs2/rgrp.h

@@ -41,7 +41,8 @@ extern void gfs2_rgrp_go_unlock(struct gfs2_holder *gh);
 extern struct gfs2_alloc *gfs2_alloc_get(struct gfs2_inode *ip);
 
 #define GFS2_AF_ORLOV 1
-extern int gfs2_inplace_reserve(struct gfs2_inode *ip, const struct gfs2_alloc_parms *ap);
+extern int gfs2_inplace_reserve(struct gfs2_inode *ip,
+				struct gfs2_alloc_parms *ap);
 extern void gfs2_inplace_release(struct gfs2_inode *ip);
 
 extern int gfs2_alloc_blocks(struct gfs2_inode *ip, u64 *bn, unsigned int *n,