Hello, Jun,
Perhaps you are looking at an old version of the exfat code.
The performance of exfat_free_cluster has been improved in the latest
version. I think the below commit could help you.
f728760aa923 ("exfat: improve performance of exfat_free_cluster when
using dirsync mount option")
Thanks.
> When a large file is deleted, it's cluster bitmap is cleared.
> After a bit is cleared, the buffer_head is synced.
> A buffer_head can be synced many times repeatedly.
> We can clear all bits first and then sync all buffer_heads.
> So each buffer_head is synced only once, which significantly improves
> performance.
>
> In my test, It takes about 2 minitues to delete a 5GB file without the
> patch.
> After applying the patch, the file is deleted in almost less than 1s.
>
> Signed-off-by: Jun <hljhnu@xxxxxxxxx>
> Change-Id: I7637032db04042b8ad1ca73fe7db09d43a253255
> ---
> fs/exfat/balloc.c | 28 ++++++++++++++++++++++++++--
> fs/exfat/exfat_fs.h | 2 ++
> fs/exfat/fatent.c | 45 +++++++++++++++++++++++++++++++++++++++++----
> 3 files changed, 69 insertions(+), 6 deletions(-)
>
> diff --git a/fs/exfat/balloc.c b/fs/exfat/balloc.c index
> 579c10f57c2b..58bdfb58bf1d 100644
> --- a/fs/exfat/balloc.c
> +++ b/fs/exfat/balloc.c
> @@ -164,7 +164,6 @@ void exfat_clear_bitmap(struct inode *inode, unsigned
> int clu)
> unsigned int ent_idx;
> struct super_block *sb = inode->i_sb;
> struct exfat_sb_info *sbi = EXFAT_SB(sb);
> - struct exfat_mount_options *opts = &sbi->options;
>
> WARN_ON(clu < EXFAT_FIRST_CLUSTER);
> ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
> @@ -172,7 +171,32 @@ void exfat_clear_bitmap(struct inode *inode, unsigned
> int clu)
> b = BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent_idx);
>
> clear_bit_le(b, sbi->vol_amap[i]->b_data);
> - exfat_update_bh(sbi->vol_amap[i], IS_DIRSYNC(inode));
> + set_buffer_uptodate(sbi->vol_amap[i]);
> + mark_buffer_dirty(sbi->vol_amap[i]);
> +}
> +
> +void exfat_wait_bitmap(struct inode *inode, unsigned int clu) {
> + int i;
> + unsigned int ent_idx;
> + struct super_block *sb = inode->i_sb;
> + struct exfat_sb_info *sbi = EXFAT_SB(sb);
> +
> + WARN_ON(clu < EXFAT_FIRST_CLUSTER);
> + ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
> + i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx);
> +
> + if (IS_DIRSYNC(inode))
> + sync_dirty_buffer(sbi->vol_amap[i]);
> +}
> +
> +void exfat_discard_cluster(struct inode *inode, unsigned int clu) {
> + struct super_block *sb = inode->i_sb;
> + struct exfat_sb_info *sbi = EXFAT_SB(sb);
> + struct exfat_mount_options *opts = &sbi->options;
> +
> + WARN_ON(clu < EXFAT_FIRST_CLUSTER);
>
> if (opts->discard) {
> int ret_discard;
> diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h index
> b8f0e829ecbd..1ecd2379022d 100644
> --- a/fs/exfat/exfat_fs.h
> +++ b/fs/exfat/exfat_fs.h
> @@ -409,6 +409,8 @@ int exfat_load_bitmap(struct super_block *sb); void
> exfat_free_bitmap(struct exfat_sb_info *sbi); int exfat_set_bitmap(struct
> inode *inode, unsigned int clu); void exfat_clear_bitmap(struct inode
> *inode, unsigned int clu);
> +void exfat_wait_bitmap(struct inode *inode, unsigned int clu); void
> +exfat_discard_cluster(struct inode *inode, unsigned int clu);
> unsigned int exfat_find_free_bitmap(struct super_block *sb, unsigned int
> clu); int exfat_count_used_clusters(struct super_block *sb, unsigned int
> *ret_count);
>
> diff --git a/fs/exfat/fatent.c b/fs/exfat/fatent.c index
> c3c9afee7418..f39a912a7da7 100644
> --- a/fs/exfat/fatent.c
> +++ b/fs/exfat/fatent.c
> @@ -183,19 +183,56 @@ int exfat_free_cluster(struct inode *inode, struct
> exfat_chain *p_chain)
>
> num_clusters++;
> } while (num_clusters < p_chain->size);
> + sbi->used_clusters -= num_clusters;
> +
> + clu = p_chain->dir;
> + num_clusters = 0;
> + do {
> + exfat_wait_bitmap(inode, clu);
> + clu++;
> +
> + num_clusters++;
> + } while (num_clusters < p_chain->size);
> +
> + clu = p_chain->dir;
> + num_clusters = 0;
> + do {
> + exfat_discard_cluster(inode, clu);
> + clu++;
> +
> + num_clusters++;
> + } while (num_clusters < p_chain->size);
> +
> } else {
> do {
> exfat_clear_bitmap(inode, clu);
>
> if (exfat_get_next_cluster(sb, &clu))
> - goto dec_used_clus;
> + goto exit;
> +
> + sbi->used_clusters--;
> + } while (clu != EXFAT_EOF_CLUSTER);
> +
> + clu = p_chain->dir;
> + do {
> + exfat_wait_bitmap(inode, clu);
> +
> + if (exfat_get_next_cluster(sb, &clu))
> + goto exit;
> +
> + } while (clu != EXFAT_EOF_CLUSTER);
> +
> + clu = p_chain->dir;
> + do {
> + exfat_discard_cluster(inode, clu);
> +
> + if (exfat_get_next_cluster(sb, &clu))
> + goto exit;
>
> - num_clusters++;
> } while (clu != EXFAT_EOF_CLUSTER);
> }
>
> -dec_used_clus:
> - sbi->used_clusters -= num_clusters;
> +exit:
> return 0;
> }
>
> --
> 2.36.1
