[PATCH 0/2] btrfs: remove btrfs_bio::logical member

[PATCH 0/2] btrfs: remove btrfs_bio::logical member

[Qu Wenruo]

Although we have two call sites setting btrfs_bio::logical, but only one
call site it really reading btrfs_bio::logical.

Furthermore, that only reader can grab the same info from
btrfs_dio_private without any hassle.

Thus it means btrfs_bio::logical duplicated and can be removed.

This in fact proves my initial suspicion, that btrfs_bio::logical is
duplicated, and the logical bytenr can be fetched using
bio->bi_iter.bi_sector.

This saves 8 bytes from btrfs_bio, without any complicated refactor.

Qu Wenruo (2):
  btrfs: rename btrfs_dio_private::logical_offset to file_offset
  btrfs: remove btrfs_bio::logical member

 fs/btrfs/btrfs_inode.h |  7 ++++++-
 fs/btrfs/extent_io.c   |  1 -
 fs/btrfs/inode.c       | 29 ++++++++++++++---------------
 fs/btrfs/volumes.h     |  1 -
 4 files changed, 20 insertions(+), 18 deletions(-)

-- 
2.33.0

[PATCH 1/2] btrfs: rename btrfs_dio_private::logical_offset to file_offset

[Qu Wenruo]

The naming of "logical_offset" can be confused with logical bytenr of
the dio range.

In fact it's file offset, and the naming "file_offset" is already widely
used in all other sites.

Just do the rename to avoid confusion.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/btrfs_inode.h |  7 ++++++-
 fs/btrfs/inode.c       | 12 ++++++------
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index 602b426c286d..ab2a4a52e0bb 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -356,7 +356,12 @@ static inline bool btrfs_inode_in_log(struct btrfs_inode *inode, u64 generation)
 
 struct btrfs_dio_private {
 	struct inode *inode;
-	u64 logical_offset;
+
+	/*
+	 * Since DIO can use anonymous page, we cannot use page_offset() to
+	 * grab the file offset, thus need a dedicated member for file offset.
+	 */
+	u64 file_offset;
 	u64 disk_bytenr;
 	/* Used for bio::bi_size */
 	u32 bytes;
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index f5faa6bedbd4..d65f7d6b7df1 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8055,13 +8055,13 @@ static void btrfs_dio_private_put(struct btrfs_dio_private *dip)
 
 	if (btrfs_op(dip->dio_bio) == BTRFS_MAP_WRITE) {
 		__endio_write_update_ordered(BTRFS_I(dip->inode),
-					     dip->logical_offset,
+					     dip->file_offset,
 					     dip->bytes,
 					     !dip->dio_bio->bi_status);
 	} else {
 		unlock_extent(&BTRFS_I(dip->inode)->io_tree,
-			      dip->logical_offset,
-			      dip->logical_offset + dip->bytes - 1);
+			      dip->file_offset,
+			      dip->file_offset + dip->bytes - 1);
 	}
 
 	bio_endio(dip->dio_bio);
@@ -8176,7 +8176,7 @@ static void btrfs_end_dio_bio(struct bio *bio)
 	if (err)
 		dip->dio_bio->bi_status = err;
 
-	btrfs_record_physical_zoned(dip->inode, dip->logical_offset, bio);
+	btrfs_record_physical_zoned(dip->inode, dip->file_offset, bio);
 
 	bio_put(bio);
 	btrfs_dio_private_put(dip);
@@ -8218,7 +8218,7 @@ static inline blk_status_t btrfs_submit_dio_bio(struct bio *bio,
 	} else {
 		u64 csum_offset;
 
-		csum_offset = file_offset - dip->logical_offset;
+		csum_offset = file_offset - dip->file_offset;
 		csum_offset >>= fs_info->sectorsize_bits;
 		csum_offset *= fs_info->csum_size;
 		btrfs_bio(bio)->csum = dip->csums + csum_offset;
@@ -8256,7 +8256,7 @@ static struct btrfs_dio_private *btrfs_create_dio_private(struct bio *dio_bio,
 		return NULL;
 
 	dip->inode = inode;
-	dip->logical_offset = file_offset;
+	dip->file_offset = file_offset;
 	dip->bytes = dio_bio->bi_iter.bi_size;
 	dip->disk_bytenr = dio_bio->bi_iter.bi_sector << 9;
 	dip->dio_bio = dio_bio;
-- 
2.33.0

[PATCH 2/2] btrfs: remove btrfs_bio::logical member

[Qu Wenruo]

The member btrfs_bio::logical is only initialized by two call sites:

- btrfs_repair_one_sector()
  No corresponding site to utilize it.

- btrfs_submit_direct()
  The corresponding site to utilize it is btrfs_check_read_dio_bio().

However for btrfs_check_read_dio_bio(), we can grab the file_offset from
btrfs_dio_private::file_offset directly.

Thus it turns out we don't really that btrfs_bio::logical member at all.

For btrfs_bio, the logical bytenr can be fetched from its
bio->bi_iter.bi_sector directly.

So let's just remove the member to save 8 bytes for structure btrfs_bio.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/extent_io.c |  1 -
 fs/btrfs/inode.c     | 17 ++++++++---------
 fs/btrfs/volumes.h   |  1 -
 3 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index b10dc75eef1c..4e03a6d3aa32 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2673,7 +2673,6 @@ int btrfs_repair_one_sector(struct inode *inode,
 	}
 
 	bio_add_page(repair_bio, page, failrec->len, pgoff);
-	repair_bbio->logical = failrec->start;
 	repair_bbio->iter = repair_bio->bi_iter;
 
 	btrfs_debug(btrfs_sb(inode->i_sb),
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index d65f7d6b7df1..b9c70a073a24 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8089,10 +8089,11 @@ static blk_status_t submit_dio_repair_bio(struct inode *inode, struct bio *bio,
 	return ret;
 }
 
-static blk_status_t btrfs_check_read_dio_bio(struct inode *inode,
+static blk_status_t btrfs_check_read_dio_bio(struct btrfs_dio_private *dip,
 					     struct btrfs_bio *bbio,
 					     const bool uptodate)
 {
+	struct inode *inode = dip->inode;
 	struct btrfs_fs_info *fs_info = BTRFS_I(inode)->root->fs_info;
 	const u32 sectorsize = fs_info->sectorsize;
 	struct extent_io_tree *failure_tree = &BTRFS_I(inode)->io_failure_tree;
@@ -8100,7 +8101,8 @@ static blk_status_t btrfs_check_read_dio_bio(struct inode *inode,
 	const bool csum = !(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM);
 	struct bio_vec bvec;
 	struct bvec_iter iter;
-	u64 start = bbio->logical;
+	const u64 orig_file_offset = dip->file_offset;
+	u64 start = orig_file_offset;
 	u32 bio_offset = 0;
 	blk_status_t err = BLK_STS_OK;
 
@@ -8122,10 +8124,10 @@ static blk_status_t btrfs_check_read_dio_bio(struct inode *inode,
 			} else {
 				int ret;
 
-				ASSERT((start - bbio->logical) < UINT_MAX);
+				ASSERT((start - orig_file_offset) < UINT_MAX);
 				ret = btrfs_repair_one_sector(inode,
 						&bbio->bio,
-						start - bbio->logical,
+						start - orig_file_offset,
 						bvec.bv_page, pgoff,
 						start, bbio->mirror_num,
 						submit_dio_repair_bio);
@@ -8168,10 +8170,8 @@ static void btrfs_end_dio_bio(struct bio *bio)
 			   bio->bi_opf, bio->bi_iter.bi_sector,
 			   bio->bi_iter.bi_size, err);
 
-	if (bio_op(bio) == REQ_OP_READ) {
-		err = btrfs_check_read_dio_bio(dip->inode,
-					       btrfs_bio(bio), !err);
-	}
+	if (bio_op(bio) == REQ_OP_READ)
+		err = btrfs_check_read_dio_bio(dip, btrfs_bio(bio), !err);
 
 	if (err)
 		dip->dio_bio->bi_status = err;
@@ -8337,7 +8337,6 @@ static blk_qc_t btrfs_submit_direct(const struct iomap_iter *iter,
 		bio = btrfs_bio_clone_partial(dio_bio, clone_offset, clone_len);
 		bio->bi_private = dip;
 		bio->bi_end_io = btrfs_end_dio_bio;
-		btrfs_bio(bio)->logical = file_offset;
 
 		if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
 			status = extract_ordered_extent(BTRFS_I(inode), bio,
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 83075d6855db..49322a43593a 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -313,7 +313,6 @@ struct btrfs_bio {
 
 	/* @device is for stripe IO submission. */
 	struct btrfs_device *device;
-	u64 logical;
 	u8 *csum;
 	u8 csum_inline[BTRFS_BIO_INLINE_CSUM_SIZE];
 	struct bvec_iter iter;
-- 
2.33.0

Re: [PATCH 0/2] btrfs: remove btrfs_bio::logical member

[David Sterba]

On Fri, Oct 08, 2021 at 03:29:58PM +0800, Qu Wenruo wrote:
> Although we have two call sites setting btrfs_bio::logical, but only one
> call site it really reading btrfs_bio::logical.
> 
> Furthermore, that only reader can grab the same info from
> btrfs_dio_private without any hassle.
> 
> Thus it means btrfs_bio::logical duplicated and can be removed.
> 
> This in fact proves my initial suspicion, that btrfs_bio::logical is
> duplicated, and the logical bytenr can be fetched using
> bio->bi_iter.bi_sector.
> 
> This saves 8 bytes from btrfs_bio, without any complicated refactor.

Great, thanks. Added to misc-next.