Re: [PATCH v15.1 04/13] btrfs: dedupe: Introduce function to remove hash from in-memory tree
On Tue, Nov 06, 2018 at 02:41:13PM +0800, Lu Fengqi wrote:
> From: Wang Xiaoguang
>
> 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
> Signed-off-by: Qu Wenruo
> Signed-off-by: Wang Xiaoguang
> Signed-off-by: Lu Fengqi
> ---
> 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 = _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(_info->lock);
> + hash = inmem_search_bytenr(dedupe_info, bytenr);
> + if (!hash) {
> + mutex_unlock(_info->lock);
> + return 0;
> + }
> +
> + __inmem_del(dedupe_info, hash);
> + mutex_unlock(_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(_info->lock);
> + list_for_each_entry_safe(entry, tmp, _info->lru_list, lru_list)
> + __inmem_del(dedupe_info, entry);
> + mutex_unlock(_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(>s_umount);
> +}
> +
> +static void unblock_all_writers(struct btrfs_fs_info *fs_info)
> +{
> + struct super_block *sb = fs_info->sb;
> +
> + up_write(>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
[PATCH v15.1 04/13] btrfs: dedupe: Introduce function to remove hash from in-memory tree
From: Wang Xiaoguang
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
Signed-off-by: Qu Wenruo
Signed-off-by: Wang Xiaoguang
Signed-off-by: Lu Fengqi
---
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 = _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(_info->lock);
+ hash = inmem_search_bytenr(dedupe_info, bytenr);
+ if (!hash) {
+ mutex_unlock(_info->lock);
+ return 0;
+ }
+
+ __inmem_del(dedupe_info, hash);
+ mutex_unlock(_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(_info->lock);
+ list_for_each_entry_safe(entry, tmp, _info->lru_list, lru_list)
+ __inmem_del(dedupe_info, entry);
+ mutex_unlock(_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(>s_umount);
+}
+
+static void unblock_all_writers(struct btrfs_fs_info *fs_info)
+{
+ struct super_block *sb = fs_info->sb;
+
+ up_write(>s_umount);
+ percpu_up_write(sb->s_writers.rw_sem + SB_FREEZE_WRITE - 1);
+}
+
+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);
+ if (ret < 0)
+ return ret;
+
+ /* now we are OK to clean up everything */
+ if (dedupe_info->backend == BTRFS_DEDUPE_BACKEND_INMEMORY)
+ inmem_destroy(dedupe_info);
+
+ crypto_free_shash(dedupe_info->dedupe_driver);
+ kfree(dedupe_info);
+ return 0;
+}
--
2.19.1
