ext4: warn when discard request fails other than EOPNOTSUPP

We should warn user then the discard request fails. However we need to
exclude -EOPNOTSUPP case since parts of the device might not support it
while other parts can. So print the kernel warning when the error !=
-EOPNOTSUPP is returned from ext4_issue_discard().

We should also handle error cases in batched discard, again excluding
EOPNOTSUPP.
Reviewed-by: NCarlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: NLukas Czerner <lczerner@redhat.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

fs/ext4/mballoc.c

@@ -2607,9 +2607,17 @@ static void ext4_free_data_callback(struct super_block *sb,
 	mb_debug(1, "gonna free %u blocks in group %u (0x%p):",
 		 entry->efd_count, entry->efd_group, entry);
 
-	if (test_opt(sb, DISCARD))
-		ext4_issue_discard(sb, entry->efd_group,
-				   entry->efd_start_cluster, entry->efd_count);
+	if (test_opt(sb, DISCARD)) {
+		err = ext4_issue_discard(sb, entry->efd_group,
+					 entry->efd_start_cluster,
+					 entry->efd_count);
+		if (err && err != -EOPNOTSUPP)
+			ext4_msg(sb, KERN_WARNING, "discard request in"
+				 " group:%d block:%d count:%d failed"
+				 " with %d", entry->efd_group,
+				 entry->efd_start_cluster,
+				 entry->efd_count, err);
+	}
 
 	err = ext4_mb_load_buddy(sb, entry->efd_group, &e4b);
 	/* we expect to find existing buddy because it's pinned */
@@ -4659,8 +4667,16 @@ void ext4_free_blocks(handle_t *handle, struct inode *inode,
 		 * with group lock held. generate_buddy look at
 		 * them with group lock_held
 		 */
-		if (test_opt(sb, DISCARD))
-			ext4_issue_discard(sb, block_group, bit, count);
+		if (test_opt(sb, DISCARD)) {
+			err = ext4_issue_discard(sb, block_group, bit, count);
+			if (err && err != -EOPNOTSUPP)
+				ext4_msg(sb, KERN_WARNING, "discard request in"
+					 " group:%d block:%d count:%lu failed"
+					 " with %d", block_group, bit, count,
+					 err);
+		}
+
+
 		ext4_lock_group(sb, block_group);
 		mb_clear_bits(bitmap_bh->b_data, bit, count_clusters);
 		mb_free_blocks(inode, &e4b, bit, count_clusters);
@@ -4854,10 +4870,11 @@ int ext4_group_add_blocks(handle_t *handle, struct super_block *sb,
  * one will allocate those blocks, mark it as used in buddy bitmap. This must
  * be called with under the group lock.
  */
-static void ext4_trim_extent(struct super_block *sb, int start, int count,
+static int ext4_trim_extent(struct super_block *sb, int start, int count,
 			     ext4_group_t group, struct ext4_buddy *e4b)
 {
 	struct ext4_free_extent ex;
+	int ret = 0;
 
 	trace_ext4_trim_extent(sb, group, start, count);
 
@@ -4873,9 +4890,10 @@ static void ext4_trim_extent(struct super_block *sb, int start, int count,
 	 */
 	mb_mark_used(e4b, &ex);
 	ext4_unlock_group(sb, group);
-	ext4_issue_discard(sb, group, start, count);
+	ret = ext4_issue_discard(sb, group, start, count);
 	ext4_lock_group(sb, group);
 	mb_free_blocks(NULL, e4b, start, ex.fe_len);
+	return ret;
 }
 
 /**
@@ -4904,7 +4922,7 @@ ext4_trim_all_free(struct super_block *sb, ext4_group_t group,
 	void *bitmap;
 	ext4_grpblk_t next, count = 0, free_count = 0;
 	struct ext4_buddy e4b;
-	int ret;
+	int ret = 0;
 
 	trace_ext4_trim_all_free(sb, group, start, max);
 
@@ -4931,8 +4949,11 @@ ext4_trim_all_free(struct super_block *sb, ext4_group_t group,
 		next = mb_find_next_bit(bitmap, max + 1, start);
 
 		if ((next - start) >= minblocks) {
-			ext4_trim_extent(sb, start,
-					 next - start, group, &e4b);
+			ret = ext4_trim_extent(sb, start,
+					       next - start, group, &e4b);
+			if (ret && ret != -EOPNOTSUPP)
+				break;
+			ret = 0;
 			count += next - start;
 		}
 		free_count += next - start;
@@ -4953,8 +4974,10 @@ ext4_trim_all_free(struct super_block *sb, ext4_group_t group,
 			break;
 	}
 
-	if (!ret)
+	if (!ret) {
+		ret = count;
 		EXT4_MB_GRP_SET_TRIMMED(e4b.bd_info);
+	}
 out:
 	ext4_unlock_group(sb, group);
 	ext4_mb_unload_buddy(&e4b);
@@ -4962,7 +4985,7 @@ ext4_trim_all_free(struct super_block *sb, ext4_group_t group,
 	ext4_debug("trimmed %d blocks in the group %d\n",
 		count, group);
 
-	return count;
+	return ret;
 }
 
 /**