diff mbox series

[7/7] ext4: improve inode table blocks counting in ext4_num_overhead_clusters

Message ID 20230221115919.1918161-8-shikemeng@huaweicloud.com
State New
Headers
Series A few patches to improve ext4 balloc |

Commit Message

Kemeng Shi Feb. 21, 2023, 11:59 a.m. UTC 
  As inode table blocks are contiguous, inode table blocks inside the
block_group can be represented as range [itbl_cluster_start,
itbl_cluster_last]. Then we can simply account inode table cluters and
check cluster overlap with [itbl_cluster_start, itbl_cluster_last] instead
of traverse each block of inode table.
By the way, this patch fixes code style problem of comment for
ext4_num_overhead_clusters.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
---
 fs/ext4/balloc.c | 90 +++++++++++++++++++++++++-----------------------
 1 file changed, 47 insertions(+), 43 deletions(-)

Comments

Dan Carpenter Feb. 22, 2023, 3:13 p.m. UTC | #1 
Hi Kemeng,

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Kemeng-Shi/ext4-properly-handle-error-of-ext4_init_block_bitmap-in-ext4_read_block_bitmap_nowait/20230221-115830
base:   https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git dev
patch link:    https://lore.kernel.org/r/20230221115919.1918161-8-shikemeng%40huaweicloud.com
patch subject: [PATCH 7/7] ext4: improve inode table blocks counting in ext4_num_overhead_clusters
config: riscv-randconfig-m031-20230219 (https://download.01.org/0day-ci/archive/20230222/202302222219.u328sqfs-lkp@intel.com/config)
compiler: riscv32-linux-gcc (GCC) 12.1.0

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Link: https://lore.kernel.org/r/202302222219.u328sqfs-lkp@intel.com/

New smatch warnings:
fs/ext4/balloc.c:153 ext4_num_overhead_clusters() error: uninitialized symbol 'block_cluster'.

vim +/block_cluster +153 fs/ext4/balloc.c

c197855ea14175 Stephen Hemminger 2014-05-12   87  static unsigned ext4_num_overhead_clusters(struct super_block *sb,
e187c6588d6ef3 Theodore Ts'o     2009-02-06   88  					   ext4_group_t block_group,
e187c6588d6ef3 Theodore Ts'o     2009-02-06   89  					   struct ext4_group_desc *gdp)
0bf7e8379ce7e0 Jose R. Santos    2008-06-03   90  {
2b59a2fd93873a Kemeng Shi        2023-02-21   91  	unsigned base_clusters, num_clusters;
2b59a2fd93873a Kemeng Shi        2023-02-21   92  	int block_cluster, inode_cluster;
2b59a2fd93873a Kemeng Shi        2023-02-21   93  	int itbl_cluster_start = -1, itbl_cluster_end = -1;
d5b8f31007a937 Theodore Ts'o     2011-09-09   94  	ext4_fsblk_t start = ext4_group_first_block_no(sb, block_group);
2b59a2fd93873a Kemeng Shi        2023-02-21   95  	ext4_fsblk_t end = start + EXT4_BLOCKS_PER_GROUP(sb) - 1;
2b59a2fd93873a Kemeng Shi        2023-02-21   96  	ext4_fsblk_t itbl_blk_start, itbl_blk_end;
0bf7e8379ce7e0 Jose R. Santos    2008-06-03   97  	struct ext4_sb_info *sbi = EXT4_SB(sb);
0bf7e8379ce7e0 Jose R. Santos    2008-06-03   98  
d5b8f31007a937 Theodore Ts'o     2011-09-09   99  	/* This is the number of clusters used by the superblock,
d5b8f31007a937 Theodore Ts'o     2011-09-09  100  	 * block group descriptors, and reserved block group
d5b8f31007a937 Theodore Ts'o     2011-09-09  101  	 * descriptor blocks */
2b59a2fd93873a Kemeng Shi        2023-02-21  102  	base_clusters = ext4_num_base_meta_clusters(sb, block_group);
2b59a2fd93873a Kemeng Shi        2023-02-21  103  	num_clusters = base_clusters;
2b59a2fd93873a Kemeng Shi        2023-02-21  104  
2b59a2fd93873a Kemeng Shi        2023-02-21  105  	/*
2b59a2fd93873a Kemeng Shi        2023-02-21  106  	 * Account and record inode table clusters if any cluster
2b59a2fd93873a Kemeng Shi        2023-02-21  107  	 * is in the block group, or inode table cluster range is
2b59a2fd93873a Kemeng Shi        2023-02-21  108  	 * [-1, -1] and won't overlap with block/inode bitmap cluster
2b59a2fd93873a Kemeng Shi        2023-02-21  109  	 * accounted below.
2b59a2fd93873a Kemeng Shi        2023-02-21  110  	 */
2b59a2fd93873a Kemeng Shi        2023-02-21  111  	itbl_blk_start = ext4_inode_table(sb, gdp);
2b59a2fd93873a Kemeng Shi        2023-02-21  112  	itbl_blk_end = itbl_blk_start + sbi->s_itb_per_group - 1;
2b59a2fd93873a Kemeng Shi        2023-02-21  113  	if (itbl_blk_start <= end && itbl_blk_end >= start) {
2b59a2fd93873a Kemeng Shi        2023-02-21  114  		itbl_blk_start = itbl_blk_start >= start ?
2b59a2fd93873a Kemeng Shi        2023-02-21  115  			itbl_blk_start : start;
2b59a2fd93873a Kemeng Shi        2023-02-21  116  		itbl_blk_end = itbl_blk_end <= end ?
2b59a2fd93873a Kemeng Shi        2023-02-21  117  			itbl_blk_end : end;
2b59a2fd93873a Kemeng Shi        2023-02-21  118  
2b59a2fd93873a Kemeng Shi        2023-02-21  119  		itbl_cluster_start = EXT4_B2C(sbi, itbl_blk_start - start);
2b59a2fd93873a Kemeng Shi        2023-02-21  120  		itbl_cluster_end = EXT4_B2C(sbi, itbl_blk_end - start);
2b59a2fd93873a Kemeng Shi        2023-02-21  121  
2b59a2fd93873a Kemeng Shi        2023-02-21  122  		num_clusters += itbl_cluster_end - itbl_cluster_start + 1;
2b59a2fd93873a Kemeng Shi        2023-02-21  123  		/* check if border cluster is overlapped */
2b59a2fd93873a Kemeng Shi        2023-02-21  124  		if (itbl_cluster_start == base_clusters - 1)
2b59a2fd93873a Kemeng Shi        2023-02-21  125  			num_clusters--;
2b59a2fd93873a Kemeng Shi        2023-02-21  126  	}
0bf7e8379ce7e0 Jose R. Santos    2008-06-03  127  
d5b8f31007a937 Theodore Ts'o     2011-09-09  128  	/*
2b59a2fd93873a Kemeng Shi        2023-02-21  129  	 * For the allocation bitmaps, we first need to check to see
2b59a2fd93873a Kemeng Shi        2023-02-21  130  	 * if the block is in the block group.  If it is, then check
2b59a2fd93873a Kemeng Shi        2023-02-21  131  	 * to see if the cluster is already accounted for in the clusters
2b59a2fd93873a Kemeng Shi        2023-02-21  132  	 * used for the base metadata cluster and inode tables cluster.
d5b8f31007a937 Theodore Ts'o     2011-09-09  133  	 * Normally all of these blocks are contiguous, so the special
d5b8f31007a937 Theodore Ts'o     2011-09-09  134  	 * case handling shouldn't be necessary except for *very*
d5b8f31007a937 Theodore Ts'o     2011-09-09  135  	 * unusual file system layouts.
d5b8f31007a937 Theodore Ts'o     2011-09-09  136  	 */
d5b8f31007a937 Theodore Ts'o     2011-09-09  137  	if (ext4_block_in_group(sb, ext4_block_bitmap(sb, gdp), block_group)) {
b0dd6b70f0fda1 Theodore Ts'o     2012-06-07  138  		block_cluster = EXT4_B2C(sbi,
b0dd6b70f0fda1 Theodore Ts'o     2012-06-07  139  					 ext4_block_bitmap(sb, gdp) - start);
2b59a2fd93873a Kemeng Shi        2023-02-21  140  		if (block_cluster >= base_clusters &&
2b59a2fd93873a Kemeng Shi        2023-02-21  141  		    (block_cluster < itbl_cluster_start ||
2b59a2fd93873a Kemeng Shi        2023-02-21  142  		    block_cluster > itbl_cluster_end))
d5b8f31007a937 Theodore Ts'o     2011-09-09  143  			num_clusters++;
d5b8f31007a937 Theodore Ts'o     2011-09-09  144  	}
d5b8f31007a937 Theodore Ts'o     2011-09-09  145  
d5b8f31007a937 Theodore Ts'o     2011-09-09  146  	if (ext4_block_in_group(sb, ext4_inode_bitmap(sb, gdp), block_group)) {

These two conditions are exactly the same so I don't see why they can't
be combined into one condition.  I have read the comment, but I guess I
don't understand ext4 well enough to really understand it.

d5b8f31007a937 Theodore Ts'o     2011-09-09  147  		inode_cluster = EXT4_B2C(sbi,
b0dd6b70f0fda1 Theodore Ts'o     2012-06-07  148  					 ext4_inode_bitmap(sb, gdp) - start);
2b59a2fd93873a Kemeng Shi        2023-02-21  149  		/*
2b59a2fd93873a Kemeng Shi        2023-02-21  150  		 * Additional check if inode bitmap is in just accounted
2b59a2fd93873a Kemeng Shi        2023-02-21  151  		 * block_cluster
2b59a2fd93873a Kemeng Shi        2023-02-21  152  		 */
2b59a2fd93873a Kemeng Shi        2023-02-21 @153  		if (inode_cluster != block_cluster &&

So this seems like a false positive to me.  But the code is puzzling for
a human or for a static checker.

2b59a2fd93873a Kemeng Shi        2023-02-21  154  		    inode_cluster >= base_clusters &&
2b59a2fd93873a Kemeng Shi        2023-02-21  155  		    (inode_cluster < itbl_cluster_start ||
2b59a2fd93873a Kemeng Shi        2023-02-21  156  		    inode_cluster > itbl_cluster_end))
d5b8f31007a937 Theodore Ts'o     2011-09-09  157  			num_clusters++;
0bf7e8379ce7e0 Jose R. Santos    2008-06-03  158  	}
d5b8f31007a937 Theodore Ts'o     2011-09-09  159  
d5b8f31007a937 Theodore Ts'o     2011-09-09  160  	return num_clusters;
0bf7e8379ce7e0 Jose R. Santos    2008-06-03  161  }
Kemeng Shi Feb. 23, 2023, 1:31 a.m. UTC | #2 
on 2/22/2023 11:13 PM, Dan Carpenter wrote:
> Hi Kemeng,
> 
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Kemeng-Shi/ext4-properly-handle-error-of-ext4_init_block_bitmap-in-ext4_read_block_bitmap_nowait/20230221-115830
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git dev
> patch link:    https://lore.kernel.org/r/20230221115919.1918161-8-shikemeng%40huaweicloud.com
> patch subject: [PATCH 7/7] ext4: improve inode table blocks counting in ext4_num_overhead_clusters
> config: riscv-randconfig-m031-20230219 (https://download.01.org/0day-ci/archive/20230222/202302222219.u328sqfs-lkp@intel.com/config)
> compiler: riscv32-linux-gcc (GCC) 12.1.0
> 
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@intel.com>
> | Reported-by: Dan Carpenter <error27@gmail.com>
> | Link: https://lore.kernel.org/r/202302222219.u328sqfs-lkp@intel.com/
> 
> New smatch warnings:
> fs/ext4/balloc.c:153 ext4_num_overhead_clusters() error: uninitialized symbol 'block_cluster'.
> 
> vim +/block_cluster +153 fs/ext4/balloc.c
[...]
> d5b8f31007a937 Theodore Ts'o     2011-09-09  128  	/*
> 2b59a2fd93873a Kemeng Shi        2023-02-21  129  	 * For the allocation bitmaps, we first need to check to see
> 2b59a2fd93873a Kemeng Shi        2023-02-21  130  	 * if the block is in the block group.  If it is, then check
> 2b59a2fd93873a Kemeng Shi        2023-02-21  131  	 * to see if the cluster is already accounted for in the clusters
> 2b59a2fd93873a Kemeng Shi        2023-02-21  132  	 * used for the base metadata cluster and inode tables cluster.
> d5b8f31007a937 Theodore Ts'o     2011-09-09  133  	 * Normally all of these blocks are contiguous, so the special
> d5b8f31007a937 Theodore Ts'o     2011-09-09  134  	 * case handling shouldn't be necessary except for *very*
> d5b8f31007a937 Theodore Ts'o     2011-09-09  135  	 * unusual file system layouts.
> d5b8f31007a937 Theodore Ts'o     2011-09-09  136  	 */
> d5b8f31007a937 Theodore Ts'o     2011-09-09  137  	if (ext4_block_in_group(sb, ext4_block_bitmap(sb, gdp), block_group)) {
> b0dd6b70f0fda1 Theodore Ts'o     2012-06-07  138  		block_cluster = EXT4_B2C(sbi,
> b0dd6b70f0fda1 Theodore Ts'o     2012-06-07  139  					 ext4_block_bitmap(sb, gdp) - start);
> 2b59a2fd93873a Kemeng Shi        2023-02-21  140  		if (block_cluster >= base_clusters &&
> 2b59a2fd93873a Kemeng Shi        2023-02-21  141  		    (block_cluster < itbl_cluster_start ||
> 2b59a2fd93873a Kemeng Shi        2023-02-21  142  		    block_cluster > itbl_cluster_end))
> d5b8f31007a937 Theodore Ts'o     2011-09-09  143  			num_clusters++;
> d5b8f31007a937 Theodore Ts'o     2011-09-09  144  	}
> d5b8f31007a937 Theodore Ts'o     2011-09-09  145  
> d5b8f31007a937 Theodore Ts'o     2011-09-09  146  	if (ext4_block_in_group(sb, ext4_inode_bitmap(sb, gdp), block_group)) {
> 
> These two conditions are exactly the same so I don't see why they can't
> be combined into one condition.  I have read the comment, but I guess I
> don't understand ext4 well enough to really understand it.
These two conditions check two kinds of bitmap block: *block* bitmap block
and *inode* bitmap block. For case that block bitmap in the block group
while inode bitmap in a different group, there is a risk to access
uninitialized  block_cluster.
I will fix this in next version, Thanks!
Dan Carpenter Feb. 23, 2023, 4:04 a.m. UTC | #3 
On Thu, Feb 23, 2023 at 09:31:54AM +0800, Kemeng Shi wrote:
> 
> 
> on 2/22/2023 11:13 PM, Dan Carpenter wrote:
> > Hi Kemeng,
> > 
> > https://git-scm.com/docs/git-format-patch#_base_tree_information]
> > 
> > url:    https://github.com/intel-lab-lkp/linux/commits/Kemeng-Shi/ext4-properly-handle-error-of-ext4_init_block_bitmap-in-ext4_read_block_bitmap_nowait/20230221-115830
> > base:   https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git dev
> > patch link:    https://lore.kernel.org/r/20230221115919.1918161-8-shikemeng%40huaweicloud.com
> > patch subject: [PATCH 7/7] ext4: improve inode table blocks counting in ext4_num_overhead_clusters
> > config: riscv-randconfig-m031-20230219 (https://download.01.org/0day-ci/archive/20230222/202302222219.u328sqfs-lkp@intel.com/config)
> > compiler: riscv32-linux-gcc (GCC) 12.1.0
> > 
> > If you fix the issue, kindly add following tag where applicable
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Reported-by: Dan Carpenter <error27@gmail.com>
> > | Link: https://lore.kernel.org/r/202302222219.u328sqfs-lkp@intel.com/
> > 
> > New smatch warnings:
> > fs/ext4/balloc.c:153 ext4_num_overhead_clusters() error: uninitialized symbol 'block_cluster'.
> > 
> > vim +/block_cluster +153 fs/ext4/balloc.c
> [...]
> > d5b8f31007a937 Theodore Ts'o     2011-09-09  128  	/*
> > 2b59a2fd93873a Kemeng Shi        2023-02-21  129  	 * For the allocation bitmaps, we first need to check to see
> > 2b59a2fd93873a Kemeng Shi        2023-02-21  130  	 * if the block is in the block group.  If it is, then check
> > 2b59a2fd93873a Kemeng Shi        2023-02-21  131  	 * to see if the cluster is already accounted for in the clusters
> > 2b59a2fd93873a Kemeng Shi        2023-02-21  132  	 * used for the base metadata cluster and inode tables cluster.
> > d5b8f31007a937 Theodore Ts'o     2011-09-09  133  	 * Normally all of these blocks are contiguous, so the special
> > d5b8f31007a937 Theodore Ts'o     2011-09-09  134  	 * case handling shouldn't be necessary except for *very*
> > d5b8f31007a937 Theodore Ts'o     2011-09-09  135  	 * unusual file system layouts.
> > d5b8f31007a937 Theodore Ts'o     2011-09-09  136  	 */
> > d5b8f31007a937 Theodore Ts'o     2011-09-09  137  	if (ext4_block_in_group(sb, ext4_block_bitmap(sb, gdp), block_group)) {
> > b0dd6b70f0fda1 Theodore Ts'o     2012-06-07  138  		block_cluster = EXT4_B2C(sbi,
> > b0dd6b70f0fda1 Theodore Ts'o     2012-06-07  139  					 ext4_block_bitmap(sb, gdp) - start);
> > 2b59a2fd93873a Kemeng Shi        2023-02-21  140  		if (block_cluster >= base_clusters &&
> > 2b59a2fd93873a Kemeng Shi        2023-02-21  141  		    (block_cluster < itbl_cluster_start ||
> > 2b59a2fd93873a Kemeng Shi        2023-02-21  142  		    block_cluster > itbl_cluster_end))
> > d5b8f31007a937 Theodore Ts'o     2011-09-09  143  			num_clusters++;
> > d5b8f31007a937 Theodore Ts'o     2011-09-09  144  	}
> > d5b8f31007a937 Theodore Ts'o     2011-09-09  145  
> > d5b8f31007a937 Theodore Ts'o     2011-09-09  146  	if (ext4_block_in_group(sb, ext4_inode_bitmap(sb, gdp), block_group)) {
> > 
> > These two conditions are exactly the same so I don't see why they can't
> > be combined into one condition.  I have read the comment, but I guess I
> > don't understand ext4 well enough to really understand it.
> These two conditions check two kinds of bitmap block: *block* bitmap block
> and *inode* bitmap block.

Ah right.  When I was reviewing this code, I copy and pasted the if
conditions so they were exactly lined up with each other and I still
didn't see the block vs inode difference until you pointed it out.  :P

Thanks!

regards,
dan carpenter
Jan Kara March 20, 2023, 12:44 p.m. UTC | #4 
On Tue 21-02-23 19:59:19, Kemeng Shi wrote:
> As inode table blocks are contiguous, inode table blocks inside the
> block_group can be represented as range [itbl_cluster_start,
> itbl_cluster_last]. Then we can simply account inode table cluters and
> check cluster overlap with [itbl_cluster_start, itbl_cluster_last] instead
> of traverse each block of inode table.
> By the way, this patch fixes code style problem of comment for
> ext4_num_overhead_clusters.
> 
> Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>

FWIW this is triggering Coverity warning:

*** CID 1536792:  Uninitialized variables  (UNINIT)
/fs/ext4/balloc.c: 153 in ext4_num_overhead_clusters()
147                     inode_cluster = EXT4_B2C(sbi,
148                                              ext4_inode_bitmap(sb, gdp) - st
149                     /*
150                      * Additional check if inode bitmap is in just accounted
151                      * block_cluster
152                      */
>>>     CID 1536792:  Uninitialized variables  (UNINIT)
>>>     Using uninitialized value "block_cluster".
153                     if (inode_cluster != block_cluster &&
154                         inode_cluster >= base_clusters &&
155                         (inode_cluster < itbl_cluster_start ||
156                         inode_cluster > itbl_cluster_end))
157                             num_clusters++;
158             }

which actually looks valid AFAICT.

								Honza
Kemeng Shi March 20, 2023, 1:19 p.m. UTC | #5 
on 3/20/2023 8:44 PM, Jan Kara wrote:
> On Tue 21-02-23 19:59:19, Kemeng Shi wrote:
>> As inode table blocks are contiguous, inode table blocks inside the
>> block_group can be represented as range [itbl_cluster_start,
>> itbl_cluster_last]. Then we can simply account inode table cluters and
>> check cluster overlap with [itbl_cluster_start, itbl_cluster_last] instead
>> of traverse each block of inode table.
>> By the way, this patch fixes code style problem of comment for
>> ext4_num_overhead_clusters.
>>
>> Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
> 
> FWIW this is triggering Coverity warning:
> 
> *** CID 1536792:  Uninitialized variables  (UNINIT)
> /fs/ext4/balloc.c: 153 in ext4_num_overhead_clusters()
> 147                     inode_cluster = EXT4_B2C(sbi,
> 148                                              ext4_inode_bitmap(sb, gdp) - st
> 149                     /*
> 150                      * Additional check if inode bitmap is in just accounted
> 151                      * block_cluster
> 152                      */
>>>>     CID 1536792:  Uninitialized variables  (UNINIT)
>>>>     Using uninitialized value "block_cluster".
> 153                     if (inode_cluster != block_cluster &&
> 154                         inode_cluster >= base_clusters &&
> 155                         (inode_cluster < itbl_cluster_start ||
> 156                         inode_cluster > itbl_cluster_end))
> 157                             num_clusters++;
> 158             }
> 
> which actually looks valid AFAICT.
Yes, there is a risk to access uninitialized block_cluster if block bitmap block
and inode bitmap block are in different groups. Patch to fix is just sent. Thanks!
diff mbox series

Patch

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index dab46274d591..689edfed231a 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -80,32 +80,56 @@  static inline int ext4_block_in_group(struct super_block *sb,
 	return (actual_group == block_group) ? 1 : 0;
 }
 
-/* Return the number of clusters used for file system metadata; this
+/*
+ * Return the number of clusters used for file system metadata; this
  * represents the overhead needed by the file system.
  */
 static unsigned ext4_num_overhead_clusters(struct super_block *sb,
 					   ext4_group_t block_group,
 					   struct ext4_group_desc *gdp)
 {
-	unsigned num_clusters;
-	int block_cluster = -1, inode_cluster = -1, itbl_cluster = -1, i, c;
+	unsigned base_clusters, num_clusters;
+	int block_cluster, inode_cluster;
+	int itbl_cluster_start = -1, itbl_cluster_end = -1;
 	ext4_fsblk_t start = ext4_group_first_block_no(sb, block_group);
-	ext4_fsblk_t itbl_blk;
+	ext4_fsblk_t end = start + EXT4_BLOCKS_PER_GROUP(sb) - 1;
+	ext4_fsblk_t itbl_blk_start, itbl_blk_end;
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 
 	/* This is the number of clusters used by the superblock,
 	 * block group descriptors, and reserved block group
 	 * descriptor blocks */
-	num_clusters = ext4_num_base_meta_clusters(sb, block_group);
+	base_clusters = ext4_num_base_meta_clusters(sb, block_group);
+	num_clusters = base_clusters;
 
 	/*
-	 * For the allocation bitmaps and inode table, we first need
-	 * to check to see if the block is in the block group.  If it
-	 * is, then check to see if the cluster is already accounted
-	 * for in the clusters used for the base metadata cluster, or
-	 * if we can increment the base metadata cluster to include
-	 * that block.  Otherwise, we will have to track the cluster
-	 * used for the allocation bitmap or inode table explicitly.
+	 * Account and record inode table clusters if any cluster
+	 * is in the block group, or inode table cluster range is
+	 * [-1, -1] and won't overlap with block/inode bitmap cluster
+	 * accounted below.
+	 */
+	itbl_blk_start = ext4_inode_table(sb, gdp);
+	itbl_blk_end = itbl_blk_start + sbi->s_itb_per_group - 1;
+	if (itbl_blk_start <= end && itbl_blk_end >= start) {
+		itbl_blk_start = itbl_blk_start >= start ?
+			itbl_blk_start : start;
+		itbl_blk_end = itbl_blk_end <= end ?
+			itbl_blk_end : end;
+
+		itbl_cluster_start = EXT4_B2C(sbi, itbl_blk_start - start);
+		itbl_cluster_end = EXT4_B2C(sbi, itbl_blk_end - start);
+
+		num_clusters += itbl_cluster_end - itbl_cluster_start + 1;
+		/* check if border cluster is overlapped */
+		if (itbl_cluster_start == base_clusters - 1)
+			num_clusters--;
+	}
+
+	/*
+	 * For the allocation bitmaps, we first need to check to see
+	 * if the block is in the block group.  If it is, then check
+	 * to see if the cluster is already accounted for in the clusters
+	 * used for the base metadata cluster and inode tables cluster.
 	 * Normally all of these blocks are contiguous, so the special
 	 * case handling shouldn't be necessary except for *very*
 	 * unusual file system layouts.
@@ -113,46 +137,26 @@  static unsigned ext4_num_overhead_clusters(struct super_block *sb,
 	if (ext4_block_in_group(sb, ext4_block_bitmap(sb, gdp), block_group)) {
 		block_cluster = EXT4_B2C(sbi,
 					 ext4_block_bitmap(sb, gdp) - start);
-		if (block_cluster < num_clusters)
-			block_cluster = -1;
-		else if (block_cluster == num_clusters) {
+		if (block_cluster >= base_clusters &&
+		    (block_cluster < itbl_cluster_start ||
+		    block_cluster > itbl_cluster_end))
 			num_clusters++;
-			block_cluster = -1;
-		}
 	}
 
 	if (ext4_block_in_group(sb, ext4_inode_bitmap(sb, gdp), block_group)) {
 		inode_cluster = EXT4_B2C(sbi,
 					 ext4_inode_bitmap(sb, gdp) - start);
-		if (inode_cluster < num_clusters)
-			inode_cluster = -1;
-		else if (inode_cluster == num_clusters) {
-			num_clusters++;
-			inode_cluster = -1;
-		}
-	}
-
-	itbl_blk = ext4_inode_table(sb, gdp);
-	for (i = 0; i < sbi->s_itb_per_group; i++) {
-		if (ext4_block_in_group(sb, itbl_blk + i, block_group)) {
-			c = EXT4_B2C(sbi, itbl_blk + i - start);
-			if ((c < num_clusters) || (c == inode_cluster) ||
-			    (c == block_cluster) || (c == itbl_cluster))
-				continue;
-			if (c == num_clusters) {
-				num_clusters++;
-				continue;
-			}
+		/*
+		 * Additional check if inode bitmap is in just accounted
+		 * block_cluster
+		 */
+		if (inode_cluster != block_cluster &&
+		    inode_cluster >= base_clusters &&
+		    (inode_cluster < itbl_cluster_start ||
+		    inode_cluster > itbl_cluster_end))
 			num_clusters++;
-			itbl_cluster = c;
-		}
 	}
 
-	if (block_cluster != -1)
-		num_clusters++;
-	if (inode_cluster != -1)
-		num_clusters++;
-
 	return num_clusters;
 }