diff mbox series

[v5,2/5] btrfs: subpage: introduce helpers to handle subpage delalloc locking

Message ID 996c0c3b0807f46f7ae722541e6a90c87b7d3e58.1716008374.git.wqu@suse.com (mailing list archive)
State New, archived
Headers show
Series btrfs: subpage + zoned fixes | expand

Commit Message

Qu Wenruo May 18, 2024, 5:07 a.m. UTC 
Three new helpers are introduced for the incoming subpage delalloc locking
change.

- btrfs_folio_set_writer_lock()
  This is to mark specified range with subpage specific writer lock.
  After calling this, the subpage range can be proper unlocked by
  btrfs_folio_end_writer_lock()

- btrfs_subpage_find_writer_locked()
  This is to find the writer locked subpage range in a page.
  With the help of btrfs_folio_set_writer_lock(), it can allow us to
  record and find previously locked subpage range without extra memory
  allocation.

- btrfs_folio_end_all_writers()
  This is for the locked_page of __extent_writepage(), as there may be
  multiple subpage delalloc ranges locked.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/subpage.c | 116 +++++++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/subpage.h |   7 +++
 2 files changed, 123 insertions(+)

Comments

Naohiro Aota May 21, 2024, 7:50 a.m. UTC | #1 
On Sat, May 18, 2024 at 02:37:40PM GMT, Qu Wenruo wrote:
> Three new helpers are introduced for the incoming subpage delalloc locking
> change.
> 
> - btrfs_folio_set_writer_lock()
>   This is to mark specified range with subpage specific writer lock.
>   After calling this, the subpage range can be proper unlocked by
>   btrfs_folio_end_writer_lock()
> 
> - btrfs_subpage_find_writer_locked()
>   This is to find the writer locked subpage range in a page.
>   With the help of btrfs_folio_set_writer_lock(), it can allow us to
>   record and find previously locked subpage range without extra memory
>   allocation.
> 
> - btrfs_folio_end_all_writers()
>   This is for the locked_page of __extent_writepage(), as there may be
>   multiple subpage delalloc ranges locked.
> 
> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> ---

There are some nits inlined below, basically it looks good.

Reviewed-by: Naohiro Aota <naohiro.aota@wdc.com>

>  fs/btrfs/subpage.c | 116 +++++++++++++++++++++++++++++++++++++++++++++
>  fs/btrfs/subpage.h |   7 +++
>  2 files changed, 123 insertions(+)
> 
> diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c
> index 183b32f51f51..3c957d03324e 100644
> --- a/fs/btrfs/subpage.c
> +++ b/fs/btrfs/subpage.c
> @@ -775,6 +775,122 @@ void btrfs_folio_unlock_writer(struct btrfs_fs_info *fs_info,
>  	btrfs_folio_end_writer_lock(fs_info, folio, start, len);
>  }
>  
> +/*
> + * This is for folio already locked by plain lock_page()/folio_lock(), which
> + * doesn't have any subpage awareness.
> + *
> + * This would populate the involved subpage ranges so that subpage helpers can
> + * properly unlock them.
> + */
> +void btrfs_folio_set_writer_lock(const struct btrfs_fs_info *fs_info,
> +				 struct folio *folio, u64 start, u32 len)
> +{
> +	struct btrfs_subpage *subpage;
> +	unsigned long flags;
> +	int start_bit;
> +	int nbits;

May want to use unsigned int for a consistency...

> +	int ret;
> +
> +	ASSERT(folio_test_locked(folio));
> +	if (unlikely(!fs_info) || !btrfs_is_subpage(fs_info, folio->mapping))
> +		return;
> +
> +	subpage = folio_get_private(folio);
> +	start_bit = subpage_calc_start_bit(fs_info, folio, locked, start, len);
> +	nbits = len >> fs_info->sectorsize_bits;
> +	spin_lock_irqsave(&subpage->lock, flags);
> +	/* Target range should not yet be locked. */
> +	ASSERT(bitmap_test_range_all_zero(subpage->bitmaps, start_bit, nbits));
> +	bitmap_set(subpage->bitmaps, start_bit, nbits);
> +	ret = atomic_add_return(nbits, &subpage->writers);
> +	ASSERT(ret <= fs_info->subpage_info->bitmap_nr_bits);
> +	spin_unlock_irqrestore(&subpage->lock, flags);
> +}
> +
> +/*
> + * Find any subpage writer locked range inside @folio, starting at file offset
> + * @search_start.
> + * The caller should ensure the folio is locked.
> + *
> + * Return true and update @found_start_ret and @found_len_ret to the first
> + * writer locked range.
> + * Return false if there is no writer locked range.
> + */
> +bool btrfs_subpage_find_writer_locked(const struct btrfs_fs_info *fs_info,
> +				      struct folio *folio, u64 search_start,
> +				      u64 *found_start_ret, u32 *found_len_ret)
> +{
> +	struct btrfs_subpage_info *subpage_info = fs_info->subpage_info;
> +	struct btrfs_subpage *subpage = folio_get_private(folio);
> +	const int len = PAGE_SIZE - offset_in_page(search_start);
> +	const int start_bit = subpage_calc_start_bit(fs_info, folio, locked,
> +						     search_start, len);
> +	const int locked_bitmap_start = subpage_info->locked_offset;
> +	const int locked_bitmap_end = locked_bitmap_start +
> +				      subpage_info->bitmap_nr_bits;
> +	unsigned long flags;
> +	int first_zero;
> +	int first_set;
> +	bool found = false;
> +
> +	ASSERT(folio_test_locked(folio));
> +	spin_lock_irqsave(&subpage->lock, flags);
> +	first_set = find_next_bit(subpage->bitmaps, locked_bitmap_end,
> +				  start_bit);
> +	if (first_set >= locked_bitmap_end)
> +		goto out;
> +
> +	found = true;
> +	*found_start_ret = folio_pos(folio) +
> +		((first_set - locked_bitmap_start) << fs_info->sectorsize_bits);

It's a bit fearful to see an "int" value is shifted and added into u64
value. But, I guess sectorsize is within 32-bit range, right?

> +
> +	first_zero = find_next_zero_bit(subpage->bitmaps,
> +					locked_bitmap_end, first_set);
> +	*found_len_ret = (first_zero - first_set) << fs_info->sectorsize_bits;
> +out:
> +	spin_unlock_irqrestore(&subpage->lock, flags);
> +	return found;
> +}
> +
> +/*
> + * Unlike btrfs_folio_end_writer_lock() which unlock a specified subpage range,
> + * this would end all writer locked ranges of a page.
> + *
> + * This is for the locked page of __extent_writepage(), as the locked page
> + * can contain several locked subpage ranges.
> + */
> +void btrfs_folio_end_all_writers(const struct btrfs_fs_info *fs_info,
> +				 struct folio *folio)
> +{
> +	u64 folio_start = folio_pos(folio);
> +	u64 cur = folio_start;
> +
> +	ASSERT(folio_test_locked(folio));
> +	if (!btrfs_is_subpage(fs_info, folio->mapping)) {
> +		folio_unlock(folio);
> +		return;
> +	}
> +
> +	while (cur < folio_start + PAGE_SIZE) {
> +		u64 found_start;
> +		u32 found_len;
> +		bool found;
> +		bool last;
> +
> +		found = btrfs_subpage_find_writer_locked(fs_info, folio, cur,
> +							 &found_start, &found_len);
> +		if (!found)
> +			break;
> +		last = btrfs_subpage_end_and_test_writer(fs_info, folio,
> +							 found_start, found_len);
> +		if (last) {
> +			folio_unlock(folio);
> +			break;
> +		}
> +		cur = found_start + found_len;
> +	}
> +}
> +
>  #define GET_SUBPAGE_BITMAP(subpage, subpage_info, name, dst)		\
>  	bitmap_cut(dst, subpage->bitmaps, 0,				\
>  		   subpage_info->name##_offset, subpage_info->bitmap_nr_bits)
> diff --git a/fs/btrfs/subpage.h b/fs/btrfs/subpage.h
> index 4b363d9453af..9f19850d59f2 100644
> --- a/fs/btrfs/subpage.h
> +++ b/fs/btrfs/subpage.h
> @@ -112,6 +112,13 @@ int btrfs_folio_start_writer_lock(const struct btrfs_fs_info *fs_info,
>  				  struct folio *folio, u64 start, u32 len);
>  void btrfs_folio_end_writer_lock(const struct btrfs_fs_info *fs_info,
>  				 struct folio *folio, u64 start, u32 len);
> +void btrfs_folio_set_writer_lock(const struct btrfs_fs_info *fs_info,
> +				 struct folio *folio, u64 start, u32 len);
> +bool btrfs_subpage_find_writer_locked(const struct btrfs_fs_info *fs_info,
> +				      struct folio *folio, u64 search_start,
> +				      u64 *found_start_ret, u32 *found_len_ret);
> +void btrfs_folio_end_all_writers(const struct btrfs_fs_info *fs_info,
> +				 struct folio *folio);
>  
>  /*
>   * Template for subpage related operations.
> -- 
> 2.45.0
>
Qu Wenruo May 21, 2024, 7:57 a.m. UTC | #2 
在 2024/5/21 17:20, Naohiro Aota 写道:
[...]
>> +void btrfs_folio_set_writer_lock(const struct btrfs_fs_info *fs_info,
>> +				 struct folio *folio, u64 start, u32 len)
>> +{
>> +	struct btrfs_subpage *subpage;
>> +	unsigned long flags;
>> +	int start_bit;
>> +	int nbits;
>
> May want to use unsigned int for a consistency...
>

I can definitely change all the int to "unsigned int" to be consistent
during pushing to for-next branch.

[...]
>> +	found = true;
>> +	*found_start_ret = folio_pos(folio) +
>> +		((first_set - locked_bitmap_start) << fs_info->sectorsize_bits);
>
> It's a bit fearful to see an "int" value is shifted and added into u64
> value. But, I guess sectorsize is within 32-bit range, right?

In fact, (first_set - locked_bitmap_start) is never going to be larger
than (PAGE_SIZE / sectorsize).

I can add extra ASSERT() to be extra safe for that too.

Thanks,
Qu

>
>> +
>> +	first_zero = find_next_zero_bit(subpage->bitmaps,
>> +					locked_bitmap_end, first_set);
>> +	*found_len_ret = (first_zero - first_set) << fs_info->sectorsize_bits;
>> +out:
>> +	spin_unlock_irqrestore(&subpage->lock, flags);
>> +	return found;
>> +}
>> +
>> +/*
>> + * Unlike btrfs_folio_end_writer_lock() which unlock a specified subpage range,
>> + * this would end all writer locked ranges of a page.
>> + *
>> + * This is for the locked page of __extent_writepage(), as the locked page
>> + * can contain several locked subpage ranges.
>> + */
>> +void btrfs_folio_end_all_writers(const struct btrfs_fs_info *fs_info,
>> +				 struct folio *folio)
>> +{
>> +	u64 folio_start = folio_pos(folio);
>> +	u64 cur = folio_start;
>> +
>> +	ASSERT(folio_test_locked(folio));
>> +	if (!btrfs_is_subpage(fs_info, folio->mapping)) {
>> +		folio_unlock(folio);
>> +		return;
>> +	}
>> +
>> +	while (cur < folio_start + PAGE_SIZE) {
>> +		u64 found_start;
>> +		u32 found_len;
>> +		bool found;
>> +		bool last;
>> +
>> +		found = btrfs_subpage_find_writer_locked(fs_info, folio, cur,
>> +							 &found_start, &found_len);
>> +		if (!found)
>> +			break;
>> +		last = btrfs_subpage_end_and_test_writer(fs_info, folio,
>> +							 found_start, found_len);
>> +		if (last) {
>> +			folio_unlock(folio);
>> +			break;
>> +		}
>> +		cur = found_start + found_len;
>> +	}
>> +}
>> +
>>   #define GET_SUBPAGE_BITMAP(subpage, subpage_info, name, dst)		\
>>   	bitmap_cut(dst, subpage->bitmaps, 0,				\
>>   		   subpage_info->name##_offset, subpage_info->bitmap_nr_bits)
>> diff --git a/fs/btrfs/subpage.h b/fs/btrfs/subpage.h
>> index 4b363d9453af..9f19850d59f2 100644
>> --- a/fs/btrfs/subpage.h
>> +++ b/fs/btrfs/subpage.h
>> @@ -112,6 +112,13 @@ int btrfs_folio_start_writer_lock(const struct btrfs_fs_info *fs_info,
>>   				  struct folio *folio, u64 start, u32 len);
>>   void btrfs_folio_end_writer_lock(const struct btrfs_fs_info *fs_info,
>>   				 struct folio *folio, u64 start, u32 len);
>> +void btrfs_folio_set_writer_lock(const struct btrfs_fs_info *fs_info,
>> +				 struct folio *folio, u64 start, u32 len);
>> +bool btrfs_subpage_find_writer_locked(const struct btrfs_fs_info *fs_info,
>> +				      struct folio *folio, u64 search_start,
>> +				      u64 *found_start_ret, u32 *found_len_ret);
>> +void btrfs_folio_end_all_writers(const struct btrfs_fs_info *fs_info,
>> +				 struct folio *folio);
>>
>>   /*
>>    * Template for subpage related operations.
>> --
>> 2.45.0
>>
diff mbox series

Patch

diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c
index 183b32f51f51..3c957d03324e 100644
--- a/fs/btrfs/subpage.c
+++ b/fs/btrfs/subpage.c
@@ -775,6 +775,122 @@  void btrfs_folio_unlock_writer(struct btrfs_fs_info *fs_info,
 	btrfs_folio_end_writer_lock(fs_info, folio, start, len);
 }
 
+/*
+ * This is for folio already locked by plain lock_page()/folio_lock(), which
+ * doesn't have any subpage awareness.
+ *
+ * This would populate the involved subpage ranges so that subpage helpers can
+ * properly unlock them.
+ */
+void btrfs_folio_set_writer_lock(const struct btrfs_fs_info *fs_info,
+				 struct folio *folio, u64 start, u32 len)
+{
+	struct btrfs_subpage *subpage;
+	unsigned long flags;
+	int start_bit;
+	int nbits;
+	int ret;
+
+	ASSERT(folio_test_locked(folio));
+	if (unlikely(!fs_info) || !btrfs_is_subpage(fs_info, folio->mapping))
+		return;
+
+	subpage = folio_get_private(folio);
+	start_bit = subpage_calc_start_bit(fs_info, folio, locked, start, len);
+	nbits = len >> fs_info->sectorsize_bits;
+	spin_lock_irqsave(&subpage->lock, flags);
+	/* Target range should not yet be locked. */
+	ASSERT(bitmap_test_range_all_zero(subpage->bitmaps, start_bit, nbits));
+	bitmap_set(subpage->bitmaps, start_bit, nbits);
+	ret = atomic_add_return(nbits, &subpage->writers);
+	ASSERT(ret <= fs_info->subpage_info->bitmap_nr_bits);
+	spin_unlock_irqrestore(&subpage->lock, flags);
+}
+
+/*
+ * Find any subpage writer locked range inside @folio, starting at file offset
+ * @search_start.
+ * The caller should ensure the folio is locked.
+ *
+ * Return true and update @found_start_ret and @found_len_ret to the first
+ * writer locked range.
+ * Return false if there is no writer locked range.
+ */
+bool btrfs_subpage_find_writer_locked(const struct btrfs_fs_info *fs_info,
+				      struct folio *folio, u64 search_start,
+				      u64 *found_start_ret, u32 *found_len_ret)
+{
+	struct btrfs_subpage_info *subpage_info = fs_info->subpage_info;
+	struct btrfs_subpage *subpage = folio_get_private(folio);
+	const int len = PAGE_SIZE - offset_in_page(search_start);
+	const int start_bit = subpage_calc_start_bit(fs_info, folio, locked,
+						     search_start, len);
+	const int locked_bitmap_start = subpage_info->locked_offset;
+	const int locked_bitmap_end = locked_bitmap_start +
+				      subpage_info->bitmap_nr_bits;
+	unsigned long flags;
+	int first_zero;
+	int first_set;
+	bool found = false;
+
+	ASSERT(folio_test_locked(folio));
+	spin_lock_irqsave(&subpage->lock, flags);
+	first_set = find_next_bit(subpage->bitmaps, locked_bitmap_end,
+				  start_bit);
+	if (first_set >= locked_bitmap_end)
+		goto out;
+
+	found = true;
+	*found_start_ret = folio_pos(folio) +
+		((first_set - locked_bitmap_start) << fs_info->sectorsize_bits);
+
+	first_zero = find_next_zero_bit(subpage->bitmaps,
+					locked_bitmap_end, first_set);
+	*found_len_ret = (first_zero - first_set) << fs_info->sectorsize_bits;
+out:
+	spin_unlock_irqrestore(&subpage->lock, flags);
+	return found;
+}
+
+/*
+ * Unlike btrfs_folio_end_writer_lock() which unlock a specified subpage range,
+ * this would end all writer locked ranges of a page.
+ *
+ * This is for the locked page of __extent_writepage(), as the locked page
+ * can contain several locked subpage ranges.
+ */
+void btrfs_folio_end_all_writers(const struct btrfs_fs_info *fs_info,
+				 struct folio *folio)
+{
+	u64 folio_start = folio_pos(folio);
+	u64 cur = folio_start;
+
+	ASSERT(folio_test_locked(folio));
+	if (!btrfs_is_subpage(fs_info, folio->mapping)) {
+		folio_unlock(folio);
+		return;
+	}
+
+	while (cur < folio_start + PAGE_SIZE) {
+		u64 found_start;
+		u32 found_len;
+		bool found;
+		bool last;
+
+		found = btrfs_subpage_find_writer_locked(fs_info, folio, cur,
+							 &found_start, &found_len);
+		if (!found)
+			break;
+		last = btrfs_subpage_end_and_test_writer(fs_info, folio,
+							 found_start, found_len);
+		if (last) {
+			folio_unlock(folio);
+			break;
+		}
+		cur = found_start + found_len;
+	}
+}
+
 #define GET_SUBPAGE_BITMAP(subpage, subpage_info, name, dst)		\
 	bitmap_cut(dst, subpage->bitmaps, 0,				\
 		   subpage_info->name##_offset, subpage_info->bitmap_nr_bits)
diff --git a/fs/btrfs/subpage.h b/fs/btrfs/subpage.h
index 4b363d9453af..9f19850d59f2 100644
--- a/fs/btrfs/subpage.h
+++ b/fs/btrfs/subpage.h
@@ -112,6 +112,13 @@  int btrfs_folio_start_writer_lock(const struct btrfs_fs_info *fs_info,
 				  struct folio *folio, u64 start, u32 len);
 void btrfs_folio_end_writer_lock(const struct btrfs_fs_info *fs_info,
 				 struct folio *folio, u64 start, u32 len);
+void btrfs_folio_set_writer_lock(const struct btrfs_fs_info *fs_info,
+				 struct folio *folio, u64 start, u32 len);
+bool btrfs_subpage_find_writer_locked(const struct btrfs_fs_info *fs_info,
+				      struct folio *folio, u64 search_start,
+				      u64 *found_start_ret, u32 *found_len_ret);
+void btrfs_folio_end_all_writers(const struct btrfs_fs_info *fs_info,
+				 struct folio *folio);
 
 /*
  * Template for subpage related operations.