On Tue, Nov 06, 2018 at 02:41:13PM +0800, Lu Fengqi wrote:
> From: Wang Xiaoguang <wangxg.f...@cn.fujitsu.com>
>
> Introduce static function inmem_del() to remove hash from in-memory
> dedupe tree.
> And implement btrfs_dedupe_del() and btrfs_dedup_disable() interfaces.
>
> Also for btrfs_dedupe_disable(), add new functions to wait existing
> writer and block incoming writers to eliminate all possible race.
>
> Cc: Mark Fasheh <mfas...@suse.de>
> Signed-off-by: Qu Wenruo <quwen...@cn.fujitsu.com>
> Signed-off-by: Wang Xiaoguang <wangxg.f...@cn.fujitsu.com>
> Signed-off-by: Lu Fengqi <lufq.f...@cn.fujitsu.com>
> ---
> fs/btrfs/dedupe.c | 131 +++++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 125 insertions(+), 6 deletions(-)
>
> diff --git a/fs/btrfs/dedupe.c b/fs/btrfs/dedupe.c
> index 784bb3a8a5ab..951fefd19fde 100644
> --- a/fs/btrfs/dedupe.c
> +++ b/fs/btrfs/dedupe.c
> @@ -170,12 +170,6 @@ int btrfs_dedupe_enable(struct btrfs_fs_info *fs_info,
> return ret;
> }
>
> -int btrfs_dedupe_disable(struct btrfs_fs_info *fs_info)
> -{
> - /* Place holder for bisect, will be implemented in later patches */
> - return 0;
> -}
> -
> static int inmem_insert_hash(struct rb_root *root,
> struct inmem_hash *hash, int hash_len)
> {
> @@ -317,3 +311,128 @@ int btrfs_dedupe_add(struct btrfs_fs_info *fs_info,
> return inmem_add(dedupe_info, hash);
> return -EINVAL;
> }
> +
> +static struct inmem_hash *
> +inmem_search_bytenr(struct btrfs_dedupe_info *dedupe_info, u64 bytenr)
> +{
> + struct rb_node **p = &dedupe_info->bytenr_root.rb_node;
> + struct rb_node *parent = NULL;
> + struct inmem_hash *entry = NULL;
> +
> + while (*p) {
> + parent = *p;
> + entry = rb_entry(parent, struct inmem_hash, bytenr_node);
> +
> + if (bytenr < entry->bytenr)
> + p = &(*p)->rb_left;
> + else if (bytenr > entry->bytenr)
> + p = &(*p)->rb_right;
> + else
> + return entry;
> + }
> +
> + return NULL;
> +}
> +
> +/* Delete a hash from in-memory dedupe tree */
> +static int inmem_del(struct btrfs_dedupe_info *dedupe_info, u64 bytenr)
> +{
> + struct inmem_hash *hash;
> +
> + mutex_lock(&dedupe_info->lock);
> + hash = inmem_search_bytenr(dedupe_info, bytenr);
> + if (!hash) {
> + mutex_unlock(&dedupe_info->lock);
> + return 0;
> + }
> +
> + __inmem_del(dedupe_info, hash);
> + mutex_unlock(&dedupe_info->lock);
> + return 0;
> +}
> +
> +/* Remove a dedupe hash from dedupe tree */
> +int btrfs_dedupe_del(struct btrfs_fs_info *fs_info, u64 bytenr)
> +{
> + struct btrfs_dedupe_info *dedupe_info = fs_info->dedupe_info;
> +
> + if (!fs_info->dedupe_enabled)
> + return 0;
> +
> + if (WARN_ON(dedupe_info == NULL))
> + return -EINVAL;
> +
> + if (dedupe_info->backend == BTRFS_DEDUPE_BACKEND_INMEMORY)
> + return inmem_del(dedupe_info, bytenr);
> + return -EINVAL;
> +}
> +
> +static void inmem_destroy(struct btrfs_dedupe_info *dedupe_info)
> +{
> + struct inmem_hash *entry, *tmp;
> +
> + mutex_lock(&dedupe_info->lock);
> + list_for_each_entry_safe(entry, tmp, &dedupe_info->lru_list, lru_list)
> + __inmem_del(dedupe_info, entry);
> + mutex_unlock(&dedupe_info->lock);
> +}
> +
> +/*
> + * Helper function to wait and block all incoming writers
> + *
> + * Use rw_sem introduced for freeze to wait/block writers.
> + * So during the block time, no new write will happen, so we can
> + * do something quite safe, espcially helpful for dedupe disable,
> + * as it affect buffered write.
> + */
> +static void block_all_writers(struct btrfs_fs_info *fs_info)
> +{
> + struct super_block *sb = fs_info->sb;
> +
> + percpu_down_write(sb->s_writers.rw_sem + SB_FREEZE_WRITE - 1);
> + down_write(&sb->s_umount);
> +}
> +
> +static void unblock_all_writers(struct btrfs_fs_info *fs_info)
> +{
> + struct super_block *sb = fs_info->sb;
> +
> + up_write(&sb->s_umount);
> + percpu_up_write(sb->s_writers.rw_sem + SB_FREEZE_WRITE - 1);
> +}
Please use the sb_ helpers, don't open code this.
> +
> +int btrfs_dedupe_disable(struct btrfs_fs_info *fs_info)
> +{
> + struct btrfs_dedupe_info *dedupe_info;
> + int ret;
> +
> + dedupe_info = fs_info->dedupe_info;
> +
> + if (!dedupe_info)
> + return 0;
> +
> + /* Don't allow disable status change in RO mount */
> + if (fs_info->sb->s_flags & MS_RDONLY)
> + return -EROFS;
> +
> + /*
> + * Wait for all unfinished writers and block further writers.
> + * Then sync the whole fs so all current write will go through
> + * dedupe, and all later write won't go through dedupe.
> + */
> + block_all_writers(fs_info);
> + ret = sync_filesystem(fs_info->sb);
> + fs_info->dedupe_enabled = 0;
> + fs_info->dedupe_info = NULL;
> + unblock_all_writers(fs_info);
This is awful, don't do this. Thanks,
Josef
