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exfat: support multi-cluster for exfat_map_cluster

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This patch introduces a parameter 'count' to support fetching multiple
clusters in exfat_map_cluster. The returned 'count' indicates the number
of consecutive clusters, or 0 when the input cluster offset is past EOF.

And the 'count' is also an input parameter for the caller to specify the
required number of clusters.

Only NO_FAT_CHAIN files enable multi-cluster fetching in this patch.

After this patch, the time proportion of exfat_get_block has decreased,
The performance data is as follows:

Cluster size: 512 bytes
Sequential read of a 30GB NO_FAT_CHAIN file:
2.4GB/s -> 2.5 GB/s
proportion of exfat_get_block:
10.8% -> 0.02%

Signed-off-by: Chi Zhiling <chizhiling@kylinos.cn>
Reviewed-by: Yuezhang Mo <Yuezhang.Mo@sony.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
This commit is contained in:
Chi Zhiling 2026-01-14 20:12:46 +08:00 • committed by Namjae Jeon
parent 88a936b7a9
commit 256694b22d
1 changed files with 17 additions and 13 deletions
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30
fs/exfat/inode.c
View file

@ -124,7 +124,7 @@ void exfat_sync_inode(struct inode *inode)
* *clu = (~0), if it's unable to allocate a new cluster
*/
static int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
unsigned int *clu, int create)
unsigned int *clu, unsigned int *count, int create)
{
int ret;
unsigned int last_clu;
@ -147,20 +147,23 @@ static int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
*clu = last_clu = ei->start_clu;
if (ei->flags == ALLOC_NO_FAT_CHAIN) {
if (clu_offset > 0 && *clu != EXFAT_EOF_CLUSTER) {
last_clu += clu_offset - 1;
if (clu_offset == num_clusters)
*clu = EXFAT_EOF_CLUSTER;
else
*clu += clu_offset;
if (*clu == EXFAT_EOF_CLUSTER) {
*count = 0;
} else if (ei->flags == ALLOC_NO_FAT_CHAIN) {
last_clu += num_clusters - 1;
if (clu_offset < num_clusters) {
*clu += clu_offset;
*count = min(num_clusters - clu_offset, *count);
} else {
*clu = EXFAT_EOF_CLUSTER;
*count = 0;
}
} else {
int err = exfat_get_cluster(inode, clu_offset,
clu, &last_clu);
if (err)
return -EIO;
*count = (*clu == EXFAT_EOF_CLUSTER) ? 0 : 1;
}
if (*clu == EXFAT_EOF_CLUSTER) {
@ -232,7 +235,7 @@ static int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
num_to_be_allocated--;
}
}
*count = 1;
}
/* hint information */
@ -251,7 +254,7 @@ static int exfat_get_block(struct inode *inode, sector_t iblock,
unsigned long max_blocks = bh_result->b_size >> inode->i_blkbits;
int err = 0;
unsigned long mapped_blocks = 0;
unsigned int cluster, sec_offset;
unsigned int cluster, sec_offset, count;
sector_t last_block;
sector_t phys = 0;
sector_t valid_blks;
@ -264,8 +267,9 @@ static int exfat_get_block(struct inode *inode, sector_t iblock,
goto done;
/* Is this block already allocated? */
count = EXFAT_B_TO_CLU_ROUND_UP(bh_result->b_size, sbi);
err = exfat_map_cluster(inode, iblock >> sbi->sect_per_clus_bits,
&cluster, create);
&cluster, &count, create);
if (err) {
if (err != -ENOSPC)
exfat_fs_error_ratelimit(sb,
@ -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 = ((unsigned long)count << sbi->sect_per_clus_bits) - sec_offset;
max_blocks = min(mapped_blocks, max_blocks);
map_bh(bh_result, sb, phys);