linux-kernel - Re: [PATCH v2 10/13] exfat: support multi-cluster for exfat_map

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Message-ID: <f7cc8f8a-81f0-4a31-9d75-983858daf985@163.com>
Date: Tue, 13 Jan 2026 16:53:20 +0800
From: Chi Zhiling <chizhiling@....com>
To: "Yuezhang.Mo@...y.com" <Yuezhang.Mo@...y.com>,
 "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc: Namjae Jeon <linkinjeon@...nel.org>, Sungjong Seo
 <sj1557.seo@...sung.com>, Chi Zhiling <chizhiling@...inos.cn>
Subject: Re: [PATCH v2 10/13] exfat: support multi-cluster for
 exfat_map_cluster

On 1/13/26 14:37, Yuezhang.Mo@...y.com wrote:
>> @@ -281,7 +285,7 @@ static int exfat_get_block(struct inode *inode, sector_t iblock,
>>         sec_offset = iblock & (sbi->sect_per_clus - 1);
>>
>>         phys = exfat_cluster_to_sector(sbi, cluster) + sec_offset;
>> -       mapped_blocks = sbi->sect_per_clus - sec_offset;
>> +       mapped_blocks = (count << sbi->sect_per_clus_bits) - sec_offset;
> 
> This left shift will cause an overflow if the file is larger than 2TB
> and the clusters are contiguous.

Thank you for pointing this out, I will change the type to blkcnt_t in 
v3 to fix this bug.

diff --git a/fs/exfat/inode.c b/fs/exfat/inode.c
index e8b74185b0ad..9c1e00f5b011 100644
--- a/fs/exfat/inode.c
+++ b/fs/exfat/inode.c
@@ -250,9 +250,9 @@ static int exfat_get_block(struct inode *inode, 
sector_t iblock,
         struct exfat_inode_info *ei = EXFAT_I(inode);
         struct super_block *sb = inode->i_sb;
         struct exfat_sb_info *sbi = EXFAT_SB(sb);
-       unsigned long max_blocks = bh_result->b_size >> inode->i_blkbits;
+       blkcnt_t max_blocks = EXFAT_B_TO_BLK(bh_result->b_size, sb);
+       blkcnt_t mapped_blocks = 0;
         int err = 0;
-       unsigned long mapped_blocks = 0;
         unsigned int cluster, sec_offset, count;
         sector_t last_block;
         sector_t phys = 0;

> 
> The others look good.
> Reviewed-by: Yuezhang Mo <Yuezhang.Mo@...y.com>


Thanks,