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ext4: improve inode table blocks counting in ext4_num_overhead_clusters

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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.

[ Merged fix-up patch which fixed potentially access to an
  uninitialzied stack variable. --TYT ]

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://lore.kernel.org/r/20230221115919.1918161-8-shikemeng@huaweicloud.com
Link: https://lore.kernel.org/r/202303171446.eLEhZzAu-lkp@intel.com/
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Kemeng Shi 2023-02-21 19:59:19 +08:00 committed by Theodore Ts'o
parent cefa74d004
commit 68e294dccc
1 changed files with 47 additions and 43 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

90
fs/ext4/balloc.c
View file

@ -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 = -1, 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) {
/*
* 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++;
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;
}
num_clusters++;
itbl_cluster = c;
}
}
if (block_cluster != -1)
num_clusters++;
if (inode_cluster != -1)
num_clusters++;
return num_clusters;
}