* [PATCH v1 8/9] exfat: support multi-cluster for exfat_map_cluster
2025-12-26 9:44 [PATCH v1 0/9] Enable exfat_get_block to support obtaining multiple clusters Chi Zhiling
@ 2025-12-26 9:44 ` Chi Zhiling
0 siblings, 0 replies; 3+ messages in thread
From: Chi Zhiling @ 2025-12-26 9:44 UTC (permalink / raw)
To: linux-fsdevel, linux-kernel
Cc: Namjae Jeon, Sungjong Seo, Yuezhang Mo, Alexander Viro,
Christian Brauner, Jan Kara, Matthew Wilcox, Chi Zhiling
From: Chi Zhiling <chizhiling@kylinos.cn>
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>
---
fs/exfat/inode.c | 33 ++++++++++++++++++++-------------
1 file changed, 20 insertions(+), 13 deletions(-)
diff --git a/fs/exfat/inode.c b/fs/exfat/inode.c
index 1062ce470cb1..8c49ab15eafe 100644
--- a/fs/exfat/inode.c
+++ b/fs/exfat/inode.c
@@ -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 = num_clusters - clu_offset;
+ } else {
+ *clu = EXFAT_EOF_CLUSTER;
+ *count = 0;
}
} else if (ei->type == TYPE_FILE) {
int err = exfat_get_cluster(inode, clu_offset,
clu, &last_clu);
if (err)
return -EIO;
+ *count = (*clu == EXFAT_EOF_CLUSTER) ? 0 : 1;
} else {
unsigned int fclus = 0;
/* hint information */
@@ -178,6 +181,7 @@ static int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
return -EIO;
fclus++;
}
+ *count = (*clu == EXFAT_EOF_CLUSTER) ? 0 : 1;
}
if (*clu == EXFAT_EOF_CLUSTER) {
@@ -249,7 +253,7 @@ static int exfat_map_cluster(struct inode *inode, unsigned int clu_offset,
num_to_be_allocated--;
}
}
-
+ *count = 1;
}
/* hint information */
@@ -268,7 +272,7 @@ 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;
@@ -281,8 +285,9 @@ 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,
@@ -293,12 +298,14 @@ static int exfat_get_block(struct inode *inode, sector_t iblock,
if (cluster == EXFAT_EOF_CLUSTER)
goto done;
+ if (WARN_ON_ONCE(!count))
+ count = 1;
/* sector offset in cluster */
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 - sec_offset;
max_blocks = min(mapped_blocks, max_blocks);
map_bh(bh_result, sb, phys);
--
2.43.0
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