Re: [PATCH RFC v3 for-6.8/block 11/17] erofs: use bdev api

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Hi, Jan!

在 2024/01/04 20:02, Jan Kara 写道:
On Thu 21-12-23 16:58:26, Yu Kuai wrote:
From: Yu Kuai <yukuai3@xxxxxxxxxx>

Avoid to access bd_inode directly, prepare to remove bd_inode from
block_device.

Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>

I'm not erofs maintainer but IMO this is quite ugly and grows erofs_buf
unnecessarily. I'd rather store 'sb' pointer in erofs_buf and then do the
right thing in erofs_bread() which is the only place that seems to care
about the erofs_is_fscache_mode() distinction... Also blkszbits is then
trivially sb->s_blocksize_bits so it would all seem much more
straightforward.

Thanks for your suggestion, I'll follow this unless Gao Xiang has other
suggestions.

Kuai

								Honza

---
  fs/erofs/data.c     | 18 ++++++++++++------
  fs/erofs/internal.h |  2 ++
  2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/fs/erofs/data.c b/fs/erofs/data.c
index c98aeda8abb2..bbe2fe199bf3 100644
--- a/fs/erofs/data.c
+++ b/fs/erofs/data.c
@@ -32,8 +32,8 @@ void erofs_put_metabuf(struct erofs_buf *buf)
  void *erofs_bread(struct erofs_buf *buf, erofs_blk_t blkaddr,
  		  enum erofs_kmap_type type)
  {
-	struct inode *inode = buf->inode;
-	erofs_off_t offset = (erofs_off_t)blkaddr << inode->i_blkbits;
+	u8 blkszbits = buf->inode ? buf->inode->i_blkbits : buf->blkszbits;
+	erofs_off_t offset = (erofs_off_t)blkaddr << blkszbits;
  	pgoff_t index = offset >> PAGE_SHIFT;
  	struct page *page = buf->page;
  	struct folio *folio;
@@ -43,7 +43,9 @@ void *erofs_bread(struct erofs_buf *buf, erofs_blk_t blkaddr,
  		erofs_put_metabuf(buf);
nofs_flag = memalloc_nofs_save();
-		folio = read_cache_folio(inode->i_mapping, index, NULL, NULL);
+		folio = buf->inode ?
+			read_mapping_folio(buf->inode->i_mapping, index, NULL) :
+			bdev_read_folio(buf->bdev, offset);
  		memalloc_nofs_restore(nofs_flag);
  		if (IS_ERR(folio))
  			return folio;
@@ -67,10 +69,14 @@ void *erofs_bread(struct erofs_buf *buf, erofs_blk_t blkaddr,
void erofs_init_metabuf(struct erofs_buf *buf, struct super_block *sb)
  {
-	if (erofs_is_fscache_mode(sb))
+	if (erofs_is_fscache_mode(sb)) {
  		buf->inode = EROFS_SB(sb)->s_fscache->inode;
-	else
-		buf->inode = sb->s_bdev->bd_inode;
+		buf->bdev = NULL;
+	} else {
+		buf->inode = NULL;
+		buf->bdev = sb->s_bdev;
+		buf->blkszbits = EROFS_SB(sb)->blkszbits;
+	}
  }
void *erofs_read_metabuf(struct erofs_buf *buf, struct super_block *sb,
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index b0409badb017..c9206351b485 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -224,8 +224,10 @@ enum erofs_kmap_type {
struct erofs_buf {
  	struct inode *inode;
+	struct block_device *bdev;
  	struct page *page;
  	void *base;
+	u8 blkszbits;
  	enum erofs_kmap_type kmap_type;
  };
  #define __EROFS_BUF_INITIALIZER	((struct erofs_buf){ .page = NULL })
--
2.39.2






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