linux-ext4 - [PATCH 2/2] ext4: modify the logic of ext4_mb_new_blocks

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Date:   Thu,  6 Jan 2022 10:45:18 +0800
From:   Xin Yin <yinxin.x@...edance.com>
To:     harshadshirwadkar@...il.com, tytso@....edu,
        adilger.kernel@...ger.ca
Cc:     linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xin Yin <yinxin.x@...edance.com>
Subject: [PATCH 2/2] ext4: modify the logic of ext4_mb_new_blocks_simple

for now in ext4_mb_new_blocks_simple, if we found a block which
should be excluded then will switch to next group, this may
probably cause 'group' run out of range.

change to check next block in the same group when get a block should
be excluded. Also change the searche range to EXT4_CLUSTERS_PER_GROUP
and add error checking.

Signed-off-by: Xin Yin <yinxin.x@...edance.com>
---
 fs/ext4/mballoc.c | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 215b7068f548..31a00b473f3e 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -5757,7 +5757,8 @@ static ext4_fsblk_t ext4_mb_new_blocks_simple(handle_t *handle,
 	struct super_block *sb = ar->inode->i_sb;
 	ext4_group_t group;
 	ext4_grpblk_t blkoff;
-	int i = sb->s_blocksize;
+	ext4_grpblk_t max = EXT4_CLUSTERS_PER_GROUP(sb);
+	ext4_grpblk_t i = 0;
 	ext4_fsblk_t goal, block;
 	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
 
@@ -5779,19 +5780,26 @@ static ext4_fsblk_t ext4_mb_new_blocks_simple(handle_t *handle,
 		ext4_get_group_no_and_offset(sb,
 			max(ext4_group_first_block_no(sb, group), goal),
 			NULL, &blkoff);
-		i = mb_find_next_zero_bit(bitmap_bh->b_data, sb->s_blocksize,
+		while (1) {
+			i = mb_find_next_zero_bit(bitmap_bh->b_data, max,
 						blkoff);
+			if (i >= max)
+				break;
+			if (ext4_fc_replay_check_excluded(sb,
+				ext4_group_first_block_no(sb, group) + i)) {
+				blkoff = i + 1;
+			} else
+				break;
+		}
 		brelse(bitmap_bh);
-		if (i >= sb->s_blocksize)
-			continue;
-		if (ext4_fc_replay_check_excluded(sb,
-			ext4_group_first_block_no(sb, group) + i))
-			continue;
-		break;
+		if (i < max)
+			break;
 	}
 
-	if (group >= ext4_get_groups_count(sb) && i >= sb->s_blocksize)
+	if (group >= ext4_get_groups_count(sb) || i >= max) {
+		*errp = -ENOSPC;
 		return 0;
+	}
 
 	block = ext4_group_first_block_no(sb, group) + i;
 	ext4_mb_mark_bb(sb, block, 1, 1);
-- 
2.20.1