erofs: support compressed inodes over fscache

Since fscache can utilize iov_iter to write dest buffers, bio_vec can
be used in this way too.

To simplify this, pseudo bios are prepared and bio_vec will be filled
with bio_add_page().  And a common .bi_end_io will be called directly
to handle I/O completions.

Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240308094159.40547-2-jefflexu@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

1 files changed, 47 insertions, 0 deletions

diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index b9fb4c4da39c..8aff1a724805 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -174,6 +174,53 @@ static int erofs_fscache_read_io_async(struct fscache_cookie *cookie,
 	return 0;
 }
 
+struct erofs_fscache_bio {
+	struct erofs_fscache_io io;
+	struct bio bio;		/* w/o bdev to share bio_add_page/endio() */
+	struct bio_vec bvecs[BIO_MAX_VECS];
+};
+
+static void erofs_fscache_bio_endio(void *priv,
+		ssize_t transferred_or_error, bool was_async)
+{
+	struct erofs_fscache_bio *io = priv;
+
+	if (IS_ERR_VALUE(transferred_or_error))
+		io->bio.bi_status = errno_to_blk_status(transferred_or_error);
+	io->bio.bi_end_io(&io->bio);
+	BUILD_BUG_ON(offsetof(struct erofs_fscache_bio, io) != 0);
+	erofs_fscache_io_put(&io->io);
+}
+
+struct bio *erofs_fscache_bio_alloc(struct erofs_map_dev *mdev)
+{
+	struct erofs_fscache_bio *io;
+
+	io = kmalloc(sizeof(*io), GFP_KERNEL | __GFP_NOFAIL);
+	bio_init(&io->bio, NULL, io->bvecs, BIO_MAX_VECS, REQ_OP_READ);
+	io->io.private = mdev->m_fscache->cookie;
+	io->io.end_io = erofs_fscache_bio_endio;
+	refcount_set(&io->io.ref, 1);
+	return &io->bio;
+}
+
+void erofs_fscache_submit_bio(struct bio *bio)
+{
+	struct erofs_fscache_bio *io = container_of(bio,
+			struct erofs_fscache_bio, bio);
+	int ret;
+
+	iov_iter_bvec(&io->io.iter, ITER_DEST, io->bvecs, bio->bi_vcnt,
+		      bio->bi_iter.bi_size);
+	ret = erofs_fscache_read_io_async(io->io.private,
+				bio->bi_iter.bi_sector << 9, &io->io);
+	erofs_fscache_io_put(&io->io);
+	if (!ret)
+		return;
+	bio->bi_status = errno_to_blk_status(ret);
+	bio->bi_end_io(bio);
+}
+
 static int erofs_fscache_meta_read_folio(struct file *data, struct folio *folio)
 {
 	struct erofs_fscache *ctx = folio->mapping->host->i_private;