[PATCH v5 net 03/10] octeontx2-af: npc: cn20k: Propagate errors in defrag MCAM alloc rollback

[Ratheesh Kannoth]

npc_defrag_alloc_free_slots() allocates MCAM indexes in up to two passes on
bank0 then bank1. On failure it rolls back by freeing entries already
placed in save[].

__npc_subbank_alloc() can return a negative errno while only part of the
indexes are valid. The rollback loop used rc for
npc_mcam_idx_2_subbank_idx() as well, so a successful lookup stored zero in
rc and a later __npc_subbank_free() failure could still end with return 0
when the allocation path had also left rc at zero (for example shortfall
after zero return values from the alloc helpers).

Jump to the rollback path immediately when either __npc_subbank_alloc()
call fails, preserving its errno. If both calls succeed but the total
allocated count is still less than cnt, set rc to -ENOSPC before rollback.
Use a separate err variable for npc_mcam_idx_2_subbank_idx() so a
successful lookup no longer clears a non-zero rc from the allocation phase.

Cc: Dan Carpenter <error27@xxxxxxxxx>
Fixes: 645c6e3c1999 ("octeontx2-af: npc: cn20k: virtual index support")
Link: https://lore.kernel.org/netdev/adjNJEpILRZATB2N@stanley.mountain/
Reviewed-by: Simon Horman <horms@xxxxxxxxxx>
Signed-off-by: Ratheesh Kannoth <rkannoth@xxxxxxxxxxx>
---
 .../net/ethernet/marvell/octeontx2/af/cn20k/npc.c    | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/marvell/octeontx2/af/cn20k/npc.c b/drivers/net/ethernet/marvell/octeontx2/af/cn20k/npc.c
index 7170dcf26200..87da43088b67 100644
--- a/drivers/net/ethernet/marvell/octeontx2/af/cn20k/npc.c
+++ b/drivers/net/ethernet/marvell/octeontx2/af/cn20k/npc.c
@@ -2338,6 +2338,7 @@ static int __npc_subbank_alloc(struct rvu *rvu, struct npc_subbank *sb,
 		__npc_subbank_mark_free(rvu, sb);
 err1:
 	kfree(save);
+	*alloc_cnt = 0;
 	return rc;
 }
 
@@ -3515,7 +3516,7 @@ static int npc_defrag_alloc_free_slots(struct rvu *rvu,
 {
 	int alloc_cnt1, alloc_cnt2;
 	struct npc_subbank *sb;
-	int rc, sb_off, i;
+	int rc, sb_off, i, err;
 	bool deleted;
 
 	sb = &npc_priv.sb[f->idx];
@@ -3529,6 +3530,7 @@ static int npc_defrag_alloc_free_slots(struct rvu *rvu,
 				 NPC_MCAM_LOWER_PRIO,
 				 false, cnt, save, cnt, true,
 				 &alloc_cnt1);
+
 	if (alloc_cnt1 < cnt) {
 		rc = __npc_subbank_alloc(rvu, sb,
 					 NPC_MCAM_KEY_X2, sb->b1b,
@@ -3544,15 +3546,17 @@ static int npc_defrag_alloc_free_slots(struct rvu *rvu,
 		dev_err(rvu->dev,
 			"%s: Failed to alloc cnt=%u alloc_cnt1=%u alloc_cnt2=%u\n",
 			__func__, cnt, alloc_cnt1, alloc_cnt2);
+		rc = -ENOSPC;
 		goto fail_free_alloc;
 	}
+
 	return 0;
 
 fail_free_alloc:
 	for (i = 0; i < alloc_cnt1 + alloc_cnt2; i++) {
-		rc =  npc_mcam_idx_2_subbank_idx(rvu, save[i],
-						 &sb, &sb_off);
-		if (rc) {
+		err =  npc_mcam_idx_2_subbank_idx(rvu, save[i],
+						  &sb, &sb_off);
+		if (err) {
 			dev_err(rvu->dev,
 				"%s: Error to find subbank for mcam idx=%u\n",
 				__func__, save[i]);
-- 
2.43.0